Electronic temp control

[Bret4207]

Someone recently mentioned adding an electronic temp controller to their Lee pot. Any idea where I'd find something like that? I just got an old SAECO and it doesn't shut off.

[Bret4207]

Found it- a PID. Why couldn't I remember that?

[mikenbarb]

Got a link to it? I need one also for a Saeco that has the same problemLOL.

[revolver junkie]

midway sells replacements for lees

[Bret4207]

Got a link to it? I need one also for a Saeco that has the same problemLOL.

http://castboolits.gunloads.com/showthread.php?t=45733

[Charlie]

I was fed up with the rotten temperature control on my old Lee Production pot so I converted it to a PID controller. I used the controller and thermocouple from the company at the link below. The controller is simple to set up, automatically programs and has an internal relay good for 10A @120V to control the heater. Now I can set the desired temp and get a read out of the actual lead temp in the pot. It holds the temp to within about 10 deg of the setting.

I temporarily wired it to try it out. The upper display is the actual temp from the thermcouple. The lower is the set temp, 700 deg in this case. The lower display is green which does not show up well in the photo.
http://i420.photobucket.com/albums/pp290/charlie1019/IMG_2379.jpg

This is the finished pot with the PID controller in a case attached to the back of the pot.
http://i420.photobucket.com/albums/pp290/charlie1019/IMG_2397.jpg

The PID & termocouple cost $60 including shipping

[URL="http://auberins.com/index.php?main_page=product_info&cPath=1&products_id=1&zenid=50084f9fcd19cecc0936d8b31a5f18c5"]

[cheese1566]

I tried the link, but it goes doesn't work... which PID did you use?

I don't see one on the website with a 10amp output without a relay... I have no experience with PID's so simplicity is best.

Nevermind, I just found it..."1/16 DIN PID Temperature Controller (Relay Output)$44.50"

Which thermocouple did you use?

I think I need an idiot's guide to setting one of these up. Can I get list of what was used and how it is set up. I have a Lee 4-20 production pot.

[RP]

I got a ? I just junked out a stove robbed the burners and controls for them. I was going to use them in a new casting pot. Useing my Lyman ther. to check the heat then mark the control for future referance. Once set to temp it should keep it at that temp? or is it the longer it sits warming or while using the lead gets hotter and hotter. I know the lead will cool off when adding new lead to the mix.

[briang]

From what I've heard as you take lead out it will get hotter, never checked myself.

[No_1]

[QUOTE=cheese1566;532637]Which thermocouple did you use?[QUOTE]

I am curious also since I do not see the thermocouple in your pics.

Robert

[Echo]

I got a ? I just junked out a stove robbed the burners and controls for them. I was going to use them in a new casting pot. Useing my Lyman ther. to check the heat then mark the control for future referance. Once set to temp it should keep it at that temp? or is it the longer it sits warming or while using the lead gets hotter and hotter. I know the lead will cool off when adding new lead to the mix.

Right. The controls on most of our furnaces are Power controls, not Temperature controls. In other words, they are not thermostats, so they are controlling a set amount of power going to the element. Less lead, less heat lost, higher temperature. I understand the RCBS 20-pounder uses an actual thermostat control.

[Charlie]

Just about any of the K thermocouples will work. They are all high temperature insulation good for at least 900 deg. The outer sheath is typically stainless steel which is good to a higher temperature than the carbon steel of the Lee pot. I welded a 1/4 20 nut to the bottom of the pot & screwed the Model: TC-K6 thermocouple in it. You can see the lead in the picture.

http://i420.photobucket.com/albums/pp290/charlie1019/IMG_2400.jpg

If you don't want to weld then just get one of the probe type TCs like Model: WRNK-171S & put it in the lead from the top of the pot. You will need to make a bracket out of wire or the like to keep it submerged in the lead.

The Aubner web site has the manuals for the controllers on line. Download one & they show sample wiring diagrams on pg 12. They show all the extra features it can do like actuate alarms but the only connections needed are power to the PID controller, the 2 wire connection for the TC(make sure you get the polarity right) and wire the PID internal relay in place of the thermostat in the pot. The terminals on the PID are all marked as to their function. Here is a wiring diagram for the numbered terminals on the back of the PID. The fuses are optional, I didn't use any.

http://i420.photobucket.com/albums/pp290/charlie1019/Wiringdiagram.jpg

The PID is set up with default parameters for K type TCs & an avg control. It worked great for me with the factory settings. If you want to get fancy, the instructions show you how to turn the learn mode feature on so that the PID will cycle on & off about 3 times while it watches the temperature response of the pot. It will set the parameters for the best operation based on that. It is very simple.

BTW, Here is the original thermostat for the Lee Production Pot. As you can see it is not really a true thermostat, it does not read the temp of the lead. It is a timer, it cycles on & off with the heating of a bimetalic strip. This is the part I took out & replaced with the PID.

http://i420.photobucket.com/albums/pp290/charlie1019/IMG_2370.jpg

[Wayne S]

[QUOTE=Echo;533385. I understand the RCBS 20-pounder uses an actual thermostat control.[/QUOTE]
Does anyone know for a fact WHAT RCBS uses ???

[RP]

Well I guess I was thinking right about the stove controls thats my luck and it was way to easy. Thanks for the imput.

[Willbird]

Any lead pot I have ever seen uses a thermostatic control. It is NOT a rheostat or a "power control"

Where the thermostat is in relation to the pot will determine how accurate it is. Somebody here took apart their promelt and showed the guts.

http://castboolits.gunloads.com/showthread.php?p=522568

Bill

[Echo]

Well - they ARE 'Power' controls. They are not rheostats, of course, but they control the average amount of power going to the heating element They do this be adjusting the duty cycle. Turning the knob higher puts more strain on the bimetal strip, causing it to maintain contact for a higher percentage of time. It is the heat generated by the current going through the bimetal strip that causes it to deform and move. Less stress (knob turned down) means that the contacts are 'made' for less time, therefore power is provided to the element for a lesser pecentage of time. Else how can we explain the control in the Lee shown above, that is completely separate from the heating element? And they do this independently of the temperature of the alloy, so the are not thermostats.

And these are what us old missile-men called 'bang-bang' systems - they are either on or off. A proportional system sends more power to the unit when there is more of a difference between what is desired and what is actual. As the desired condition is neared, the input is reduced until it hits zero when the desired condition is achieved. The thermostat in our house works as a bang-bang system - when the temperature drops a degree below where we have it set, the furnace comes on full bore, and stays that way until the temperature rises to one degree above the setting, in which case the furnace shuts off. Samo with the electric blanket - samo with most control circuits we encounter daily. Seldom is a fully proportional system needed in our daily life.

One example of a proportional system we use every day, or at least dang often is the thermostat in our car's cooling system. When we start the car, and the coolant is 'way cool, the thermostat is closed, so there is no transfer of heat from the engine to the radiator. As the engine warms up, the thermostat slowly opens to allow coolant flow to the radiator, and stays open just enough to keep the coolant at the desired temperature. And if we really flog the car,the thermostat will open wider to allow more flow, allowing more heat to be discharged from the radiator.

And I believe the above electric thermostatically controlled system is probably a bang-bang system, in that it probably controls the temperature by sending full power, or no power, to the element. A probable very positive aspect of the above system is its sensitivity - will probably keep the alloy where you want it, within a very few degrees. Undoubtedly much more sensitive than the bimetal strip controller most of our furnaces use.

As I've said before - I DO go on...

[Willbird]

I may have misspoke about the LEE, if that is how they truly work and radiant heat from the Pot is not somehow having an influence on the bimetal strip then the guy who insist "LEE is just as good at 1/4 the price" are smoking something :-).

One advantage of the PID is that it uses fuzzy logic to use past performance to try to do a better job next cycle than it did last time.

Bill

[Echo]

Wow. Just googled PID controllers, and I want one! Profound devices that are more than proportional! I have an old Lyman pot that seems to be confused, so will make a controller as shown above. Will probably need some help from forum experts, but Hey...

[thebigmac]

YOU OLD GUYS WITH YOUR ANCIENT SAECO AND LYMAN LEAD POTS NEED TO DO WHAT I DID.
(Plastic Process Equipt. Inc--8303 Corporate Park Dr.---Macedonia, Oh. 44056). IS THE PLACE TO CONTACT FOR A REPLACEMENT THERMOSTAT. I JUST COMPLETED REPLACEING MINE, AND WITH A LITTLE MINOR ENGINEERING(?) MADE IT FIT. WORKS GREAT, JUST LIKE HAVING MY OLD POT BACK. YOU WANT MODEL B-200. SORRY, DON'T HAVE ADDRESS OR WEB, BUT GOOGLE IT.. WORTH A TRY. $23.00 PLUS UPS/// Mac

[jhrosier]

YOU OLD GUYS WITH YOUR ANCIENT SAECO AND LYMAN LEAD POTS...

You been peekin' in my cellar window?:-D

Thanks for the info.

Jack

[Lee W]

The RCBS pro pot does use a themostat. Not that I have taken one apart, I know where they get them from.
Look here for a little more info.

http://castboolits.gunloads.com/showpost.php?p=435537&postcount=8

[jsizemore]

The RCBS pro pot does use a themostat. Not that I have taken one apart, I know where they get them from.

Well. What's the model # and where do you get it. Come on, share.

[Lee W]

Unfortunately you can get replacements only from RCBS. It's a contract thing.

[thebigmac]

YOU OLD GUYS WITH YOUR ANCIENT SAECO AND LYMAN LEAD POTS NEED TO DO WHAT I DID.
(Plastic Process Equipt. Inc--8303 Corporate Park Dr.---Macedonia, Oh. 44056). IS THE PLACE TO CONTACT FOR A REPLACEMENT THERMOSTAT. I JUST COMPLETED REPLACEING MINE, AND WITH A LITTLE MINOR ENGINEERING(?) MADE IT FIT. WORKS GREAT, JUST LIKE HAVING MY OLD POT BACK. YOU WANT MODEL B-200. SORRY, DON'T HAVE ADDRESS OR WEB, BUT GOOGLE IT.. WORTH A TRY. $23.00 PLUS UPS/// Mac

THAT WEB SITE IS; WWW.PPE.COM AND YOU WANT PAGE 702.. Mac

[TAWILDCATT]

I just repaired my old Saeco.$15 at harbor freight. its called a router speed control.I jumped the old control and pluged into the speed control,works great.
its actuall a voltage regulator and is rated 115 vts at 15 amps.which comes to 1700 wts. :coffee:[smilie=1:

[lurch]

Just about any of the K thermocouples will work. They are all high temperature insulation good for at least 900 deg. The outer sheath is typically stainless steel which is good to a higher temperature than the carbon steel of the Lee pot. I welded a 1/4 20 nut to the bottom of the pot & screwed the Model: TC-K6 thermocouple in it. You can see the lead in the picture.

http://i420.photobucket.com/albums/pp290/charlie1019/IMG_2400.jpg

If you don't want to weld then just get one of the probe type TCs like Model: WRNK-171S & put it in the lead from the top of the pot. You will need to make a bracket out of wire or the like to keep it submerged in the lead.

The Aubner web site has the manuals for the controllers on line. Download one & they show sample wiring diagrams on pg 12. They show all the extra features it can do like actuate alarms but the only connections needed are power to the PID controller, the 2 wire connection for the TC(make sure you get the polarity right) and wire the PID internal relay in place of the thermostat in the pot. The terminals on the PID are all marked as to their function. Here is a wiring diagram for the numbered terminals on the back of the PID. The fuses are optional, I didn't use any.

http://i420.photobucket.com/albums/pp290/charlie1019/Wiringdiagram.jpg

The PID is set up with default parameters for K type TCs & an avg control. It worked great for me with the factory settings. If you want to get fancy, the instructions show you how to turn the learn mode feature on so that the PID will cycle on & off about 3 times while it watches the temperature response of the pot. It will set the parameters for the best operation based on that. It is very simple.

BTW, Here is the original thermostat for the Lee Production Pot. As you can see it is not really a true thermostat, it does not read the temp of the lead. It is a timer, it cycles on & off with the heating of a bimetalic strip. This is the part I took out & replaced with the PID.

http://i420.photobucket.com/albums/pp290/charlie1019/IMG_2370.jpg




I too found the temperature control on the Lee pot somewhat lacking and added a PID control to it in a very similar fashion to this. I found it to make a world of difference.

Some suggestions if anyone decides to go this route:

1. I would be a little afraid of mounting the housing for the controller directly to the column on the back of the pot. The column gets plenty warm in normal operation and will transfer that heat to the controller housing. Electronics in general don't much care for heat unless they are designed to take it, and even then, elevated temperatures will shorten their life. If you want to mount the controller housing to the pot I would at a minimum uses some standoffs so the controller housing is at least a half inch away from the pot column. An even better solution would be to mount a heat shield (simple piece of aluminum or other metal) between the column and the controller housing to keep radiant heat from affecting the controller housing temperature too much. You need an air gap between the column and the heat shield, and an air gap between the shield and the controller housing. No need to get crazy with the gaps, 1/4 inch so on each would be fine.

2. If you use a controller with a direct relay output, set the cycle time to a larger value. This will reduce wear & tear on the controller output relay contacts, extending their lifetime, without causing any detrimental effects on the ability to control the lead temperature accurately.

3. Some controllers have an output that is intended to drive a solid state relay. If using the solid state relay, the relay will need to be mounted on some form of heat sink. If the add on housing is large enough, simply mounting the relay to the housing will suffice. The relay does get a little warm when starting up a cold pot as it stays on continuously for the first few minutes. Once things are up to temperature and the relay starts cycling, the amount of heat generated by the solid state innards of the relay generate significantly less heat.

4. I mounted the thermocouple to the bottom of the pot using a welded on 1/4-20 nut as well. I found that to get a good bite in the threads, I needed to use a spacer to set the nut off the pot by about 1/8 inch or so. The reason is the thermocouple has a "button" on the end that wouldn't let more than a thread or two engage the nut before the button bottomed on the pot. A taller nut would work as well in place of the spacer.

5. No. 4 generated an issue with the nut bearing on the bottom cover of the pot and the bottom of the pot started acting as a heat sink, dropping the temperature that the thermocouple saw. This caused an offset (OK - not a true offset, but in the casting temperature range, it looks like a fairly constant offset) from what a traditional immersion thermometer was reading. You can either ignore this and simply set the desired control temperature higher on the controller or you can insulate the nut from the bottom cover of the pot and any ambient airflow. Be sure and use something that can take the heat like some Nomex (look up Aramid strips at McMaster-Carr) or mineral wool.

Kurt

[Norseman]

I finally found a suitable box in the dumpster at work today. The entire evening have been used to fit the wiring inside.

So now, I have a box with a socket that I can plug my 4-20 or my Production pot into it and use the same thermocoupler on both.

I have the thermocoupler floating ontop of the melt, but I don't think there's much variance of the temperature in the melt.

[angus6]

Think I'll order an extra and add to my lee pot as I need to pick up a new one for the Bullet Master
Thanks for the link , great price

[TAWILDCATT]

I did it the cheap and easy way.HARBOR FREIGHT HAS A ROUTER SPEED CONTROL.
IT IS A VOLTAGE CONTROL plug it into power and plug the pot into the control box.
$15 to $19.depends on sale.works on my Lee and Saeco.:coffee:

[RoyRogers]

I did it the cheap and easy way.HARBOR FREIGHT HAS A ROUTER SPEED CONTROL.
IT IS A VOLTAGE CONTROL plug it into power and plug the pot into the control box.
$15 to $19.depends on sale.works on my Lee and Saeco.:coffee:

How constant does the speed controller keep the temp? Did you bypass the factory control?

[evan price]

A PID controller is the simplest thing in the world to use.

I used to build steam-heated autoclaves and I used either proportional control with a pneumatic transducer to activate the steam valve with a diaphraghm, or a direct-acting pneumatic solenoid activated valve for on/off control. Proportional control is really cool- you can teach the controller the thermal characteristics of the device and it will hold your setpoint temp at the level of accuracy of the PID controller- we were holding +/- 0.5 degree F at 300 degrees F.

I added a PID to several pieces of my equipment such as the label marking machine and the Lee pot; the only thing I would advise is to go ahead and add a cheap "ice cube" relay to drive the heater instead of direct wiring- a $5 relay is a cheap replacement in case of failure VS a new PID controller.

Oh yeah, and with the "J"-type thermocouples, there are two wires, one red, one white- and the red is NOT positive, the white is.

[sciguy]

A PID controller is the simplest thing in the world to use.
I added a PID to several pieces of my equipment such as the label marking machine and the Lee pot; the only thing I would advise is to go ahead and add a cheap "ice cube" relay to drive the heater instead of direct wiring- a $5 relay is a cheap replacement in case of failure VS a new PID controller.

Oh yeah, and with the "J"-type thermocouples, there are two wires, one red, one white- and the red is NOT positive, the white is.

Evan,

Which specific PID would you recommend for this conversion? Link appreciated:)
I agree that the relay takes pretty much all of the wear and tear and is cheap to replace.

Best Regards,

Hugh

[RoyRogers]

A PID controller is the simplest thing in the world to use.

I used to build steam-heated autoclaves and I used either proportional control with a pneumatic transducer to activate the steam valve with a diaphraghm, or a direct-acting pneumatic solenoid activated valve for on/off control. Proportional control is really cool- you can teach the controller the thermal characteristics of the device and it will hold your setpoint temp at the level of accuracy of the PID controller- we were holding +/- 0.5 degree F at 300 degrees F.

I added a PID to several pieces of my equipment such as the label marking machine and the Lee pot; the only thing I would advise is to go ahead and add a cheap "ice cube" relay to drive the heater instead of direct wiring- a $5 relay is a cheap replacement in case of failure VS a new PID controller.

Oh yeah, and with the "J"-type thermocouples, there are two wires, one red, one white- and the red is NOT positive, the white is.

I thought an icemaker used a timer that controlled a solenoid valve? You talking about modifying a solenoid valve to close a set of contacts?

The PID referenced here has a built in relay. Any problems using the built in relay?

[TAWILDCATT]

I dont know how constand as I would guess it might change as the pot got empted.I will find out today if I feel up to casting and the rain does not come.It is a constend on.not a make and break. and yes I jumped the thermostat as it was bad.there is an on off and constant switch.and the Price is between $15 and $19

[lurch]

The PID referenced here has a built in relay. Any problems using the built in relay?

The problem using the internal relay is that it will wear out eventually - contacts usually give up and once the internal relay is gone, get a new controller. This may or may not be a concern depending on how you look at it.

The Lee element is around 700W resistive. I would want a relay rated 10A, 120V resistive as a minimum for any life expectancy at all - preferably substantially more rating. If you can get that, set the cycle time on the PID control for at least 10 to 15 seconds. This will reduce the number of times the relay contacts have to actuate and prolong their life. I'm guessing that the cycle time could even be set longer without introducing significant ripple in the temperature of the melt - just have to try and see.

The advantages to the solid state relay are that the external relay is:


Cheap (relatively) compared to a whole controller if it does fail.
Easily replaced
Not generally prone to wear out (though you may very rarely get one that fails rather soon due to infant mortality. If it lasts a while, it's probably going to last a very long while as long as you keep it from getting too hot)
Not bothered by a short cycle time wearing out the contacts - none to wear out.
The cycle time set at two seconds becomes a nice timer for keeping you casting cadence constant.


I'd get one rated 25A or better and use that if it were me - and it was a while back. No problems so far - thousands of boolits later...

[sciguy]

The advantages to the solid state relay are that the external relay is:


Cheap (relatively) compared to a whole controller if it does fail.
Easily replaced
Not generally prone to wear out (though you may very rarely get one that fails rather soon due to infant mortality. If it lasts a while, it's probably going to last a very long while as long as you keep it from getting too hot)
Not bothered by a short cycle time wearing out the contacts - none to wear out.
The cycle time set at two seconds becomes a nice timer for keeping you casting cadence constant.


I'd get one rated 25A or better and use that if it were me - and it was a while back. No problems so far - thousands of boolits later...


Lurch,

Could you do us a huge favor and throw up a link to a specific relay that looks pretty ideal. I would also love one to specific PID contoller as well.

Thanks a ton for great information,

Hugh

[lurch]

Links:

Here are a couple of suitable controllers, slightly different different but capable:

http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=14

http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=3

The relay I'd use is this one:

http://www.auberins.com/index.php?main_page=product_info&cPath=2&products_id=9

This is just the stuff from Auber. There are lots of similar on evil bay from other sources. It all comes from China and I'd almost bet from the same shop with a different sticker on the front.

Depending on how you physically set the thing up, you may or may not need a separate heatsink for the relay. In my setup, the relay and controller are in a steel box that used to house a cheap venturi vacuum pump from Horror Freight. Mounting the relay to the inside of the box with a little heatsink compound transforms the box into the heatsink as well as mechanical enclosure. DO NOT mount the controller or relay to the back of the pot - it gets way to hot there for long life of electronics. If you go plastic or wood for the box, you need a heatsink.

[sciguy]

Lurch,

Just the information I was lookig for. Thanks so much!!!!!

Hugh

[RoyRogers]

Rough math is $80 for all the parts listed above - including a $20 high temp thermocouple. Add that to a $70 Lee pot comes to $150. Better overall value than ~ $300 for an RCBS pot?

[Ugluk]

I got me a PID from Auber Instruments for my home made bottom pour, and I LOVE IT!
Now I'm gonna get me an external relay so I can keep loving it for years to come.. Thanks for the heads up in burning the PID out.

[lurch]

Rough math is $80 for all the parts listed above - including a $20 high temp thermocouple. Add that to a $70 Lee pot comes to $150. Better overall value than ~ $300 for an RCBS pot?

Please don't think I'm taking exception to your post - you raise a valid point. This is just how I see it.

I don't know how you are coming up with $80. The first controller - $36, and a $4.00 thermocouple (http://www.auberins.com/index.php?main_page=product_info&cPath=3&products_id=6) comes to $40. Add the relay and your up to $55 plus some shipping. Toss in $10 for some additional nice to have hardware (mainly a receptacle to mount on your box) and you're at about the cost of the Lee pot. If you need to buy a box you can spend next to nothing or a lot depending on what you want. I figure that the reason to do this is you already have a Lee pot and are dissatisfied with the temperature control. That's a sunk cost and not pertinent to the money side anymore - it's already spent. You could sell the pot to help offset, but you won't get all your money back by a long shot.

For somebody wanting to fix what they already have and not afraid of a little electrical tinkering (my situation), this seems a very viable option to me. No, it doesn't quite hold as much as the RCBS pot, it's gonna drip some too. Assuming I blow the whole thing up, I can do this almost 3 times for what I'd spend on a single Pro-melt. Both ways melt lead, both ways will let you get good boolilts. You'll get something that works well (enough for me anyway) for a lot less than another $300 out of the wallet.

Again, not trying to step on toes, just presenting how I looked at it.

[Ugluk]

The PID is also a digital thermometer, saving you the cost of buying one if you (like me) don't already own one. Wasn't a good one in the neighborhood of $50?

[lurch]

The PID is also a digital thermometer, saving you the cost of buying one if you (like me) don't already own one. Wasn't a good one in the neighborhood of $50?

You should still get a good thermometer - if you care about the ACTUAL temperature of the melt, and not just a repeatable setting.

Depending on how you mount the thermocouple and how you insulate it (or not...) you could wind up with a substantial difference in the PID readout and the actual melt temperature. I found this out the hard way. I tack welded a 1/4-20 nut and 1/8" spacer to the bottom of the Lee pot (pot - spacer - nut) and drilled a hole in the bottom pot cover to allow me to screw in the thermocouple. The spacer was necessary as the "nub" on the end of the thermocouple wouldn't let but about 1 thread engage in the nut I had when bottomed against the pot. I wound up with enough of the whole assembly "hanging in the breeze" to cool the thermocouple some and at casting temperatures I got about a 50F difference in the PID reading vs. what the thermometer was telling me - PID reading low. Insulating the thermocouple brought the two readings into a lot better agreement and gave me the confidence that I was really doing what I thought I was... If you let the bottom cover contact the thermocouple the same thing happens, but because the cover acts like a heat sink on the thermocouple. Originally, my spacer/nut assembly was bearing on the bottom cover. Relieving that contact helped a good bit and the insulation finished it off.

I still got repeatable, well controlled results without the insulation around the thermocouple and with the bottom cover in contact with the nut, just not at the temperature the PID said I was controlling to. The thermometer running all over the place - especially as the lead level changed - was what prompted me to go PID on the Lee pot in the first place.

[Ugluk]

I got the probe type thermocouple and it's fixed in the lead 1/2" from the spout inlet.

Seems to work ok, room temp was spot on but I can't be absolutely sure of working temp accuracy.

[RoyRogers]

Please don't think I'm taking exception to your post - you raise a valid point. This is just how I see it.

I don't know how you are coming up with $80. The first controller - $36, and a $4.00 comes to $40. Add the relay and your up to $55 plus some shipping. Toss in $10 for some additional nice to have hardware (mainly a receptacle to mount on your box) and you're at about the cost of the Lee pot. If you need to buy a box you can spend next to nothing or a lot depending on what you want. I figure that the reason to do this is you already have a Lee pot and are dissatisfied with the temperature control. That's a sunk cost and not pertinent to the money side anymore - it's already spent. You could sell the pot to help offset, but you won't get all your money back by a long shot.

For somebody wanting to fix what they already have and not afraid of a little electrical tinkering (my situation), this seems a very viable option to me. No, it doesn't quite hold as much as the RCBS pot, it's gonna drip some too. Assuming I blow the whole thing up, I can do this almost 3 times for what I'd spend on a single Pro-melt. Both ways melt lead, both ways will let you get good boolilts. You'll get something that works well (enough for me anyway) for a lot less than another $300 out of the wallet.

Again, not trying to step on toes, just presenting how I looked at it.

Guess my 'value' question might have been taken the wrong way. It was not intended to question anyone's credibility or choices. To my novice way of thinking the Lee pot modified with a better means of temp control seems to be the way to go - especially for my budget. My question was intended to get feedback from RCBS owners as to whether they thought a Lee pot with superior temp control was as good or a better value than the RCBS pot that seems to be held in high esteem by many on this forum and elsewhere. The question was not meant to imply that anyone else’s' choice of a Lee pot, modified or not, was a poor one. Never been too good at communication, even with much practice.

As to prices, the thermocouple I found at the web site referenced that was rated over 780*f, was this one: http://www.auberins.com/index.php?main_page=product_info&cPath=3&products_id=22. It also has the type bulb I want as I intended to secure it to the pot so it is immersed in the melt instead of just contacting the pot's surface. If the k type with a small contact area works well I may change my mind.

Should have listed all the items I used in the calculations. The dual readout PID for $45 seemed to be a good choice to my way of thinking. That with the $20 thermocouple, & the contactor comes to +/- $80. I didn't include a wiring box as I hope to fabricate one from scraps (I'm cheap) and save the ~$20 they wanted for a generic box. If the $4 thermocouple will do the job I'm all for it - thanks for the link.

All the advice, links, and comments are appreciated - good shooting...

[JIMinPHX]

Another thread on the same subject from a little while back.

http://castboolits.gunloads.com/showthread.php?t=22624&highlight=temp

[trevj]

You should still get a good thermometer - if you care about the ACTUAL temperature of the melt, and not just a repeatable setting.

Depending on how you mount the thermocouple and how you insulate it (or not...) you could wind up with a substantial difference in the PID readout and the actual melt temperature.

With all due respect, there really isn't anywhere, except in direct contact with the melted metal, for a thermocouple to be, if you want reasonable results.

Whether you punch a hole in the pot, or hang it over the side and into the pot that way, it's pretty much the only way to be sure of getting a reasonable reading.

Having it anywhere except possibly in direct, hard contact with the side of the pot that will be in direct contact with the molten metal (and thus, the same temperature) is asking for exactly what you got, which is the wrong reading.

Man! The prices on these controllers has come down huge, in the last few years!

I have been eying the resistance wire sites, looking for a good price on wire to make heating elements for an oven, for a heat treating/annealing/general hot spot kind of benchtop arrangement. It surprises the heck oit of me that the heat treat oven fellas, still sell an oven for $3K, when they have less than $100 worth of materials in them, including the electronics.

Great thread! Thanks for the great info!

Cheers
Trev

[lurch]

Having it anywhere except possibly in direct, hard contact with the side of the pot that will be in direct contact with the molten metal (and thus, the same temperature) is asking for exactly what you got, which is the wrong reading.

Yep - exactly correct. That's exactly where my thermocouple is too - threaded through a nut holding it in hard contact with the bottom of the pot. Even that is not enough to get an accurate absolute reading unless you take steps to make sure the heat transfer away from the thermocouple into the surrounding environment (breeze, conduction into the cooler outside material surrounding the pot, etc.) is reduced to a point that the errors introduced are minimized to an acceptable level. There can only be so much heat transfer through the point contact of the thermocouple housing and the pot before the temperature drop due to the thermal impedance of the assembly from the actual melt to the junction itself becomes significant. If it's not actually in the melt (which the little cheap thermocouple listed above will not tolerate) , best plan on insulating it if you want an accurate temperature reading on the PID controller and not just a repeatable but not necessarily accurately displayed temperature.

The saving grace that gives the repeatability is that for the temperature differential from the melt (at normal casting temperatures) to ambient, the amount of heat transfer is relatively constant, giving a relatively constant offset from set point (the actual thermocouple junction temperature) to actual melt temperature. If the ambient varies wildly form one casting session to the next, then there will be some degradation in the repeatability of the melt temperature vs. what the set point on the controller is between the two sessions. I cast in a relatively temperature controlled location so this was not an issue for me and the melt temperature was alway a pretty constant offset from the set point according to my thermometer. I should have mentioned that before. Insulating the thermocouple will greatly reduce this error but not completely eliminate it as you'll never totally eliminate the heat flux through the assembly - even the wires conduct heat away. It's certainly good enough for the task at hand though. For me, it was a case of "this is what I have and I'm going to make it work to my satisfaction", which I eventually did after a little head scratching. Bottom line is, you can get good readings this way if you take time to pay attention to what is going on.

[evan price]

I thought an icemaker used a timer that controlled a solenoid valve? You talking about modifying a solenoid valve to close a set of contacts?

The PID referenced here has a built in relay. Any problems using the built in relay?

Sorry, "Ice cube relay" is a common term for the small square-packaged relays used for light control duty. They look like an ice cube. THey actually have nothing to do with ice cubes.

For example, the Omron MY or LY series general-purpose relays. These are a generic platform that there are a whole bunch of makers that make the same thing that plugs in the same sockets.

http://base0.googlehosted.com/base_media?q=http://www.drillspot.com/pimages/3067/306739_300.jpg&size=16&dhm=b370c8a&hl=en

[RoyRogers]

Sorry, "Ice cube relay" is a common term for the small square-packaged relays used for light control duty. They look like an ice cube. THey actually have nothing to do with ice cubes.

A good illustration of my ignorance :confused:

Thanks for the clarification...

[Ugluk]

So I can expect my cheap and beloved thermocouple probe to do.. what?

Give the PID false data? Just stop funktioning?

D*mn! I was so happy with my pot setup and the pricetag of it.. Even if the thermocouple is only rated to 750F.

[thx997303]

Ugluk, they are discussing a situation where the thermocouple is held in contact with the bottom of the pot, not in the melt.

If your probe is actually inside the molten lead, then you should not have a similar issue.

[trevj]

Heres a tip re: probes.

Scrounge up some 1/4 301 or 304 Stainless Steel tubing. Wall thickness is not critical, but thicker is better, though slower to react (OK, because we are not dealing with anything that needs fast reaction. At lead melt temps, I suspect that brake line would last a very long time, too.

Get some K type thermocouple wire, with glass insulation.

String the wire through the tube, with a bit sticking out the "working" end. Start squeezing it flat in a bench vise. adjust the position of the two wires to the opposite corners of the duckbill so formed. Crimp the wires down tight.

Now the "hard" part. Find a TIG welder. Have him run a quick bead across the end of the duckbill to seal it. Just a straight fusion weld.
I suppose that a neutral flame with a Oxy torch would do it, but have not tried it.

Now you have a K thermocouple probe, that will handle anything your lead cooker will dish out.

Friends of mine that are casting aluminum, bronze and cast iron, are buying ceramic beads made for this sort of probe, and running stripped thermocouple wire through those, to withstand the higher temperatures at the working end. The life of a stainless probe at those temps is short, but the price is right.

Maybe not as cheap as some of the probes that are showing on Ebay, but you would know what was in them.

Cheers
Trev

[plumber]

As I need to get a thermometer, I see this as a good low cost alternitive to an analog. I plan on fabricating a bracket to keep the probe sumberged in the melt. Is there a way to set this up to control an outlet? I dont want to alter my pot, as its brand new and don't want warranty issues.

[Zbench]

Trev,

I was thinking along the same lines as you were. However, in looking at the auberins site, I turned this up:

http://www.auberins.com/index.php?main_page=product_info&cPath=3&products_id=39

The probe is a foot long, and it says it can be shortened. Imagine if you bought one of these, slid it inside some SS tube and wired up the top with the block, wouldn't that be the ultimate? You could make a bracket which would hold it near the bottom of the melt, it would be durable, and best of all, unlike the other probes which are rated at 750 degrees, this one goes up to 2000!!!

It's more money, but, what isn't? Any reason why that wouldn't work?

Pete

[lurch]

Ugluk, they are discussing a situation where the thermocouple is held in contact with the bottom of the pot, not in the melt.

If your probe is actually inside the molten lead, then you should not have a similar issue.

Right. Submerged in the melt, there is a lot more contact with what is desired to be measured and the thermal impedance to the sensing element is greatly reduced - to the point that any error from that source will be negligible. Just make sure that the probe is covered sufficiently and all will be well.

[lurch]

As I need to get a thermometer, I see this as a good low cost alternitive to an analog. I plan on fabricating a bracket to keep the probe sumberged in the melt. Is there a way to set this up to control an outlet? I dont want to alter my pot, as its brand new and don't want warranty issues.

That's how mine is. Without drawing a pretty picture, let me try and describe it for now. The power circuit to the pot goes like this:

120V Hot connects to one power terminal of the SSR. The other SSR power terminal goes to the hot side of a receptacle. The neutral side of the receptacle goes to the 120V neutral.

Basically, you just place a receptacle in between the SSR and the pot. It should be fairly obvious once you look at a wiring diagram for a heater control application. Check out one of the instruction manuals for the controllers on the Auber Instruments site.

[machinisttx]

Hmm, I don't have a thermometer(yet), but my Saeco pot dial seems to be cranky. This looks like it may be a very good upgrade option...even though I think I'll likely end up building my own bottom pour with more capacity.

[lurch]

Trev,

I was thinking along the same lines as you were. However, in looking at the auberins site, I turned this up:

http://www.auberins.com/index.php?main_page=product_info&cPath=3&products_id=39

The probe is a foot long, and it says it can be shortened. Imagine if you bought one of these, slid it inside some SS tube and wired up the top with the block, wouldn't that be the ultimate? You could make a bracket which would hold it near the bottom of the melt, it would be durable, and best of all, unlike the other probes which are rated at 750 degrees, this one goes up to 2000!!!

It's more money, but, what isn't? Any reason why that wouldn't work?

Pete


This one would probably be more durable, less work (inconel can be thought of as a "super" stainless steel in this case) and is a little cheaper:

http://www.auberins.com/index.php?main_page=product_info&cPath=3&products_id=22

[Ugluk]

Thanks guys, that's pure peace of mind. Still got te get me a relay and perhaps a probe with a higher temp rating. I sometimes run mine at 780F.

I keep lead level high with a minimum of 10# or so in the pot, so the probe is well covered.

[jsizemore]

Does the bulb for the thermostat in a RCBS pot come in direct contact with the molten lead or is it in direct contact with the outside of the pot? If it's on the outside of the pot, how come it's OK for the RCBS and not OK for the thermocouple for the PID? If I read correctly, regardless of the length of a thermocouples probe, the bimetal strip is contained in the tip of the probe that generates the voltage to signal the PID. Sounds like it's just a matter of calibration which I assume an RCBS would require over it's lifetime. What's the big deal?

[lurch]

AFAIK, the thermostat bulb in the RCBS is probably not in direct contact with the pot - at least not screwed to it to provide a solid contact for optimum heat transfer... Don't own one and haven't taken one apart to know for sure. I know the Lyman Mag 20 is not screwed down in this manner. I would assume both are mounted very close to the pot, probably lightly touching it. The reason that they work pretty well is because the area around the pot is insulated. The heat flux across the insulation, and by extension the area where the bulb is (between the insulation and the pot), is pretty small because of that and hence the temperature in the vicinity of the bulb is darn close to the melt temperature.

The thermocouple placed on the outside of the Lee pot is not in an insulated environment and therefore has a heat flux across it much higher than the thermostat bulb in the RCBS/Lyman. The junction is buried in it somewhere and is not directly at the tip, and the contact point at the pot is not a perfect thermal conductor either. Consequently the actual junction of that thermocouple can be significantly lower in temperature than the melt. Insulating the thermocouple reduces the heat flux through it and gets the junction temperature closer to the melt temperature.

Calibration would work (throwing in an offset and gain adjustment - most of the cheap ones have at least an offset but not necessarily a gain adjustment) well in the case of a relatively constant ambient. When the ambient varies, the amount of heat flux across the thermocouple varies as well and the calibration is off (unless the ambient is close to the ambient where the calibration was done). If the variation in ambient is significant then the repeatability of melt temperature vs. indicated temperature degrades. The RCBS/Lyman pots don't have a calibrated knob anyway so calibrating those is a moot point (if you want to correlate a knob setting to a given temperature on your own, then that might require fiddling with over time). The PID controller has a readout and having it display the correct temperature is nice, but not strictly necessary if you don't need it to display an accurate temperature. Personally, I was using my setup just fine with the temperature reading off. It gave me perfectly repeatable performance in my reasonably controlled ambient - for a given set point and temperature reading, the melt temp was the same from one time to the next. I finally got around to insulating the thermocouple when I decided I wanted the temperature display to be better - a nicety, not a necessity.

[Zbench]

Sizemore,

As I understand it, the RCBS pot has neither. It has a bimetallic strip in the temperature control which is no where near the pot or the lead. As current flows through the circuit, and the strip, the strip warps due to the current (not unlike the way a light bulb filament gets hot) and breaks the circuit. When the circuit breaks, the strip cools and then starting carrying current again.

The fact that the lead is getting warmed and melted is a secondary consequence...the strip is calibrated with the dial to give approximate temperature readings.

The thermocouples we are talking about actually get hot, directly in the lead or the bottom of the pot, and therefore directly provide feedback to the PID.

So, there is quite a bit of difference in any of the commercial pots and the PID set up we are talking about.

Pete

[Lee W]

The RCBS pro melt is a thermostat. There is a stainless steel bulb clamped to the bottom of the pot.
Here is a link to the instruction sheet. Read the introduction on page 4.

http://www.rcbs.com/downloads/instructions/ProMeltElectricLeadFurnaceInstructions.pdf

[evan price]

There is a big difference between a THERMOSTAT and a THERMOCOUPLE.

A thermostat is usually some form of bi-metallic strip that the two metals making up the strip expand at different rates as heated. The difference in expansion causes the strip to curl (or uncurl) and this is used to either directly turn on and off an electrical circuit (by the curling metal strip touching across an electric contact), or (such as in your home thermostat for the furnace) move a mercury switch to turn on a circuit.

A thermocouple is a device which is very simple. It is made from two dissimilar pieces of wire that are joined at one end. When the two wires are heated they will create a voltage difference. This voltage difference is linear depending on the rate that the heat changes. The temperature controller looks at the voltage and performs a calculation depending on what type of thermocouple it is to get the current temperature. The different types of thermocouples (designated with letters, such as J, K, T etc) have a specific chart of voltage VS temperature that is a standard worldwide.

The only difference between thermocouple types is the type of dissimilar wires used to make the junction. For instance, a Type J thermocouple is made of Iron and Constantin. A Type K thermocouple is made of Chromel and Alumel. A Type T thermocouple is Copper and Constantin.

The temperature range for a thermocouple is dependant on the construction materials (type of wire) used- if your wire melts at 800 degrees, it is no good for a furnace flame. You need a type that allows a higher temperature. However that 800 degree melt point wire would be OK to measure the temperature in a swimming pool.

Please note that this describes an ACTUAL thermocouple. There are devices that are used for example to control the pilot gas supply for a gas-fired appliance that are called "thermocouples" but are actually a tube filled with wax that expands or contracts as it warms; this is a safety device to shut down the gas if the pilot light blows out. They are not the same sort of thing.

The temp sensor in a car engine works the same way. There is a rheostat (a sliding scale made of wire, it varies in resistance by position, also called a "varistor") that has a contact which moves across it. There is a wax pellet in the bottom. As the wax pellet heats up, it expands, pushing the contact up. The rheostat changes the resistance based on the position of the contact on the wires. The guage measures the resistance and shows the temp.

The way a process controller (PID is a type of process control) works is it looks at the value supplied by the temperature sensor. It compares that real-time value with the "setpoint" which is the desired temp you program. IF the temp is at or above that temp, the controller does nothing. If the temp is below that setpoint, the controller turns on the heat source. Better controllers are able to calculate how fast the device it is controlling loses heat, and how fast the heat supply is capable of raising the temperature, and they will balance the temp as close to the setpoint as possible with the least amount of off-and-on as possible. You can also program the hysteresis so that it will stay much more closely to the setpoint. Obviously for something that is not considered "process critical" such as a simple lead melting furnace, if you go up or down ten degrees from setpoint it's not a big deal. But let's say you are manufacturing construction adhesives by chemical reaction. It may be critical that you hold to a certain temperature within one degree. You can then program the controller to be more aggressive at keeping the temperature at setpoint and not allowing drops. The only problem is this leads to more on-and-off and short-cycling, which can damage the heat source or the contacts in the device due to arcing or wear. A more sophisticated controller with PID looping will monitor the rate of heat loss and know that if it turns on the heat at a certain point before the temperature falls below setpoint, it will prevent the temp from dropping below setpoint in the first place. When used with a proportional control heat source (one which is analog or scalable- it can turn on 10% or 100% or anything in between) it can hold setpoint temp +/- less than one degree.
With an ON/OFF sort of control (such as the electric heat element in the lead pot), you will have more overshoot and undershoot and you have to balance the setpoint with being a little hotter or cooler sometimes.


That was more than I originally meant to say- but hope it is useful.

[RoyRogers]

Please note that this describes an ACTUAL thermocouple. There are devices that are used for example to control the pilot gas supply for a gas-fired appliance that are called "thermocouples" but are actually a tube filled with wax that expands or contracts as it warms; this is a safety device to shut down the gas if the pilot light blows out. They are not the same sort of thing.


Evan - thanks for the excellent post. However, this it is not the way the thermocouples used in many gas appliances are utilized. Typically they are there to prove pilot or main burner flame. Ovens also use thermocouple(s) to signal a thermostat as to when to light a main burner or to send current to an electric heating element. All these thermocouples generate a small (mv) current when heated. When used as safety devices on a gas appliance this current is employed to hold a control magnet in operating position. When in this position, the internal passageways that allow gas flow through the gas valve/thermostat are open. If no voltage is generated by the thermocouple, the magnet releases which in turn closes the gas passageways inside the gas valve/thermostat. I believe you may be thinking of the way expanding contracting wax in a gas water heater's thermostat's immersion bulb signals for heat?

[x_il_towman]

YOU OLD GUYS WITH YOUR ANCIENT SAECO AND LYMAN LEAD POTS NEED TO DO WHAT I DID.
(Plastic Process Equipt. Inc--8303 Corporate Park Dr.---Macedonia, Oh. 44056). IS THE PLACE TO CONTACT FOR A REPLACEMENT THERMOSTAT. I JUST COMPLETED REPLACEING MINE, AND WITH A LITTLE MINOR ENGINEERING(?) MADE IT FIT. WORKS GREAT, JUST LIKE HAVING MY OLD POT BACK. YOU WANT MODEL B-200. SORRY, DON'T HAVE ADDRESS OR WEB, BUT GOOGLE IT.. WORTH A TRY. $23.00 PLUS UPS/// Mac

Anyone here ever use this thermostat???

I too am rebuilding an old Lyman 61 pot & this thread has been very helpful.
I am concerned that the temp setting listed for the b-200 is not within operating range. ( 100-550F see enclosed picture).

Thanks in advance for the help...

http://images9.fotki.com/v447/photos/1/1416379/6868434/B200-vi.jpg

[Lee]

If I understand correctly, the TC for a furnace or hot water heater is just that. It is a device that generates a small millivolt voltage. That is supplied to a small coil in the gas valve. THAT opens or closes the main gas valve. No wax at all. Or am I missing something in the definition of what we are trying to control??
(Never had to replace either, always thought they "were all alike":p You know, kinda like ..........Lee

[RaymondMillbrae]

Just curious to know HOW folks are "fine tuning" their PID temperature controllers.

I just finished making my PID devise the other day, and I am still working with it to stabalize the molten lead temperatures.

I know that if I set my PID controller for 700-degrees, it will shut the power OFF before the molten lead hits 700-degrees. But since the coils retain so much heat, the temperatures will keep rising until it goes 20-degrees higher than the preset 700-degrees.

My home-made PID devise has a "self optimization" function...but is that what I need?

I was also looking at playing with the "differential" (hysteresis), but I am not sure if this is the way to go, as I do not completely understand how to set the differential parameters.

I'll keep my ear to the ground in the meantime.

In Christ: Raymond

[lurch]

Raymond,

The "auto tune" or "self optimization" works well enough in my experience to get to a very workable solution. Unless you are versed in PID theory, I would definitely suggest filling your pot about half or a little more full and let the controller decide what it's parameters are going to be. Without knowing what the "differential" parameter on your controller really is, I would assume that it is a dead band adjustment, essentially meaning that the sensed temperature has to be off from set point by a given amount before any correction is applied to the on-off duty cycle of the power to the heating element. Messing around with the PID parameters can lead to an unstable or oscillating temperature if not done carefully. When I let mine auto tune, I found that the initial startup gives me a decent initial overshoot but once that has subsided, temperature is maintained very nicely. Any significant deviation is due to adding metal to the pot in such quantity that the power of the heating element is insufficient to kick the temperature up any quicker.

[jeff423]

I use the auto tune or self optimization feature. I have 3 pid's on various types of units. Aquarium, coffee maker and lead pot. One thing that I noticed is that the better pid's had a longer self tuning cycle. My real cheapie went through one cycle and that was it. My better unit went through 3 cycles and my best one has a continuous learn feature that is always monitoring. It listed for $300 but I got it used on ebay for $75.
One thing you might try for the self tune is to let it get to the correct temperature, then turn off the controller. Restart it and go back through the auto-tune. This will reset the PID for casting conditions - as opposed to bringing it from cold all the way to casting temp.
I would also use as large a solid state relay as you can afford and a heat sink. They last much longer if kept cool. I mounted a cheap computer cooling fan to blow on my 25 amp SSR on my lead pot. I have not had any problems with it so far but would probably get a 40 amp next time. I have a 50 on my espresso machine, but no fan.

YMMV

Jeff

[RaymondMillbrae]

Lurch,

below is a picture of the PID temperature controller I recently finished.

Are you telling me that you keep your casting pot half full (or a little over half)...and when the "self optimaization" is done, you fill it up normally? Or are you telling me you ALWAYS keep your casting pot half full?

By the way, I am using a Lee Pro 4-20. Shoulld I keep the knob turned all the way up to the HI position, or should it be kept lower? What are your observations?

Jeff423,

I will try what you said above.

QUOTE: One thing you might try for the self tune is to let it get to the correct temperature, then turn off the controller. Restart it and go back through the auto-tune. This will reset the PID for casting conditions - as opposed to bringing it from cold all the way to casting temp.

I am using a 25 amp SSR, with a large aluminum heat sink cannibalized from an old mother board. I believe it should do the trick.

Thanks, and if someone has something else to add...add right on!

In Christ: Raymond

PS: I'll be doing a tutorial soon...so stay tuned. ;)

http://xb9.xanga.com/8c0f506459531265602146/b211816004.jpg

http://x8c.xanga.com/1e0f406420430265601871/b211815750.jpg

http://x6e.xanga.com/13bf717220433265601883/b211815762.jpg

[blikseme300]

2c added to the mix.

My experiences with temperature stability due to experimentation and observation made me conclude these things:

1. Use a pot that is large enough. The level must not change rapidly when volume casting larger boolits, ie using 2x .45 6-banger molds in tandem.

2. The pot needs to be properly insulated. Use kaowool for this.

3. Use a PID controller and let the temperature stabilize before starting to cast. Initial overshoot of the temperature is normal. Once stable it will stay very close to the set temperature even when cold ingots are added.

See my solution to my needs here: http://bliksemseplek.com/boolits.html

Bliksem

[lurch]

Lurch,

below is a picture of the PID temperature controller I recently finished.

Are you telling me that you keep your casting pot half full (or a little over half)...and when the "self optimaization" is done, you fill it up normally? Or are you telling me you ALWAYS keep your casting pot half full?

By the way, I am using a Lee Pro 4-20. Shoulld I keep the knob turned all the way up to the HI position, or should it be kept lower? What are your observations?

Jeff423,

I will try what you said above.

QUOTE: One thing you might try for the self tune is to let it get to the correct temperature, then turn off the controller. Restart it and go back through the auto-tune. This will reset the PID for casting conditions - as opposed to bringing it from cold all the way to casting temp.

I am using a 25 amp SSR, with a large aluminum heat sink cannibalized from an old mother board. I believe it should do the trick.

Thanks, and if someone has something else to add...add right on!

In Christ: Raymond

PS: I'll be doing a tutorial soon...so stay tuned. ;)

http://xb9.xanga.com/8c0f506459531265602146/b211816004.jpg

http://x8c.xanga.com/1e0f406420430265601871/b211815750.jpg

http://x6e.xanga.com/13bf717220433265601883/b211815762.jpg


Your setup looks very nice. Your questions are valid, so here goes. Fill your pot half or so full (or about at the halfway point of where you intend on running the fill while casting) and let the thing autotune. The lead level in the pot does not need to remain there when casting. The amount of lead in the pot acts like a "lag" or time delay to the temperature we see vs. the amount of heat energy we put in. More lead is more lag and less is less. That time delay is an integral part of the tuning process and getting it somewhere in the middle of the range of where it will operate is a way to get a compromise on the overall system response for a range of pot fill levels. I have not tried this, but tuning with a full pot might improve the response when adding ingots, with possibly reduced performance (oscillation...?) at low fill levels. Try it and see if you are so inclined - can't really hurt as you can always just re-tune...

Jeff gives good advice about letting the pot get to temperature and then starting the autotune. That's what I did, but neglected to mention. The controller I have tunes itself based on what is called the step response of the total system. Without getting too technical, the step response is just what the system does when given an input disturbance that looks like, well, a step - raise (or lower) the input (power from the heating element) from one level to another and observe the system response over some time period. From that with a little math it is possible to figure out what the "optimum" PID parameters are. Optimum can be defined several ways with fastest time to temperature with no overshoot and fastest time to temperature within a certain window with over and undershoot not exceeding x probably being the most relevant. Also, the rate at which heat leaves the system at casting temperature is greater than the rate at which it leaves at room temperature. This also affects how the final "ideal" PID tuning will turn out. If the controller you have tunes itself once the temperature has reached the "set point" of the controller then you can just establish your set point and start the tuning process and be done with it. If the controller does not tune at its set point, then get things to temperature and then start the tuning to take care of the heat loss factor. For a pot like the Lee, the heat loss at temperature is a lot higher than say for a Lyman or RCBS due to the insulation of the latter two as opposed to the essential lack of for the Lee.

For the Lee pot, definitely keep the control turned up all the way if you keep it in the circuit as it appears you will be doing from the pictures. That is what I did. Think of this as sort of a backup system to keep things from getting out of hand should the SSR or thermocouple fail. The SSR will fail shorted when it does and this would just turn on the heat full blast with no secondary stop to keep things in line if the Lee control is bypassed. Keeping the Lee control at max also keeps it out of the way of the PID controller. One point to mention here is that if the Lee control actuates during the autotune, the autotune results will be off. You definitely want that control out of the PID controller's way when running, but still able to keep the lid on in the event of any failures.

[RaymondMillbrae]

Thanks,

good advice! (Especially about NOT bypassing the Lee heat controls, which I was about to do).

In Christ: Raymond

[mac1911]

Been poking around CB for ideas on upgrading and building new things.
Any up dates to available PID controllers for upgrading old lee pot

Seems many of the links are long dead

[Mal Paso]

These guys have good quality products and support. https://www.auberins.com/index.php?main_page=index&cPath=1

FAQs here. https://www.auberins.com/index.php?main_page=page&id=6

[jsizemore]

I see a lot of builds that use a sealed box. The box needs to stay relatively cool to operate correctly. My original Auberins instructions stated this. I've used an ONEAC power conditioner case, computer bower supply perforated box and a Sony camera power supply carry case. All have plenty of ventilation. The case for the ONEAC/Auberins build is made of aluminum so the SSR is attached directly to the case bottom with silicone grease. All run cool to the touch.

[Mike W1]

Don't remember reading this thread when I built my units but it's kind of interesting to see how things evolved since it was started. By the time I got around to doing mine the consensus seemed to be mount the TC 1/2" from bottom and sides and that seems to have worked out for me. Mine are removable ones.

Somewhere along the way I read to just do the autotune when the PV comes to within about 20° of the SV. Haven't done any casting for quite awhile now but I don't remember a lot of overshoot on mine. Wired a neon to light when the SSR is shooting power to the pot and believe it stays on till SV is reached without cycling like it does when all it's trying to do is maintain a steady temperature. Will have to monitor that a little more closely when I get back at casting.

Personally I use 2 REX C100s on the pots and an Auber on the hotplate. You do have to know what to look for when buying a REX but have had fine luck with mine. I didn't have that good luck with the Mypins.

[mac1911]

These guys have good quality products and support. https://www.auberins.com/index.php?main_page=index&cPath=1

FAQs here. https://www.auberins.com/index.php?main_page=page&id=6

Thanks for the link,
i have not read it yet but found this.
https://drive.google.com/file/d/0B14y9IPNqGuoVTloMm80VGdlNEk/view

[pcmacd]

midway sells replacements for lees

LEE will replace faulty parts for free. Forever.

[pcmacd]

That's not a timer. It is a simple, cheap bimetallic thermostat.

The problem is that the TSTAT is not measuring the lead pot temp, just the air outside it in the pedestal.