PID controller for Lead Furnace Question

[epox]

If you were going to build a seperate PID Controller to control the lead pot but wanted to wire a switch to allow direct power to the pot until the lead melted and then flip the switch to control the temperature where in the attached diagram would you wire it in at? 37326

[kitsap]

From another thread.

PIDSwitch-Model.jpg (http://i1139.photobucket.com/albums/n546/kitsap1/Lead%20Pot%20and%20Controller/PIDSwitch-Model.jpg)

[Sonnypie]

Between T1 and L1 of the SSR (Solid State Relay). AKA: On the terminal block T1 & T4. (T1 on the left, T4 on the right.)
The Neutral is T2 & T3.
(Pay close attention. If you screw it up, you will blow it up and have some expensive junk)

When the switch is closed (on), it bypasses the controllers output and puts straight line current to the furnace.
Once you reach melt, you can open the switch (off) and that puts the SSR and PID in the circuit controlling things.
Label the switch as BYPASS, or PREHEAT.
Set your Lee control to 5 or 6 as a safety devise for when you forget it is bypassed.

Also, install a thermowell for your thermocouple. It'll last longer.

[Mal Paso]

Between T1 and L1 of the SSR (Solid State Relay). AKA: On the terminal block T1 & T4. (T1 on the left, T4 on the right.)
The Neutral is T2 & T3.
(Pay close attention. If you screw it up, you will blow it up and have some expensive junk)

When the switch is closed (on), it bypasses the controllers output and puts straight line current to the furnace.
Once you reach melt, you can open the switch (off) and that puts the SSR and PID in the circuit controlling things.
Label the switch as BYPASS, or PREHEAT.
Set your Lee control to 5 or 6 as a safety devise for when you forget it is bypassed.

Also, install a thermowell for your thermocouple. It'll last longer.

No Clue!

1 Setting the Lee Control to anything but high will defeat the PID Control.

2 Warm up is like Freeway Miles. Not much wear and tear. I can see the LED and hear the heating element. It is on until it approaches set point then cycles deliberately as it figures how to hold the set temperature. A standard relay would do the job but because of the high number of cycles, once the pot reaches temperature, a solid state relay is often used. This Is The SSRs Job and what it was built to do. You don need no estinkin bypass.

Sorry but...........:bigsmyl2:

[Powellcole5490]

So I was planing on building my own PID controller with the bypass too. So is there any benefit to installing a bypass?

[Mal Paso]

I looked up the specifications for Auber's $15., 25 amp Solid State Relay and it's designed to handle a one cycle surge of 275 amps so it could handle the Lee max theoretical incandescent load Times 4+.BUT My lee pot is 6 amps Resistive. Just measured it Cold, 20 Ohms, into 120 Volts is 6 Amps Cold and a little less warm. No Big Surge. Don't know how the rumors get started. Auber's SSR FAQ:http://auberins.com/index.php?main_page=page&id=10&chapter=0

The SSR will generate about 8 watts Of Heat controlling the lee pot. I have mine bolted to the inside back of the project box with vents above and below.

This is good technology. Watch out for hot Lead not an extra switch.

I set my Lee Pots to High which is on all the time, when plugged into the PID, but if your Lee Control is in question take it out of the circuit like snuffy says next post.

[snuffy]

Yeah, no need for no steenkin bypass.

As for the lee heat control, get it completely out of the circuit. Take the top off the lee control tower, take the jumper off the thermostat under the knob, remove it from the heater element, then move the hot wire from the cord that goes to the other side of the thermostat and plug it direct onto the heater element.

Otherwise the thermostat will open when it gets hot inside the tower, defeating the pid control. The lee thermostat is a simple open or closed bi-metal thermostat, that senses heat inside the tower. Which is why it has giant temp. swings from full to nearly empty.

[MikeS]

I was concerned about setting up a bypass, but was told by a friend that's a lot more familiar with electronics than I am (after he looked at the schematic of my PID controller) that with a SSR you really don't need to worry, and can just startup cold with the PID in the circuit, and that's what I do. While the lead is heating up the PID just supplies constant current, and doesn't start switching on/off till it's close to the set temp. So far so good, my PID controller hasn't lost it's blue smoke yet. :)

[Powellcole5490]

Yeah, no need for no steenkin bypass.

As for the lee heat control, get it completely out of the circuit. Take the top off the lee control tower, take the jumper off the thermostat under the knob, remove it from the heater element, then move the hot wire from the cord that goes to the other side of the thermostat and plug it direct onto the heater element.

Otherwise the thermostat will open when it gets hot inside the tower, defeating the pid control. The lee thermostat is a simple open or closed bi-metal thermostat, that senses heat inside the tower. Which is why it has giant temp. swings from full to nearly empty.

Whoa, Whoa, Whoa Snuffy,

You are blowing my mind with all them big words and things... :shock:

I am electrically challenged and since I don't have my pot here to look at and reference, can you explain, in more detail, how to remove the Lee heat control from the circuit. I'm sure it's very easy, but I'm having a hard time picturing what you are saying. Thanks!

[snuffy]

Powell, the term "jumper" is what I call the short wire that goes from the thermostat to the heater coil. It has a bayonet type sliding connector on it's end. Simply remove that short wire, take the wire off other side of the thermostat, connect it directly to the heater element. Done!:popcorn:

Now you can plug the original cord into a receptacle on the pid cabinet, or hard wire it into the circuit. I put a receptacle in my pid cabinet, because I use it on 2 pots, will be using it on three as soon as I install a thermocouple/temp probe in an old saeco melter.

http://photos.imageevent.com/jptowns/bullets/websize/IMG_0335.JPG

You also have to be able to plug in the thermocouple to use on more that one pot. Be sure to use the same wires that connect the TC through the plug, to the PID and use that yellow plug available from Auber. And maintain polarity.

http://photos.imageevent.com/jptowns/bullets/websize/IMG_0336.JPG

[Powellcole5490]

Snuffy,

Ok, great! Breaking it down Barney style (or Army style if you please) works great for me! thanks

[Sonnypie]

No Clue!

1 Setting the Lee Control to anything but high will defeat the PID Control.

2 Warm up is like Freeway Miles. Not much wear and tear. I can see the LED and hear the heating element. It is on until it approaches set point then cycles deliberately as it figures how to hold the set temperature. A standard relay would do the job but because of the high number of cycles, once the pot reaches temperature, a solid state relay is often used. This Is The SSRs Job and what it was built to do. You don need no estinkin bypass.

Sorry but...........:bigsmyl2:

"If you were going to build a seperate PID Controller to control the lead pot but wanted to wire a switch to allow direct power to the pot until the lead melted and then flip the switch to control the temperature where in the attached diagram would you wire it in at?"

That was the OP's question.
I gave him a direct and correct answer. A way to bypass the SSR.
And having the Lee control in there as a safety device. And a way to make his thermocouple last indefinitely by using a thermocouple well.
But hey, you geniuses just roll along with your $200 controls for a $63 lead pot.
You are right about one thing though.
You are a sorry butt. ;-)

[smilie=s:

[Lee W]

But hey, you geniuses just roll along with your $200 controls for a $63 lead pot.
You are right about one thing though.
You are a sorry butt. ;-)

[smilie=s:

Sonny,
I check all of these PID threads and it seems you cannot grasp the idea of someone wanting a precisely controlled lead pot. What is so difficult to understand? A constant temperature will yield consistent boolits if the process is done consistently.
Pretty easy.

I might be the only one to say it, but leave you negative comments about the cost to yourself. It is not your money and your comments are not helpful to the discussion at all.

Thanks.

Lee W

[snuffy]

But hey, you geniuses just roll along with your $200 controls for a $63 lead pot.
You are right about one thing though.
You are a sorry butt.

My lee 4-20 would swing 75 degrees from full to ¼ full. 75 degrees HOTTER! Maybe you like frosty boolits or weight swings of 5 grains in a 250 grain boolit, buT I don't. I like them all to be the same size and weight, and a constant temp does that.

Speaking of butTs, what is going on with yours in your avatar?

[Mal Paso]

"If you were going to build a seperate PID Controller to control the lead pot but wanted to wire a switch to allow direct power to the pot until the lead melted and then flip the switch to control the temperature where in the attached diagram would you wire it in at?"

That was the OP's question.
I gave him a direct and correct answer. A way to bypass the SSR.
And having the Lee control in there as a safety device. And a way to make his thermocouple last indefinitely by using a thermocouple well.
But hey, you geniuses just roll along with your $200 controls for a $63 lead pot.
You are right about one thing though.
You are a sorry butt. ;-)

[smilie=s:

Ok

Everything past T1 and L1 in post 3 was utter nonsense from someone who has never done it.

Why try to scare people. This equipment is so well protected and would be difficult to hurt it even if you did cross a wire. I have yet to see a post from someone with a bad experience.

The PID Control won't work with the Lee Control set to 5 or 6.

A thermowell will screw up your readings. The probe is $7 and stainless steel and if it can handle me ripping it out and soldering it back in it will last as long as I care about.

I spent $128 because I wanted the Deluxe Box, Extra Probe, and Plugs. I've seen the controllers for sale here for $15 and a lot of guys here have put PIDs together for $50. For better temp control than a $250 pot, it's worth it.

[Sonnypie]

Mal,
42 years as a professional in electrical controls and Industrial and Utillity electrical maintenance. Those are my quantification.
So it can only be utter nonsense to someone who really has not a grasp on electrical control.
If you knew anything about electrical control, you would see that what I posted is really two explanations to do the exact same thing, bypass the electronic control section and apply direct line voltage and current to the output.
Precisely what the OP asked for. A way to bypass.

Scare people? Advising they pay attention is scaring people?
Do you know anything about electricity? Did you look at his pdf file? Can you read a schematic?
Tell us, oh wise one, what happens if somebody not in this post decides to attempt to hook up their own bypass switch, and instead of the terminals and circuits described, they hook T1 and L2 (The neutral) together?
Bam!
And the control is instant junk. A dead short on the SSR's output.

A thermowell will screw up your readings?
More than having crud build up insulating the probe from the heat?
Yeah, sure. That is why every major piece of critical equipment has the thermocouple just hanging in the process fluids bobbing around and being beat on.
Yeah, you're right. Industrial control is wrong. All those industries controlling processes and critical utility equipment really don't know what they are doing.

My Lee pot will easily run over temperature at 5-6 settings. That's why I have a thermometer in it to monitor my alloy.
IF one wants to put a solid state control on the pot, it is prudent to have the original control in the circuit as a safety device. Safety devices help reduce human errors, and equipment failures.
Let's try something really basic, what is an over temperature device for in your home's heater? Or the oven?
So you advocate that since there is a temperature control there anyway, the high limit device is unnecessary?
That is exactly what you are advocating. I have seen not one of these temperature controls that have an over temperature, or high limit, designed into them.
Merely settings and control. All based on the thermocouple input. No secondary safety devices, no high limit or over temperaturecontrol.
Normally (in my experience) they will fail in the open condition. But I have seen them fail closed and run away. I've been on failure analysis teams for major catastrophic equipment failures.

Even a portable electric heater has an over temperature limit switch, and a tip over switch.
Just the facts. But hey, what do I know?

But you boys have fun. When it burns out, just buy another one. :wink:

[OuchHot!]

'bout time for a moderator high colonic

[epox]

Geez guys. Sorry I brought up the subject. I just wanted to know if it was possible. I'm just getting into casting and was asking questions on this since I had read that you probably shouldn't heat up a cold pot with the PID hooked up and that it should be wired direct for a cold pot and then switch it over to controlled once the lead is hot. Guess from reading the above that it can be used on a cold pot with no bad things happening. Thanks for everyone's input

[theperfessor]

I built a dual PID controller with Auber parts. I use it to control a hot plate and a Lyman Mag 20. I didn't put in a power switch at all. I make sure both are turned down/off, then I plug them into the PID box, plug the PID box power cord in to the wall, and turn on the units all the way on. Seems to work fine. The SSRs don't even get warm.

Note: I'm NOT an electrical engineer, and I know nothing about Lee pots or their internals. I'm nit giving expert advice. I'm just sayin' what works for me.

[edler7]

I just built a PID controller and love it ! After reading this and the other thread about switching out the SSR/PID during warmup, I thought about it a while and came up with a low cost solution...I just plug the pot in directly to an outlet till stuff starts to melt, then plug it into the PID controller.

Works for me.

[SkookumJeff]

Wow, this is the first time I"ve seen any snarlin on this forum. Must be the holiday season eh? Ho ho ho....[smilie=p:

[sqlbullet]

First time I think I have really spent any time here.

:popcorn:

[epox]

Thanks everyone. I'm going to build one without the bypass.

[Pigslayer]

"If you were going to build a seperate PID Controller to control the lead pot but wanted to wire a switch to allow direct power to the pot until the lead melted and then flip the switch to control the temperature where in the attached diagram would you wire it in at?"

That was the OP's question.
I gave him a direct and correct answer. A way to bypass the SSR.
And having the Lee control in there as a safety device. And a way to make his thermocouple last indefinitely by using a thermocouple well.
But hey, you geniuses just roll along with your $200 controls for a $63 lead pot.
You are right about one thing though.
You are a sorry butt. ;-)

[smilie=s:

I'm with you Sonny![smilie=b:

[Pigslayer]

I'm building a PID Temperature controller now. But I will not disconnect heat control on the furnace. I'm going to make it so I can bypass the PID in case something should happen to the PID controller. It's called a double pole, double throw switch with the OFF position in the middle.
Don't know why people were coming down on Sonny. He makes perfect sense . . . but then what do I know . . . I'm just a service technician that works with electronics all day.

[edsmith]

I am waiting on parts for one, I am going to build it so I can plug the pot into it, I will be using it for two pots. I am also going to use a thermocouple well on both. Sonny, what would you suggest I use for the thermocouple well ? alu. ,brass, steel ? thanks

[Mal Paso]

I never touched my Lee Controls except to set it on High. Any other setting will disrupt power to the heating element defeating the PID.

I researched the parts we are using and they are very rugged. My controller is short circuit protected. The SSR is way overbuilt for the Resistive load we put on it and doesn't NEED a bypass. If you want one great.

I made the mistakes and rebuilt pots. As it turns out Unless the probe tip and a fair amount of the shaft is immersed in the liquid you are measuring you will get " Thermal Drain " and your reading will be inaccurate. That's why most of the guys are using that long probe and some sort of holder above the pot. I used a $7 probe silver soldered through the bottom for a more " Built In " operation. The probe is Stainless Steel so it should last as long as that carbon pot and is cheaper to replace.

If you got a welder friend it's $1 worth of materials. I built up a bead of brazing rod on the bottom to add meat, angle drilled a hole, and silver soldered the probe in place next to the spout.

I too have an electrical background but I've built and tested PID Controllers. It's what I use now.

[Pigslayer]

Sonnie is absolutely correct in his instructions for a bypass. I am going to incorporate it into mine. I will also leave the Lee Temp. control in the loop. I like the idea of having that choke in the loop. I got a good deal on a couple of thermocouples with a high parameter of 788F. I think the Lee pot wide open will go higher than that & I don't know if that would hurt the thermocouple so it's nice being able to put a limit on how hot the pot will get and no it's not compromising the PID's function as a good casting temp. is somewhere in the low 600's. At least that is what I read. The Lee molds I have found like it hotter . . . closer to 700F.
Money is tight so I really shopped & I got my PID shipped for $26.00. All in all I'll have less than $50.00 into it when finished.
I was looking for a project box on a number of sites including Ebay. Auberins wanted about $26.00 for one the right size & I said no, I'm not paying that for a piece of tin! I remember that I had some galvanized sheet metal in the basement from when I was putting in my new furnace a couple of years ago. I found a nice piece that was 22ga. & I also have a neat little 18" sheet metal brake that I got from Grizzly Industrial for cheap but it works well.
So, last night I came home from work & made a nice project box for my PID. Been out in my little shop making the cutouts for the PID, Indicator lights, receptacle etc.. Then I roughed up the galvanized with some emery paper & primed all the pieces. So far, so good.:Fire: