Electronic temp control

[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 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?ma...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/show...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.

[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

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?ma...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?ma...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?ma...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.