PID controller for lead melting pots?

[Greg_E]

Anyone want to start us off with parts, knowledge, etc. on making a PID control for our lead melting pots?

[triggertreat]

Here's the one I built and some videos of how to build it and where to get the parts:

1st attempt - Airguns & Guns Forum (gatewaytoairguns.org)

[Firewalker]

Anyone want to start us off with parts, knowledge, etc. on making a PID control for our lead melting pots?

It's much easier and harder than you would think. I used the Inkbird kit:

This kit will control the lead temp up to 752° F. I also decided to tap the bottom of the pot (LEE #10 bottom pour) for the K Thermocouple near the spout.

[triggertreat]

I bought my PID controller and K probe and SSR (40 amp) off of eBay along with an old computer power supply I used for a case.  It's not that hard to build but did have to wait for China shipping a few weeks.  Just follow the videos I linked.  This PID has a range up to 999° and I like how it works and this one is stateside.

TA4-SNR RNR SSR Digital PID Temperature Controller Relay Output Dual Display AC | eBay

[Bob Pratl]

A PID is a good way to eliminate heat variations which will result in more consistent casting, "Set-it-and-forget-it".

[rkr]

Auber is a reliable source https://www.auberins.com/index.php?main_page=product_info&cPath=99&products_id=1016

[scion19801]

here are some of the random pics I took of my PID controller as I was building it and how I set mine up. the plug socket on the back is split. one(bottom port) is always powered and uncontrolled. the other(top port) is the pid controlled for the pot to hook into. well based on my pic the ports would be reversed given the orientation. but when in use the ports are as stated.
the top and bottom are aluminum plate. the black square on the bottom is the heat sink for the relay.

[triggertreat]

Auber is a reliable source https://www.auberins.com/index.php?main_page=product_info&cPath=99&products_id=1016

This is a very good deal and comes with the type of K probe needed along with the heat sink for the solid-state relay and thermal grease.  I am surprised at the low cost.  An on/off switch, some wires and terminal strips along with the panel mount socket for the thermo couple and an A/C socket and fuse holders and a box to put it all in is about all that is needed besides this kit.

[Greg_E]

I did see some cheap cases for these controllers on amazon, didn't really investigate yet.

[superchikn]

following

[Firewalker]

Auber is definitely better but the cheap Amazon kits do fine for the hobbyist.

[customcutter]

Auber is definitely better but the cheap Amazon kits do fine for the hobbyist.

Thanks for the comment.  I was wondering what the difference was in the kits, for almost 2X the price?  Inkbird seems to have great reviews.

[Greg_E]

Is there a PID system that uses PWM to control the heating element? All of these seem to just bang the heater on and off as needed, a more tightly controlled fashion of what the stock control does.

That said I'm thinking about a PID for both my lead pot and my PC oven, also need some rock wool for the PC oven. Since I'm never running both at the same time, I may use the same box to control both, I already drilled a hole in my oven and stick my Lyman temp. probe through the hole to keep an eye on the oven temps.

[Bob Pratl]

That said I'm thinking about a PID for both my lead pot and my PC oven, also need some rock wool for the PC oven. Since I'm never running both at the same time, I may use the same box to control both, I already drilled a hole in my oven and stick my Lyman temp. probe through the hole to keep an eye on the oven temps.

That is exactly what I do, one PID for 3 different sources.
A PWM controller might give you more precise control, but I don't think that it is needed for the additional expense.

[triggertreat]

I agree with Bob.  The PID pulses the SSR on and off very rapidly once up to temp that it has no issue keeping up or keeping precise temps good enough for what we need for a melting pot.  The swings are very minimal if not adding lead back in as you cast and does a great job at maintaining the temp as the material decreases in quantity.

[Greg_E]

Yeah, I did some reading on PID for ovens, most guys set them for about a 2 second cycle because the oven just can't react fast enough. For the lead pot I'm guessing a 1 second cycle time is probably fast enough. Need to spend some time on it and make a nice one that I can use for both devices.

Need to mod my oven too, looked into that a little bit already DEI gold tape inside, ceramic high temp insulation between the cooking box and the outside shell.

[Firewalker]

Is there a PID system that uses PWM to control the heating element? All of these seem to just bang the heater on and off as needed, a more tightly controlled fashion of what the stock control does.

That said I'm thinking about a PID for both my lead pot and my PC oven, also need some rock wool for the PC oven. Since I'm never running both at the same time, I may use the same box to control both, I already drilled a hole in my oven and stick my Lyman temp. probe through the hole to keep an eye on the oven temps.

The PID is a "Proportional–integral–derivative controller (PID controller or three-term controller) is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control. A PID controller continuously calculates an error value {\displaystyle e(t)}e(t) as the difference between a desired setpoint (SP) and a measured process variable (PV) and applies a correction based on proportional, integral, and derivative terms (denoted P, I, and D respectively), hence the name.

In practical terms, PID automatically applies an accurate and responsive correction to a control function. An everyday example is the cruise control on a car, where ascending a hill would lower speed if constant engine power were applied. The controller's PID algorithm restores the measured speed to the desired speed with minimal delay and overshoot by increasing the power output of the engine in a controlled manner."

Here is a simple video explaining the basic function.



In reality, the PID sends a signal to the SCR and the SCR turns the power on and off as necessary to maintain your desired heat. It will 'pulse' the power faster and faster the cooler it gets until the PID is sending 100% ON signal and as it approaches, the PID sends smaller signals further and further apart. This is displayed by the red LED on the face of the PID.

I personally like PID's, I have several of them in a few different configurations for different jobs. An STC-1000 for my Logerator, a Mypin PID for my brewing boil kettle and an Inkbird in my LEE pot. No pic of the lead pot, it's in the pole barn and there is NO WAY I'm going out there until it warms up a bit.

[Bob Pratl]

Not a bad price. You can tack weld or tap the bottom of your pot to accept the 1/4-20 thermocouple.

[cosmic]

[Greg_E]

I may get back to this subject tonight, I need to cast up a bunch of 50 cal, or buy a bunch of 50 cal ammo. Since I have the mold in hand, lead to spare, and a sizing die, I really should get out in the garage and fire up a heater and get going. Need some more 357 too.