PID Project

Precision Melter, Magnum Melter, Production Pot IV, and Pro 4-20

PID Project

Postby leadslinger » 26 Dec 2016 15

I finished the PID temperature controller for my Lee Pro 4-20 pot a while back. I don't know how I was ever able to cast anything without it.
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You can see that it makes a liar out of that stem thermometer.

The controller and SSR cost $32.99 and the thermocouple cost $6.39, both from evilbay.
The single ac outlet was about $6 from Lowe's.
The fuseholder and switch cost about $10 from a mail order surplus dealer.
The cabinet is an old printer a/b switch from the junkbox.
The rest of it is junk box salvage stuff, but I'm betting it wouldn't have cost more than $20-$30 if you shopped around.
I could have added additional features like a PID bypass switch for heatup, and a maybe a few indicator lights, but I wanted to keep it down and dirty, and simple.
A heat sink has not been necessary. I mounted the SSR directly to the bottom of the cabinet with thermal compound. The cabinet only gets slightly warm. If this controller was driving a higher current pot, heat sinking might be needed.
I did not bypass the thermostat in the pot. It serves as some protection against temperature runaway, if something goes wrong with the controller.
The most difficult and time consuming part of the project was fabricating all the hardware items.
Wiring was dirt simple.
The only issue is that you have to use crimp type connectors on the chromel/alumel wires from the thermocouple. They won't take solder. So hooking them up to the connector took a little extra doing.

No modifications were required to the lead pot except for the mount bracket for the Thermocouple. Just plug the pot into the socket on the PID and turn the thermostat on the pot on high.

Layout:
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Schematic.
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Re: PID Project

Postby daboone » 26 Dec 2016 16

Very nice.
An ignorant person is one who doesn't know what you have just found out.

When setting a job up for myself it must be Idiot Proof as well, as I am a bigger idiot than most people I know, and I prove it to myself everyday.
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Re: PID Project

Postby GasGuzzler » 26 Dec 2016 18

Very nice. These are fulfilling endeavors. I built two, one for my lead pot and a second simpler version for my lube heater/sizer.

In reverse chronological order:

Lube Heater Link

PID for Pot Link
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