My take at a PID on an old Lee pot

[Chicken Thief]

Here’s my take on a PID Lee pot.
My first pot from 1985 and it is on it’s second heating element.
I used a PID from dx.com that came with a thermal probe delivered for just $17.80
http://dx.com/p/digital-temperature-controller-66334
It will go to 400degC~752degF

1: I started by dismantling the pot and polished a spot on the bottom for the probe mount.


2: The thread on the probe is ¼-20 and i made up a brass mount that i (high-temp) silver soldered onto the pot. (What I could with what I had!) You can weld 2 nuts onto the pot and achieve the same but remember to close the hole so the end of the thermal probe has something for proper contact.



3: The controller electronics will pop out and make mounting a breeze. I was lazy and used nuts and washers for spacing when I mounted the controller house onto the back of the pot stand. I added some holes for wires.




4: To counteract the sad sagging from pic. 1 i used more nuts as spacers with some self tapping screws into the pot couling.



To be continued.

[Chicken Thief]

5: Probe mounted and bottom cover back on.



6: Here 2 new wires from the heating element and the probe wire.


7: Don’t panic ‘bout the electric I’ll talk you through it! Here is the diagram. Both of the live wires goes to the controller box. Both the new wires from the heating element goes to the controller box. 1 live wire and 1 heater wire goes into the same connector (pin 2). The other live wire (pin 3) doubles back onto the relay (pin 5). The last wire from the heater goes to the relay (pin 6). The Thermal probe is connected onto pin 13 (blue) and pin 14 (red). I modded the connectors as you can see.






To be cintinued

[Chicken Thief]

8: To be posh I made a screen from 2mm polycarbonate plastic. That will take the lead splash.



9: I tried to take pics of the controller but it only lights up one segment at a time so it didn’t work to well. But it does work!

[Chicken Thief]

In the last pic i just plunged the lead bar in and then the temp went south after i had taken the pic!

[w0fms]

752°F isn't hot enough, and usually exceeding that will damage the sensor.. I heat my hot plate up to about 810°F for the Lee Aluminum molds-- now granted that's the element temp. Is it a RTD type probe? If so, get a bead type K thermocouple (~$10) and mechanically strap it to the pot (exercise left up to the reader) -- electrically insulated if possible) and set the PID for K type and re-auto tune it. Then you should be fine from that aspect.

My other concern is that your PID is a relay type. The 1000W element draws 9A or so at 120V. THE RELAY IN THE "REX-700" is rated at 3A! Can the relay in the PID handle it? NO! Use that relay to trigger an external relay. A better choice would have been a 40A Solid State Relay and a SSR output PID (12V DC pulse). It might be possible to open up that PID and use the internal control voltage for the built in relay to instead trigger a SSR. If you burned up the internal relay, that would fix your problem. 40A SSR's from e-bay are like $20 shipped with a heatsink.

If you continue to use a relay, that is fine but make sure that the hysteresis is set so the relay is on for like 5 seconds and off for 5 seconds. If you were using a SSR, then the pulses could be a fraction of a second.

I need to take some pictures of my $35-ish "MyPin" PID & 40A "Fotek" SSR/Heatsink and $17 Amazon hotplate that I use with a $3 clearance Wal-Mart aluminum saucepan with a notch cut in it to cast, direct "top pour". I will need to upgrade the $3 pan to a $17 "Lodge" saucepan instead as not having the thermal mass in the pot is annoying near the end of a casting session. (I have to lead about 1/2 lb of lead in the pot).

The PID hot plate I also use as a warmer for surface mount electronic project soldering, heating up tumble lube, and a host of other things.. it's very handy to have.

[Chicken Thief]

752°F isn't hot enough, and usually exceeding that will damage the sensor.. I heat my hot plate up to about 810°F for the Lee Aluminum molds-- now granted that's the element temp. Is it a RTD type probe? If so, get a bead type K thermocouple (~$10) and mechanically strap it to the pot (exercise left up to the reader) -- electrically insulated if possible) and set the PID for K type and re-auto tune it. Then you should be fine from that aspect.

My other concern is that your PID is a relay type. The 1000W element draws 9A or so at 120V. THE RELAY IN THE "REX-700" is rated at 3A! Can the relay in the PID handle it? NO! Use that relay to trigger an external relay. A better choice would have been a 40A Solid State Relay and a SSR output PID (12V DC pulse). It might be possible to open up that PID and use the internal control voltage for the built in relay to instead trigger a SSR. If you burned up the internal relay, that would fix your problem. 40A SSR's from e-bay are like $20 shipped with a heatsink.

If you continue to use a relay, that is fine but make sure that the hysteresis is set so the relay is on for like 5 seconds and off for 5 seconds. If you were using a SSR, then the pulses could be a fraction of a second.

I need to take some pictures of my $35-ish "MyPin" PID & 40A "Fotek" SSR/Heatsink and $17 Amazon hotplate that I use with a $3 clearance Wal-Mart aluminum saucepan with a notch cut in it to cast, direct "top pour". I will need to upgrade the $3 pan to a $17 "Lodge" saucepan instead as not having the thermal mass in the pot is annoying near the end of a casting session. (I have to lead about 1/2 lb of lead in the pot).

The PID hot plate I also use as a warmer for surface mount electronic project soldering, heating up tumble lube, and a host of other things.. it's very handy to have.

For what?
Lead melts at 620degF and alloys even less than that.
As to the relay, hmmm the heater in the Lee US models are way bigger than we foringers get! (9A x 120V = 1080W)
Mine is a "only" 500W heater and that evens out at 240V @2A so i'm good.