PID controller

[Critr]

Another extension of reloading as a hobby!

I started building a PID Controller for my lead pot. For those inquiring minds, PID stands for "proportional-integral-derivative". Aren't you glad you asked?

It will control my lead pot temperature at any set temperature, plus or minus 2 degrees.

First, cutting an opening in the aluminum project box for the temperature controller (the digital brain). Using my Dremel Moto-Tool with a cutting disc, I was almost finished (finally) when the coupling in my Dremel gave out. Since it was probably 30-40 years old, it was as much age as use. Ordered pkg of 2 from Amazon, 2 day delivery. Opening was almost done, so I finished it with a file.

Was going to use a household light switch that I had on hand, to save a few bucks. It is physically too large for my project box, so off to Home Depot this am for a 110-volt 20-amp toggle switch, and some misc hardware.

To be continued...…………………

[Ringer]

Do I see an alias change coming?

Tn Piddler

[Critr]

Drilled holes in project box to proper sizes for switch, fuse holders, power input cable, ground bolt, legs, heat sink, and …….……….    Anyway, I think I got them all except two. The thermocouple wire (location not determined) and the power out, which is another square hole to be cut with the Dremel.

Waiting...……………………………..

[Critr]

Saturday: Dremel coupler from Amazon arrived. Inserted part, assembled Dremel, cut power outlet hole.
Ready to start wiring. Cannot find wire stripper/crimper. Searched hours...…

Sunday: Was at Home Depot when they opened. Bought new wire stripper/crimper. Got one a little better than the one I can't find.

[Critr]

Finished wiring. Seems to work. At least there is no smoke or flames...……

Now,.... this thing has umpteen parameters to set. I got it switched from Celsius to Fahrenheit. Easy stuff first.

Struggling………..

[Ranger Z]

Passing the smoke test is always a good thing.

[Critr]

Success is sweet!

In the PID controller, each letter, P, I, and D has a value. Juggling these values changes the performance characteristics on the unit.

After most of a day juggling values, I am finally satisfied.

With the temp set at 700 degrees, starting with a cold pot of lead, it heated up to 705 degrees, then backed off to 692. Then the lead pot temp readout settled on 699-700 degrees. I watched it for almost one-half hour, and it just varied back and forth from 699 to 700 degrees.

To say that I am pleased with this little device would be a drastic understatement.

[Tombstone]

And only two trips to Home Depot, very impressive.

[Critr]

Now I have a message for that lost stripper/crimping tool. I don't need you anymore, so you can reappear any time!

[Jackalope]

 

[Critr]

I have the thermocouple wired directly into the controller unit. But I don't like not being able to disconnect it easily. So I will put a thermocouple plug/receiver in the case. But here is the question. Will running from the case to the controller unit with regular wire introduce an error in the readings?

I'll find out. First, today I heated the lead again, watching the temperatures. With the temperature set at 700, it overran to a high of 705, then backed off to 694. After 15 minutes, it was varying from 699-701.

When I get the parts, I will try it with a disconnect in the case.

[Critr]

My RCBS lead thermometer, which I have been using for years, reads about 70 degrees lower than the thermocouple. As the lead melts, the thermometer reads 510, and the thermocouple reads 577. The melting point of lead is 621.4 degrees, but alloys, which wheel weights certainly are, can influence the melting temperature. For example, a lead-tin alloy melts at 369 degrees. So a little tin in the wheel weights can dramatically influence the melting temperature.

The thermocouple is closer to the temperature I would expect, so I tend to trust it.

I stuck the thermocouple in a bucket of ice water. It read 31.9 degrees. OK, I'll trust the thermocouple readings. (It probably doesn't matter all that much anyway.)

[Critr]

Received the parts, wired the thermocouple from the entry point of the case to the controller through a disconnect in the case, with #18 wire from the case to the SSR controller.

Starting with a cold pot of lead, and the target temperature set on 700, the overrun reached 709 degrees, then fell back to 695 before eventually settling at 698-700.

Conclusion, NO EFFECT!

But...…. what if the wires used were not the same size, or not the same length? Would that affect the thermocouple's performance?

DON'T KNOW! DON'T CARE!!! Gonna cast some bullets!