View Full Version : PID controller

November 13, 2009, 12:28 AM
PID means;PID stands for Proportional, Integral, Derivative. Controllers are designed to eliminate the need for continuous operator attention.

They are a tiny microprocessor, that is a fancy thermostat. I was unhappy with the wide temperature swings on my lee 20# pot. Besides I love to tinker and challenge new technology. I darn near bit off more than I could chew! Took me over a week to make sense of the directions that came with the PID!:( Turns out I had the PID programmed right, just had the polarity of the SSR,(Solid State Relay), bassackwards!

Anyway here's some pics,,,---you didn't really think there wouldn't be pics???¿


That's the PID. Not seated all-the-way-in yet, I'll fix that before putting the cover on.


That's the heat sink, I was told I needed one, well I'm only drawing maybe 6 amps through a SSR capable of 40 amps, it doesn't even get warm!


On-off switch and the cover's laying on top.


Thermocouple in the bottom of the pot, it senses directly into the molten lead.


Wiring terminal block, on the outside where it's easier to hook up.

BBS can't count, says I had 7 pics, I dunno, I only counted 6-------.

Overkill? Maybe, but it's cool factor is off the chart! It's neat to see it react to temp changes, like dipping a mold in the melt to warm it up, then see the PID react instantly to try to raise the heat, and see the readout in degrees. Or see the temp instantly drop when you drop some cooled sprues into the pot. The heat, or in this case cold, travels fast in the melt!

November 13, 2009, 12:38 AM
Here's the terminal block.




The thermostat that the lee comes equipped with does NOT read actual pot temp. It simply reads the air temp INSIDE the oblong tower pictured here. In other words, it's indirect sensing, leads to a long lag before it switches on.


November 13, 2009, 08:43 AM
I used a PID controller on the caster I built too. I even have a few that are fancy enough they have a self learn capability than can save hours in set up in some cases. I use them to control the temperature on my BBQ smokers, as there needs change based on wood and atmospheric conditions in any given cook session.


November 13, 2009, 09:48 AM
Very nice!
I was noticing that my Lee pot did not have a temperature probe going to the pot. Just curious, since I don't have a thermometer yet (on order), how much does the melt temperature swing?

November 13, 2009, 01:46 PM
Here's where I got the idea;


The links on there give you where to go to buy the stuff, if you're interested that is.

Jector, I'm not sure how much the lee pot used to vary from on to off. I do have a Lyman thermometer, but the scale is hardly all that precise. By that I mean it's hard to tell with marks so close together that total 10 degrees/mark!

Jmorris, mine will "learn" all by itself, or if I tell it to, it'll pick it's own parameters. It's capable of maintaining +-1 degree. It'll also alarm if the temp goes 15 degrees above or below the set temp.

November 13, 2009, 02:09 PM
When you said it reads the lead temp directly, is the thermocouple in a well? or is the sensor DIRECTLY in the lead?

November 13, 2009, 02:18 PM
Freonr22, yes the probe of the thermocouple is through the bottom of the steel pot, and sticks up into the molten lead by about ½ inch. I could have gotten a much longer TC that would have to be lowered down from the top into the lead. It would always be in the way and have to have a bracket of some sort made to hold it in position. I didn't like that idea, anything that gets in the way of fluxing and stirring the melt is to be avoided, at least for me!

November 13, 2009, 07:36 PM
Whatever happened to heating up lead in a cast iron pot over the campfire??? Like the good old days??? :D Lookin' Good Snuffy!!!!