mattW is steering you in a good direction, and everyone else as well.
I built my first one almost twenty years ago, but that's what I did for a living and I had the parts and it was, "easy." As far as spreading our wings and exploring new stuff, I agree completely with the notion, but electrical stuff - ESPECIALLY ELECTRONIC stuff can be intimidating. The problem is that you do not get the sensory feedback - the "clunk" of an electro-mechanical relay, which won't last long in this application AND will drive you batsh... hearing it clunk,...clunk,clunk,...clunk,clunk, clunk, clunk,....clunk,.....
When someone says something's "easy," we are imposed upon with an element of guilt, and either dive in and try it, or shut up and forget about it. With electronics, an element of FAITH is REQUIRED that the unit will do what it's supposed to do. No sensory feedback. "Young people," (I generalize) think the have the workd by the a... because they "embrace technology" and use it to good effect, but in fact, the do NOT. Many (think "smart" phones) only learn the doggy tricks - which series of swipes and pokes cause what to happen. We can train dogs, chickens and pigs to do that!
MOST PEOPLE WHO "EMBRACE TECHNOLOGY" do NOT know SQUAT about TECHNOLOGY, PERIOD! Sorry. This is what I teach,and yet, I am often scolded for not "embracing technology" by some airhead who thinks he or she has the workd by the a.... because they finger that stupid phone all day.
But, we're "old guys," right? Been there, done that, got the T-shirt and wore it out and are now using it to wash the car. Or truck. We KNOW STUFF for REAL. So, here's the deal with the electronic "black box" we call a "PID controller:" if you can muster the ability (this is NOT easy) to NOT try to completely understand what is going on in there, you CAN be OK and still not be an airhead. This is complicated stuff they hire eggheads to figure out so the rest of the world can benefit from not REINVENTING THE WHEEL every time we star ta new project. Non else is SUPPOSED to be able to understand what goes on in there because it's all benign, boring, redundant and tedious MATH which would take any of us hours (even if we're really good) to figure out.
Esoteric language is the real problem here; what does "output" mean? What's an "input?" BUT, if you can roll back the experience and skepticism - the NEED to have proven to you that something is doing what it should, you can put one of these units together. It's not that you're not smart enough, it's more like you're TOO smart. Honest! We have to scale it back and let the little "black box" take over. It's almost like a trick on us old guys, but it's been around a long time. Everything about one of these units is pretty objective and REAL, except the black box - the controller and the SSR (solid state relay).
Let's get the SSR out of the way; it works just like a real relay - or like the solenoid in your starting system on a truck, tractor or a car - it "RELAYS" a signal - a smaller voltage,and allows a larger voltage (OK - CURRENT) to flow. It just doesn't make noise like a real relay. Easy enough. here's no coil, but you still attach two "small" wires for the "signal." Yo also attache the two "large" wires carrying the bigger current to power the pot. When you don't need heat, you "open" the circuit on the larger current. When you do need heat, you "close" the circuit on the large current - just like a real relay. You just can't hear it and it really doesn't "open" and "close" the circuit. So, who cares? it works like a relay, has the same number of wires and those wires do the same thing. Signal and power.
The controller - it needs power to run - two wires. It also has an "output" which is the "signal" to run the solid state RELAY. The wiring diagram for the controller will show you which two terminals are the "output," which would be what would run the coil on a regular relay. It will also have an "input," which is the temperature sensor that tell sit how hot the lead is. This sensor has two wires (if a thermocouple) or three (if an RTD). Go with the thermocouple, hereafter referred to as "TC." That's pretty much it for the basic wiring.
How the "black box" "auto-tunes" can be resolved after the basic wiring, but there will be instructions and it WILL save you a lot of superfluous education - which IS superfluopus because of the auto-tune feature.
I do NOT intend to come off as being an expert on this. I do NOT intend to put anyone's experience or education down WITH this. I am an old guy and I get old guys in class. Guess wh's the hardest on themselves and learn the most - the old guys.
I'm not on here often, but will help if you e-mail me. I should get an e-mail if I get a PM, but that doesn't seem to work that reliably.
Anyone here can make one of these, and if it's not cheaper than buying one, at least it's gratifying to do it yourself.
Then again, there's NO shame in just buying something you want if you don't WANT to have to figure it out. But, if you WANT to do it, there's NO reason you can't.
Sorry for the lecture. The "virus" has kept me out of the lab and classroom and it's starting bubble out.
Drive on guys, love the bunch of ya.
Jeff
