I want to teach myself how to build a DC temperature controlled circuit, and use a thermo-probe for a closed-loop feedback to dial-in a specific temperature.
For the hot plate, I have the bottom surface of a coffee machine. A metal top, on the bottom looks like ceramic coated, with two leads sticking out where the A/C wires used to go.
I am measuring 9 ohms of resistance between the two leads.
I know how to drive mosfet with a PWM signal. I was going to hook that up to the coffee-plate. Since it's pretty much a short circuit, I suspect that's probably not a good idea. What circuit or device should I use to connect from my pulse signal to drive a 12-volt DC power into this hot-plate?
Boardburner2:
Coffee maker hotplates are generally designed to operate at 110 or 240 V ac.
12V at 9 ohms has no chance of achieving that sort of temperature.
Do you mean the drive requirement for an SCR. ?or similar.
I didn't know what an SCR was, until I looked it up just now. I wasn't planning to use A/C current if that's possible. I don't need to use this coffee plate, it's just some trash I had around that I could use without buying something specific.
Ok well, I guess it's probably not going to get too hot. I just want to test and start with something, but I was uncertain about run power through the mosfet to it. I realize now, it's about the same thing as an incandescent bulb so it's enough to get me started.
I also have this nichrome wire, someone asked me to build them a foam cutting tool - I will test out on that too.
There's a whole bunch of things, like making a bag-sealer for my foods to freeze in. A heated jig for bending thin plastics to make an enclosure box. Maybe a molded concrete/rubber top for the steps and walkway for the front of my house, so I can hit a switch then smile while I watch the snow melt away as I enjoy hot coffee while watching the neighbor's do back-breaking snow shoveling on their walkways.
From what I learned about the termocouple's, is two different material metal wires, welded at the point - as shown in the picture "terryking228" post. That is definitely interesting. These pre-made temperature probes seem to be cheap enough for me to buy a few to try them.
There are video's where people just use car batteries attached to jumper cables and a stick welder, to do dirty quick farm equipment repairs. I see video's some people tie the batteries into IRF3205 mosfets, to do small pulse welding.
This is an air solenoid. Not sure what it has to do with a hot-plate circuit on this thread. Ironically, I actually have got this air solenoid to work. I have 8 of them into a manifold, driven my tip 120's to trigger musical sequenced air horns. It's definitely one of the must fun projects I've done, that everyone loves. Unfortunately, I do not live on a farm, where I can test 90+ decibals of horns for hours without driving the people around me mad crazy. I don't know what to do with the project, since I have to tune the horns for frequencies.
