There is a lot of talk of PLC, PID and PIC computers for a variety of projects. Would someone who uses these components post where they get them and where I could learn more about them? Also are there many kinds/types and what would be good to control a siphon nozzle furnace.

Do a search on eBay for “Watlow”, “temperature controller”, and “digital controller”. Also “thermocouple” I use the small Watlow 935A, 120v , PID temp controller because usually there are cheap, under $50, use a readily available standard J thermocouple and are sturdy.I will email you the manual for a Watlow 935A PID temperature controller for you to look at.

I think your endorsement of Watlow temp controllers has caused a run on them on eBay. :) Just to throw a curve in there, there’s plenty of other ones out there that fit the bill, not just watlow… omega’s are good, too.

A PLC in an industrial Programmable Logic Controller. They replaced racks of interconnected mechanical relays and timers that were once used to control automated machines. They usually have a number of inputs and relay or solid-state outputs. You buy (usually expensive) software for your PC to set up the PLC programming and then download it to the PLC, which then runs on its own. PID is a control algorithm (method) that has three parameters: Proportional, Integral and Derivative. Most digital temperature controller use PID. To me, PIC is Microchip’s line of microcontroller chips. They are component-level parts that are soldered to a PC board, much like the CPU chip in your PC but much less powerful. You might find a PIC inside a PLC. What you should use depends on what you’re doing and your aptitude. I wouldn’t recommend PICs unless you are already a serious electronics hobbiest. PLCs and digital temperature controllers are not real cheap – try automationdirect.com or eBay if you know what you’re looking at.

There’s a whole lot of difference between PLC’s and PIC’s and PID’s. PID – as in temperature controller. Uses a thermocouple or RTD to turn on a heater and keep temps near a setpoint. PIC – A Programmable computer that can be set up to do a lot more than temps. All kinds of uses. PLC – Process control technology. Various inputs, and outputs. Tend to be expensive. Some cheap ones available at Automation Direct. At least a $100 new for cheap ones. I think most folks here, with the exception of Chad are using PID temp controllers rather than the other two.