Low cost PID control box for heating/cooling

Assembling a PID temperature control box-1795

One of the joys of the modern world is the availability of low cost PID temperature control modules.  These have been around for a long time in the industrial world but in the past were cost prohibitive for home hobby use.   Now you can buy a pid temperature controller for $25 from Amazon.com.   Adding  in a type K thermo couple ($6),  a 25A SSR ($7) , and some items from your parts bin (switch, outlet, plug, fuse holder) you can build a nice little temperature control panel capable of keeping a piece of production equipment at a fixed temperature while running for less then $50.

Assembling a PID temperature control box-1793   Assembling a PID temperature control box-1792

Only basic instructions are included with the controller, if you aren’t familiar with set up and tuning search the web

This project is more for documentation for future use by myself but here is some back story.  I was in need of a temperature control unit for a piece of production equipment for my company.  We had purchased a cheap control unit that was essentially a solid state pulse width modulator, ie. turning the device on and off  with control of the cycle times.  During production runs the PWM unit did not keep the temperature fixed and we were seeing variations in the final quality of the product.   This is a low risk, non hazardous process and so this quick cheap but very accurate PID temperature controller was the way to go.

***  Disclaimer – I would not use parts of this cost/quality when working on a chemical process or a piece of process equipement where a failure of temperature control would result in something bad happen such as a run away reaction or explosion.  ***

Assembling a PID temperature control box-1787

The wiring is fairly straight forward as shown in my rough, chicken scratches on paper diagram above.  I’m not proud of the drawing, but it was more for the dimensions of the switches then the actual wiring diagram.   I used my cnc machine to mill out the panel that houses all of the components. (dimensioned drawing of panel – PID Temperature Control Panel Drawing)  You could just as easily hand cut openings in a small electronics box if you were building one at home.

Assembling a PID temperature control box-1790   Assembling a PID temperature control box-1791

Be sure to carefully follow hook up instructions on the PID temperature controller.  The unit has makings labeled (Note:  the part numbers in the above picture are for future my reference) on it as well as in the instruction sheets.  These were taken during the first assembly. I have since added a fuse holder between the line in and the switch with an appropriately sized fuse for my device.  Fuses are important as they protect your equipment in the case of a failure.

Assembling a PID temperature control box-1789   Assembling a PID temperature control box-1794

When you wire up projects like this, take time to do a tidy job of it.  While as a hobbiest we do not have 100 colors of wire to choose from, make choices that follow standards if you can.  A few I always keep are white is for neutral and green is for ground in any AC wiring.  Standards are there for a reason. I recently worked on something where the manufacturers chose black wire to be the V+ and green the  V-.  It was nothing but a headache to work on so choose your wire colors appropriately, you might need to go in and add or change something in a few years and keeping to standards makes life easy.

Assembling a PID temperature control box-1788

The finished PID panel works and looks great. It resulted in a significant decrease in reject rate on our production (15rejects/1K reduced to 1 reject/1K). I will build a second identical PID temperature control unit  to run my filament extruder that I am working on building to feed my 3d printer using recycled scrap plastic.

2 thoughts on “Low cost PID control box for heating/cooling”

    1. The cable in the top picture with the blue end goes to a K-type thermocouple. It is connected directly to the PID controller and is what allows the PID controller to detect the temperature.

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