Bench PSU Fan control

Intelligent fan controller using ESP8266 for bench power supply

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I bought a cheap bench power supply for powering my development projects. The psu is great but its fan ran constantly and isn't the quietest of fans. As my power needs were fairly low (40-100mA) it seemed somewhat pointless that the fan was continually running.

I removed the cover of the psu and inside there are 2 large heatsinks, one for the AC side and one for the DC side of the psu. The dc side was barely warm but the ac side was warm so it appears this is the side to monitor.

I use a 10K NTC thermistor (the resin encapsulated type), salvaged from an old air conditioning unit, stuck onto the heatsink with hot glue. I didn't want to remove the heatsink to attach the sensor with screws as this would have involved un soldering the power transistors. Hot glue should be sufficient fot the temperatures involved.

The pcb with the esp8266 is one I made for another project that I had left over. It had most of the circuitry I needed so was a perfect salvage board.

Power for the board

On the bottom corner of the psu pcb there is a connector that powers the front panel. The voltage is around 10VDC so this is ideal to power the control board.

Existing fan

The existing fan is rated at 24V. The fan varies its speed depending on the power being supplied from the psu but in its default configuration it runs constantly when power is being supplied from the psu. This is both un-necessary and as the fan isn't a particularly quiet one, noisy.

The fan with the new fan control runs at maximum 10VDC which seems adequate for the psu ventilation.  It might be worth changing the fan for a 12V model if you intend to use much power from the PSU.

Variable speed fan

The fan from the control board is run using the PWM output from the ESP8266. This allows thresholds to be set for the fan speed. There are 3 settings that change depending on the temperature difference between the switch on temperature and the actual temperature.

Fan override

From the PSU Fan status page you can force the fan to run at 100% speed by clicking on 'Manual'. Clicking on 'Auto' will return control to the fan control.

Arduino ESP8266 source code

x-zip-compressed - 11.83 kB - 10/27/2018 at 04:34



Schematic of the controller

Adobe Portable Document Format - 43.98 kB - 10/27/2018 at 04:29


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