Uprating a Fan controller
Posted: Wed Jan 18, 2023 4:04 pm
I have been using nice little automatic fan speed controllers like this unit https://www.ebay.co.uk/itm/193665387194 ... R-Tv3Ni4YQ although my PCB is slightly different.
Its designed for running standard 12V fans, a job it does admirably, even a high-flow 0.7A monster I recently fitted to my MRF300 amp. As the amp warms up, the fan speed increases. It is apparently configurable, but the method is so obscure and the standard programme it comes with works so well...if it ain't broke, don't fix it....
The next project uses 2 MFR300's and with a potential to absorb 750W at 50V I found a BNIB 48V fan on eBay. Its a beast at full voltage - almost certainly more than I need even for key-down operation with CW. Looking at the circuit and doing a bit of probing I have gleaned that its probably a uC that does the temperature sensing and an output then drives a SMPSU section with a ramping up voltage as the temperature rises. The board has an on-board regulator for the uC at 5V. The SMPSU diode is a 40V 1A part and the output capacitor is only a 16V unit. Unfortunately the switching transistor/MOSFET has no markings, but I'd assume its not anything special. On my PCB it looks like the uC drives a switching transistor which then drives the SMPSU switch. If I isolate the +12V feed to the SMPSU switching device, replace it with 50V and upgrade the switching device and diode to something with a higher VDS/VCE/Id/ICE, along with a suitable rated output capacitor, I think I might have a solution. Other than finding a high side P-Type or PNP device, any possible problems anyone can see? The alternative is a thermal switch and a suitable series resistor, but it would be nice to do a low-loss load dependant job on it.....the +12V line is the track labelled 123.
Gareth
Its designed for running standard 12V fans, a job it does admirably, even a high-flow 0.7A monster I recently fitted to my MRF300 amp. As the amp warms up, the fan speed increases. It is apparently configurable, but the method is so obscure and the standard programme it comes with works so well...if it ain't broke, don't fix it....
The next project uses 2 MFR300's and with a potential to absorb 750W at 50V I found a BNIB 48V fan on eBay. Its a beast at full voltage - almost certainly more than I need even for key-down operation with CW. Looking at the circuit and doing a bit of probing I have gleaned that its probably a uC that does the temperature sensing and an output then drives a SMPSU section with a ramping up voltage as the temperature rises. The board has an on-board regulator for the uC at 5V. The SMPSU diode is a 40V 1A part and the output capacitor is only a 16V unit. Unfortunately the switching transistor/MOSFET has no markings, but I'd assume its not anything special. On my PCB it looks like the uC drives a switching transistor which then drives the SMPSU switch. If I isolate the +12V feed to the SMPSU switching device, replace it with 50V and upgrade the switching device and diode to something with a higher VDS/VCE/Id/ICE, along with a suitable rated output capacitor, I think I might have a solution. Other than finding a high side P-Type or PNP device, any possible problems anyone can see? The alternative is a thermal switch and a suitable series resistor, but it would be nice to do a low-loss load dependant job on it.....the +12V line is the track labelled 123.
Gareth
- Fan controller.jpg (229.25 KiB) Viewed 9012 times
) The fan doesn't quite start (needs a bigger KICK at power-on, something I believe may be configurable on the Fan controller board, a ZF1X3L) but if the thermistor is warmed up it quickly ran up to speed and drew 0.45A.