Thank you for looking at this. I have some design questions and need some advice. I have 8 fan cartridges that contain 2 fans each. Fan cartridge spec sheet: https://www.delta-fan.com/Download/Spec/GFM0412SS-BL4F.pdf Each cartridge contains 2 pwm lines to control the fan speeds. I would like to control the fan speed myself with a photon. The control board has 42 temperature sensors on it of which are available via rest api in json format. Figured this was perfect for the photon to manage since the board no longer appropriately manages the fan speeds. But one step at a time, I’d like to figure out the circuit and learn how to pwm control the fan speed. So according to the spec, it will drive the fan based on the square wave I send to it. Which I found in the particle library analogWrite. I want all the fans at the same speed, not going to fiddle with these sensors are hotter run the fans faster on that side.
More Info:
Currently the fans are powered by 12V DC from the control board.
There is an available USB port on the control board that is powered.
I can wire in power if needed.
Questions are:
- Can the photon directly send the pwm signal to all the fans?
- If not do I acomplish this with a transistor? and how do I determine the wattage requirement of the transistor?
- The spec sheet shows an example of 2K ohm resistor to go to the pwm line but how do I determine what this value should be for hooking all 8 cartidges up (16 fans/lines)
- Does the photon need to be tied in to the same ground (-) as the fans? Maybe I am if I am powered off the usb on the board.
- How do if figure out what value in the analogWrite corresponds to what fan speed?
1st pass I am going to just see if I can set the fans at certain speeds.
2nd pass read the sensor rest api, average out the temp and figure out what speed to run at.
Any help is greatly appreciated.