Using External Power to Run a Fan


I wanted to know if it is acceptable to run a small fan for a FARS from the external power on the 1-Wire CAT-5 cable. The external power is provided from the power supply for my Hobby Boards barometer. The fan is a small computer fan that runs off of 12VDC and draws approximately 0.08A. I have an extra power supply, but wanted to avoid running an additional cable if I could avoid it.

Seth Cohen
80ma shouldn't be too much. But I asked a similar question of Eric about using the cat5e 12vdc to run the relay board and he said a short run shouldn't be a problem with voltage drop. BUT, the relays might introduce noise into the 1-wire lines. So possible a fan would do the same thing.

Guess the best thing would be to try it and look for sensor reading errors. Or if you have an O'scope you can look yourself to see if you have noise on the lines from the fan (stop and start and running).
Wanted to follow up with the results of my initial test. I attempted powering the fan using external power from the CAT-5E cable. The fan powered up and I was able to read all of the sensors except the barometer disappeared. Unplug the fan and the barometer came back. I could have spent some more time troubleshooting and maybe even gotten it to work. But instead I just decided to save myself a lot of grief and use one of my spare wall warts and 25 feet of wire to run power directly to the fan.

Thanks for your help.