Hi,

I bought a few 50mm 2 wire 12V computer fans for blowing against the cooling block of an audio power amplifier. Something like this one. The fans draw around 110 mA each.

Would it be a good idea to place a current source as a limiter or something similar between the power supply and each fan for the case that the fan stalls? Does a PC motherboard condition the fan power supplies in such ways or is it just 12V from the PSU straight into the fan?

 

Most 2 wire fans are going to be power and ground. if it was a 3 or 4 wire they can have protection and other things to help add more power ot the fan when things get hot. So 2 wire fan just on and off nothing special in the fan in most cases.

 

Does a PC motherboard condition the fan power supplies in such ways or is it just 12V from the PSU straight into the fan?

Most PC fans are three wire types and most in addition to a tachometer output run on a PWM (Pulse Width Modulation) signal to control fan speed. A simple two wire fan has no need for anything fancy unless noise is an issue. I would just directly power your two wire fans from a 12 VDC supply source and not give it any further thought.

Ron

 

I would just directly power your two wire fans from a 12 VDC supply source and not give it any further thought.

I probably would, too, but there's nothing wrong with putting a 200mA so-blo in line with the fan.

 

I probably would, too, but there's noting wrong with putting a 200mA so-blo in line with the fan.

Really a good idea to fuse each fan. Good point I overlooked.

Ron

 

Thanks for the replies. I think I'll test the stall current and add some fuses depending on the results.

 

I think I'll test the stall current

The fan motor is most likely a BLDC type with internal electronics. It might not be happy if deliberately stalled. Just assume 110mA and do what Wayneh suggested.

 

PC fans and even muffin fans in general are Impedance protected and will survive a forever stall. There are transformers called "energy Limiting" which can survive an indefinite short.

Back in the day (Before the PC), computer fans died and stopped regularly. The guys that maintained the computers replaced the fans every so often. I'd retrieve the broken fans for personal use , take them apart and clean the bearings and back to the races,