Recommendation for a better sized potentiometer? (& W Ratings)

D

deadpool_

n00b
Joined
Jul 11, 2013
Messages
50
I recently downsized to a itx system & lost my physical fan controller. Speedfan/HWInfo allow for PWM control on this board's CPU fan header, but no control via SYS fan header. My H60 pump was running at full speed & a bit loud, so I looked into options. I chose a 300 ohm potentiometer I found on the shelf, wired in series +12V as a variable resistor. Proof of concept works, but the range of adjustment is very small. I can make +/- 500 RPM increments, which is adequate (full adjustment range is ~4500RPM), but can I do better with a different sized/style pot? I really like the PCB style, I'd like to leave it as small as possible. I don't mind sourcing online etc.

nP38x
http://imgur.com/a/nP38x

Also, is there any evidence to suggest this is unsafe? I'm not clear about wattage ratings of potentiometers & matching max wattage vs. observed. So long as it doesn't burn down the house or damage critical components; I'm not going to shed tears over the pump itself.

I couldn't find specs for the H60, but when I got home I plugged in some numbers for the similar looking Alphacool DC-LT. I found something that might be better suited(?) 50 Ohm, and 100 Ohm, both are linear & rated to 5W/500V. I don't fully understand the ratings, but the PCB style design seems plenty capable of transmitting 0.5A(?)

Thanks for clearing anything up. ITX has been an awesome case to build, cable management is so simple when you can flip your case upside down & reach all the nooks & crannies. I got lucky with Speedfan & can set up a profile for the radiator fans once I get PWM fans. I think I can set up an alert to monitor minimum pump speed as well. I'm still looking for a way to manually shut down the auxillary HDD, now it's the loudest component in the system. The next time I downsize I'm going for the NCase, it looks amazing.
 

Attachments

  • temp wiring diagram h60 potentiometer.jpg
    temp wiring diagram h60 potentiometer.jpg
    269.1 KB · Views: 54
Last edited:
deadpool_ said:
I recently downsized to a itx system & lost my physical fan controller. Speedfan/HWInfo allow for PWM control on this board's CPU fan header, but no control via SYS fan header. My H60 pump was running at full speed & a bit loud, so I looked into options. I chose a 300 ohm potentiometer I found on the shelf, wired in series +12V as a variable resistor. Proof of concept works, but the range of adjustment is very small. I can make +/- 500 RPM increments, which is adequate (full adjustment range is ~4500RPM), but can I do better with a different sized/style pot? I really like the PCB style, I'd like to leave it as small as possible. I don't mind sourcing online etc.

nP38x
http://imgur.com/a/nP38x

Also, is there any evidence to suggest this is unsafe? I'm not clear about wattage ratings of potentiometers & matching max wattage vs. observed. So long as it doesn't burn down the house or damage critical components; I'm not going to shed tears over the pump itself.

I couldn't find specs for the H60, but when I got home I plugged in some numbers for the similar looking Alphacool DC-LT. I found something that might be better suited(?) 50 Ohm, and 100 Ohm, both are linear & rated to 5W/500V. I don't fully understand the ratings, but the PCB style design seems plenty capable of transmitting 0.5A(?)

Thanks for clearing anything up. ITX has been an awesome case to build, cable management is so simple when you can flip your case upside down & reach all the nooks & crannies. I got lucky with Speedfan & can set up a profile for the radiator fans once I get PWM fans. I think I can set up an alert to monitor minimum pump speed as well. I'm still looking for a way to manually shut down the auxillary HDD, now it's the loudest component in the system. The next time I downsize I'm going for the NCase, it looks amazing.
Click to expand...
Potentiometers are supposed to be used with low current - signals and similar.
You could build a simple, transistor based voltage controller ( http://www.pcbheaven.com/circuitpages/Simple_Linear_Fan_Controller/ ) or use a rheostat. I used a similar design (no capacitors) and the transistor gets quite hot (it dissipates all the extra voltage as heat, so whatever the Vdrop x amps will be heat), I recomend using a heatsink on it.
 
You might want to approach this from a different angle. Since you can control that pump via PWM it might be a better idea to use PWM intead of undervolting the pump to adjust the speed. I'm not sure that it would damage the specific pump in your h60, but I'm not sure it wouldn't (and I KNOW adjusting the speed using PWM will NOT hurt it.)

If you want to build your own PWM signal generator you can, it wouldn't be too tough IMO (I'd use a simple micro-controller like an arduino) or you can buy something like this: temperature controlled or this: manual and be done with it.
 
Koween said:
I used a similar design (no capacitors) and the transistor gets quite hot (it dissipates all the extra voltage as heat, so whatever the Vdrop x amps will be heat), I recomend using a heatsink on it.
Click to expand...

Thanks, that's how I understood it too. The PCB style potentiometer is hot to the touch, but it's sitting near the ~50-60c board. I'll change it to a different solution for peace of mind. I found this 3W 25 Ohm rheostat at RadioShack which seems almost right, but capt_cope's PWM speed controller for $7 seems like the easiest solution.

capt_cope said:
You might want to approach this from a different angle. Since you can control that pump via PWM it might be a better idea to use PWM intead of undervolting the pump to adjust the speed. I'm not sure that it would damage the specific pump in your h60, but I'm not sure it wouldn't (and I KNOW adjusting the speed using PWM will NOT hurt it.)

If you want to build your own PWM signal generator you can, it wouldn't be too tough IMO (I'd use a simple micro-controller like an arduino) or you can buy something like this: temperature controlled or this: manual and be done with it.
Click to expand...

Thanks capt_cope, that sounds like the answer to me. Time to learn a bit more about PWM. $7 for a 2A fuse & 30W capability sounds like a bargain.
 
You must log in or register to reply here.
Back
Top