Uctronics POE HAT fan speed control

Support Product Questions
1

Hi, I recently purchased this rack mount for Pi4B with POE hats. All works well but POE HAT fans are quite loud. Is there any way to control the speed of these fans?

2

Hi Peter,

Welcome to the forum! I’ve managed to find a bit of info for those boards and their PoE HATs. These fans are only operating off a DC voltage and ground so as is there isn’t a way to control the fan speed and you may lose functionality elsewhere trying to change that.

3

Thanks Jack, I’ll have a play and see what can be done.

4

Quick update: I placed a 33 ohm resister in series with the fan which drops the fan voltage to about 3.8v and the fans are considerably more quiet whilst still providing plenty of airflow. The fans reliable kick start from about 3.6v so that should be fine.

5

Hi Peter

Are you sure about that. Personally I would keep an eye on it.
There might be some headroom for cooling but reading between the lines on Forum posts I think that some of these RPi devices can run quite hot and I don’t think the good people at RPi would tend to provide lots of excess air if it is not needed.

I just noted the actual rack mount is a Core product but I would guess the Hats are RPi. If you are not stressing the Pis much you might have enough cooling but keep an open mind on this problem.
Cheers Bob

6

Nah, it’s not a RPi HAT, they can be controlled with PWM. This HAT is branded Uctronics, same as the whole rack mount.

The need for cooling fans depends on the Pi load but in my case I measured the temp (using vcgencmd measure_temp): without the fan it runs around 55 degrees, with the fan on full speed, about 35, with the fan speed limited by the resister, about 41.

To be honest, the fans not needed at all in this case.

7

Hi Peter.
Sounds like you have quite a bit of wriggle room as long as you don’t stress your Pi(s) too hard. A lot depends on the air circulation in the final installation. If you have several devices running you will get some mutual heating but provided your ventilation is adequate you should be fine.
Cheers Bob

8

Hi Peter,

It seems like your doing pretty well as is. The recommended operating temp for that Raspberry Pi board is 0-70 degrees Celsius so you are well within that.

POE hats are generally designed with a high load server environment in mind so you seem to be well within the clear as long as you keep an eye on the temps if the load demand increases.