cancel
Showing results for 
Search instead for 
Did you mean: 

Do I need to use a Freq to Voltage converter for a tacho signal from 4 wire fan?

SHamm.2
Associate

Hi all,

I am using a 4-wire fan supplied by 24V. I was wondering if the tacho output from the fan needs an external timer or a Freq to voltage converter; or can I just use a pull up resistor and connect the tacho signal straight to the input of STM32 using one of its internal Timer.

I appreciate your help!

Regards,

Sabrine

1 REPLY 1
Cristiana SCARAMEL
ST Employee

Hello @SHamm.2​,

the first suggestion is to check the specifications of the tacho signal on the fan datasheet (output type, pulses per revolution).

If it is a open-drain (open-collector) output a pull-up resistor to supply motor voltage is needed. Then by adding a voltage divider you can get the appropriately shifted signal than can be connected to the STM32 GPIO.

I hope this post can help you; if so, consider to mark it as best answer by clicking the label "Select as Best".