Measureing Fan Tacho Signal

[SparkyChris1976]

Hi All,

I want to control the speed of a fan by measuring the tacho signal in the feedbac loop.
I am using a micro-controller to implement the circuit, and plan to use the micro's timers to 'time'
the tacho signal and calculate the speed.

My question is, is it ok to just stuff the tacho signal into the micro or should I apply any kind of filtering?
Bear in ind I probably need clean sharp edges for the timers to catch the edges realiably.

Any thoughts appriciated.


Chris

 

[HTA]

Hi Chris,

what kind of tacho signal you get from the fan motor? Usually the fan datasheet tells you how to interface to the micro. If it is an open collector output you need a pull-up on the micro input. If you have long lines to the micro for the tacho signal you might need a buffer. For interfacing the micro to the outside world you might find this application useful: https://ichaus.biz/mcu_interface .

Enjoy your design work!

 

[SparkyChris1976]

Hi Chris,

what kind of tacho signal you get from the fan motor? Usually the fan datasheet tells you how to interface to the micro. If it is an open collector output you need a pull-up on the micro input. If you have long lines to the micro for the tacho signal you might need a buffer. For interfacing the micro to the outside world you might find this application useful: https://ichaus.biz/mcu_interface .
Enjoy your design work!

Thanks HTA,

I have not decided on a particular fan just yet. That would be good if the fan data sheet gives some info on how to interface to the tachometer. At this point I was just wondering if tachometers bring any noise issues with them, that I should be aware of.

Thanks for the link, that's really useful.

Cheers,
Chris