RPM counter

[G8RPI]

Hi see my eariler post,

http://www.picbasic.co.uk/forum/show...58&postcount=6

for some example code.

[Luciano]

Hi,

A simple way to read fan RPM:

A 3-wire fan has a tach output, which usually outputs 1, 2, or 4 tach
pulses per revolution, depending on the fan model.

With the PicBasic "COUNT" you can count the pulses on the
tach output and with simple math calculate the fan speed.


Luciano

[Charles Linquis]

Additional information:

Fan tachs are open-collector. You have to pull them up to 5V or you won't see any signal. I recommend values from 4.7K - 10K.
Also, fans produce 2 pulses/revolution which means that a 3600 RPM fan will have a 120Hz signal on the tach line.
Don't plan on the duty cycle being exactly 50%.

[RUBiksCUbe]

Im using a case fan instead of a processor fan so it dosent have a tach line. I was going to use a processor fan but it wasnt big enough for my project. I basically just need the motor inside the fan, but I need to know how fast it is running at 9v before I can use it. I was looking around and I just found the COUNT command which should work perfectally.