tacho for comp fan

[Neil Williams]

how would a bar graph be conected to a tacho wire in order for it to show
the approx. speed of the fan when used in conjunction with a fan speed
controller

 

[cpemma]

Neil Williams wrote:

how would a bar graph be conected to a tacho wire in order for it to
show the approx. speed of the fan when used in conjunction with a fan
speed controller

Via a digital-to-analogue converter and an LM3914, it's 2 pulses per rev
(RPM/30 Hz). Note the fan sensor output is generally open-collector, so
you'll need a pull-up resistor.

LM2917 is a suitable DAC, but it's far easier just to get a bargraph of the
fan voltage. My cpu fan RPM is damn near linear with voltage between 7.5v
and 12v, though it's y=mx+c, not y=mx.