- on Computer/Software/Internet
- Published in issue 1/2011 on page 68
Three Out of Two Ain’t Bad
Add a tachometer output to 2-wire fans
If you replace a broken three-wire fan in a PC or other device with a more readily-available two-wire fan, the missing tachometer (‘tacho’), signal will cause the system to report a fault and possibly even refuse to function at all. The problem is solved with the circuit shown here, which analyses the fan current to generate a signal that corresponds to its rotation speed.