AC instrument fan failure

[vimalkhanna]

AC fan in my modem/concentrator heats up and slows down to stop .This causes my thermal drift and shutdown without info.
need to have alarm LED indication when the speed of fan lowers to 80% of full RPM /CFM of air delivery .

 

[kak111]

Solution 1:

Put a small reflector in blower blade, take out pulsetrain with reflective IR-sensor
and connect pulses to missing pulse detector circuit ( look picture )

Steady Output - Missing Pulse Detectors - Two Comparators

**broken link removed**

Solution 2.

Make very lightweight air-flow resistant pendulum and check the pendulum
position in air-flow with IR-sensor (reflective or gap ).

Regards KAK

 

[chuckey]

Lubricate the fan or replace it.
Frank

 

[vimalkhanna]

Solution 1:

Put a small reflector in blower blade, take out pulsetrain with reflective IR-sensor
and connect pulses to missing pulse detector circuit ( look picture )

Steady Output - Missing Pulse Detectors - Two Comparators

**broken link removed**

Solution 2.

Make very lightweight air-flow resistant pendulum and check the pendulum
position in air-flow with IR-sensor (reflective or gap ).

Regards KAK

________________________________________________________
Thanks for the reply.I had executed the same earlier with the following problems .:
a)When speed of fan goes lower ,ie low CFM delivery ,the IR detector stilll gives pulses which infor that it is running .
b)The derating has already started and the time taken for changeover action of an alternate concentrator gives data loss .
c)The hub temp. has started rising with heatsink airflow lowering .Thermal inertia settles in.
d)The pendulum method seems more fruitful as this may solve my query.
e)However , Mass and built in fans need to have swivel jewels with hairspring balancing torque .This is very subjective phenomena.
Let me attempt the same and emperically confirm acceptability.
d)