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Low Speed Relay

Andreb6

Dec 21, 2016
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Dec 21, 2016
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Hi , I need to make a safety circuit using a relay to cut the 220vac when one of 2 or 3(running simultaneously) PC cooler fans, get low RPM or stop rotation, using the tachometer wire.Any Idea?
 

cjdelphi

Oct 26, 2011
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Oct 26, 2011
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So you need a micro controller or frequency( or whatever it's outputting) to voltage converter, i have no clue what that pin outputs voltage wise?

Then use a single transistor to energize or cut power to the relay
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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25,510
One obvious thing you'll also need is a method to override it for a short period of time. Without this you can't turn the PC on.

It could be as tricky as having the microcontroller turn power on, control the power on signal from the power supply, and wait some time for the fans to come up to speed.

Or it could be as simple as a momentary contact switch across the relay contacts.
 

cjdelphi

Oct 26, 2011
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What if you rectified the pwm to a dc voltage and a drain resistor?

When the pwm is cut, the cap will discharge
 
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