alot yet to do! This is just the 'germ' of the idea but, as you probably can tell, it needs a printed circuit board (pcb) to mount the opamp and other components. The HE sensor is mounted on a board that will 'plug-in' (most likely solder) into the second pcb.

All I've done is designed you a ckt that will work but you need to build it and make it 'practical'. Right now it's a 'science-project'. But it will do what you wanted: something to show when the fans are 'on' and how fast they're turning.

The nice feature of this ckt is that you do not have to 'break-into' the fan wiring so it takes no power or disrupts the fan ckt. But you probably figured that out!

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Regards . . . . JimF
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'94 S500 Cpe

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