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Last Updated on: Tuesday, June 01, 2021 03:06 PM

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More  Indicator Circuits

Moving Air Indicator Circuit
designed by David Johnson, P.E.

Many months ago a Discover Circuits reader wanted a method to indicate when a fan was blowing air.  He didn't want to route any electrical wires to a sensor near the fan.  Instead he wanted all the electronics for both the fan and other circuits mounted some distance away from the fan. 

I scratched my head a bit and came up with the simple solution shown below.  I found an inexpensive sensitive pressure switch, which when a piece of plastic tubing was attached, could detect when the fan was blowing air. 

As shown below, the open end of the tubing was positioned in front of the fan.  The small pressure produced by the air blown into the tube was enough to activate the switch.  In theory, the switch could be positioned perhaps 10 or 20 feet from the fan.

Click on Circuit Below to view PDF of Schematic

Moving Air Monitor, David Johnson, Aug 16, 2006

More  Indicator Circuits

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