| 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. |
