| 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. |
