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Circuits designed by David Johnson,
P.E.
Last Updated on:
Monday, December 25, 2017 02:06 PM
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Control Circuits
Hour Meters
Testers |
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AC Current Controls Hour Meter
-- February 13, 2010
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| Many systems require
routine maintenance based on machine operation time. The circuit below is a
simple way to turn on a hour meter whenever AC power is supplied to the machine.
An inexpensive snap-on current transformer from Magnetics Inc, is used to detect
the AC current. |
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The output of the transformer is fed to a voltage doubler circuit. When 0.5 AC
Amps or more of current is flowing, the circuit generates sufficient voltage to turn
on the n-channel MOSFET. Once tuned on, the transistor routes voltage to the
hour meter. Some hour meters contain their own battery, so no external power is
needed.
In those cases, the transistor switch alone will turn
on the hour meter. |
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Magnetics Inc CR3110-3000
Current Transformer |
Hour
Meter |
Hour
Meter |
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Click on Drawing Below to view PDF version of Schematic |
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