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DiscoverCircuits.com -- Hobby Corner
"Hobby Circuits for your
Hobby Projects"
Last Updated on:
06/19/2009 03:02:07 PM
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Title
Aug 3, 2008
designed by David A. Johnson, P.E. |
Isolated Power Supply for Digital Panel Meters --
September 13, 2008
Many inexpensive digital
panel meters, such as the one shown below, are designed to operate from a 9v
battery. However, the nature of the panel meter internal design often requires
that the DC supply used to power the device be isolated from the ground terminal of
the panel meter’s input. This often makes it difficult to use with a common
connection between a DC power supply ground and a sensor’s circuit ground.
But, you can generate this floating voltage fairly easily using the simple circuit
below. |
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The circuit below is powered from a 12v to 15v supply and generates a
100KHz square wave signal, using a CMOS version of the 555 timer. This AC
voltage is rectified and limited to +9v using a charge pump method. The two
0.01uF capacitors maintain a floating voltage for the panel meter, so its voltmeter
ground input can also be connected to the DC power supply ground. |
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Schematic below to view PDF version of this Circuit |
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