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Circuits designed by David Johnson, P.E.
Last Updated on:
Saturday, December 23, 2017 03:21 PM
List of Dave's Circuit Designs
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More
AC-DC Power Supply
Testers |
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Energy Harvesting Using a Current
Transformer
-- January 17, 2010
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| Energy harvesting is all
the rage these days. With some modern electronics, information from low power
sensors can be sent to a distant data collection point using a low power RF
transmitter. To power these remote sensors, various energy sources can be tapped
into. Machine vibration, temperature differences, ambient light and stray RF
have all been used as low power energy sources. Sometimes, the sensors are
located near AC power cables. Rather than making a direct connection to those cables,
an AC current transformer, such as the one shown below, can be used to capture a bit
of power. |
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| The
CR3110-3000 current transformer is one example of a useful energy-harvesting device.
It is a fairly small device and can easily be snapped onto a thick cable. Its center
hole measures about 0.4 inches. It has a high turns ratio, so even with a low AC
current, the device can produce a useful voltage. The circuit shown below is an example of
converting the AC from these devices into DC. |
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Magnetics Inc CR3110-3000 Current
Transformer |
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| The
circuit is a classic voltage-doubler, using two efficient schottky diodes. With 1
Amp of AC current flowing through a single wire in the center of the transformer, a
voltage of 3v DC with an 86uA load can be produced. The circuit tracks a square law
function so with 2 Amps of current through the center wire, 360uA of DC current can be
generated. With 4 Amps nearly 800uA of DC current can be collected. To
increase the power collected you can also wrap more than one turn through the center hole.
Although the part is small there is room enough for 3 turns around a heavy 10 gage
insulated wire as the photograph shows. |
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Click
on Drawing Below to view PDF version of Schematic |
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