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A low cost low voltage power monitor

A low cost low voltage power monitor

A low cost low voltage power monitor

(OP)
On another thread here was a high speed 50,000 rpm motor and driver from the hobby world. That got me
thinking there are probably lots more things in the hobby world that are comparatively low priced compared
to the industrial world.

One device I have been useing is the TURNIGY 130A Watt Meter and Power Analyzer for about $30 shipped from
Hobby King onlinw. The device is rated up to 60V DC and 130A peak. The two line lighted LCD displays the
the voltage and amperage to two decimal places and wattage to one decimil place. A sequencing fourth number
indicateswatt hours, V max and min, peak amps, amp hours, and peak watts. This device was given to me because
the 2937H 3.3V regulator failed (left cornerSMD) and the boards folded open in the picture. Current sensing is
in the negative leg with a better than expected current shunt and only senses current flow in one direction.
On message boards there are numerous reports of these solder connections melting with high continuous currents.
The wires are very flexible #12 with a silicone jacket. Passing current through the red positive lead should be
avoided since this will only cause additional IR loss and bring more heat into the case. The two pots allow
calibration of the volt and amp display. That may make it possible to divert some current to an external shunt
for higher currents. The three pin connector on the side allows external power to keep the electronics alive
and external reset. Diodes isolate external and line power. Top to bottom, common, power, reset to ground.

As said before, the maximum voltage is 60V, the rating of the regulator. I recommend that this device be
disconnected from internal power and always be powered externally if measuring higher voltages. On the back side
of the board there is a single perpendicular trace that can be cut to isolate power from the red sense wire.
That may also allow higher voltages to be monitored. This low cost device is pretty handy for solar panel and
battery monitoring.

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