Do It Yourself Power Meter
Do It Yourself Power Meter
Find out how to make your own power meter to measure electricity consumption
electronics | education | energy efficiencyThere are now quite a few different
power meters available on the market offering the same main feature - the ability to measure directly the power used by any electrical appliance plugged into the mains. See our articles
Buy UK Power Meter,
Kill a Watt, and
EcoSavers Plug in Power Meter for more information on these products.
Such commercial power meters are available relatively cheaply and they work well, but it is also perfectly possible to put together your own
DIY power meter as a fun and educational project.
EnerJar
EnerJar is a plug-in energy monitoring device which can be put together following a set of open-source schematics available online free of charge, and it was the Grand Prize winner of the
Greener Gadgets design competition.
The
EnerJar uses an LED display to show the current power level, and a
PIC16F877a PIC microcontroller (see our article on
PICAXE microcontrollers for information on the PICAXE system - an excellent introduction to PIC programming). The
current (via 0.01R shunt resistor) and
voltage (via a voltage divider) is measured, and then
Ohm's Law (power = current x voltage) is used to calculate the
power and it is then displayed.
The original EnerJar design is for use with US 120 VAC mains electricity, however it can be used with 240 VAC (UK mains) by changing the value of one resistor.
EnerJar Safety and Support
The
EnerJar design as it stands is not particularly
safe since there is no isolation between the mains AC line and the low voltage circuitry. Using two power supplies, relays, hall effect sensors, and/or signal transformers resulted in increased complexity, cost, and a loss of sensitivity. For that reason, the designers of EnerJar (Matt Meshulam and Zach Dwiel) no longer support the
EnerJar project, but they are interested to hear from anybody who can improve upon their design making it safe and still simple.
More Information
For full details on
EnerJar including full hardware schematics and software code, click here to visit the official
EnerJar website. The hardware
Schematic is here.
Article Last Modified: 11:02, 7th Jan 2009Comment on this Article
If you have any comments on this article, please email them to
neil@reuk.co.uk.
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