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Homemade Radio Electronics
Variable Power Resistor Load

what is this good for : to test small power supplies like a BEC for model hobby
This is the most simple and most easy to do homemade project I can come up with, and at the same time the most usefull

I used a 24 position hi current rotary switch, a make before brake type is best
For this single knop type load. I used 0.47 and 1.0 ohm resistors 3Watt wirewound.
This load handle a range 0-14.7 ohm
at 5V supply this give a load from 340mA to 12A
offcourse the user must know ohms law and be sure the power rating of the resistors is not exceeded too much !!

Example: at 5V supply, the 1.8 ohm setting gives 5/1.8 = 2.77 A
The total power is 13.8 Watt, and since 5 resistors are a part of this load
13.8/5 = 2.76 Watt pr resistor, so they are within specificated power level.

it is quite simple, just glue to the alu plate for good cooling, and solder them all in series

The dual know model shown here, uses several different resistors
like left knob go from 0-90 ohm, in 2.2 ohm and 4.7 ohm and last 6.8 ohm steps
the right knob go from 0-47 ohm, in 6.8 ohm and 15 ohm and last 47 ohm steps.

http://www.vimeo.com/10593709 video clip of power load in action

Thanks to OZ7AKT for the donation of resistors and switches for this project.

April 2010 OZ2CPU