PROJECT BACKGROUND / ACKNOWLEDGMENTS:
A while back I was turned on to a very interesting video blog called the EEVBLOG (www.eevblog.com). The blog is created and run by an interesting Australian fellow by the name of Dave Jones. In one of his blogs he discussed a little side project of his - a simple constant current electronic load. In the episode he showcased his DIY Constant Current Dummy Load, episode #102 - http://youtu.be/8xX2SVcItOA
I quite enjoyed the simplicity of this little circuit and decided to build one myself. My design, which is roughly based on Dave's circuit, I had decided to beef it up a bit to handle about 4 amps. The name, Bogus Burden 4000 comes from a silly synonym of Dummy Load - the 4000 for 4 amps. I hope that is enough cheese for you!
The design is in the public domain. For this design I have tried to follow the Open Source Hardware protocols outlined by OSHWA (Open Source Hardware Association). (http://www.oshwa.org/) (http://freedomdefined.org/OSHW)
Please let me know if you have any questions: smilinvamp@gamil.com
PROJECT DESCRIPTION:
The Bogus Burden 4000 is an adjustable constant current dummy load that can help in the testing of power supply designs as well as power supply troubleshooting.
The circuit uses a feedback opamp circuit to monitor the output of your power supply. The opamp controls the switching of a MOSFET device to control the current drawn by the supply under test. I won't go into the details because Dave does a very good explaination of the circut's operation here: http://youtu.be/8xX2SVcItOA
The device is powered by a 12 volt wall transformer. There is a voltage (supply) input on the back. This is where you connect your supply under test. I have not implemented any sort of polarity protection, so be careful to connect your supply under test with the correct polarity. Also on the back is a range switch. With the switch in the HIGH position you should be able to adjust the constant current load from 0-4 amps. Keep in mind this is at 5 volts output from your supply under test. The constant current capabilities of the circuit are very much dependent on the output voltage of your supply under test.
NOTE: Before you email me a bunch of flame... I didn't design this to be perfect... I just wanted a constant known current. Which this circuit provides.
With the switch in LOW range, you can switch over to a milliamp range. Here you can get something like 0-1000 milliamps at 5V from your supply under test.
On the front panel, there is a current display. This display will give you Amps with the range switch in the HIGH position and milliamps with the range switch in the LOW position. Also, next to your panel meter is an adjustment pot. This pot is used to adjust the amount of constant current available to the supply under test.
And that is about it... fairly simple.
Now on with it.... click here to review my BUILD LOG for the BOGUS BURDEN 4000. Enjoy!
Questions can be emailed to me. Please limit your troubleshooting issues, I can't really account for user error. This circuit is give on an as is basis. It works for me, not sure why it maybe not work for you.
Thanks!
-Richard Galambos
(Technologist)
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