4 Channel Electronic DC Load Project

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This is a backlog entry for my 4 channel electronic DC load project build which started on 26th December 2012 and completed on 27th May 2015. This build is the 3rd iteration of electronic load I've build so far.

Completed 4ch dc load

My 1st load (right) can do up to 1.5Amperes n the 2nd version (left) up to 2.2Amperes. They are based off the design of Dave Jones from EEVblog.

Mk1 mk2 load

My main motivation for this project was to test the PicoPSU at its maximum ratings. A standard ATX spec power supply has 3 voltage rails (3.3v, 5v, 12v) and I require a load that can sink at least 5Amperes simultaneously on all the voltage rails.

Block Diagram

The block diagram shows the individual part and section of the overall electronic load system.

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I' used 4x IRFP240 N ch mosfets. One of these can safely dissipate 150w of heat @ 25°c (but still take note of its derating factor.)
Each of them are isolated and mounted to a large heastsink I purchased from Kaichin shop in Sim Lim Tower. The heatsink height is ideal with 40mm fans for active cooling. The case I used was from a 19" rack-mounted industrial PLC equipment.

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Initially, as a proof of concept, potentio meters were used to manually set the sinking current for each channels.

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Next step was to add an LCD display to display the voltage, current, wattage and set value on each channel.

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Followed by a keypad to enter the menu system and set each channel parameters.

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I used Eagle Cadsoft to create a 1 to 1 scale template of the front panel dimension and mounting holes.

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Completed and fully assembled

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Shot of it in action on my workbench.






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