FIRST DRAFT: Programmable dummy load

in Prototypes by DP | 4 comments


This is a programmable current sink, usually used to simulate  different current loads for power supplies. We have always wanted to build one, but we’ve stalled several times. This design is based on the simple analog load posted by Bearmos. It’s not intended to be a final project, it’s just an experimental prototype to see what might go into an eventual project.

We’re using an MCP4725 I2C 12bit digital to analog converter to set the current instead of a pot. Everything is controlled via the USB capable PIC18F2550 microcontroller, The relevant data is displayed on a 2X16 character HD44780 LCD. The UART interface is also available for datalogging and debugging. You can check out the schematic below.

This is only a initial test version, as we plan to develop this project more. If you have any suggestions, tips, or questions please head for the forum.

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  1. megabug says:

    Wow very nice! I am thinking of buildung this a long time… but never had the time… if you need someone to help testing and have a spare pcb… ;) dibs!

  2. Kaz says:

    Would it not be able to upload load profiles? so a simple table with load data – with simple “goto” profiles?

    so example

    1. After 5 minutes set load to 1a
    2. After 15 min set load to 1.5a
    3. After 20 sec set load to 0.5a
    4 After 30 sec set load to 1a
    5. Repeat from step 3 25 times
    6. Goto Step 2

    And finally a “cutoff” voltage (great for battery discharging)
    Set Min V = 8 volt.

  3. Rubi says:


    I love this project.
    What I miss on my current sink is the possibility of temp control.
    It would be way much easier to put an ntc on the dut and watch the temp on the lcd display, instead of using an extra device for temp control.


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