The Spark Gap Podcast - Episode 14

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Show Synopsis

Karl and Corey discuss the operation of an Adjustable Constant Current Dummy Load.

Note about today’s episode:

Corey and I were trying something different with this episode.
I am not sure how clear the information will actually come across.
It is pretty hard to describe a circuit’s operation just using audio.

Please let us know if you learned something or if this came across as a jumbled mess.
Also, please feel free to ask questions.

Dummy Load Schematic for today’s episode

I tried to create a shareable online simulation of this circuit.
I tried all of the online tools I could find. They were all a disaster except for CircuitLab.
CircuitLab does not have a free version, so I could not save and share the simulation.

Next best thing is a simple schematic of the circuit.
Thank you Upverter for having a free, useable version.

Dummy Load by thesparkgap aaa02f52f24ded2e - Upverter

You could simplify the circuit further by using one voltage source to power both the OpAmp and set the requested current.

I did not want to do that because you typically need to power the OpAmp with a higher voltage then the voltage you use to set the current.
The reason for that is noted on the schematic, but I’ll repeat it here for clarity:  You need to make sure the OpAmp has the ability to drive it’s output high enough to turn on the FET.

Note: You could always swap out that potentiometer for a DAC. That way you could control the amount of current using a microcontroller.

It spawned numerous copies and iterations of the design Dave presented.

The original design:

Hackaday article about the original design:

EEVblog Inspired Dummy Load #1:

EEVblog Inspired Dummy Load #2:

Re:load is a nice simple Adjustable Dummy Load

Original version:

Slightly updated version:

Fancy version:

There are a million more of these on the web, but here are a couple good ones:

I don’t care for instructables normally but this one is pretty dood:

Best name ever? Nice, simple design though.