Variable / Programmable Load – Get your kits now!

Posted by on October 12, 2012

Thanks to Jameco one of my projects is currently being offered as a kit at their great site. It was also featured at their home-page!

About the kit:

The circuit is a variable load with the possibility of using an external voltage to control the load. There’s a lot of flexibility in the design, you can actually use the spare OpAmp (which has a break-out) to suit your own needs. Being able to use an external voltage means you can easily control the load with a third-party circuit, for instance you could have a micro-controller providing step functions, pulses, etc.

This means you can test power supplies and other circuits with ease and flexibility.

In technical terms…

The circuit is actually a current sink and it’s comprised of an error amplifier implemented through a single OpAmp. The shunt is on the low side and we simply use a MOSFET as the current pass device.

You could also turn the kit into a current source to charge up cells and batteries or to measure small resistances (milli-ohms). But the main focus is on having a variable load for your projects.

Being able to make kits that actually explain you why and how things work is a lot harder than I would’ve thought, but hopefully I’ll get better at explaining things as I work on new and exciting kits.


I must thank those who sent me their input with regard to the kit and pointed out the grey areas as well as the mistakes on the PCB / instructions. I really appreciate it!

A note on receiving extra components: Jameco already has pre-packaged bundles and it turns out it’s cheaper to send out 10x resistors in cases where only 1 or 2 are required, so don’t worry if you end up with a lot of spare “nuts and bolts”!.


 In case you missed it, click here to view the kit.


To wrap it up, I encourage you to start publishing your projects as kits at the Jameco site, so others can learn from your circuits and everyone can benefit.

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