An LED tester soldering kit

Project infographic · PDF

An ideal constant current driver supplies a specific amount of current regardless of supply voltage and other environmental conditions, like temperature. The LIGEMDIO's simple circuit does this reasonably well using only two NPN bipolar transistors and two resistors. It allows the driving and testing of many types of LEDs, through-hole and surface mount.

The name LIGEMDIO is made of the first letters of Light Emitting Diode, LED.

The circuit

The circuit relies primarily on the near constant voltage drop between the base (B) and emitter (E) of transistor T2 to keep the voltage across R1 also 'constant'. In turn this keeps the current for the LED 'constant'.


Here is a list of components that come with the kit

Refer to the infographic for further circuit and assembly information.

Further information

LIGEMDIO is an open source design, as is most of our work. You can find the design files for the hardware and packaging at our GitHub repository. You can edit the design files using our own PCB design open source software, PCBmodE.

LIGEMDIO project was Project #8 of the Boldport Club. If you'd like to purchase a kit, become a member and add one to your order through the shop.

The board was manufactured by Eurocircuit.

A full gallery of the kit is here. The remarkable photos were taken by Erbsland Art, @ErbslandArt.