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An LED tester soldering kit

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.

LIGEMDIO was project #8 of the Boldport Club.

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What’s included?

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'.


Refer to the infographic for further circuit and assembly information.

Project assembly infographic · PDF

Additional information