Figure 1 – LED current monitor
The brightness is largely independent of the amount of current flowing.
The three diodes cause a voltage drop of about 2.1 V. The red LED needs about 1.6 V to be forward biased and lit up. If you are using another type of LED (such as yellow, which needs 1.8 V, or green, which needs 2.1 V), you may need to add one or two diodes to the circuit to the voltage drop.
In any case, remember that the dodes reduce the voltage that will be applied to the motor.
The diodes are 1N4002 for DC motors up to 1 A and 1N5404 to motors up to 3 A.
The circuit can also be used with other loads remembering that the voltage fall in the indicator must be considered.
