This circuit can be used to test up to three LEDs at once, connected in series. You can easily increase that number by using a higher supply voltage. If you do so, you should allow 2.7 V for each ...

3V is sufficient to turn on any LED, but is within its reverse break down voltage rating (that is why I did not use the common 9V battery). Short circuit current is approx. 30mA. I used a 3V lithium ...

The simple Diode and LED Tester presented here costs under £5 to build (including all components, the battery and a cheap case) and will indicate the polarity of almost all types of LED and other ...

Snap-on’s Digital Display Circuit Tester (EECT400) is designed to detect voltage, ground and circuit integrity. An LCD display provides the circuit’s voltage value, while a backlit LED indicates red ...