Build a Logic Probe

In building a probe, I built a simple circuit using a breadboard, an LED, and a couple resistors. The LED, when giving a power supply, lights up when the probe is connected to the positive source, and turns off when unplug.

In the next step I added a third resistor and when power is supplied the LED is at its brightest. When the LED is open it is dim and when closed it is the LED is off.

In the final parts I constructed the bread board simple circuit onto a circuit board, and also made a serial connector. Basically transferred all components onto a circuit board, and soldered each point along with two alligator clips. I also soldered three wires to the serial connector each wire is about 2 feet in length.