Every multimeter has a continuity tester. But what do you do when you don't have a multimeter or if it is broken and you want to test continuity of a circuit. That's right you make a continuity tester yourself. In this instructable you will learn how to make a cheap and easy continuity tester yourself.
Step 1: About the 555
This continuity tester is made from a 555 ic. I think before making this continuity tester you should first know the pinout of 555 ic. It is given in this step.
Step 2: Collecting the Materials
The material that you need to make this continuity tester is found easily. The things that you need to make this continuity tester are
39 ohms resistor
0.01 uf capacitor- 2 ( number 103)
Bc547 transistor (you can also use 2n2222 or 2n3904)
Some pieces of metal to act as probes
6v dc power supply (6v battery)
Step 3: Making It!!
Make the whole circuit on a perfboard or pcb and put it in a box. This circuit will detect low resistances and high resistances to produce a tone from the speaker. It will detect up to 200k and the circuit automatically turns off when the probes are not used. The schematic is given in this step. All comments are welcome. The schematic and info were taken from talkingelectronics.com