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...
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.