An astable 555 multivibrator circuit, where the timing characteristics are determined by the interplay of an inductor, resistor, ... Figure 1 An astable 555 timer circuit based on an inductor, diode, ...

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 ...

The circuit is an astable multivibrator with a 50% pulse duty cycle. The difference from the standard design of a 555 timer is the resistance between pins 6 and 7 of the IC composed of P1, P2, R2, D1 ...

For both of these purposes we can use the ubiquitous 555! For the clock we can use a simple 555 astable oscillator. The schematic below should produce a clock with a suitably variable range (from ...