An astable 555 multivibrator circuit, where the timing characteristics are determined by the interplay of an inductor, resistor, and diode.

Let’s Look at the Schematic In a PWM circuit, the 555 timer will output a logic signal “high” and “low” depending on a ratio derived by the value of a few components connected.

Whenever I use the 555 timer, it seems that the output polarity is invariably incorrect, and the way the 555 functions, it normally cannot generate a duty cycle of less than 50% — 90% yes, 10% NO!

The 555 timer is a versatile integrated circuit (IC) that can control timing in electronic circuits. It's one of the most widely used ICs due to its reliability and flexibility.

Each of the candle lighting circuits, however, use a 555 timer both for its intended purpose of providing a timed power-on reset pulse, and another 555 is used as a simple flip-flop.

When it comes to the venerable 555 timer, Paul Rako agrees with Bob Pease—avoid using it if your application demands any kind of precision.

[FightCube] wrote in recommending a very helpful piece of circuit simulation software for those of you still constructing entries for the 555 design contest. LTSpiceIV, available from Linear Tech… ...