Wiparat Circuit Electronics

This is a touch control switch which keeps the circuit on about 100 seconds after touching the plate connected to the 2 numbered pin. At the end of this time duration, relay releases and the circuit gets to off position.
The impedance of the trigger input of the 555 timer IC is very high and the [...]

This circuit gives a burst of pulses to fire 2 SCRs, when pin 4 is taken to 12V the SCR is turned on, to use this circuit you need 12V short pulses phase shifted with respect to AC sine wave on bridge.
This way you can control the bridge from near 0% to near 100% ON, [...]

This 555 timer based PWM controller features almost 0..100% pulse width regulation using R1, while keeping the oscillator frequency relatively stable. The frequency is dependent on values of R1 and C1, values shown will give a frequency range from about 170 to 200 Hz. Any 555 chip will do, CMOS is fine as well. Diodes [...]