Toggle on off

This simple circuit is supposed to toggle on and off a led light with a single button. At the start condition the led light is off; at the node 2 of the circuit the signal is high.

Car electric window circuit

This basic circuit may be useful to control a car electric window. The electric motor is controlled by two relays.

Security alarm

This security alarm  works by NE555 timer and logic gates. When the ON-OFF selector is open the input pins of the  IC2 timer take the low level from the Q11 collector. The security alarm does not work because the IC2 output is high, so the Q12 collector keeps down the Q3-Q4 transistors.

The CD4017 counter

The CD4017 counter is an integrated circuit that switches on ten outputs one at a time, due to a clock signal on the input pin 14.   The input pin 13 enables the clock signal, while the input pin 15 is supposed to reset the output condition.