Momentary switch circuit

This circuit turns on and off a monostable relay with a singol momentary switch. It is supplied with 12 Volt DC and uses a small 5 Volt relay. When the momentary switch is pressed the coil takes a voltage of about 2,5 Volts and the relay turns on once the switch is released.
When the button is pressed again the coil keeps on due to the hysteresis.

Timer switch circuit

Based on NE555 this timer switch circuit may be used to control an interior car light, by a manual and a door switch. By activating one of them the second transistor leads the output to the high level, then the led switches on.

Ladder logic traffic light

Ladder logic is an instruction standard used in automation technology. Basically a ladder diagram is a virtual relay logic circuit. Developed for industrial PLC ladder logic is also used on PIC microcontrollers.
Just for fun  I wrote a ladder diagram for a traffic light, and tested it on my S7 PLC.

Bistable relay

This circuit could be used to drive a monostable relay by a singol momentary switch. Powered by 24 Volts it works for a 12 Volts relay.

Led flasher circuit

This led flasher circuit works as a bidirectional shift register for a line of six led. Since the outputs of the CD4017 are connected to PNP transistors the led line takes the inverted signals from the outputs. In other words each led is ON when the related outputs of the CD4017 are OFF.

Earthquake alarm circuit schematic

Some time ago I built an earthquake detector which feels the small shaking of the primary wave and turns on a sound alarm. Basically it works fine, but sometimes failed due to a switching problem, so I had to modify the circuit schematic.

Led driver circuit

I discovered my passion for electronics when I was a kid, even though I 'm not an electronics engineer. Just for fun I made a led driver circuit based on 4017IC. A 555IC as astable multivibrator is used for the clock signal circuit.