Various toggle switches



1. Toggle switch with normal relay

This circuit features an on-off switch which can be operated with a single push button. Pressing the pushbutton once switches on the relay, pressing it another time switches off the relay. The pushbutton is debounced by the circuit.

2. Toggle switch with latched relay

Another version of a toggle switch, this one has the following interesting features:
- zero power consumption when button is not operated
- uses fewer components
- memory effect, will remember last position when power is disconnected

This circuit is operated with voltages between 10 and 15V. We make use of a bistable (or latched) relay, this is a relay that has two coils: one to activate and one to deactivate.
The 78L05 is important to produce a stable 5V. The circuit works as follows: when the pushbutton is operated, a current will flow shortly (until C1 is charged) through one of the relay coils. The relay is then in its other position and so the next time the button is operated, the current will flow through the other relay coil. Timing is an important factor in this (the time for C1 to charge must match the switching time of the relay), that's why the value of C1 is important and also a stable 5V.
Values of R2 and C1 are critical and are only valid if the relay is an Omron G6AK-274P. If another type of relay is used the values for R2/C1 probably must be different.

GND: ground
+12V: 12 volt power in
OUT: to consumer

Eagle schematic diagram Eagle PCB PDF file PCB
The finished device: Testing setup:
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