|
 |
Circuits designed by David Johnson,
P.E.
Last Updated on:
Saturday, December 23, 2017 03:21 PM
Master Category List - Dave's Circuits
The contents &
graphics of Discovercircuits.com are copyright protected.
LINKING to Dave's circuits is permitted but DO NOT COPY any files to your WEB
SITE server |
|
|
|
|
More
Driver Circuits, Switches,
Latching Circuits, Relays |
|
ON/OFF SWITCH WITH LATCHING
RELAY (December 24, 2009) |
The circuit below switches AC or DC power to a load using an ultra low power 3v
latching relay with two coils. The relay can handle about 10 Amps of
current, up to 250vac. Each time the small pushbutton is pressed, the
circuit either latches the relay contacts closed or unlatch them open. The
3v powered circuit uses a single 74HC14. This device contains six Schmitt trigger
inverters in the one 14 pin package. Two inverters form a flip/flop circuit.
Each time the pushbutton is pressed, the circuit changes state and stays in that
state until the button is pressed again. With each state change, a 25ms
latching or unlatching pulse is produced and is routed to the correct relay coil.
The coil resistance is about 45 ohms so about 70ma of current is drawn from the 3v
battery for each relay pulse. The average power is so low that the circuit
can operate for many years on one set of batteries. I would suggest using
two AA or AAA alkaline cells. |
|
|
|
|
Click on Drawing Below to view PDF version of Schematic |
|
 |
|
|
|
|
|
|
