|
DiscoverCircuits.com -- Hobby Corner
Last Updated on:
Tuesday, November 29, 2011 08:14 PM
Hobby Circuits'
Category List
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
Latch Circuits
Light Flasher Circuits
Relay Circuits |
|
Universal Flasher Circuit Using
a Latching Relay
designed David Johnson, P.E. |
| Latching relays are
nifty devices. Most contain two separate coils. When a voltage is
applied to one coil the relay latches in one state and stays in that state until
voltage is applied to the unlatch coil. Since the latching and unlatching
pulses only need to last about 25 milliseconds, it is possible to control a
sizeable amount of power using little energy. |
|
|
There are many applications where you would like something to be cycled on and off.
Perhaps you want to flash an advertising sign on and off or maybe you want to flash
some Christmas trees lights. This kind of flashing need is a perfect application
for a latching relay. The hobby circuit below controls a latching relay from a
simple 9v battery. The time between flashes can be adjusted from 0.25 seconds to
5 seconds. |
|
The electronic circuit is powered by a 9v battery.
It uses a single 74C14 (CD40106) CMOS hex Schmitt trigger inverter logic IC.
One inverter is configured as a square wave generating oscillator. I
included a 1M variable resistor in the oscillator circuit so the frequency could
be adjusted from about 0.1Hz to about 2Hz. Other on/off times can also be
achieved by changing the value of C2.
The
output of the oscillator is split into two 25ms pulse generator circuits.
One circuit pulses the latch relay coil, when the oscillator output swings from
zero volts to +9v, while the other circuit generates a pulse for the unlatch coil,
when the oscillator output swings from +9v to zero volts. Two n-channel FETs
drive the two different coils. The relay selected is rated for 10 amps of
current. This should be heavy enough for most flashing applications.
The relay contacts are wired into the device to be flashed on and off. The
contacts can handle AC or DC loads. |
|
|
|
|
Click on Drawing Below to view PDF version of Schematic |
|
 |
|
|
More
Latch Circuits Light Flasher
Circuits Relay Circuits
Hobby Circuits'
Category List
eMail David A.
Johnson, P.E. about this circuit |
