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Circuits designed by David Johnson, P.E.
Last Updated on:
Friday, March 23, 2012 08:46 AM
Master Category List -
Dave's Circuits
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Latch
Circuits
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- Low Voltage
Latching Relay Driver
Using some small super capacitors, this circuit can latch and unlatch a
mechanical relay with 10 amp contacts, from a small 3 volt power source.
By using a latching relay, power can be controlled to a load with a tiny
battery. (added 7/06)
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- On/Off
Switch with Latching Relay
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.
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On/Off Latch
Circuit Update
Often you want to turn on and off power to a device with a single pushbutton switch.
The circuit below performs this logic function with just a few tiny parts and can
operate from DC supplies between +2v and 5v. It uses two inverters within a 6 pin
SN74LVC2G14 device from Texas Instruments. Each press of the button toggles
between the two on/off logic states. The logic output is connected to a PMV65XP
p-channel FET from Philips. This component should be able to handle 2 amps of current.
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- PUSHBUTTON ONESHOT AND
LATCH
This circuit uses a single IC to convert a noisy pushbutton switch signal into a clean
pulse or a sustained push on-push off signal. It can operate from 3v to 18v.
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Ultra Low Power Latching Relay Circuit
The circuit below takes advantage of some inexpensive small super capacitors. The
circuit pumps 6 volt pulses into the separate 5 volt latching and unlatching relay
coils. A short 25ms pulse is all that is needed to flip the relay states. A
third super capacitor is used to supply a higher peak current than a small lithium cell
might otherwise be able to supply.
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Ultra Low Power Latching Relay Circuit
The circuit below takes advantage of some inexpensive small super capacitors. The
circuit pumps 6 volt pulses into the separate 5 volt latching and unlatching relay
coils. A short 25ms pulse is all that is needed to flip the relay states. A
third super capacitor is used to supply a higher peak current than a small lithium cell
might otherwise be able to supply.
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- Universal
Flasher using Latching Relay
This circuit is powered by a 9v battery and controls any AC to DC load through a set of
relay contacts, rated at 10 amps. To conserve power, the circuit uses a latching
relay. A variable frequency oscillator controls the flashing speed from 0.2Hz to
2Hz. A pair of pulse generators first latch the contacts closed then unlatches
them open. The power consumption is so low that a 9v battery will last for several
months.
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Latch Circuits
Master Category List - Dave's Circuits |
