Toggle to Momentary Switch Using 555 Monostable

Toggle to Momentary Switch 555 timer Monostable

This is a toggle switch to momentary (latch to push button) switch converter. Most of the time we need a momentary to toggle switch. But sometimes we need to convert some latch signal to momentary signal. This article from Globalspec about Toggle Switches can tell you more about momentary states if you need more information.

The following circuit base is on 555 timer IC and it uses monostable mode.

Toggle to Momentary Switch circuit diagram - 555 timer as Monostable


Parts List
C1 0.1µF Ceramic
C2 10µF 25V Electrolytic
C3 0.1µF Ceramic
C4 10µF 25V Electrolytic
C5 0.1µF Ceramic
R1 47k?
R2 47k?
R3 10k?
R4 1k?
D1 1N4148
D2 1N4148
Q1 2N3904
RL1 Relay (voltage same as supply voltage)
IC1 555 Timer IC

The Monostable 555 Timer circuit triggers when negative pulse applied to pin 2.This negative pulse need to go down 1/3Vcc. Once triggered, the 555 Monostable will remain pin 3 output on until the time period (T) set up by the R1 × C2 network has elapsed.

T= 1.1 ×R1 × C2

T in seconds, R in ? and C in Farads

T=1.1 × (47× 1000) × (10/1000000)

=0.517 ? 0.5 seconds

555 timer ic Functional Block Diagram

When the switch is closed C3 capacitor will charge through the SW1 and R2, Because the voltage at pin 2 move below 1/3Vcc. Then 555 triggers and start timing cycle. The output at pin 3 immediately moves up to near the supply voltage and remains at that level until the C2 timing capacitor charges to about 2/3 of the supply voltage. When the switch is open, the C3 capacitor discharges through the R2 and R3 resistors. The D1 across the R2 prevents the voltage at pin 2 from rising above the supply voltage when the capacitor discharges.

Update: Toggle to Momentary Switch Youtube Video

Toggle to Momentary Switch Latch to push button converter on off switch to momentary

Update 2: Toggle to momentary switch PCB

Toggle to Momentary Switch Printed Circuit Board PCB Layout Toggle to Momentary Switch PCB Copper tracks with Drilling Holes Latch to Push button Switch PCB Component Side


Latch to push button PCB Toggle to momentary PCB Toggle to momentary Switch Soldering Toggle to momentary PCB design

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