Hello,

I have build this circuit that I got from the greatscott youtube channel.



This circuit latches a relais when a momentary push button is pressed. This circuit works for my application however I have one issue with this circuit. When power is applied to the circuit, sometimes the relais turns on and latches. I understand why it does this but I would like to change this since this is undesired for my application.

Anyone know how I can modify this circuit so when power is aplied that the relais does not turn on and latch on it's own? If there are better latch circuits which also use 1 momentary switch please do tell me, I have tested alot of circuits already without alot of succes.

BR

Tim

 

Welcome to AAC!
You could try adding a low value capacitor from Q2 base to ground; also a high value resistor across C1.

 

Just delete the following components:



And latch the relay with its own contact, as shown:

 

Just delete the following components:

It is also designed to shut off the relay with a second brief press of the switch.

 

A capacitor (e.g. 100nF) across R1 should also keep it off when powering up.

 

I just tested the circuit with the 100nf cap across R1 cruts mentioned and it works fine as expected.
However I did find the OFF press works better with C1 at 47uf up to12 volts Vcc as it is dependent on the supply.

 

For your interest, here's the simulation of a similar circuit that uses only one NPN transistor:

 

Hello,

I have build this circuit that I got from the greatscott youtube channel.

View attachment 295265

This circuit latches a relais when a momentary push button is pressed. This circuit works for my application however I have one issue with this circuit. When power is applied to the circuit, sometimes the relais turns on and latches. I understand why it does this but I would like to change this since this is undesired for my application.

Anyone know how I can modify this circuit so when power is aplied that the relais does not turn on and latch on it's own? If there are better latch circuits which also use 1 momentary switch please do tell me, I have tested alot of circuits already without alot of succes.

BR

Tim

Move the connection of R3 from the VCC line to the OUT line.

 

Move the connection of R3 from the VCC line to the OUT line.

If you did that the relay would never come ON.
Problem previously solved with the addition of a 100nf cap across R1