#22: 5v Soft-Latch Pushbutton Circuit on a Breadboard

[@mikesmith6838]

I've seen this done with a 555 timer. It's really nice to see how it is done without one!

[@not-me45288]

I really like this video. It help me to understand circuit design as a beginner. Thanks a lot.

[@lorantkovacs5827]

Thank You very much, I am impressed because of your professionalism and helpfullness 😁

[@bassamskafi1384]

It's very good of this circuit

[@ivolol]

Can you get any better performances using a mosfet?

[@leighbrooks9573]

Could you post a close-up of the breadboard? I'm trying to figure out how to wire R4, R5, and R6 on the breadboard. They all meet Q2 at a single point in the diagram - not sure how to do that. Thanks!

[@BBCircuitsbySteveMorrison]

More info including a schematic and detailed walk-through of the circuit can be found at breadboardcircuits.com/5v-usb-transistor-soft-latch

[@ItsGoolMCz]

Can you make this but instead of driving led to driving 5v relay, what I have to change?

[@ChandrashekarCN]

💖💖💖💖

[@mendebil]

Works with BC337 without modifications

[@sandrobahry2558]

Interesting. In my real case, I need to provide 3.7 v to run a micro motor. The problem is that this device draws more than 2 A at peak. Could I use your circuit as is or do I need to replace any component? Thank you!

[@BBCircuitsbySteveMorrison]

You'll need an output buffer to lower the circuit's output impedance (power transistor, N-channel MOSFET, relay, etc) as the minimum output impedance is currently 100 ohms, which if you try to draw 2A of of, would gobble up all of the available voltage and leave nothing for the motor. The simplest solution would be a relay that has a coil resistance of no less than 100 ohms. If you use an an N-channel MOSFET, you would replace Q3 with that, then replace the LED (load) with your motor, while only supplying 3.7 volts to the top of the motor. You might need to adjust some of the resistor values near the output to accommodate the particular MOSFET's Vgs.

[@mikepanchaud1]

I've breadboarded this and it works well. But the quiescent current when off is 5mA, due to Q2 being on. So this is not suitable for battery powered projects as it will drain the battery when off.

[@BBCircuitsbySteveMorrison]

Appreciate the feedback. I will look into that and possibly revise or redesign it to take that into account.

[@EGLOVEzicgo]

재설계하였으면 공유해주세요.

[@anandhan.a3744]

Can you make a on off latch with a triac?

[@BBCircuitsbySteveMorrison]

That would be easy. - although I generally don't do videos or publish circuits that involve mains voltage. You would want to replace the LED with the input of a triac optocoupler. Here is a link to lots of information about how to do that. www.google.com/search?q=triac+circuit+with+optocoupler