1 pulse toggle with simple non programmable electronics

Question

I need to create a simple circuit that toggles when one pulses a push button and then stays on no matter what you do with the push button again. The toggle will reset when the system is powered off (starts off)

Any clues where to start from ? I've playing with relays,push buttons and those but .. cannot really get it. I'm currently working with logic gates to see where it leads..

Any idea ?

Answer 1

This is actually quite simple to do with a single SPST relay:

^{simulate this circuit – Schematic created using CircuitLab}

This is completely generic. The power source can be AC or DC. The only requirements are:

• Both the switch and the relay contacts must be rated to handle the load current.
• The relay coil must accept the same power (AC or DC, same voltage) as the load.

When you push the button, power is applied to both the load and the relay coil. After that, the relay contacts keep the current flowing until the power source is removed.

I once built a high-power version of this to run all of my computer systems. I was living in an area that was subject to bursts of short-term power outages. Since computers and other electronic gear don't particularly like to be "short cycled" like this, I used the circuit to make sure that once the power went off, it stayed off. I would restart everything manually by pushing the button, once the power had settled down again.

Answer 2

The most simple circuit can be made using a sensitive gate thyristor (SCR), like this:

^{simulate this circuit – Schematic created using CircuitLab}

You can also make a one shot trigger with NPN and PNP couple immitating the SCR:

^{simulate this circuit} Depending on load (pull up) current and transistors used R2 can be shorted.

Both circuits act in a similar way.