Consider again the option of an alternate action push-button switch. They are available i that same form factor as the small normally open switches.Zero power consumption and long life and the same size. Or just slightly higher, perhaps 1 to 2 mm higher. No external circuitry at all. You can look them up in the Digikey catalog On Line from almost any place with internet access. AND you can discover the manufacturers name and model number and search for an equal from your favorite local vendor.

 

Consider again the option of an alternate action push-button switch. They are available i that same form factor as the small normally open switches.Zero power consumption and long life and the same size. Or just slightly higher, perhaps 1 to 2 mm higher. No external circuitry at all. You can look them up in the Digikey catalog On Line from almost any place with internet access. AND you can discover the manufacturers name and model number and search for an equal from your favorite local vendor.

Oh yeah, I am looking for those one too, even those one made of plastic cost about like that of a single MOSFET, metal one is about double. Haha, I was hoping I'd buy them in packs. For cheapness and easy set up, I am going for the rocker switch.

 

The last time I priced them, the alternate action PCB-mount push-button switches were about seven cents each in quantities of a thousand pieces. A lot more than the simple normally open ones, at a bit less than five cents each. That was quite a few years back.
"Rocker" switches come in a variety of sizes and ratings and mounting styles. The main downside is that they mostly require a rectangular mounting opening.

 

I would recommend this circuit:
As with all logic gates, it does consume some power when off, but if you build it with a 74LVC2G04, its typical current consumption will be 100nA, which is probably less than a battery’s self-discharge current.

 

Hi blink13,

Here's how a lamp could be toggled on & off using an SCR (Thyristor) and two momentary push button switches.

View attachment 268786

No power is consumed when the lamp is off.

This AC version uses a Triac.

View attachment 268842

Nandu.

Doesn't work for AC, though! It doesn't latch, as the triac turns off at the end of each half-cycle.

 

The circuit in post #24 will work, HOWEVER, the output current is not enough to be useful except for driving more similar logic. So for the circuit to deliver any useful function an output section is required. So it is not quite so very simple to actually apply.
That is the issue with all of the proposed logic-based circuits presented so far.
The SCR circuit is different, at that point the only load carrying portion besides the SCR itself is the OFF button, the normally closed switch. Not as commonly available as the normally open button switches.

 

Here's how a lamp could be toggled on & off using an SCR (Thyristor) and two momentary push button switches.

Doesn't work for AC, though! It doesn't latch, as the triac turns off at the end of each half-cycle.

Everything in post #1 indicates a low voltage DC application.

ak

 

Doesn't work for AC, though! It doesn't latch, as the triac turns off at the end of each half-cycle.

Hi Ian,

It's conditional. Here's a reference.

https://www.st.com/resource/en/appl...riacs-latching-current-stmicroelectronics.pdf

Many thanks.

Nandu.

 

Everything in post #1 indicates a low voltage DC application.

ak

Hi ak,

Yes, it's not pertinent to this thread. I added that as an afterthought.

Many thanks.

Nandu.

 

Hi Ian,

It's conditional. Here's a reference.

https://www.st.com/resource/en/appl...riacs-latching-current-stmicroelectronics.pdf

Many thanks.

Nandu.

What's conditional?
When you release the ON switch, the load will switch off at the end of the next half-cycle.

 

Yes, it's not pertinent to this thread.

Actually, it is critical. Everything about the circuit changes if the input, output, and only power source for the timing circuit are all AC.

ak

 

What's conditional?
When you release the ON switch, the load will switch off at the end of the next half-cycle.

The cheating trick there is to use a rectifier and a filter capacitor. Then it can work using non-isolated, rectified mains power. That means that all mains power usage cautions apply. But all of mains wiring is associated with potentially lethal voltages, otherwise our houses would be dark and cold.