One component LED booster circuit!

[bikeNomad]

After designing a 2-component booster that required an IC, I figured out that you could do the same thing with a single component. And it's not even an IC! Nor a transistor...

Anyone guess what I used? It'll drive a 3+V white LED from a 2-3V source, though in pulse mode (i.e. not 100% brightness).

Of course, it has an annoying characteristic that would keep anyone from actually wanting to use it, and it's not too efficient, but it was entertaining to come up with it

Guess what it is yet?

No? Well, here's the circuit:

How it works: initially, current flows into the coil until the magnetic field builds up to the point where the relay activates (opens).

The magnetic field then collapses, raising the voltage to the point where the LED will conduct. When the magnetic field is dissipated enough, the relay closes again, repeating the process.

Of course, this buzzes annoyingly...

 

[lambda]

No, tell me it isn't so. This actually works; what a stroke of retro briliance! Now I'm going to have to try, only thing is I know I have some reed relays around here from about 20 years ago, just halve to find them....

Very creative!

What next, the no component booster?

 

[machspass]

Wow, that IS pretty clever, BikeNomad!

I remember making a circuit like this when I was a kid, using my old Radio Shack project kit. This circuit was described as a buzzer circuit, as you said was one of its features. At the time, I had never thought of utilizing a relay's flyback energy to power an LED. I'm so used to using relays in applications where you want to get rid of the flyback energy to prevent it from damaging the switching transistor that is controlling it. Good work!

 

[**DONOTDELETE**]

A vibrating SPDT relay was in one of the first circuits I ever made!

I used it as a morse code transmitter. If you hook a long straight wire to the relay contact, it acts as an antenna, and the buzzing can be heard on an AM radio in another room.