It is a pretty common first project to use an Arduino (or similar) to blink an LED. Which, of course, brings taunts of: you could have used a 555! You can, of course, also use any sort of oscillator, but [Mustafa] has a different approach. Blinking an LED with three resistors and a capacitor. Ok, ok… one of the resistors is a light-dependent resistor, but still.
In reality, this is a classic relaxation oscillator. The capacitor charges until the LED lights. This, however, causes the capacitor to discharge, which eventually turns off the LED, and the process starts again.
There is one wrinkle that could be considered a feature. In daylight, the capacitor will stay in the off state, so the blinking only occurs in darkness. Of course, the resistor also has to have a sufficient view of the LED. You might use this as a safety light that only works in the dark.
A simple circuit, but it just goes to show that we tend to forget the simple solutions in a world where a computer costs less than a dollar.
Of course, you can get a chip whose sole purpose is to blink LEDs. We always like examples of doing more with less.
LED is an active component.
it’s not, it has two legs, it’s passive.
Wrong definition. I have 2 legs, but I’m clearly not passive.
There’s a useful definition and a pedantic-but-useless definition in play here. By the latter, surely the only passive component is a superconductor. Maybe let’s use the former?
The definition to which you refer may be: passive components can only dissipate energy (convert electrical energy to another form, and maybe back, such as capacitors and inductors). Standard def, and an LED is passive in all senses
Lamps were passive components. Traditionally, at least.
The little incandescent lamps for 6v, I mean, as used by vintage bicycles who had a dynamo. They worked with both AC and DC.
They also existed as a blinking type, which had a bi-metal inside.
One difference was, however, that the blinking was a bit softer in comparison to an LED.
The wire inside did heat up/cool down each time which caused an afterglow.
As a modern replacement, halogen lamps can be used.
They don’t blink, however. Or maybe they do? I don’t know.
It’s in the same vein as the usual “It’s forbidden to forbid.” Notice that the voltage source is also using active components. You can probably blink a led by using a capacitor + resistor and the LED and a photodiode to charge the capacitor, but you’ll still need semiconductors in the circuit. It’s simply not possible to have something intermittent without some kind of threshold somewhere, and this threshold will always be from an active component.
Grow up.
First time I see this in 3 decades!
Gosh now I wonder if you could make this work with lightbulbs — and if you could turn these into NAND gates.
I remember my first electronics project, an LED blinker from EKI… a green PCB with a silkscreen of R2D2 (or similar robot) on it. Parts list was dirt simple: 4x LEDs, 2x caps, 2x transistors, 4x resistors. No 555, no CPUs, just a 9V battery. And I learned how to solder putting it together.