Creating a slowly pulsing LED lamp without uC

Other Hardware General Electronics
1

Hey,

I'm looking to make a little pulsing lamp. The lamp should use 2 LEDs(channels) that are are lit in terms, but not only on and off, but I want them to fade in and out.

Thinking of the multivibrator circuit where the two LEDs turn on and off after another but with a slow fade in and fade out.

I'm also looking to make this project with only "passive" components... transistors, capacitors etc. a 555 if really necessary.

I hope the idea of what I want to make is understandable (not a native speaker and a bit at a loss of words)

Cheers
Jazzar

2

Welcome.
A controller is best for this.
What you are wanting is doable.
Do you know how to use PWM.
Show us what you have done on the project.

3

I don't want to use a controller, I know how it is easily done using an arduino or programming an attiny.

I thought of using maybe a mosfet, i.e. using the classic astable multivibrator circuit and using the outputs to maybe feed a mosfet.

Ah nevermind found the fitting search terms to find what i was looking for.

http://www.axiris.eu/en/index.php/project-corner/breathing-led

This will do nicely. I know of a different circuit to easily adjust speed. This will in time be integrated to this.

Cheers!

4

jazzar:
I'm also looking to make this project with only "passive" components... transistors, capacitors etc.

For future reference a transistor is not a passive component it is an active one.

5

This kind of fading can be done with two 555 oscillators running at slightly different
frequencies and powering the LED(s) from the difference of their outputs (in bridge mode).

For analog fading you would need some sort of triangle wave source and a buffer amp
to drive the load.

6

jazzar:
I don't want to use a controller, I know how it is easily done using an Arduino or programming an attiny.

Truly bizarre approach! :astonished:

One ATtiny, one resistor versus a dozen or more components operating in a far less power-efficient manner.

7

one resistor versus a dozen or more components operating in a far less power-efficient manner.

Quite agree.
Mind you I started with that sort of approach in the 60s and now micro controllers make it so much easier, but there is no accounting for ****.

8

I used to make artwork with a circuit glued to the back, and LEDs poking through. Check out this page to see an example. You don't need a transistor, just a resistor and a cap.

EDIT: Whoops, yes you do need a transistor, a resistor and a capacitor.

9

Have you ever had a look at ATtiny (e.g. ATtiny 85)? A chip with only 8 pins. It will do whatever you need in your case. Maybe transistors and resistors for the LEDs to protect the chip.

And if you have got an Arduino board you can easily program the chip. Just use the same programming environment.

Everything else seems to be a lot more complicated. (And I do love 555 chips).

Arduino Aleman

PS:

While I posted this message someone else also had the same idea. So noew you have 2 recommendations - both are basically the same.