Electronics > Beginners

Looking for a simply circuit using a 555 timer that will fade an LED in and out.

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level42jeff:
I'm looking for a super simple circuit that I can use to fade an LED in and out at a constant rate. The problem is that there are too many tutorials out there, and they all seem to vary slightly.

I'm quickly becoming overwhelmed and frustrated trying to figure out what caps and resistors I'd need. I already tried following one tutorial, which ended up in the LED just coming on constantly, and not fading at all. when I did this on breadboard, it sort of worked, but when I tried transferring this to a PCB, that's when I had the issue with the solid LED only.

Anyone have any suggestions here. Hoping to have this done by Christmas.

Wimberleytech:
1) Did you translate these instructions into a schematic first?
2) Can you show us your breadboard?
3) Can you show us your PCB?

Then we can help.

I think the video instructions have reversed emitter and collector.  At least from what he said.  Maybe he connected it right but said it wrong.  <<No, it appears that is what he did.  Using the transistor is a diode essentially (base-collector diode)>>

level42jeff:
Thanks for the feedback,

Here is my breadboard, and I'll have to get shots of my PCB when I get home.

https://imgur.com/a/C3uowpA

I did my best to translate this video into schematics before I did anything else. I took the shopping list of components to my hobby shop and got as close as I could parts wise to the video.

nali:
There's a link to a schematic in the video description - yes it is a fixed freq astable but the LED (or LEDs plural in the schematic) are driven by emitter followers from the timing capacitor.

Can't really decipher the birds nest on the breadboard!

Wimberleytech:

--- Quote from: level42jeff on December 05, 2019, 05:13:23 pm ---Thanks for the feedback,

Here is my breadboard, and I'll have to get shots of my PCB when I get home.

https://imgur.com/a/C3uowpA

I did my best to translate this video into schematics before I did anything else. I took the shopping list of components to my hobby shop and got as close as I could parts wise to the video.

--- End quote ---

Looks like it is connected correctly.  Bear in mind that the base of the transistor is a sawtooth varying from 1/3 to 2/3 of the supply.  This voltage is dropped by the base-collector junction (should be base-emitter imho) and that is the voltage available to turn on the led.  Depending on the led choice and the power supply chosen, you get widely varying results.

I suggest that you swap the collector and the emitter connections.

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