Throbbing/Fading/Flashing LED with 555 Timer

This tiny circuit is a simple way to make a fading led without having to program chips or writing code. Just a few simple components and you're ready to fade all day.
The end result is a constant fade up and fade down just like a Mac on standby.
Try it! See how small you can build it.
If you like it rate my Instructable. If you don't, rate my Instructable.

Step 1: Gather Tool and Components

For this project you will need:

Electrical Components

470 ohm resistor (or a resistor to drop the current for your desired led from around 8 volts.)
33k resistor ( or a 100k potentiometer for adjustable fade times)
LED ( I used Blue)
100uf Capacitor
555 Timer
Generic NPN Transistor
Copper clad board. breadboard, or project board.

Tools

Dremel or other rotary tool for drilling
1/32" drill bit for wires
Cutting wheel or tin snips if necessary to trim board down
Soldering iron
Scotchbrite pad or fine sandpaper. ( I used sandpaper because it happened to be there)
Muriatic Acid (concrete cleaner or pool chemical) Home Depot and other hardware stores have it.
Hydrogen Peroxide (standard wound cleaner) Found in drugstores, grocery stores, you probably have some at home.


Misc
Latex or Nitrile Gloves
Acetone to clean ink off of board after etch.
Outdoors area to etch in
Plastic or glass container to put etchants in.
Helping Hands clamp with magnifying glass (nice to have a third hand)
I've included the files for Express PCB software. Free download.

Comments

[MrBeta]

Here's the detailed schematic I printed to etch and drill my PCBs. Keep in mind that this image was flipped to hopefully reduce confusion. You're looking at the top of the board.

The plus signs (+) are there to help with the polarity. They do not mean that you connect the positive voltage there.

The main problems I had when prototyping this project were the following.

Capacitor polarity
LED polarity
Proper/improper orientation of the NPN transistor.

Hopefully this clears things up a bit. Post a comment if you have any further questions or if you get it to work. And don't forget to rate my instructable.

[MrBeta]

*ETA*
The orientation of the resistors usually does not matter though the capacitor, the led, the transistor, and the timer MUST be positioned correctly.

[gameshark888]

nice! i built it and works fine upon powering up.. i used it to replace the led on the switch in my cpu.. looks cool! thnx!

[gameshark888]

here I built it and it was workin.. installed it on my cpu switch.. thnx for the instruc

http://tinyurl.com/23h4638

[Platfus]

Hey man!
I'd like to ask. I have no clue, how to do it, in order to the LED will be ON only for about 2 sec. I'm planning to build a TARDIS. Timing can be seen here:
http://www.youtube.com/watch?v=r3Ng91qfNkE
Any idea how to makde the fade quicker/shorter? Because I am kind of noobie haha :)

[MrBeta]

It's quite easy. The timing is controlled by the 33k resistor. The best way to dial the timing in is get a 100k potentiometer and install it in the place of the 33k resistor. Literally turn the pot until you get a timing to your liking, and then measure the resistance of the pot. You can then find a resistor with the same or similar value, or just leave the potentiometer connected.
Hope that clears it up. Please let me know if you have any further questions and don't forget to rate the 'ible!

[Platfus]

Thanks man! Very fast reply :) I will buy the parts I need and then will do so :)

[Alex337]

When I have more than 2 LEDs with this array, they only fade up once and stay on. I'm using 6, and they're all wired in parallel. White. 25mA 3.3-3.6v When I used 100 ohm resistor at the LED it stays on, so i'm using 270 instead. They obviously don't get as bright as they could, but the main problem now is them not fading at all. Do you think I need to switch my 33k-ohm resistor out for something smaller now that there's more resistance in the total circuit?

[MrBeta]

What kind of transistor are you using and what is it rated for? You might be overloading the transistor. Just a guess though.

[Alex337]

So now a new problem. Running a total of 8 LEDs. I'm under the rating of the 555 and the transistor. Using an adjustable pot, I can get the LEDs to blink, but they won't fade anymore. It's either blinking like a strobe light or about 3 times a second. Do I need to adjust the size of the cap?

[Alex337]

I am using a regular NPN 2n222 rated for 600ma. I figured it out though! This was my first attempt at something like this, so wiring diagrams are still a little confusing (which is ironic because I look at them when working on cars a lot). Anyway, I switched out the 33k resistor for a 100k pot, found where the LEDs started flashing (~7.3k), went to radioshack and bought a 10k pot, and stuck it in there. I have great control over the speed of the flash now. If I used a different sized cap, would that effect the dwell?

[EET1982]

Just thought i would let you know i made your LED fader without the homemade board. It was pretty cool. Thank you for the instructable. People underestimate the 555 :).

[dsmith84]

top notch instructable! this project was a lot of fun to build.

[MrBeta]

Glad you enjoyed it. I'm going to be redoing it soon so that things are a bit more clear and include videos. I'm going to also try an SMS version of the same circuit.

[stuffstuffa]

could I remove the 470 ohm resistor and the 9v battery and attatch it to my computer's led power wires, cut right below the led and attach it there?

[ShadowDragonz]

For those still confused, you can find the original schematic for this at

http://www.555-timer-circuits.com/up-down-fading-led.html

[stuffstuffa]

How could I do this with my computer? I want to make my case lights throb.

[stuffstuffa]

I don't want to have to buy anything or solder, just something to control all of my case lights.

[rancid_84]

thank you!

[Lazarus65]

For the life of me I can't seem to figure out how to connect the negative and the positive. I tried connecting it like I see in the picture: Positive to pin 8, and negative to pin 3, then I tried pin 1. Can anybody tell me if they got it right, and where they connected the power source?

[MrBeta]

Sorry, I'm in the process of rewriting this 'ible but it should be pin1 as ground and 8 is power

[Lazarus65]

I hope you do, because I end up coming back to this one by so many people who have successfully figured it out.

[biteme556]

i have just made the fadeing light but i cant get it to fade when i put the battery wires in difrent places on the 555 timer and it will be bright in one spot and dimm in another but it doesent fade can you help me?

[nodoubtman]

I only succeed fading once.. after nothing happens..what would be wrong??

thanks !:)

[brit]

Try it like this..

[gnub_daemon]

I'm trying to follow your schematic on perf-board but the only thing that happens when I apply power is that the 555 gets really effing hot. :( I've spent 2 days on a 30 minute project. lol I don't have a clue what I'm doing right or wrong. -.-

[brit]

Check you have not bridged the tracks on your board with Solder. Also check you have the pin numbers correct. It may be you have done the Soldering upside down and not allowed for the Pins being mirrored.

[gnub_daemon]

Hmmm. I did have pin 2 bridged with pin 7 instead of 6 but when I fixed it I still got the same result. Maybe i fried the 555? Aside from a couple Velleman kits from Radio Shack I've never done any circuit building. Guess I'll buy a breadboard and try to get it working on there first. Thanks for the help.

[brit]

If you cooked the 555 then it will more than likely need replacing. The Breadboard is a good idea. You did remember to Cut the tracks Under the 555 to prevent the Pins shorting?.
Let me know how you get on.Good Luck :-)

[gnub_daemon]

I finally got it with a new 555 and after watching a youtube video of someone who already had it set up. The breadboard confused me at first but I think I have the basic concept. Was using round pad perf board so no tracks to cut. Here's a short video of my project all finished and working. http://youtu.be/LvWgBM89QBs. Thanks for the help. :)

[brit]

Good Job, well done!!

[mischka]

Thanks for the schematic. It helped a lot building the circuit!

[Ugifer]

Thanks for the schematic - very clear and useful.

And MrBeta - good project. Thanks.

[nedfunnell]

If I wanted to scale this up to about 80 LEDs, could I just change the transistor to one rated for the current and the resistor to match?

[MrBeta]

That should work. As long as the transistor will handle the current and there's enough voltage to drive your array of LEDs.
If you get it working, please post a picture or a link so that I can show it here.

[tobster9103]

I cant seem to get my circuit to work. The led just stays on with no fading in and out. I have a 100uf 35v cap., a 2n2222a transistor, 555 timer, and the resistors in 1/8 watt. Would the resistors have to be 1/4 watt? What am I not getting here?

[MrBeta]

Without looking at your build, it's difficult to debug. In theory, that NPN should work.

[silentstone7]

I am trying to make something like this for a PC mod, using either 5V or 12V DC source voltage. I have no idea what to buy, with what specifications to make this work off that voltage. Can anyone help me out?

[Ugifer]

The 555 should be happy at 5V so the only things you might need to change are:

At 5V the current limiting resistor doesn't need to be so large - about 120 Ohm for blue/white or 150 Ohm for red I think.

The frequency might change as the voltage decreases (I'm not too sure on that one) so you might prefer to use the 100K pot in place of the 33K resistor so that you can tune it to your preferred rate.

Beyond that it should be fine.

[Anthony_Uk]

Hi. The text description doesn't seem to match the schematic - For instance, Pin2 and 3 are not going to the NPN in the diagram, and your text only has one leg of the LED wired.