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

[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..

[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.

[zzzee]

Hey i made the circuit but when i connect it to the power supply, the 555timer heats up and the LED stays on. Does anyone know what the problem might be?

[jmerisalu]

I had exactly the same problem, I did the project 2 times had the exact pieces. Could someone help whats the problem?

[doraemon3]

only 555 Timer works on the flashing effects, or is there other types of timer that works too?

[sume29]

hey.. do you know how i could increase the fade out time of the led?

[chipper35]

A top rate instructable!! ....I mean that!!

[bvan zijverden]

Great job!
I have a question though :P , I will hook my circuit up to a 3.3v power supply. And I also use a 3.3v led, so what is my schematic for this?
Sorry I'm a bit of a noob when it comes to figuring out value's :(
But thanks for the instructions :)

[sprasad1]

I used the circuit as " Brit " says above. i replaced 33k R with 100k pot, 100uF with 1000, 220R with 470R, source 14.4V.    Flashing of 1 led did happen. But when i connected it to an array of 5(series) X 8 in total 40 led. Voltage dropped across output, only max of 10 led flashed and later on npn failed. now its not flashing, glows steady. Plz suggest me " Capacitor and NPN ". amp used by array is 250 mA and 3012 mW

[fourniersd]

How can I get the LED to strobe from full brightness to completely off. When I build it with the specs you provide The Led goes from Full to about 30% brightness.

[coleyy]

i have transistors that are 2N3904, 2N3906, 2N5457, 2N2907A, 2N2222A, whish one(s) are NPN?

[robot1398]

2n3904,2N2907A,2N2222A are npn
2N5457 is a n channel transistor
2N3906 is pnp

[jcaresheets]

My first LED project I want to do is make a red LED heart for my fiance and I think I will add this into it and it will make a great gift. Thanks for the post.

[tinkerunique]

Upon completion, the board can be coated with "rattle-can" urethane or varnish to stop oxidation. - Like many auto and boat controls.

[texasdave]

Mr Beta thanks for the video, it sealed the deal for my circuit, and also all your help on this. I modified it very slightly, I wanted a controllable slowwwww pulse, like, verrrrry slow. so I swapped the capacitor for a 220uf and a 50k trim pot. couldn't have gotten to this point without your help though!

[MrBeta]

Glad it worked for you!

[gmd393]

Dude, you confused me quite a bit. Your diagram doesn't have the 50k(var)/10k resistor connected right, it should go between terminals 2 and 3. You also should have the capacitor connected to terminal 2 and a jumper wire between terminal 2 and 6. Once I made these changes, mine started blinking.

[an4rchyy]

I have gone by this schematic and no blinking occurred, and made the changes gmd393 said and still no blinking occurred. The transistor collector seems to be immediately applying power to the LED skipping the entire 555 circuit and staying on. I can disconnect all leads to the base and the LED remains on. I can't figure out why it won't work