Instructables

Throbbing/Fading/Flashing LED with 555 Timer

Picture of Throbbing/Fading/Flashing LED with 555 Timer
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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.
 
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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.

Step 2: Breadboard it

Picture of Breadboard it
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Break out the breadboard and proto it up.

555 Timer
Pin 1- To Ground
Pin 2- Jumper to Pin 6, Jumper to Base of NPN
Pin 3- 33k resistor to base of NPN
Pin 4- Jumper to Pin 8
Pin 5- NC
Pin 6-Jumper to Pin 2
Pin 7-NC
Pin 8-Jumper to Pin 4, Connected to Positive voltage

Emitter of NPN to 470ohm resistor to LED
Base of NPN to + side of cap, then ground - side
Collector of NPN to + voltage
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LeumasYrrep made it!5 months ago

I needed a circuit to test etching with and this worked great!

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MrBeta (author)  LeumasYrrep5 months ago

Awesome! Glad you made it work. Nice etching too? What etching method did you use?

bobbotron made it!8 months ago

Thanks for the instructable, I made this last night, works as specified! :)

LED.jpg
MrBeta (author) 4 years ago
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.
Schematic.jpg
MrBeta (author)  MrBeta4 years ago
*ETA*
The orientation of the resistors usually does not matter though the capacitor, the led, the transistor, and the timer MUST be positioned correctly.
daova.nigca1 month ago

hello and thank you for this guide. i managed to breadboad this and swap the 33k res for a 50k pot. the pot lets me control the pulsing speed great. now im stumped at how i would swap out the pot and attach this to say an anolog pc fan controller. the fan controller should function as a pot? but it would also be a 12v power source. any help would be magnificent.

hello the fan controller is a NZXT Sentry 3 its touch screen.

NZXT-Sentry-3-pwm-connectors.jpglabel.jpg
MrBeta (author)  daova.nigca1 month ago
It's difficult to say without looking at your fan controller. Most fan controllers use a similar circuit to this one as a PWM circuit. You could gut the fan controller and use your own pot or just tap into the existing pot. No telling what the specs of the fan controller pot are. With more details and pics, I might be able to assist further.
Hi I need help with this can't get it to fade
Thanks
mr_exit made it!1 month ago

Thanks so much for this circuit. I made 6 of these for some halloween decorations. Dolls with red glowing eyes are creepy as hell.

I had to make a few changes. At first this just stayed on. I'm in New Zealand so maybe our parts differ a little. First was 2 leds in series after the 470 ohm resistor. I didn't have time to etch boards so I made them on some predrilled boards, messy but they do the job.

I wanted a very slow fade in and out so I swapped out the 33k resistor for a 100K pot, I should have used a 50K pot as the range of where this works from so slow it's stopped to strobing is about 5 degrees.

I also had to increase the capacitor to get a reasonable fade. I ended up using 570uf, try stacking a few in parallel to work out what works for you – you can add the value of capacitors in parallel to get the total.

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kitc2 months ago

Thanks OP, can I ask what part do I change If Im going to use a 12v supply with several super bright green LEDs?

MrBeta (author)  kitc2 months ago

For 12v, you'll want to change the resistor for the LEDs. In my case the 470ohm resistor (blue).. You'll also want to make sure that all of your components will handle 12v.

Good luck!

Any ideas why the light is so dim when I made this??

dkaph5 months ago

Hi Guys,

I am looking to do something similar this on a large scale.

What I want is my band's logo to be created out of Ice White LEDs, and it to be triggered by sub drops from my IPOD. My Ipod has a click track in the Left ear and the samples in the Right ear

So basically,

Ipod L+R > Mixer Tape In > Phones

> R Tape Out > Low pass Filter > Light Controller > LEDs

>R Main > Front of House

I would probably power it from a 240v UK mains socket, I would think some kind of switch triggered by the Audio signal, i would probably want it to consist of LED strips, and basically I want the band Logo to illuminate quickly with the Sub drops and fade out as the sound fades.

Does that sound at all possible and if so, could you possibly suggest a method and any information that may aid me, as I don't really know where to start when it comes to the implementation of the controller itself.

Thanks

agent ziek5 months ago

i would like to ask u something , keep this whole ciciut same , just by removing this one led and making seperate series of leds and inserting the postive wire and negative wire , into where the orignal led was , will they all fade? and heres my email adress
anthrax.void@gmail.com , plz email me cause i would like to ask u more questions abt 555 ic and ty for ur reply in advance :)

agent ziek5 months ago

i would like to ask u something , keep this whole ciciut same , just by removing this one led and making seperate series of leds and inserting the postive wire and negative wire , into where the orignal led was , will they all fade? and heres my email adress
anthrax.void@gmail.com , plz email me cause i would like to ask u more questions abt 555 ic and ty for ur reply in advance :)

agent ziek5 months ago

i would like to ask u something , keep this whole ciciut same , just by removing this one led and making seperate series of leds and inserting the postive wire and negative wire , into where the orignal led was , will they all fade? and heres my email adress
anthrax.void@gmail.com , plz email me cause i would like to ask u more questions abt 555 ic and ty for ur reply in advance :)

agent ziek5 months ago

i would like to ask u something , keep this whole ciciut same , just by removing this one led and making seperate series of leds and inserting the postive wire and negative wire , into where the orignal led was , will they all fade? and heres my email adress
anthrax.void@gmail.com , plz email me cause i would like to ask u more questions abt 555 ic and ty for ur reply in advance :)

agent ziek5 months ago

i would like to ask u something , keep this whole ciciut same , just by removing this one led and making seperate series of leds and inserting the postive wire and negative wire , into where the orignal led was , will they all fade? and heres my email adress
anthrax.void@gmail.com , plz email me cause i would like to ask u more questions abt 555 ic and ty for ur reply in advance :)

imanewbetoo7 months ago

This is a great project for a newbe like me. I finished it on strip board today and I am now reconstructing the circuit and expanding it to fire a 4017 decade counter where I can light as many as 10 LEDs, one after the other.

afultz18 months ago
Hello! I'm SUPER new to electronics so please forgive me. I checked and double checked the circuit step by step and I still can't figure out why my led doesn't fade in and out. I would really appreciate a little guidance. Here's a couple pics of the breadboard. Maybe one of you can spot a mistake I missed.
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gameshark8889 months ago
(removed by author or community request)
MrBeta (author)  gameshark8889 months ago

Well if you're connecting it to a led strip, you'll want to make sure that you're getting enough voltage out to the led strip and you'll also want to make sure that whatever transistor you use will handle the current required for the led strip. What are the specs on the strip you want to use?

hi again! I tried to connect your design to a 12vdc 2meters led strip.
(input voltage to the circuit was 12vdc by the way)
then I replaced the 33k resistor with a 100k pot. I get the fade in and fade out effect from the led strip, but my problem is the led strip is not bright enough.

MrBeta (author)  gameshark8889 months ago
If the power source is 12 volts, the led strip is only getting around 10 volts because of the 555 timer voltage drop. You'll have to bump up the voltage to around 13 or 14 volts to get a full power to the LEDs.
MrBeta (author) 11 months ago
@gree7r
I'm not sure if I understand what you're asking. The 33k resistor controls the pulse time so that can be adjusted to flash/throb faster or slower. If you want it to fade out/decay slower than the fade in, you might have to play with the capacitor values. Please not I'm not an electrical engineer so you'll have to play around with it.
Be sure to post the results!
gree7r MrBeta11 months ago
@MrBeta
Here's a quick video I shot of mine so you can see. http://www.youtube.com/watch?v=CsX8QpLvq38

If you compare it to the video of yours running than you can see that when yours is on, the led is illuminated (whether fully or partially during the fade) most of the time with it only being fully off for a split second.
For some reason mine is doing the opposite, it's fully off for a longer duration with the led only being illuminated for a very quick duration.
Do you see what I mean, by comparing the video of mine to the one of yours?
When I try and change the resistor that controls the fade time, it only speeds up or slows down the fade of when the led is actually on but there is still a much longer period of time with the led fully off than in your video.
Does that make sense? Any idea what could be causing this?
MrBeta (author)  gree7r11 months ago
That's interesting. It seems like the capacitor is drained very quickly. Is that a large led? If so, have you tried swapping the led for a smaller one? You may be able to replace the capacitor with a larger capacity cap and see if that prolongs the fade. Keep me posted. I'd be curious what the solution turns out to be.
gree7r MrBeta11 months ago
Well this is embarrassing, it turns out it was just the battery. After replacing the 9v battery with a brand new one it now seems to be working properly.

Here's another question you might be able to answer though. Would it be possible to/what would be the best way to add 1 (or 4) additional LEDs to this circuit that would stay solid on? So that would make it so it has the 1 flashing LED and 1 (or 4) solid LED(s). If it's possible, where in the circuit should they go?
Thank you.
MrBeta (author)  gree7r11 months ago
Glad it works! It's always the simple things we least expect.
As far as the other LEDs, you can just wire them directly to the battery with the appropriate resistors. If you're adding 4 LEDs, you can wire two sets of two in series with a 150 ohm resistor on each set (assuming 3.2v @ 20mA). You can find an online led array calculator that will figure out the best way to wire it and give you the proper resistor values.
gree7r11 months ago
Hi, I'm trying to make this on a breadboard. I followed the instructions exactly and after watching the video of it I believe I have it set up correctly. When I connect the power it does turn on and start flashing/fading however it does it in a way where when the LED fades on its only on for a short time and then when it fades off it stays off for a longer time before it fades back on again. In the video (and others similar videos I've seen) the LED seems to fade on long and fade off short. Mine seems to be doing the opposite. It is off much longer than it is on where as yours is on much longer than it is off. Does that make sense? For my purposes I want it to work the way yours works but I'm not sure what's making it do this. Do you have any idea? I may not have explained this clearly/correctly so if you need me to explain further/better just let me know. Any help would be greatly appreciated. Thank you.

what I'm using:
2n2222 npn transistor
100uf 16v capacitor
33k ohm resistor
led with 330 ohm resistor
9v battery
555 timer
MrBeta (author) 1 year ago
@9W2XO
What are you trying to do?
9W2XO1 year ago
this is a cool weekend project...
can anyone share the fading 12vdc LED circuit(when power off)
thank you
Marctttt1 year ago
Hi folks - I've built two of these using the schematic posted by Brit. Thank you!
Wonderful project. Both circuits work fine if I use an old 9V battery. However, if I use a new 9V battery, the LED turns on but does not fade off. It just stays on. Any ideas what could be going on?
dan108k1 year ago
Thanks for the instructable! Made it and it works perfectly! With this setup the LED fades from fully-off to fully-on repeatedly... Have you any idea what I would have to change if I wanted the LED to fade from half-on to fully-on repeatedly?
MrBeta (author)  dan108k1 year ago
Well I'm no electrical engineer so I'd have to play around with it but I'm thinking that if you replaced the 100uf capacitor with a larger one, it might lengthen the fade time allowing the next pulse to begin before the previous pulse ends. This is just a guess, though. Let me know how it works out!
dan108k MrBeta1 year ago
Thanks very much, I'll give it a go!
Platfus1 year ago
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 (author)  Platfus1 year ago
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 MrBeta1 year ago
Thanks man! Very fast reply :) I will buy the parts I need and then will do so :)
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