Capacitor & Resistor Values for Flashing LED on 5V

I ain't sure about using capacitors (possibly used for charging) but resistor could be used for LEDs (helps the LED to be on and minimizing the chances of blowing up?). Let me see if I can find the accurate resistor value that we happened to use in a test jig project way back in 2004-05...:)

So you think it would function fine if I eliminated capacitors from the circuit? As for the resistor values could I just divide the values used in a 9V circuit by 9 then multiply by 5 to get resistor values for my 5V circuit?

The poster, Fredski, below or above has derived the theoretical resistor value you would need. Its so long for the project we have done using LED's SEG. (many) and the connector. Now I remember, out of blue, we had placed 1 Kohms or 500 ohms in between. You could try both, but for 5V 500 ohms worked for us (sorry it doesn't match the Fred's theoretical value though) ;) I can't comment on the cap. purpose in your circuit at this very moment, cuz I have switched to Power systems ever since I landed in the Gulf countries for a job (left USA).

Flashing LEDs are available as factory-made packages.

http://uk.rs-online.com/web/c/?searchTerm=flashing+led&cm_mmc=Google-_-1-EEM-_-flashing%20led-_-PPC-Page

(usual disclaimer)

Unfortunately postage from UK would be too long. I need this lighting system to be ready for a launch on monday. I am going to go to the local electrical store tomorrow and buy components. It is pretty cheap to make anyway. Just need to confirm the equipment.

Well, RS does have outlets elsewhere in the world...

As you don't say where you are its impossible to be certain, but self flashing leds have been available probably around 20 years. They are available world wide as well. Its old technology.

If you built the circuit shown, do reverse the LED between pin 3 and attach the other end to the +5 volts instead of ground, you should use a 220-500 ohm resistor in series with the led as well, not connecting directly as shown with no resistor. That way you can control brightness and therefore current drain.

The circuit as shown will still work at 5 volts with the changes I mentioned. but a 555 sinks current better than it sources, which is why the led should be turned around.....

Telling us the flash rate needed would have helped us further for values.

There are many 555 cookbooks and websites with better and useful infos, just shop around.

Do not use the older versions of the 555, for example the old NE version which can still be found. Versions like the 7555 or the ICM555 in CMOS are far better.

Look here for further infos:-

http://en.wikipedia.org/wiki/555_timer_IC

I hope this helps.

Will this circuit be able to power about 6 LED's?

Build it and try it out! With one led first.
It will power 6 leds but the total current draw will be limited by the capabilities of the IC. IF you can't work it out from the 555 data sheet then find out by building it and testing.
Del

See my previous post, you must use it as I described, then assuming say 20ma per led which means a series resistor (one per LED!!) of around 250 ohms or slightly higher.

I am assuming that the 555 you use can handle more than 120ma, check and make sure. Usually up to 200ma is OK.....

Connect the LEDs as shown here (in my awful diagram):-

I hope this helps.

A month ago you couldn't spell artist. Now you are one.

LOL!!!

On the schematic you're pointing to, the most important resistor is totally MISSING. I see no means to limit current on the led, so it's just an interesting race on what will blow first, the led or the 555. Since most 555s will handle ~200mA+, I'll bet $5 on the LED (If it's not a high power type, in which case I'll bet on both) S.M.

Would you be able to point me to better schematics? I just need something that will run 6 LED's fine on 5V 2A with about 3 flashes per second.

Look at the manufacturers data sheet or just google 555 applications or flasher circuits. There is tons of stuff out there.
Manufacturers application notes are generally the most reliable source.
Del
<My job here is done, swishes cape and exits left>

What color LEDs are you trying to use? This will have a large impact on an answer for you at least as far as output configuration goes. As for the other question about resistors and capacitors, yes you still need the caps to set the speed of the flash. http://www.bowdenshobbycircuits.info/555.htm this calculator should allow you to play with the resistor and capacitor values to see how they would change the flash rate in your circuit. The output is where you should probably focus for now, getting your LEDs to light is definitely the first step, and for that, we need color to advise you. Jarred

Fredski, I think you have gone WAY overboard on your response here. A Yootoob video? What a great idea.

Well done and GA!

Thanks and I agree, I spent more time on than I should have. Hopefully it's useful to someone!

You can buy at Radio shacks, LEDs that flashes every seconds without any additional circuitry needed for it to blink or flash. Can be connected directly or with a series resistor to the 5 volt battery supply. No additional components that will drain energy from your small battery.

Yeah I saw them at the local electronics store, but unfortunatly these LED's only come as diffused not clear.

Okay so I decided to totally ditch the 555. I found a simpler circuit except now it isn't working. http://www.youtube.com/watch?v=K0A2gnlNe64&feature=player_embedded. I checked with the meter in the place of where to LED is and I seem to not be getting any voltage at all :\. The difference between my circuit and the one in youtube is I am using a 16v capacitor. Also with the transistor. Should I use the inner and one of the outer pins or both outer pins? Do you reckon if I lower resistance on the circuit, that I could run 3 LED's rated at about 2-3V.

If you look at #20 I clearly laid it out. If your LEDs are rated for 1.5V that means that's the MAX voltage. They will work with less voltage you'll just lose brightness as you reduce voltage. It took me about 20 minutes to make that circuit, most of that time was scrounging through my pile of resistors to get the values I needed. It's a pretty simple circuit. You can take 1.5V batteries (AAA) and run them in series to make 3, 4.5, 6V, etc.

Is there anyway I can get this circuit to run on 12V? I will need it to be 12V, because the receiver it is hooked up to puts out 12V.

"...the output power from the radio reciever that controls it is 5V."

At first 5 VDC and now 12 VDC?

Of course, just change the resistor values for whatever voltage you want. The 555 will handle up to 18V. Use the math I showed you in the picture with the blue ink.

I do believe (but nowhere near certain), that he means the NEW circuit that he has found.......

But I could be completely wrong!!!!

He started off with a 555 circuit, then to a single transistor with no base connection.....now he has changed the voltage........wait up, I am sure further changes are on the way, which means I have no interest whatsoever......

Long time ago I bought red LEDs that blinks by themselves from RShack and connected them to my car battery with a resistor in series. I used them as pseudo car alarm indicator with out any problem. Each LED is about 1/2 inch or less in diameter..

Do you have the remotest idea of what you are doing here? Switching voltages AGAIN? You keep moving the goal posts!!!!!

Feel free to correct, but I'm pretty sure that's wrong. If the LED's are rated for 1.5V that's the minimum voltage you have to have to put the diode into a conducting state and produce light. Unless I missed it, we still haven't gotten a response about the color of his LED's, and don't even know the actual rated voltage. It would be really helpful if this information was given.

You're right. I've made two projects on here (as in, did all the work and actually took the time to construct both) and posted both of them on YouTube. Somehow they actually worked (must have been lucky on my part). I've also clearly posted the math I used.

Please school me, I'm lost without your expertise.

Fredski, not trying to get into a fight here, but please try to run 3 of any LED's off of 3V, or 2 off of 1.5 or maybe (since I'm assuming you have a 5V supply since you've built 2 projects) 6 LED's off of a 5V source, by "lowering the voltage" to them. If you're talking a parallel hookup, fine, no problem, If you do it in series, it won't work. Since your math show's that you are hooking them up in series... "Line 3, 9-7.4=1.6V...Take line 1 and subtract line 2, so if you had 5V in line 1 and a single 1.5V LED your answer would be 3.5V. If you had 2 LEDs the answer would be 2V." For the record, I don't care about "schooling you" I care that the poster's (who doesn't seem to have much experience in electronics) project will fail because he thinks he can put 12 LED's in series on a 12V supply and just feed each one 1 volt or something.

The LED's being used in this circuit is 3 White LED's rated at 3.2V with 30mA.

Sorry everyone for the change in voltage. I had to change the setup after running out of channels on the 5V receiver, so I had to integrate a 12V one. This time it will definitely being staying at 12V.