Blinking an LED repeatedly

[des_a]

I'm building a circut. I haven't really designed as much circuts as I have assembled, but now I'm starting to design my own. I'm essentially wanting to make an LED blink. The catch? I'm wanting it to blink repeatedly. This is not the final circut yet, but it's a proof of concept.

I've connected a switch to a 9V battery. Next to that is a 100uF capacitor, connected to what is now a single LED. When given power and switched on, the LED will blink once and then go out. If you repeatedly switch it on and then off, it will blink repeatedly.

How do you make the LED continue this pattern repeatedly, with just one flip of the switch until you flip the switch off, or until it runs out of power? I also tried 2 AAA batteries, instead of a nine volt, but that wasn't enough power to operate.

If I have to, I can add more 9V or something, but I can't have the LED on when the switch is not flipped to on. Prefferebly, I'd also not like to waste power, so the switch is important.

I've tried a transister in several configurations and it doesn't seem to work. It's back to blocking the current at the point of the transistor when I do this. Is the transistor bad like I found the other capacitor is?

 

[mdanh2002]

Just google for 555 timer circuit you can do what you want. The R and C values of the 555 timer will determine how fast you want your LED to blink.

It's better than blinking the LED based on the charging/discharing effect of the capacitor. In case you really want to do it, this link may provide some hints: https://forum.allaboutcircuits.com/showthread.php?t=8904

 

[Gayan Soyza]

I just roughly read your post.My be I missed something.

Here is the worlds simplest flasher for LED's.

http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html

 

[Torben]

Lack of power isn't the problem; neither is a bad transistor. And with only 9V I don't think you've killed the transistor yet, but anything's possible. You just need a little more than a capacitor to flash an LED.

You say you want to design this, so would you like some hints and pushes, or just a circuit?

Here's a hint: you'll need 2 transistors, at least 2 capacitors, and probably 4 resistors. (Actually you can do it with 1 transistor, 1 capacitor, and two resistors plus the LED, but the technique doesn't work with all transistors and you need somewhere in the neighbourhood of 12V input power to run it; read this thread to learn more about it).

If you Google for "LED flasher" you will find about a million of them. Many can flash one LED, but with the same number of parts, you might as well built a 2-transistor 2-LED flasher which alternates between the LEDs.


Good luck!

Torben

 

[Torben]

Hehe. Gayan got there first. That's the 1-transistor method I was mentioning, but again, it comes with the caveat that you might find that one 2N2222 (for instance) works, but the next doesn't. If you want to build it, try a few different transistors before giving up if at first they're not working for you.


Torben

 

[k7elp60]

I would just us a blinking LED, needs no other parts and will work on 9V.

 

[ericgibbs]

Hehe. Gayan got there first. That's the 1-transistor method I was mentioning, but again, it comes with the caveat that you might find that one 2N2222 (for instance) works, but the next doesn't. If you want to build it, try a few different transistors before giving up if at first they're not working for you.


Torben

hi Torben,
Did you see the guy had the cheek to slap a 'copyright' statement on probably one of the oldest transistor relaxation oscillator circuits since semiconductors were invented...

 

[mvs sarma]

I just roughly read your post.My be I missed something.

Here is the worlds simplest flasher for LED's.

http://cappels.org/dproj/simplest_LED_flasher/Simplest_LED_Flasher_Circuit.html

Very Nice Gayan.
Of late we also get get flashing LEDs, with built in flasher element. all we need is a series resistor and a suitable power source.

 

[Torben]

hi Torben,
Did you see the guy had the cheek to slap a 'copyright' statement on probably one of the oldest transistor relaxation oscillator circuits since semiconductors were invented...

Hi Eric!

Looks cheeky at first, but I don't think you can actually copyright an idea; that's what patents are for. You can copyright a depiction of an idea though, so as far as I know it's OK for Cappels to copyright his own drawing of it. If he tried to patent the idea, though, he'd need a slap with a wet fish.

Disclaimer: I am not a lawyer, I am not related to any lawyers, and the above is not legal advice.


Torben

 

[Torben]

I would just us a blinking LED, needs no other parts and will work on 9V.

I would've suggested that, except the OP implied that he's trying to learn to design simple circuits. Since he's already managed to light an LED, lighting a flashing LED wouldn't be much fun.


Torben