Inexpensive and simple LED flasher

[amore]

Hi,

I'm looking for the cheapest and simplest possible design to flash a led. It is for an academic exercise unrelated to electronics but related to how to organize processes.

We were using the LM3909 before but it is too expensive now and we need to buy hundreds of components. We have tested an alternative design with a 555 that is cheaper but is too complex for our purposes. The idea is to organize the process to assemble as many flashers as possible in the least possible time (on breadboards). Our design with the 555 has two resistors and it takes a lot of time to assemble.

Does anyone know of a simpler design (e.g. involving no resistors at all) with a chip that is cheaper than the LM3909? No concerns about energy efficiency, elegance and so on, the point is just how to design a process that allows to assemble as many kits as possible.

Thanks a lot!

 

[blueroomelectronics]

They make flashing LEDs

 

[pc88]

will this work?

**broken link removed**

edit: sorry - missed the requirement that it contain no resistors. but is it allowed to contain other discrete components?

 

[amore]

Thanks for your answers. This is more complicated than what we need... We would like to have at most 3 components on the breadboard: chip, led + up to 1 extra component... Do you think this is possible?

 

[Andy1845c]

Heres about as simple as its going to get:
Simplest_LED_Flasher_Circuit

Never made it and can't vouch for how well it works. The only solution I can think of that uses less components is a micro controller.

 

[bee]

What about the leds that flash that "blueroomelectronics" suggested just add power and away you go.
regards
bee

 

[amore]

Thanks folks, this is really helpful!

Toni

 

[Torben]

Heres about as simple as its going to get:
Simplest_LED_Flasher_Circuit

Never made it and can't vouch for how well it works. The only solution I can think of that uses less components is a micro controller.

I've made one; worked like a champ--with the right transistors. And I don't mean the right part; I mean the actual transistor. 2N2222As seemed the most likely to work with it, but you'd have to experiment to see if any given NPN would do the trick. Check this thread for more information.

Given that you never know if a given transistor is going to work, it's probably not a suitable choice for a fast assembly process. You can't just say "use 2N2222As" since one may work, and the next may not.

I think your best bet is to use flashing LEDs which have the flash circuit built in. Expensive but it's the only way you'll do this without resistors [Edit: or a microcontroller, but that would be silly].


Torben

 

[Ubergeek63]

ever hear of a PUT? https://www.electro-tech-online.com/custompdfs/2008/12/2N6027-DPDF.pdf

Dan

 

[Hero999]

Indeed, a small SCR will also work but both probably work out more expensive than a flashing LED.

Here's a link to a place which sells flashing LEDs. They come in red, yellow, green, blue and white. The coloured LEDs cost 23p and the white is slightly more expensive at 40p.
**broken link removed**

 

[mneary]

ever hear of a PUT?

Needs resistors. For some reason OP is opposed to using resistors.

 

[ScareCrow]

Hi, I'm new to this forum. If AMORE just wants the LED to flash then how about a blinking LED from Radio Shack? Everything is already in the LED except the current limiting resistor. 'bout $2.


read the customer comments at the bottom of the web page and see if this meets your needs...
5mm 880 MCD Blinking LED - RadioShack.com

**broken link removed**

 

[Hero999]

Needs resistors. For some reason OP is opposed to using resistors.

That's totally ridiculous, resistors are cheap, you can buy a packet of 100 carbon film resistors for well under a pound.

Even most flashing LEDs require resistors.

If you don't want to use a resistor, just use button cells which have a high enough internal resistance to safely limit the LED current.