The cheapest way to blink a led

Buy a Blink-LED. That's all!

- Henry

Ralph Mason schrieb in Nachricht ...

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I suppose a blinking LED just wouldn't do the job? (*Someone* had to ask.)

A flashing LED should do the trick :)

Farnell - part number 515-723, Oz$0.55 each per 100

Mike Harding

If you really just want a cheap blinking LED, buy a blinking LED! The only external part will be a current limiting resistor. Can't get much cheaper than that!

Mark Borgerson

Nope, not even an external resistor is needed; which is a blinking good job :)

Mike Harding

A flashing LED- there's a die inside in series with the LED chip. No other parts.

Best regards, Spehro Pefhany

Cheaper still, get a grab bag of LEDs, about 3c each LED then open and close your eyes quickly.

Al

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Logic

You can add some other non-blinking LEDs in series with the blinking LED and they all become blinking LEDs all at the same blinknig rate.

Blinking hell! I didn't know that!

Mike Harding

(Must be 35+ years since I heard "blinking" used as a profanity - perhaps we haven't advanced all that much? :)

Rob said for all posterity...

I had a flashback to "Airplane II - The Sequel":

"Sir, these lights keep blinking out of sequence. What should we do?" "Get them to blink in sequence." (William Shatner) "Yes sir!".

Casey

way

into

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Yep. My brother got invited to this black tie bash back in the lat 1970s, and he wanted to do something "different". He came to me with the request about an hour or two before his date was picking him up. Luckily, I had a blinking LED in my junkbox. Luckily, HE had a camera flash NiCd pack that provided an acceptable voltage for the blinking LED and two series LEDs. I don't remember now if I already knew the blinking LED could be used that way or if I tried it on the spur of the moment and it worked.

Previous respondants have it right, if you just want a ~50% duty cycle use a blinking LED. However if you want anything else, or are anxious to use a microcontroller, consider the Cygnal C8051F305 which is only $0.99 each. 2k of flash in a 3mm package and with judicious programming (sleep mode) it sucks essentially zero current. Kind of a waste but the cheapest uc solution I can think of unless you're in huge quantities.

Heck, you could even have is send out morse messages!

--Albert

-- Regards, Albert

---------------------------------------------------------------------- AM Research, Inc. The Embedded Systems Experts

----------------------------------------------------------------------

what about those often bogus LEDS that blink in cars. They have a short duty cycle. Are they blink-leds too?

Meindert

What quantity is it supposed to be $0.99 in? Digikey sells them for $2.55 in 100's, whereas a PIC12C508 is $0.96 in the same quantity. A boring old LM555 is less than $0.25 in 100's, and half that in 1K.

Best regards, Spehro Pefhany

A boring old LM3909 would be a better solution than a 555, probably same price range.

I had no idea that the bottom end uCs were so cheap now. Perhaps I'll buy a small jar of them and label it "Whatever". :^)

Not really, as that part was discontinued half a decade ago... those with NOS are probably rather proud of it.

Best regards, Spehro Pefhany

Oh yeah... What on Earth do all the electronics magazines use for bicycle blinky-light projects then? (Tesla coils, lie detectors, bicycle blinky-lights = 75% of the project content.) They could use a uC, but I'd worry that someone would include a "black-box" data recorder as part of the design. (Kidding. Ones for cars are in the news here, and everyone is Shocked and Surprised.)

As I said, _each_, quantity one, $0.99. I have no idea how much Digikey marks them up, you can purchase directly from Cygnal with a credit card. Here's pricing:

As to using a 'boring old LM55', remember that you have to add a few external components, the duty cycle is not very controllable without a handfull of extra parts. Even then you have to change h/w to change frequency or duty cycle. Using a micro gives a lot more options.

-- Regards, Albert

---------------------------------------------------------------------- AM Research, Inc. The Embedded Systems Experts

----------------------------------------------------------------------

No, you did not say "quantity one". You merely said "each", which is probably correct (in some quantity).

Unh, that page says the 10,000 quantity price is $0.99 each. When I add one to the shopping cart I get $4.46 US each. At 100 pieces the price drops to $255/100 = $2.55 each. That is in line with Digikey's price, as it darn well ought to be.

If you know a way to get the Cygnal parts in qty. 1 for the 10K price, I'd like to know, I'm planning to use the C8051F123 in a low-volume project and $12 would be better than $33 US each.

Not for just anybody, anyhow.

Not true, you can get any duty cycle you like with the same 2 resistors and a cap you need for astable operation. Plus one series resistor for the LED which you'd need anyway. And it can drive a lot of current and stay within spec.

Also the Cygnal parts will operate from 2.7 to 3.6V supply voltage, whereas a 555 will operate from as much as 16V supply voltage (and down to about 1V for some versions). The maximum 3.6V supply voltage means that you can't directly drive a blue LED from the Cygnal part without extra circuitry.

True. Three fast blinks and a pause, for example.

Best regards, Spehro Pefhany