At 01:32 AM 8/4/2005 -0700, you wrote:
>On Aug 4, 2005, at 1:14 AM, Tony Smith wrote:
>
>>Anyone know what chip bicycle flashers use?  They're 1.5v, blink AND have
>>on/off.  Must be billions of the buggers made...
>
>I don't think I've ever seen one that ran off 1.5V; most use several
>cells.  In fact, I might add "improved batteries" to the list of thing
>leading to the demise of the 3909 - even the smallest, cheapest (thing
>trade show giveaway) blinky things throw in extra batteries.
>When you can go to a web site and buy a couple lithium batteries,
>several LEDs, a COB IC to drive them, and some magnets to hold them
>somewhere, all for less than $2 in ones; why would anyone use a 3909?
>
>BillW

Yes, the one I just bought uses 2 AAA cells. They probably use a cheap CMOS
COB chip designed for the task (not even a low-end COB micro). I have not
yet taken it apart.

Another issue is that LED forward voltages have been climbing and the
LM3909 won't handle white, blue or some green LEDs. It's obsolete for good
reason.

The blinking Logitech mouse packages used two AA alkaline Duracells powering
a COB CMOS circuit that has two resistors (one to set the flash frequency
and one to set the super-bright LED current). The RC oscillator uses an
on-chip capacitor in the 20pF range and an external 1M resistor. Flash
duration to period ratio is fixed. This device creates an eye-catchingly
bright flash to attract shoppers to the product.

>Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
->> Inexpensive test equipment & parts http://search.ebay.com/_W0QQsassZspeff


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