why dont you buy one and open it up?

----- Original Message ----- 
From: "Spehro Pefhany" <speff@interlog.com>
To: "Microcontroller discussion list - Public." <piclist@mit.edu>
Sent: Thursday, August 04, 2005 5:34 AM
Subject: Re: [EE] A replacement for the LM3909?


> 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
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http://search.ebay.com/_W0QQsassZspeff
>
>
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