LM3909 Flasher IC

The chip is no longer available but the page

shows a discrete version of it.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

Could the venerable 555 timer be rigged to drive a similar circuit? Or has that too bitten the dirt?

Jay Back in action once again

Doesn't anybody know how to use Google?????

gives a circuit that replaces the IC

NTE876 is a replacement

may have some, but you'll have to call.

Norm

Not since they went public.

The 555 IC seems to have a life of its own now and is still available, even in a CMOS version but it doesn't like to run on the 1.5V that the LM3909 does. Just another case of a special purpose IC that has died an early death. I suspect (haven't bothered to look tho) that there is another IC that can do some, if not all of the job that the LM3909 did.

Try reading the newspapers. It hasn't happened yet. At least not in this space-time continuum. You from a different one?

IIRC the LM10 OpAmp will run even below 1.5V and could be used to build an oscillator that would flash an LED. I'm sure that there are many newer ICs that will do the same thing with fewer components. But as long as you're redesigning the curcuit, why not change the battery too to a 9V and then you've got a world of choices -- including CMOS 555s. Norm

Ok, not since they decided to go public.

available, even

the LM3909

an early

IC that can

Bob,

See

for a descrete component replacement circuit for the LM3909.

-- Len Head Rust Scraper KL&B Eastern Lines RR Museum

I found out some time ago that our Australian cousins are very active electronic hobbyists, developing and building circuits using discrete components.

One Az supplier that I have used is FuturLec:

list the LM3909 in stock at $2.45 and postage is $3.00 for an order less than $30.00. They list all prices in US dollars. Takes about 7-10 days to receive the order.

Ray Schwarz

Len wrote:

Last time I checked, (about a year ago,) NTE had obsoleted the 876, too. There may be some available scattered about, but no-one's making them any more.

The primary advantage to the 3909/876 was the small 1.5 voltage needed. You could use an "N" size 1.5v battery that would fit into N scale.

A 555 circuit is easy enough to do, but the larger voltage (battery) requirement makes it unsuitable for most N or even some HO scale applications.

Running a 555 circuit off track power is a good solution, eliminating the need for a battery.

Mike Tennent "IronPenguin"

Go to 9V and you have access to a whole range of voltage regulators that are in the 90% efficient range but then again, the little 1.5V battery is lost there. But then you don't have a flashing LED unless you use one.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

Here's a LED flasher circuit claimed to operate off a 3V lithium battery. It uses just a few cheap, discrete components. I haven't tried it yet.

Or just one of the many LEDs now being manufactured with a flasher circuit built into it:

Hmmm, I might have to try that one, too. The components are small enough...

I haven't found one that flashes realistically enough to pass for a FRED, though.

Mike Tennent "IronPenguin"

On a hunch, I did an EBay search.

There's a guy in South America offering lots of twenty 3909's for $35

• shipping. .00 each isn't too bad.

Feedback is 100% Positive.

That may be too many for an individual, but a club might spring for them.

I went ahead and got some, since I have a FRED board I designed around the 3909 but stopped offering since I couldn't find the chip.

Mike Tennent "IronPenguin" Operating Traffic Lights Crossbucks Special Effects Lighting

Using surface mount parts will help make the finished circuit a lot smaller. You could probably build the whole circuit inside the volume of the original IC package size without any problems.