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Hello everyone,
For my first offical project I am making a small l.e.d. flasher with some parts I found. All I have to do is buy the board from radio shack. Oh yeah, I want to be able to control the speed of the l.e.d. Any help would be appreciated. Thank you. ~ Some guy

lm3909 makes an excellent flasher. It will flash a super-bright LED from an alkaline "D" cell for 3 years. Excellent car alarm simulator.<p>NS applications handbook has dozens of 3909 circuits, from alarms to dual-color-flashers to a radio.<p>I'm not sure how you're gonna control the speed, but placing a pot in the timing path should work fine.

What are the parts that you found?

where can i find a 3909 ?
i have looked in a few parts catalogs i have as well as my local radio shack and haven't been able to find any.

the LM3909 was discontinued in '95 by National Semiconductor. The LM3909N was around till '98, but then it was discontiuned also. So, you'll have a tough time finding it.<p>On another thought: it was pretty funny reading the description of this chip. It's actually described as an "LED Flasher/Oscillator 8PDIP" haha <p>I don't know any alternate sources.

There was a place, called Vanguard Electronics, that had LM3909's a while back.<p>Never bought any, cause I couldn't get a quote.<p>Have to search again.<p>Michael Fagan

Okay, should have checked first, but here it is.
http://www.vanguardelectronics.com/
Go to their "Search" section, and type in LM 3909.<p>Michael Fagan

The power supply is one place to start.
A 9 Volt battery is an excellant choice.

A zener diode such as a 6.2V could be used so the voltage stays the same at the heart of the circuit the (resistor-capacitor) or "RC" makes up a two part combination that charges and discharges to produce a tiny frequency. <p>Since the voltage remains at 6.2 V the amount of current that is supplied to the RC tank can be controlled or limited by a limiting resistor.<p>If you connect the LED directly to the RC tank then the tank is affected by the load so an amplifier or buffer will help maintain the frequency. When a signal is passed to the next stage without loading previous stage. This amplifier is said to have a high input impedance. <p>Going further you could insert an adjustable resistor so that you can adjust the frequency.
A nice range for an LED might be .3 Hz to 30 Hz.<p>I think that if you start with the power supply and work your way forward with an these objectives that you will have success.

variable speed flasher? led?<p>heres a simple one... use a ordinaly 555 timer
and a few simple parts.. and your flashing at variable speeds....<p>allparts can be gotten at the SHIT SHACK
i mean radio shack...lol<p>if you need a help let me know...
send me a e-mail to.. [email protected]
good luck

NTE, a replacement parts reseller, calls the LM3909 their NTE876. Their website<p>http://www.nteinc.com/<p>says there are two left at Mountain States Electronics, 2107 South College Avenue Fort Collins, CO 80526 United States, Tel 1-970-484-1044 1-877-325-1321. Since this is a one-off, I suppose it wouldn't hurt to snag 'em.<p>Even if the part's obsolete, don't give up, and always check the repair parts sources. If the NTE/ECG/SK dodge didn't work, and I just HAD to have one for some reason, I would try to find an electronic widget sold by somebody which had the IC built in (by doing a Google check), and then call that company's repair depot. When an IC is obsoleted, the manufacturer gives notice, engineering departments will notify their purchasing agents, and then a "lifetime buy" will be arranged, while the engineers design a replacement. Repair departments sometimes keep these parts in stock for decades.<p>Happy hunting, and good luck with the flasher. It was a cool chip. Ah, Danny, we hardly knew ye.

Wonder what happened to “some_guy” no come back, and……He’s got Mail… I thought that IC was neat in the respect of letting a 1 ½ Volt battery being used for its DC supply.If one is not familiar with the device it is located :
http://www.national.com/ds/LM/LM3909.pdf
And,alas, it is a discontinued device but if one really needed to make one up from discrete devices it could be done by referring to :
http://home.cogeco.ca/~rpaisley4/LM3909.html
Yup, looks like one of these would also do it. Ckt's about half way down the page:
http://ourworld.compuserve.com/homepage ... page10.htm [/URL]
While doing a refile and combination of my IC devices I did happen to find that I had one pristine/ new OEM device of that number in my stock……so if there should be some one that really, really, really needs one of the devices I would contribute the device .It is going to be pricey however….say, upwards of a SASE.<p>73's de Edd
[email protected] .......(Interstellar~~~~~Warp~~~~Speed)
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<p>[ March 31, 2003: Message edited by: Edd Whatley ]</p>

Do a Google search for "1.5 volt LED flasher". There are a multitude of circuits out there that are simpler than a discrete version of the LM3909.<p>Ron

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Edd Whatley:
[qb]Wonder what happened to “some_guy”<hr></blockquote> I'm back! . I've been away on a vacation to sunny wisconson :p ) see ya ~ Some Guy<p>[ April 01, 2003: Message edited by: some_guy ]</p>

some_guy:
So you’re back after a trip all the way from “America” to Wisconsin, and yes heavy rains and ….forbid…lightning does put a damper upon a game of cow pasture pool.
The reference to mail was an apt reference to AOL’s familiar quip…”You’ve got mail” as in reference to all of the informative responses to your initial post that were submitted to you.
Nothing was “mailed” to you, if you read the last para and see that I only had one unit and if you are to be the sole candidate, I need the Self Addressed Stamped Envelope which will thereby be pre addressed to yourself. All you need to do is hit me at the atti addee so that I can supply you with mine for you to mail to.
This is considering that you don’t opt for the URL with Bill Bowden’s CMOS circuitry or some with just a few discretes as per the third [URL] in my post.<p>73's de Edd
[email protected] .............(Interstellar~~~~Warp~~~Speed)
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Edd, I am humbled by your quick wit.Anyway..... I have it designed but of course I have no idea if it will work. I will be using two double A batteries (1.5 v), a 555 timer IC on a small board from radio shack. Using Bill Bowden's help I think I can do this ! . I can't post my drawing because I don't really know how to draw circuits. It looks a lot like the third link from Edd's posting though (under 1.5 V led flasher). Yeah I know I should have this done by now, but hey! It'll be the first thing I ever built (well circuit wise anyway) ~Some_guy