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From: gz@pta.oz.au (Electric Blue)
Newsgroups: sci.electronics
Subject: Re: LED flasher
Summary: just use a flashing led
Message-ID: <1803@pta.oz.au>
Date: 1 Oct 90 23:51:58 GMT
References: <1990Sep30.043045.22757@sisd.kodak.com>
Organization: Pyramid Technology Corporation, Sydney
Lines: 47

In article <1990Sep30.043045.22757@sisd.kodak.com>, rg@sisd.kodak.com (Rich Gortatowsky) writes:
> 
> I am a auto modeler and wish to add blinking lights (ie: turn signals)
> to a model. I have the LED's all set and working for running lights etc.
> How... preytel... does one make a "flasher". I'm basically using only

Just use a flashing led. They look just like a normal led and are available
for under $1. Looking at the Radio Spares catalogue they are available in 
red, green or dual colour. Just connect power and flash away. 

> 2 volts er so imput current. I assume there is a simple (cheap?) way?
> Does it require a relay? If so... well... A simple? diagram of such a
> circuit would be most appreciated!

If you really want to build your own cct you can use an LM3909N led flasher
ic made by National Semiconductors. These retail for about $1.50 and run 
on 1.5 to 3V. the cct is as follows:

			+------------------+
			|     ________     |   LED
		  	+-----|1    8|-----+---|<---+
			+-||--|2    7|              |
			  C1  |3    6|--------------+
			  +---|4    5|---+
			  |   --------   |
                          |              |
			  | V-        V+ |
			  +---        ---+
C1 is 300 uf for a flash rate of 1HZ. To have a faster rate simply decrease
the value of C1. LED can be any normal led. The cct uses the voltage across 
the timing capacitor C1 as a boost voltage so it can flash green leds from
a supply voltage of as low as 1.5V. 

> 
> 						THanks!
> 
							Hope the above helps.
> 
> --

Login name: gz        			In real life: George Zisis
+61 2 415 0515 (RTC, CSC, RTOC, or any other acronym you care to think of..)

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