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Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ihnp4!ptsfa!ames!husc6!cmcl2!phri!cooper!gene
From: gene@cooper.UUCP
Newsgroups: sci.electronics
Subject: Re: electronic circuit for flashing indicator?
Message-ID: <998@cooper.UUCP>
Date: Mon, 31-Aug-87 16:06:17 EDT
Article-I.D.: cooper.998
Posted: Mon Aug 31 16:06:17 1987
Date-Received: Wed, 2-Sep-87 06:44:46 EDT
References: <14297@topaz.rutgers.edu>
Organization: The Cooper Union (NY, NY)
Lines: 57

in article <14297@topaz.rutgers.edu>, dalal@topaz.rutgers.edu (Mukesh Dalal) says:
> I am looking for an electronic circuit diagram for flashing
> indicators, like those used in automobiles to indicate turns.

How about just taking a 555 in conjunction with a power relay?
555s are pretty insensitive to power supply fluctuations, VERY stable,
and can sink/source up to 100 (200?) mA. The relay could be used as a switch
for the indicator lights.

Points to remember:
	* if the 555 output can't sink/source enough current, a power
		transistor with appropriate ratings can be used as a buffer.
		ALWAYS heatsink the thing, even if it just gets warm on your
		workbench; in a confined space, such as in a car nook or
		cranny, heat could build up to a dangerous (for the xstr)
		level.
	* remember to install a freewheeling diode across the relay coil to
		kill off inductive spikes.
	* use the formulae
		D = ( Ra + Rb ) / ( Ra + 2 Rb )         /* duty cycle */

		f ~= 1.4 / ( Ra + 2 Rb ) C              /* frequency */

		from the "schematic"

			+V	 O	pins
				 |-----	(8)
			Ra	 Z
				 |----- (7)
			Rb	 Z		<555 connections>
				 |----- (2,6)
			C	===
				 |----- (1)
				---
				///


> Any help (pointers, etc.) would be appreciated.

	char		*s;
	struct foo	*fooptr;
	float		*f;

(I couldn't resist!  ;^) )

					Gene

					...!ihnp4!philabs!phri!cooper!gene


	"If you think I'll sit around as the world goes by,
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	 You got another thing comin'!"

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