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From: grege@gold.GVG.TEK.COM (Gregory Ebert)
Newsgroups: sci.electronics
Subject: Re: Need Scematics for DC Motor Speed Control.
Keywords: Speed Control
Message-ID: <807@gold.GVG.TEK.COM>
Date: 23 Feb 90 21:13:33 GMT
References: <3609@tahoe.unr.edu>
Distribution: usa
Organization: Grass Valley Group, Grass Valley, CA
Lines: 20

In article <3609@tahoe.unr.edu> isaac-b@tahoe.unr.edu (Benjamin Isaac) writes:
>I have had a lot of problems locating a decent schematic for a speed controler
>for a cordless drill.
>  
>The type of schematics I am looking for is one that:
> 
>       1. DOESN'T use a transitor/resistor design (i.e. heat/excessive drain).
>       2. doesnt require extremely hard to find components.
>       3. can handle around 1amp at 6volts.
>       4. will hopefully have some torque at lower speeds. 
>
	Easy. Use a tapped-voltage power source. If you have 4 batteries
	rated 1.5 volts apiece, you get 4 possible voltages: (1.5,3,4.5,6).
	The 1.5 might be useless, but the other 3 should be OK. Some
	batteries get 'bogged-down' by internal series resistance, so
	you may want to use 5 cells for 7.5 v (MAX).

	Be careful you don't overload the batteries. Some reachargeable
	cells will 'vent-off' at high drain-rates due to excessive heating.
	This puts yucky corrosive fumes in your equipment :( .