Power controlers... on another note. - relays

alvin at Maggie.Linux-Consulting.com alvin at Maggie.Linux-Consulting.com
Tue Jun 4 06:56:23 PDT 2002

hi ya 

relays are bad .... very bad ....
	- all kinds of mechanical failures
	- all kinds of inductive currents

use an SCR instead .... and it can be turned on and off with
a simple +5v circuit on the gate and turned off with a negative
pulse ...
	-- same thing as a relay only 10x better ??

c ya

> all you need is a 5A 110V DC-control relay.  the way this works is 
> essentially wire the relay + outlet like so:
>    110V gnd/netural ----------> to outlet
>    110V hot -----> relay -----> to outlet
>                    v   v  
>    +V DC signal ___|   |______ DC Gnd
> when you put a +DC signal to the relay, it will pass up to a 5A load.
> these relays cost around $4.  toss in a $1 outlet, $1 worth of wire,
> and you've got a little setup that's usable. (of course, you can go 
> more A's for more $.  a 20A relay runs around $7.)
> for a DC control signal, you can either hijack (for a few nodes) the 
> parallel port outputs, or get a $10 PIC or HC11 micro with a bunch of 
> digital I/O pins that you can drive.  
> it's quite straightforward.
> -josh

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