Altair-what do I do first

From: Carlos Murillo <carlos_murillo_at_epm.net.co>
Date: Wed Sep 25 21:33:01 2002

At 10:54 PM 9/25/02 +0100, you wrote:
>A better solution is to use a crowbar circuit. It's only 3 components!
>
>
>
> +5V o--------------+-----------------------+
> | |
> | |
> --- |
> ^ | 5v6 Zener |
> | |
> +-------------------\ |
> | \ V Thryistor/SCR
> / ------ to carry full PSU current
> \ 100R |
> / |
> \ |
> | |
> | |
> 0V o---------------+-----------------------+
>
>> ground? Seems like you'd want inline fuses between the unregulated supply
>> and the backplace as well for this kind of test...
>
>You want something that will fail safely if the crowbar trips, sure.... A
>fuse is a pretty good choice.
>
>-tony

Excellent advice. However, repeated "accidents" can stress the
SCR enough that it will eventually fail. The trick is to
insure that the peak safe current for the SCR is not exceeded
before the fuse blows. So you either
include somewhat higher resistance wiring between the regulator
output decoupling caps and the SCR or a very small inductor in series
before the SCR.

carlos.


--------------------------------------------------------------
Carlos E. Murillo-Sanchez carlos_murillo_at_nospammers.ieee.org
Received on Wed Sep 25 2002 - 21:33:01 BST