"Norm of Bandersnatch" wrote:

> Arlid wrote to me suggesting several sources for latching relays to 
> turn
> on/off loads connected to a buss using a remote switch.  (see below)


>From a safety stand point, latching relays are a disaster waiting to 
happen.

As an ex control design engineer who spent a major part of my career 
designing and selling control systems, I can tell you that every major 
motor control user had as part of their electrical specifications, the 
specific exclusion latching relays being allowed in their plants.

The smaller users would say, if it is good enough for GM, FoMoCo, and 
Chrysler, it is good enough for us.

AS a result latching relays had almost universal exclusion.

Why exclude latching relays? SAFETY.

If you loose power, the only safe way is to reset every thing to the off 
position and start over.

A relay with a basic holding circuit accomplishes this by providing 
under voltage protection.

As far as trying to use a single circuit for oil and temp alarms for the 
engine is concerned, it could be done with frequency shift technology; 
however, you could by 10,000 ft of 14 AWG COPPER wire for less money.

BTW, closing a contact from a device to ground is a less than desirable 
way to do things.

Again, it is a safety issue.

Lew

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