🚀 go-pugleaf

DaveC wrote:
> 
> On Thu, 15 Aug 2002 10:51:02 -0700, Dave Freejack wrote
> (in message <ajgplu$lif$1@news.colba.net>):
> 
> > One way would be to monitor the Batt light, which is normally on before you
> > start the engine and off when the alternator is ok...
> >
> > And make it as a trigger so if the batt light will lit up it will not
> > interfere with your alarm.
> 
> This could cause problems. The water pump is driven by the same belt as
> drives the alternator.
> 
> 1) Belt breaks
> 2) Alternator light comes on, disabling alarm
> 3) Water pump stops pumping
> 4) Temperature rises, unnoticed
> 
> Hmmm. Maybe I should also monitor the ALT light rather than use it as an
> enabling signal.
> 
> Ideas?

Thta's a good idea.  With diodes you can monitor all the
idiot lites with a single circuit.

Enabling the alarm via the idiot lite circuit is a bad idea.

I'll propose a different approach:
wire up an SCR to the accessory circuit and to your
alarm buzzer, through normally closed relay points, and
through normally open points of a second relay.
Wire the gate of the SCR to idiot lites through
diodes. You'll have to figure out the polarity
of things, which depends upon whether the idiot
lite is switched in the ground lead or in the +
lead.

Wire both relay coils to the starter circuit. When the
starter is energized, the relay with the open points
closes and tries to send power to the SCR to enable it.
Call that relay 1.  Use a second set of points on that relay
to hold it energized after voltage is removed from the
starter. It will stay energized until the car is shut off.
Meanwhile, while cranking, relay 2, the one where you wired the
closed points, prevents power from reaching the SCR, so
the alarm does not sound.  When you stop cranking, relay
2 drops out and the normally closed points close,
enabling the SCR.  Drive along merrily until an idiot
lite comes on. The SCR will turn on and stay on until the 
car is turned off, and the buzzer will sound.  BUT - when
you first get in the car, prior to cranking the starter,
the alarm will not work, regardless of idiot lites.
This eliminates a delay circuit and positively assures
enabling the alarm every time you start the car.

> --
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> Thanks,
> Dave
> ---
> Dave Carpenter
> Sound Logic
> voicebox@d8n8a8i.com
> 
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