🚀 go-pugleaf

"DaveC" <anon@example.net> wrote in message
news:0001HW.B9809AF0003B6CA309D78310@news.covad.net...
> On Wed, 14 Aug 2002 23:09:16 -0700, Paul wrote
> (in message <ajfgej$lmt$1@kraken.itc.gu.edu.au>):
>
> > "DaveC" <anon@example.net> wrote in message
> > news:0001HW.B97FE8A5001B1B1E09D78310@news.covad.net...
>
> >> I want to make a circuit that will sound an alarm when oil pressure
goes
> >> to zero, or temperature goes to max. The alarm must not trigger for
about 10
> >> seconds after I turn on the ignition. (I don't want the alarm to sound
> >> before I start the engine.)
> >>
> >> The simplest circuit seems to be:
> >> 1) a relay triggered by the oil and temp idiot light circuits, that
sounds
> >> an audible alert
> >> 2) a relay that provides power (or ground) to relay (1)'s coil
> >> 3) an R-C circuit that delays the activation of relay (2) for about 10
> >> seconds.
> >>
> >> Is there a simpler way to do this? With just one relay, and that
relay's
> >> activation delayed by the R-C?
>
> Thanks for your suggestions, Paul.
>
> > The turn on delay would only need to be on the oil pressure sender,
because
> > if the engine temp is already at max when you go to start it, there is
> > something seriously wrong.
> >
> > Most temp senders are a themisters used to drive the temp gauge in the
> > vehicle. Hotter the temp the lower the resistance of the termistor.
Voltage
> > at the themistor terminal gets less (closer to 0V) as the engine heats
up,
> > but it may not reach 0v, you will need to work out what voltage
represents a
> > high temp. You will also have to be carefull as any low impedance
> > connections to the sender output will change the reading on the dash
temp
> > gauge.
>
> So far, I follow you.
>
> Any idea how I can implement the delay while I start the engine?

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.

Or you can also monitor the tach input, it's a pulsed signal, whenever the
engine is running.

> > Also, in many cars the temp sender is in or near the themostat housing
at
> > top of the engine. This can prove a problem if the coolant rapidly
drains
> > from the system due to a burst hose, water pump seal, etc. I have heard
of
> > several stories where the temp gauge read as "normal", yet all the
coolant
> > had drained out of the engine and the engine seized.
>
> Oh, great! Any ideas how to side-step this shortcoming in the design?
> --
> Note that my return address is corrupted in an attempt to reduce spam. If
you
> choose to e-mail me, please correct my address as described below.
>
> Thanks,
> Dave
> ---
> Dave Carpenter
> Sound Logic
> voicebox@d8n8a8i.com
>
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