Simple circuit design question for warning light.

[VinceAtReal4x4s]

I was thinking about adding a warning light/buzzer that would warn me of a major oil pressure drop.

I'm curious if anyone knows how hard it would be to make a circuit that could activate this light but hesitate the activation when starting the motor so it doesn't go off every time you start up. I have glow-plugs on the diesel so it's a bigger deal than with a gas motor... I have to wait each time before turning to the start position. I already have an oil idiot light so I was thinking maybe I could piggy-back off of that somehow, but keep this new light from going off for 5 sec. or so. Maybe a small relay that has a timer built in like this (video in link too)? My electronic know-how has faded in favor of camera/lens technology over the last 8 years.

http://www.oznium.com/12v-delay-timer-relay I thought maybe there'd be something more contained/simple.


The light is a very cool! It blinks and beeps when it goes off so I don't have to rig up some homemade solution. Check it out here: https://www.youtube.com/watch?v=LdU6u8bfxa4

I recently had a scare with my little everyday car where the temp went way up into red and I didn't notice it until maybe 5 minutes after it happened. I also saw a recent post where someone dropped oil pressure in their diesel and lost the engine because they had no idea until it just seized up. Lights and gauges alone aren't worth much in daylight.

My Mercedes diesel also uses a small chain to drive the oil pump and although rare, I have heard of a couple of them breaking in recent years. Add to that two big oil cooler lines that go to a small radiator/cooler, and 30+ years of age... I'd just like some more insurance.

[VinceAtReal4x4s]

I assume in that circuit above I would:
-Ground the appropriate terminal on the right.
-The "vcc" positive terminal would get the idiot light wire, which would still stay wired (in parallel) to the idiot light as well.
- The "com" would get a 12v source
- The "ck" terminal would get the positive side of the two warning buzzer/light wires.

Or am I missing something? Or is there a much simpler solution?

[rmel]

You can get this functionally right out of the box from Prosport Gauges.
http://prosportgauges.com/amber-white-p ... gauge.aspx

I have one of their Fuel pressure gauges set for Over and Warn pressure trip. You
won't have any trouble hearing it when it goes off -- V E R Y loud.

Oh, if anyone is interested in the fuel pressure gauge, go with the Premium series, it
uses a solid state sending unit. I have had bad luck with the Bosch type variable
impedance/mechanical types -- Air cooled engines vibrate these senders to oblivion.
I went through 3 of these Bosch type senders before realizing that

ron

[Jimm391730]

I assume in that circuit above I would:
-Ground the appropriate terminal on the right.
-The "vcc" positive terminal would get the idiot light wire, which would still stay wired (in parallel) to the idiot light as well.
- The "com" would get a 12v source
- The "ck" terminal would get the positive side of the two warning buzzer/light wires.

Or am I missing something? Or is there a much simpler solution?

That sounds right, given a 12V system. Depending on how the buzzer/light operates at lower voltages (like if it doesn't operate below 8V, for example) you could power the buzzer/light through a resistor and capacitor go give a very simplistic time delay - but this would depend on the particular device, and is not a guaranteed fix. The timer you show would definately solve your 10 second delay.

[VinceAtReal4x4s]

Thanks. I found one that looks more like a conventional relay but specs are unclear. Also saw a couple listed as 24v.