Low Pressure Warning Light Fed From Gauge Feed

Shaun

Supporter
Ok so one here for the electronic whizz kids out there, so I have a oil pressure gauge, the sender does have an output for a warning light but its a real ball ache to get a cable back to the dash so I was thinking is there a way to trigger a light from the gauge feed, its a resistance based circuit, ETB tell me the gauge runs 10 Ohms static (0)
184 Ohms full scale so I was thinking of a system where a light was triggered say 20 Ohms, if its a linear scale then its about 3 Ohms per psi
A light would always eye catch more than a dropped gauge so its something I wished I had done at the time of wiring....
Done a web dig but nothing
Thoughts
 

Neil

Supporter
While looking for a suitable comparator I found this:


It is a complete printed circuit board with parts mounted. It is powered by 12V and the trip point is adjustable from zero to +10V. There is a small LED indicator as well as a 10A relay on board so you can switch almost anything. The price is $12.99. You can't build one this cheap.
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
I may not be understanding the issue fully....
Why not just install a “T” in the oil pressure feed line, then screw in a light sender from a 65-66 Ford Mustang? I believe they tigger at 10 PSI pressure...
 

Bill Kearley

Supporter
You could add a T at the oil pressure port, but like you said another wire to run and a hole to drill for the light, a pain.
I think I'd T into the oil port and use it for an auto ignition shut down with an over ride for startup, a hidden button on the firewall like mine.
 

Ian Anderson

Lifetime Supporter
Hi
could you ask ETB if they can do a pressure gauge with a warning light fitted that works with a single wire?

i know when I asked them to do my gauges they said they could make adjustments if required.

The only thing they could not do was a fuel gauge with two needles one for left and one for right tamks

ian
 

Shaun

Supporter
Hi al, thanks for the info and tips, I had seen a comparator Neil but could not find a suitable circuit, I agree a wire best but a pain to fit my sender actually has a feed for a light but its a long way from the dash!! ETB Ian I will ask. Nice idea re left and right tank bit like an aircraft manifold pressure gauge!!!
I'll ask ETB and look at that comparator as well, thanks all
 

Shaun

Supporter
Got the comparator Neill you suggested, my gauge is resistance based so not sure ot has a voltage across it or is it detecting the voltage drop the resistance gives, but hard to test on a oil pressure as I have not got the engine running yet.
 

Howard Jones

Supporter
I actually think it would be a mistake to source both forms of fault indication and protection from one sensor and associated wiring. You will have lost the redundancy of a two-source monitoring system. I have had a low oil light come on indicating less than 30PSI only to look at the pressure gauge and see 50-70PSI changing with engine revs. It turned out to be a bad pressure sensor and saved a red-flagged session, long delay for everyone else, and a tow back to the paddock for me.

I would recommend two sensors sampling two separate locations on the engine, two sensors with no common wiring, and two separate indicators, pressure gauge, and idiot light.
 

Shaun

Supporter
Fair point Howard, if I have to run a cable it may as you say be on a totally different circuit....Cheers
 
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