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One For The Electronic Buffs

Posted: Sun Mar 23, 2008 7:59 pm
by Coops
Im looking at building a custom dash with autometer gauges,
the fuel gauge is giving me a headache,

the autometer one works at these settings.
240 ohms empty to 33 ohms full.

the Capri sender reads: (tested 8 senders 6 were all different readings and 2 were the following within a few ohms of each other)
empty: 70-80 ohms,
full: 10-15 ohms

now, can i get the autometer gauge to work with the capri sender?

Posted: Mon Mar 24, 2008 10:23 am
by ChrisJC
I think you'd need a little op-amp circuit.

But there must be some little box of trick you can buy already, as it must be a common problem???

Chris.

Posted: Mon Mar 24, 2008 3:31 pm
by r2d2hp
If you look at Elliot's Digital Fuel Gauge >> http://www.mez.co.uk/ms13.html#fuelgauge it should be possible to replace the leds with semiconductor switches.

As each switch is turned on it could enable a divider circuit and then therefore the voltage seen by the fuel gauge. Its something I have to do to mine when the car return home in a weeks time.

Will try and draw a picture so you can see what I mean. Maybe some others could confirm it will work ok.

Posted: Mon Mar 24, 2008 8:52 pm
by ChrisJC
Here's my suggestion:
Image
It assumes that your new gauge has no internal resistance (i.e. it needs to see 360mA to give a full reading, and 50mA for an empty reading). This circuit sinks approximately those currents for 80/10ohms on the tank resistance.

Of course you need a handy mate who can understand the cct, work a soldering iron, and fill in the blanks (e.g. choose a single supply op-amp, and add some decoupling).

Chris.

Posted: Sun Mar 30, 2008 1:05 am
by Coops
cheers guys will ask a mate who is good with electronics, unless someone else has any ideas?

Posted: Sun Mar 30, 2008 8:17 am
by monty man
yeah ok m8 i'm sure i can work somthing to get it working.

Posted: Sun Mar 30, 2008 8:28 am
by Ian Anderson
Tony

do the guage makers not also make a transmitter?

Probably easier to buy a "matched" set than play around with electronics.
(But then I cannot see electricity so can't understand it!)

Ian

Posted: Sun Mar 30, 2008 9:35 am
by Coops
yeah they do a matched sender,
but when they room is limited and the sender they use is for a top mounted tank and my sender is a side mounted one,
there is no room to put a sender into the top of my tank, as it will foul the boot floor,

Re: One For The Electronic Buffs

Posted: Sat Jul 05, 2008 7:49 pm
by Coops
thev8kid wrote:Im looking at building a custom dash with autometer gauges,
the fuel gauge is giving me a headache,

the autometer one works at these settings.
240 ohms empty to 33 ohms full.

the Capri sender reads: (tested 8 senders 6 were all different readings and 2 were the following within a few ohms of each other)
empty: 70-80 ohms,
full: 10-15 ohms

now, can i get the autometer gauge to work with the capri sender?

found this autometer gauge tonight,

Auto Meter 5715 - 2-1/16 Electrical
Phantom Fuel Level Gauge 2-1/16" electrical 73-10 ohms Fits most pre-1989 Ford vehicles and most Chrysler vehicles
2-1/16 Electrical
Item# 105-5715
Only $39.99

so i may of solved my problem :lol: