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heppy36

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Joined: 29/07/2011
Location: Australia
Posts: 54

Posted: 09:58am 23 Nov 2012

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Hi I am trying to get my maximite to measure my feul sender in my tank and turn of a pump ,the fuel sender is 10 ohms empty and 190 full,I was think of making a reistor divider and connect to pin 1 ,read pin 1 if this value then pin2 off which turns of pump (and flash a led near full).
I think I would need very little current as its in fuel?is there a safe way as I dont want to put in power to a fuel tank?
Any thoughts would be great (dont want to blow my self up)
Thanks martin

Heppy

JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 4038

Posted: 10:37am 23 Nov 2012

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Is there not an existing device (probably a computer) that reads it?

Could you not query it?

John

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5116

Posted: 11:47am 23 Nov 2012

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Can you give some more info Heppy? Is this a factory fuel tank and sender from a car, and if so, a make and year.

Fuel senders changed a lot over the years. With your ohm readings it sounds like you have a older type that used a variable wire wound resistor. A float would be attached to the resistor wiper. The low ohms range of values would suit the older style fuel guages, which were usually a heating element wrapped around a bi-metal strip, attached to a needle.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

heppy36

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Joined: 29/07/2011
Location: Australia
Posts: 54

Posted: 06:37pm 23 Nov 2012

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Thanks its a univeral one,I hooked it up on the bench and measured the voltage on the sender unit,it went from 0 to 6V full,I hooked up a resister divider with 2 2.7k reistors so the votlage was 0 to 3V on the maxi,I wrote a program if pin 2 goes over 2volts turn on pin 1 which turns off the pump.
It all works but I wasn't sure if it was too much voltage at the sender?didn,t want it to spark?
Cheers

Heppy

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5116

Posted: 09:04pm 23 Nov 2012

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Glad you got it sorted.

The atmosphere inside a fuel tank ( someone tell me if I'm wrong ) generally isn't flamable, the gas mixture is too rich to ignite. Most cars now fit the fuel pump inside the tank, the sparking brushes are bathed in fuel, but with so little oxygen, there is no way for an explosion or fire to start.

That said, I do recall a tv show about early jet planes exploding when struck by lightning, due to the explosive atmosphere in the fuel tanks. Now they fill them with nitrogen or some other inert gas I believe. So I dont know why they are different, maybe kero has a different evaporative rate to petrol. Just guessing here.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

BobD

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Joined: 07/12/2011
Location: Australia
Posts: 935

Posted: 12:26am 24 Nov 2012

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Here is the story of a 747 that blew up in 1996 due to sparks off the fuel quantity sensor. http://en.wikipedia.org/wiki/TWA_Flight_800
Are you sure you want to put that gadget in the tank?

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