Right got all connected up , tested resistance across sensors before connected and got 55ohms, jacked the up car to see any fluctuation and did see a change ie went down to 51ohms before adding 1k resistor.
Ive put a 1k resistor across and connected upto lite monitor, shows around 0.014v ish
tried jacking car up to see any change but does not change or very little
would this mean I dont need the resistor in?
Cheers Adam
Fuel gauge help
I'm getting the feeling that you might not know what a pull up resistor does...
The fuel tank sender represents the "sensor". The 1k resistor is in the diagram.
55 ohms is about right for a fuel sender gauge. I think you will need a 500Ohm resistor to have enough voltage swing. A 1K will only give you about a 1 volt swing from an empty tank to a full tank. 500Ohm will give you about a 1.6-2 volt swing. Depends on how accurate you need to be. If you are measuring to 1/10ths of a tank, it should be fine. But if you want to measure fuel consumption, it might not have enough resolution.
Calculator: http://www.electronics2000.co.uk/calc/p ... ulator.php
The problem with a lower Ohm resistor is that you will draw more current from your DL1. You will need to add up how many sensors you have and what they draw to figure that out.
Ohm's law: V=IR to figure out the current draw on a pull up resistor network.
Simplest solution is to use a $5 linear voltage regulator from Radio Shack with $5 in other misc parts.
The other solution for better resolution is to use a 10 volt regulator to boost the voltage going to the sensor. (12 VDC is too close to the 13.8 VDC that most cars run at - it will not be a stable voltage signal.) That will give you more volts out and a higher resolution.
The fuel tank sender represents the "sensor". The 1k resistor is in the diagram.
55 ohms is about right for a fuel sender gauge. I think you will need a 500Ohm resistor to have enough voltage swing. A 1K will only give you about a 1 volt swing from an empty tank to a full tank. 500Ohm will give you about a 1.6-2 volt swing. Depends on how accurate you need to be. If you are measuring to 1/10ths of a tank, it should be fine. But if you want to measure fuel consumption, it might not have enough resolution.
Calculator: http://www.electronics2000.co.uk/calc/p ... ulator.php
The problem with a lower Ohm resistor is that you will draw more current from your DL1. You will need to add up how many sensors you have and what they draw to figure that out.
Ohm's law: V=IR to figure out the current draw on a pull up resistor network.
Simplest solution is to use a $5 linear voltage regulator from Radio Shack with $5 in other misc parts.
The other solution for better resolution is to use a 10 volt regulator to boost the voltage going to the sensor. (12 VDC is too close to the 13.8 VDC that most cars run at - it will not be a stable voltage signal.) That will give you more volts out and a higher resolution.
BMW 2000 M Coupe
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Don't wire them in parallel or you will get strange results. If one of the senders goes to 0 ohms (short), then the parallel reading will also be zero regardless of how much fuel is on the other side of the tank.
Peter Carroll, Toronto, Canada
DL1 and Dash2 - http://DriversMeeting.com/pcarroll
DL1 and Dash2 - http://DriversMeeting.com/pcarroll
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- Posts: 110
- Joined: Wed Jul 04, 2007 11:33 pm
- Location: Toronto, Canada
- Contact:
We had problems wiring dual senders in parallel. If one goes to zero, then the parallel resistance also becomes zero. This will give you impossible readings in high G corners. Wiring the senders in series resolves the problem. We use a 1K resistor with good results on BMWs.
Rc = (R1 + R2) /2
except when R1 or R2 = 0!
Rc = (R1 + R2) /2
except when R1 or R2 = 0!
Peter Carroll, Toronto, Canada
DL1 and Dash2 - http://DriversMeeting.com/pcarroll
DL1 and Dash2 - http://DriversMeeting.com/pcarroll
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