fuel sender

craig87
Posts: 1
Joined: Thu Jan 07, 2010 3:58 pm

fuel sender

Postby craig87 » Thu Jan 07, 2010 4:15 pm

Quick question guys:

my fuel sender shows roughly 3ohms full and 110ohms empty.

Now what resistor would i wire in parallel to show this as a voltage to the input on the Dash 2?? Ive already got the 5v reference going out.

Thanks

osborni
Posts: 497
Joined: Fri Dec 07, 2007 9:08 pm
Location: USA, Michigan

Postby osborni » Thu Jan 07, 2010 4:56 pm

I'd use a 500 ohm - but you need to check how much current you can draw without exceeding the capability of your unit.

That will give you a ~0.9 to a 0.03 VDC swing.

To increase that you will need to lower the 500 to a 250 - but at the risk of more current draw.

You can also use a 8 or 10 volt linear voltage regulator to increase the voltage swing. The other benefit is that you don't need to really worry about frying your DL1 if you use an external voltage supply.

From the other thread on this same topic:

osborni wrote:
Image

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


Return to “Sensor-related questions”

Who is online

Users browsing this forum: No registered users and 33 guests