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Pull up resistor?
lsdweb - 28/11/07 at 08:11 PM

Hi All
I'm wiring in my DL1 data logger and trying to work out the wiring for the oil temperature and pressure sensors.

The manual says
When supplied with a cable for use with the Data Logging Units, the sensor is supplied with a series 1k "pull up" resistor. There are 3 leads that come from the sensor: the red lead should be attached to the +5v supply from the Data Logger Unit, the black lead should be connected to the ground connection and the white lead should be connected to an analogue input.

I'm a bit confused on where the pull up resistor sits and how they use a three wire cable on a two terminal sensor (is one the screen?) I'm not using their cable or sensors - have a look at their prices !!

Any thoughts?

Wyn


MikeRJ - 28/11/07 at 08:24 PM

The 1k resistor will be inserted somewhere in the red wire. Three wires are used because you have to supply a current to the sensor via the pullup resistor in order to get a voltage to measure. The voltage is measured via the white cable connected to the analog input of the datalogger, and eveerything is referenced to the ground connection. Essentialy the red and white wires will be joined togther at one terminal of the sensor.

In practice you should be able to connect the pull-up resistor between the +5v supply and the analog input at the datalogger itself, so you would then only need two wires going to the sensor.


lsdweb - 28/11/07 at 08:40 PM

Thanks Mike

Any chance of one of your great diagrams.....


tegwin - 28/11/07 at 10:17 PM

Mike RJ- Im not convinced you are correct...

Logic would suggest that "pull up" resistor should go on the white cable so that the analogue input to the module is not allowed to "float" (And is, by deffinition, pulled "high" when it is not being signaled to reduce spurious results...)

I may be wrong though...these things happen...


Bob C - 28/11/07 at 10:18 PM

I'd say between red wire and white wire....
best of luck ;^)
Bob


MikeRJ - 28/11/07 at 11:10 PM

quote:
Originally posted by tegwin
Mike RJ- Im not convinced you are correct...

Logic would suggest that "pull up" resistor should go on the white cable so that the analogue input to the module is not allowed to "float" (And is, by deffinition, pulled "high" when it is not being signaled to reduce spurious results...)

I may be wrong though...these things happen...


Correct, the resistor does connect to the white wire as I said, and is also connected to the red wire which provides the pull-up.

The sensor is resistive and the datalogger measures voltage. The simplest way to convert resistance to voltage is to put the variable resistor in one side of a potential divider, the other half is formed by the "pull-up" resistor.


Sorry for ultra crappy ASCII art, the forum is horribly broken so it eats back slashes and the code tags double space everything.

+------1k Resistor-------o +5v
|
+----------------------------o Datalogger Input
|
#
#
# Sensor
#
|
|
+----------------------------o 0v


lsdweb - 29/11/07 at 08:47 AM

Like this? Rescued attachment logger2.jpg
Rescued attachment logger2.jpg


MikeRJ - 29/11/07 at 09:45 AM

Not quite! In that schematic the 1k resistor is rather redundant as it has both sides connected to +5v, so the datalogger would only ever see +5v irrespective of the sensor resistance.

By the power of MS Paint I have corrected it

Logger-sensor connection
Logger-sensor connection


lsdweb - 29/11/07 at 01:43 PM

Thanks Mike

It's obvious now!!!

Regards

Wyn


omega0684 - 16/4/11 at 04:07 PM

can anyone post up a diagram of how to wire up the fuel sender please?


daniel mason - 20/4/11 at 08:54 PM

as far as im aware alex the fuel sender wire from the dash connects directly to the wire through the sender to ground. then before you actually connect the wires together you need to take a resistance reading across the sender with tank empty,half full,full and enter these when programming the dash!
i am currently trying to set up the can lo and high from my dta s60 to transmit data direct from ecu to dash, as the ecu monitors loads as standard,meaning less wiring