femster87
|
| posted on 16/4/11 at 03:41 PM |
|
|
Sensors and Dash wiring questions
Am about to start wiring my Race technology dash, I need to do some research so i thought to pick people brain first.
1) From what I understand VDO sensors output varying resistance for whatever parameter they are measuring. The race tech dash range is in volts. how
do I make erm compatible?
2) How do VDO sensors work, ignoring their specific application ( i.e. pressure, temp sensors) Just a generic how do they work.
please correct me if am wrong on any term,
Thanks in advance.
[Edited on 16/4/11 by femster87]
|
|
|
|
|
lsdweb
|
| posted on 16/4/11 at 03:50 PM |
|
|
This topic may help - http://www.locostbuilders.co.uk/viewthread.php?tid=78938
Regards
Wyn
|
|
|
Tris
|
| posted on 16/4/11 at 04:05 PM |
|
|
I have just about finished wiring up my dash2 and was also useing vdo sensors.
Firstly the dash2 provides a 5v regulated output - it's best to use this reference for all your sensors. You then need a pull up resistor for
each sensor between the 5v reference and one pin on a sensor (normally a 1k although this can change). It is also from this pin where the refference
voltage is taken. The other pin on the sensor goes to ground.
It's then just a case of calibration. You need to find out from each sensors data sheet what resistance is to be seen for a given pressure/temp.
A bit of ohms law calculation any you will be able to plot a graph for each sensor for pressure/temp against voltage. The pc utility for the dash 2
then allows for you to input this graph, which then goes and figures out the formula to use.
Cheers
Tris
|
|
|
omega0684
|
| posted on 16/4/11 at 04:11 PM |
|
|
can you use the 5V output on the DASH2 for all the sensors, connect multiple (up to 4) resistors to it, i already have my oil pressure sensor
connected to it, how do i connect up the fuel gauge sendor to it. it says on the RT Website that you can't exceed 100mA on that output.
sorry to hijack a little
I love Pinto's, even if i did get mine from P&O!
|
|
|
femster87
|
| posted on 16/4/11 at 04:14 PM |
|
|
thanks wyn and tris
[Edited on 16/4/11 by femster87]
|
|
|
Tris
|
| posted on 16/4/11 at 04:37 PM |
|
|
Yes to many sensors, you need to control the current anyway as the wattage of the pull up resistors becomes a small issue.
Its a little hard to explain via typing, but i drew graphs for each sensor. The current for each sensor changes depending on the sensors internal
resistance, with the 'pull-up' resistor being used to 'scale' the output.
With my VDO oil pressure, the output (ie resistance) is not linear to pressure (it gets less accurate the more pressure is applied). Therefore the
moment of maximum current is at 0 PSI (which is just 5V over the combined resistance of both the pull up resister and the internal resistance of the
sensor).
[Edited on 16/4/11 by Tris]
|
|
|
daniel mason
|
| posted on 16/4/11 at 07:28 PM |
|
|
so you cant just tag the wires from the dash outputs to the engine loom? tacho, speed sensor, oil pressure,oil temp,coolant temp.
|
|
|
