Datalogging and/or Gauges reusing the car's sensors

5825 Views 26 Replies 9 Participants Last post by dave_n_ruth, Oct 2, 2009

FEO

Discussion Starter · May 11, 2009

I made a run-on rambling post .... and I want to explain myself now

what: tap the car's sensors electrically
why: to make pretty gauges and learn more about workings of the car, either in real-time or by datalogging
where: well the first sensor I plan to attack is the IAT/MAP (combined sensor). Later may attempt oil press/temp?, have little to no info on that at the moment. In theory you could monitor many other sensors
how: tapping the wires that go into the sensors, feeding those to a microcontroller board and then what you do with them is up to you. I plan to read them to a laptop for datalogging, and then move on to realtime display (laptop screen (yes I will code up a danger to the manifold, and eventually moving the whole setup to the trunk area, and feed it to the imiv for display

variants
-have the microcontroller produce the video (PIA) or feed a video dedicated chip (cheap)
-for those without nav, feed it to bluepower's hu or similar
-drive a digital display/gauge (juve's OLED is a prime example)

1 - 20 of 27 Posts

FORD420diesel

· #2 · May 11, 2009

Re: Datalogging and/or Gauges reusing the car's sensors (FEO)

YES!!!!

.....and subscribed.

These could also pull data from additional sensors, correct? Examples being juve's oil temp sensor or an EGT probe.

-Steve

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FEO

Discussion Starter · #3 · May 11, 2009

Re: Datalogging and/or Gauges reusing the car's sensors (FEO)

step 1: tapping the sensor

this little guy provides a 5V Source, GND, and 2 analog signals for pressure (MAP) and temperature (IAT)

it is located by the intercooler

it even has the wires marked 1,2,3,4, how helpful of them

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FEO

Discussion Starter · #4 · May 11, 2009

Re: Datalogging and/or Gauges reusing the car's sensors (FEO)

Step 2 the microcontroller

based on no knowledge at all (last time I did microcontrollers the century had not turned) I decided to buy an arduino board

http://arduino.cc/ (low cost, open source board, based on atmel microcontrollers http://********************/smile/emlove.gif, with 6 builtin ADC channels)

I got the one with a usb interface (received last week)

I am anal and careful, so I don't plan to just hack the wires in the car. I will
a) source the cable shown above (with the 1,2,3,4) new from Volvo (need Vadis help with the P/N)
b) tap the wires
c) add analog buffers, to not disturb the values seen by the ECU
d) protect the whole thing from the elements. Interestingly enough, I am not concerned about water (easy to deal with) but HEAT. As we know our engine bays on a cold day are hotter than a household oven, I don't want some plastic insulation cracking and setting my beloved car on fire...

so I will take my time and do it slowly over the next 15 years

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FEO

Discussion Starter · #5 · Oct 1, 2009

Re: Datalogging and/or Gauges reusing the car's sensors (FEO)

well after a long break from this project, someone IM'd me for an update..

CONVENIENTLY ENOUGH I am right now at the dealer taking care of rear diff fluid (scheduled) and PS groan (unscheduled)....SA advisor just told me angle gear is slightly leaking (POS R

I need some Megan)

In any case, I was chatting to the parts person here, and the cable that connects to the MAP sensor is part of the "network" (not a network, rather big-ass integrated tree-like cable)...worth thousands

So the best bet to source a replacement for this is our friendly grim reaper. Chilled Man do you have any leftovers from any of your P2s?

PS He gave the "they all do that" after my AG face

...Only thing I could think was Magoon http://********************/smile/emlove.gif

PS2 In S60R1's words, angle gear, you can take a number. I'm not fixing it right now

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juve021

· #6 · Oct 1, 2009

WTH...I totally missed this thread

Vadis has detailed info about the signals coming out of this sensor and I've spoken to JimLill about doing this before. Totally doable with just splicing into the wires = no need to spend thousands on oem wiring

AthruC

· #7 · Oct 1, 2009

Re: (juve021)

Agreed, no need to replace the entire wiring harness in the car.

Fernando, if this is of any help, you can pull the little rubber plugs where the wires lead into the plug for the sensor to expose wiring. You can then insert new wire leads right in there to 'tap' it without splicing anything.

Option 2 - find out what kind of plug is used and make an 'extension' (one male, one female) - do whatever you need to do in that section.

FEO

Discussion Starter · #8 · Oct 1, 2009

Re: (AthruC)

Quote, originally posted by AthruC »

Option 2 - find out what kind of plug is used and make an 'extension' (one male, one female) - do whatever you need to do in that section.

This is exactly what I was planning on doing, with the (non existent) OEM cable..... I will see what Justin can let go for a can of cheap beer, otherwise I will be hunting connectors http://********************/smile/emthup.gif

after I cool down from the stupid angle gear news...

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FEO

Discussion Starter · #9 · Oct 1, 2009

Re: (juve021)

Quote, originally posted by juve021 »

Vadis has detailed info about the signals coming out of this sensor

http://********************/smile/emthup.gif I was getting my info on voltage ranges from the Bosch datasheet.... should be the same

Quote, originally posted by juve021 »

Totally doable with just splicing into the wires = no need to spend thousands on oem wiring

yeah but it is kind of a difficult to reach location, and I don't have Adam's skills ...I want to make something on a workbench and then transplant it to the car

a gettho-fail splice could be bad news in this location....and trust me my splices are not exactly stellar

Modified by FEO at 6:27 AM 10-1-2009

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AthruC

· #10 · Oct 1, 2009

Re: (FEO)

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juve021

· #11 · Oct 1, 2009

Re: (AthruC)

Quote, originally posted by AthruC »

awesome

Chilled Man

· #12 · Oct 1, 2009

Ever notice in most pics she hides her freaky thumbs ?

Anyhow she needs to eat more shes a bit to skinny

juve021

· #13 · Oct 1, 2009

Here's some more info from Vadis about the IAT sensor:

NTC resistor type, integrated within boost sensor
supply voltage: 5V (pin #3)
measured between pins #1 & 2
0 degrees C = 5886 ohms
10 = 3791 ohms
20 = 2510 ohms
30 = 1751 ohms

-Pascal

· #14 · Oct 1, 2009

Re: Datalogging and/or Gauges reusing the car's sensors (FEO)

Yet another great thread. http://********************/smile/emthup.gif

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FEO

Discussion Starter · #15 · Oct 1, 2009

Re: (Chilled Man)

Quote, originally posted by Chilled Man »

Ever notice in most pics she hides her freaky thumbs ?

Anyhow she needs to eat more shes a bit to skinny

I'd appreciate if you offer less insights on her weight and more on the actual cable

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Dextrobrick

· #16 · Oct 1, 2009

FWIW unless one electrically isolates the wire tap that one will use to read off of a sensor's signal from the sensor itself and its associated factory wiring, the tap may very well adversely affect the signal and/or resistance of the sensor's reading.

juve021

· #17 · Oct 1, 2009

Re: (Dextrobrick)

Quote, originally posted by Dextrobrick »

FWIW unless one electrically isolates the wire tap that one will use to read off of a sensor's signal from the sensor itself and its associated factory wiring, the tap may very well adversely affect the signal and/or resistance of the sensor's reading.

Yes, very good point! I thought about this as well. Have an idea of how to tap these wires without affecting the readout to the rest of the car? Since we are reading resistance, what is the best way to do this without adding more resistance?

dave_n_ruth

· #18 · Oct 1, 2009

Re: (Dextrobrick)

How well would the Rev app for iPhone work for data logging. If the ECU gets a signal it should be recorded by the iPhone right? Are there things you are looking for that do not send signals to the ECU? I will probably end up with the Kiwi Wifi adapter after I install a boost gage.

http://www.plxkiwi.com/kiwiwifi/hardware.html

Evos_R

· #19 · Oct 1, 2009

FV-QR

Quote, originally posted by juve021 »

Yes, very good point! I thought about this as well. Have an idea of how to tap these wires without affecting the readout to the rest of the car? Since we are reading resistance, what is the best way to do this without adding more resistance?

Because the sensor appears to be a simple thermistor (temperature sensitive resistor), what the ECU is really doing by "measuring" resistance is measuring current. Ohm's law states that Voltage = Current x Resistance, or for this application, R = V/I. Voltage is 5V, and by using an ammeter in series with the thermistor, you can find the current. Ammeters inherently have very little internal resistance, so if you chose carefully, the output signal of the sensor will be unaffected. Divide 5V by the current returned by the ammeter, and you get resistance. Correlate this back to a temperature, and there you go. The currents based on the temperatures listed by juve range from .8mA to 2.9mA, so look for something in that range. Just be sure to look for the lowest internal resistance in your ammeter circuit possible.

Evo

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juve021

· #20 · Oct 1, 2009

Re: FV-QR (Evos_R)

Quote, originally posted by Evos_R »

Because the sensor appears to be a simple thermistor (temperature sensitive resistor), what the ECU is really doing by "measuring" resistance is measuring current. Ohm's law states that Voltage = Current x Resistance, or for this application, R = V/I. Voltage is 5V, and by using an ammeter in series with the thermistor, you can find the current. Ammeters inherently have very little internal resistance, so if you chose carefully, the output signal of the sensor will be unaffected. Divide 5V by the current returned by the ammeter, and you get resistance. Correlate this back to a temperature, and there you go. The currents based on the temperatures listed by juve range from .8mA to 2.9mA, so look for something in that range. Just be sure to look for the lowest internal resistance in your ammeter circuit possible.

Evo

Very nicely put! http://********************/smile/emthup.gif http://********************/smile/emthup.gif

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