I2C DAC output connection to ECU

Other Hardware General Electronics
1

Hi All,

I am trying to make a remote that can rev my engine. I tested the principle by finding the ECU inputs from the throttle position sensor and just injecting (adding) a voltage to it. The engine revved OK.

I then made an arduino with I2C DAC, when I connect the output of the DAC to the ECU input and try to rev the engine usng the vehicles manual throttle it does not respond! I disconnect the arduino and it works again. I assume the DAC is holding the input low preventing the normal throttle working, I'm looking for advice if adding an open collector transistor to the DAC output would work?

voltages are low 0-1.3v DC

Thanks

Steve

2

Did you collect voltage output data from the pedal sensor ? Do you know it is a variable analog dc in the
0-5V range and not PWM ? Please post the DMM measurements of the pedal sensor output for the full range of the pedal. I assume you don't have a scope ?

3

Yes, it's variable analog 0-5v definitely not PWM, I found the wires, got a variable PSU and injected a voltage, the vehicle revved OK.

Regards

Steve

4

What did your insurance company say about your modification?

5

Nothing. It is not insured. :grin:

6

Did you diconnect the peddle first ?

7

When I contacted them they said, "well agree we think it might be pulling the line down but better ask on the Arduino forum" :roll_eyes:

8

No, the vehicle was "as is" I found the TSP wires, injected a voltage and it revved, I then added the arduino (with DAC) and whilst connected the vehicle's throttle did not work. disconnect the arduino and everything was back to normal.

9

The question was did you replace the peddle with the arduino or were BOTH connected SIMULTANEOUSLY ?
(NOT implying they can't be, just asking.! If the peddle output is the wiper of a pot with one end
GROUNDED and the peddle not depressed, then the DAC output is GROUNDED.
That's Electronics 101A) Are you ESL (Electronics second language) ?

10

sorry, I thought I was very clear

The vehicle was not touched in any other way than finding the wires into the ECU and injectiong a voltage from a PSU, the vehicle revved using that voltage and also could be revved using the throttle.

Then I attached the Arduino to those wires and the throttle no longer worked.

By "injecting" I mean all existing wires remained connected and the external voltage was added by splicing a new wire into the old wire.

Thx

11

Please post a schematic. It sounds like there are two cases
CASE A. NO ARDUINO, PS 'spliced' to vehicle (WHERE?)(ACCEL PEDDLE CONNECTED?)
CASE B: ARDUINO+DAC 'spliced' to vehicle (WHERE?)(ACCEL PEDDLE CONNECTED?)
DEFINITION OF TERMS:
An unmodified vehicle is accelerated by pressing on a pedal. If you are using the
term 'THROTTLE' for the physical PEDAL, please state that.
Still need a schematic of how it was wired.

12

Sorted, the DAC has a power down mode that puts the output at circa 300k to ground this fixed the problem.

Thanks

13

Glad to hear it.

14

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