ir_fuel

Discovered something today.

Was planning on installing an AiM steering angle string pot sensor in the car, but on a 996 Cup it is way too complicated. However since the 996 Cup has the same steering column as the RSR we could fit a MoTeC steering angle sensor on top of it very easily. Just a matter of rewiring the connectors and done.

Install went fine, then came the time to test. MoTeC pot in center position, readout on my laptop from the AiM analog channel: 5000mV. Now that's not right if we are using a 0-5V potentiometer. MoTeC pot completely turned to 1 side: 0mV, opening .. went up from 0mV to 5000mV and then from halfway through to completely open still 5000mV.

I had the AiM string pot still around so I connected that to another channel to test. Worked perfectly from 0 to 5000mV. So what could it be?

Measured the output voltage of the EVO4 logger. I supposed it was 5V (considering the sensor ranges and the max voltage the hardware reads in the online view), but no, it seems to deliver 12V to the sensors connected to it. No word about the actual voltage in the EVO4 documentation however. So apparently the sensors built for AiM somehow cope with this 12V signal giving 5V max back, but of course a 3rd party sensor doesn't do this compensation, and AiM seems to clamp voltage values at 5V in the hardware.

Next step will be to destroy a USB phone charger to use the hardware to go from 12 to 5V to power the potentiometer. Another lesson learnt it seems.

Matt Romanowski

There are two power feeds from the Evo4 (or any AiM system for that matter). One is 12V and one is 5V. It's shown in the AiM pinouts. I'll shoot you an email with more info.

ir_fuel

Aha.
Seems the guy in the workshop connected the wrong one

ir_fuel

And thanks to Matt, yet another lesson learnt.

ir_fuel

FYI: Sensor rewired and works fine now.

Matt Romanowski

Great! You'll like having the steering data.

ProCoach

Even more correlated to steered angle!