PWM TPS

[greenamex2]

Hi

Not sure if this really an enhancement request but thought I would highlight it.

For a PWM ouptut throttle position sensor the current GPA firmware is fixed at a "100%" value of 5ms. Assuming using the full range of a cycle this equates to a frequency of 200Hz.

So far most of the throttle position sensors I have found are well in excess of this. For example the Curtis Wright sensorss are 244Hz (OK, this one is pretty close!), 500Hz and 1000Hz and the Vishay 981 sensor is 1000Hz.

For example, if you use a 1000Hz the maximum pulse duration would be 1ms, or one fifth of the 5ms assumed for 100% Add in the fact that you are incredible unlikely to even hit 1ms, or have 0ms as 0% throttle opening, you are possibly beginning to restrict resolution.

In short...any chance of making the 100% duration configurable? Would improve compatibility with more sensors.

[Stephen Dean]

Hi,

The Vishay TPS uses PWM at 1khz to encode its position location information, ranging between 10% and 90% DC. The M1 can best decode this by measuring Duty Cycle, not Pulse Width.

An example of setting this up would be as follows;

Sensor wired to UDig8

Throttle Pedal Sensor Main Resource - UDig8 Hybrid B
Throttle Pedal Sensor Main Digital Decode Resource - Universal Digital Input 8
Throttle Pedal Sensor Main Digital Decode Type - Frequency

As per the help for the Throttle Pedal Sensor Main Digital Decode Type, selecting the Frequency B Resource reports a Normalised Duty Cycle.

Udig.png (32.48 KiB) Viewed 13577 times

The M1 UDig input timing can resolve this duty cycle to a very high resolution regardless of the frequency.

[greenamex2]

Thanks

Any tips on the Curtis Wright sensors, although I suspect that would be the same?

[Stephen Dean]

Most likely the same, but I haven't been able to find any definitive information on their signals yet.

[greenamex2]

From the product catalog -

Electrical characteristics

Capture1.JPG (23.92 KiB) Viewed 13531 times

[greenamex2]

And -

PWM graphs

Capture2.JPG (26.12 KiB) Viewed 13531 times

[Stephen Dean]

Similar setup for that throttle as well, where you would measure the pulse width for the position data.

[David Ferguson]

I think you mean set the decode type to Frequency, and the Duty Cycle measurement (Hybrid B) will have the position data.

[greenamex2]

Thanks, I'll give it a go once I have machined the pedal rest and report back.

Thought I had tried the combination before, probably just got confused!

Thanks for the help.

[greenamex2]

That has doubled the resolution. That will do for now.

Thanks for the help.