Wheel Speed Sensor Setup

ADU
1

I don’t know if it’s just me, but I’m not feeling like there are very clear instructions for setting up a wheel speed sensor to be used by the adu. Is there somewhere I should look? I have a hall sensor, looking at 5 teeth per rotation, the sensor is wired, I’m mostly just not sure what to do with the multiplier and divider options on the digital input. I have it setup as frequency, and have chosen my adu input. I’m just at a loss regarding the multiplier and divider.

The tire it is watching is a 145/65r15.

I have an EMU Pro 8 connected to the ADU. Do I need to do any setup in there as well to grab the data?

Also, is there a way to get the ECU/ADU to calculate gear based on rpm and speed?

Thanks for any help you can give this ECUMaster newb!

2

If you have free digital inputs in EMU PRO, it is easier to connect the sensor directly to the PRO and then send the speed via CAN to the ADU using the EMU Black CAN stream.

In EMU PRO you only need to select the source and set the ratio in km/h per Hz.

3

Thank you for your response. I do have the free inputs, however, the ECU wiring is kind of stuck where it’s at for now. I converted from another ECU, so everything is semi limited to what was there before, and there wasn’t much. Also, being rear engined, the ECU is in the rear, and the dash is in the front nice and close to the front wheel I’m trying to get data from. I plan to rewire from scratch, eventually. But there will be some major drivetrain reconfiguring that will come with that change.

As of about 10 hours ago, using the base settings for wheel speed on the ADU, I got a reading when spinning the airborne wheel with my foot. I haven’t driven the car yet, as I’m still trying to sort out a few other input issues, but hope to tomorrow, probably. A brief explanation of the multiplier and divider would be very helpful. AI has tried hard, and using info it gave me I got now reading at all at foot spin speed. So I feel like I’m closer now with 1 in both boxes than I was with “calculated” values.

Also, on the pro, regarding gear ratios, I can’t see what it says on the side menu that describes the calculation. Am I supposed to put the mph at a certain rpm for each gear?

4

The Divider and Multiplier options are very self-explanatory.
A digital input with type Frequency measures the frequency of the input signal.

  • If you set the divider and multiplier to 1, then your output value will simply be the frequency of the signal.

  • If you set the multiplier to 10, then the output value will be 10 × input frequency.

  • The same applies to the divider.

Example with your wheel size (145/65R15):

To calculate speed from pulses, you need to know the wheel circumference.

  • Profile = 0,65 × 145 mm = 94,25 mm

  • Diameter = 2 × 94,25 mm + (15 × 25,4 mm) = 188,5 mm + 381 mm = 569,5 mm = 0,5695 m

  • Circumference = π × diameter = 3,1416 × 0,5695 = 1,788 m

So the wheel circumference is about 1,788 m.

If you have 5 pulses per revolution, then:

Speed [m/s] = (Hz × circumference) / pulses

Speed [km/h] = (Hz × circumference × 3,6) / pulses

Example calculation:
If the sensor reads 100 Hz:

(100 × 1,788 × 3,6) / 5
= (100 × 6,4368) / 5
= 643,68 / 5
= 128,736 km/h

So, using multiplier and divider, you can configure the ADU to output speed directly:

Formula:

(Freq × circumference × 3,6) / divider = speed [km/h]

Here, circumference × 3,6 is the multiplier.

  • 1,788 × 3,6 = 6,4368 → multiply by 10000 to make it an integer.

  • Multiplier = 64368

  • Divider = 50000

With this setup:

  • If the sensor gives 100 Hz, then PMU will show 128 km/h.

To add the unit, you need to use a Number element.
If you want 1 decimal place, then the divider should be 5000, and so on.

image
image370×414 9.39 KB

1 Like
5

Haha! You and I have very different ideas of self-explanatory! I don’t have and engineering or coding background, I just machine parts for a living, and turn wrenches and hook up wires for fun.

I appreciate the detailed response. I’m confident I can turn that data into something useful!

Do you have a response to my question about gear ratio on the pro? My screen cuts off the last bit when looking at the place where you input the speed data. I can’t read what I’m supposed to input. Even changing that particular page into a full page on my screen still cuts the right column down to small to hold all of the text.

6

Could you paste a screenshot?

image
image910×263 15.4 KB

If you click on the Value and press the Insert button, then this value will go to the graph log where you can check the unit.
We are aware of the issue with longer units being cut, and it will be fixed in the future. Until that time, you can use the workaround I showed.

1 Like
7

Okay perfect! Thanks for the tip. That’s what I was thinking the value was, 1000rpm.

8

I have edited my previous post, please check it.

1 Like