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-   -   VSS using ABS ring and hall effect sensor? (https://www.miataturbo.net/megasquirt-18/vss-using-abs-ring-hall-effect-sensor-103639/)

MM89 08-18-2020 07:10 AM

VSS using ABS ring and hall effect sensor?
 
Wondering if anybody has used one of these hall effect sensors with ABS rings on NB driveshafts before?

https://au.rs-online.com/web/p/hall-...ta99fj3APohm3Q

Manufacturer recommendations:
Tooth height: 5mm
Tooth width: 2.5mm
Distance between teeth: 10mm
Target thickness: 6.35mm

NB ABS rings are:
Tooth count: 44
Tooth height: 3mm
Tooth width: 2.7mm
Distance between teeth: 3.5mm
Ring thickness: 11.7mm

Quite different in most respects, so I'm wanting to know if this will work before committing.
Setup is MS3X - plan is to use tableswitchin, tps vref for 5v and spare ecu ground.

MM89 08-18-2020 08:35 AM

Excuse the metric units, taking a punt here...for sake of example I assumed 250km/h

Sensor maximum speed detection = 15kHz

ABS ring OD = 90mm
ABS # teeth (n) = 44

v = 70m/s
r = 0.045m
w = v/r = 1555 rad/s = 14850RPM

tooth passing frequency = (w*n)/60 = 10890 Hz

tpf < 15kHz so all good in the hood?

deezums 08-18-2020 01:12 PM

Seems about 100 times as fast as normal miata VSS, pretty sure usually tops out at like 150hz at 160 or so.

PT4 can use a hardware timer and so can read a higher frequency, I use it for a EFR wheel sensor that caps at ~1.5KHz, but there's jack shit documenting when it will cap out. It also updates slow as fuck, as in maybe ~10hz.

Otherwise everything else uses software timers and maxes out at like 250Hz from what I've read. Might need to divide the frequency down.

MM89 08-18-2020 11:17 PM

Thanks, good to know. Also came across below video today.


Key points:
- PT4 tested to 2kHz
- Tableswitch tops out at 600Hz

Also been discussing with a mate, alternative way to look at it:

Tyre diameter = 577mm = 0.577m
Circumference = 1.812m
Revolutions per m = 0.552
Velocity @ 250km/h = 70m/s
Revolutions per s = 38.616
Revolutions per min = 2317
by 44 teeth = 1700Hz

Within the limits of PT4. He also suggested to use cam input table switch, with the filter capacitor removed, he tested on a MAF sensor up to 9kHz, which, if going by my previous calc, would still get to 210km/h (input could potentially take more than 9kHz, unknown at this point)

I'll grab one and test to see if it drops out at all on cam input.


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