Hall Effect - Driveshaft

I tried to do that. It works, however it is not reliable.

1. The crap gets caught between the shaft and the sensor, so the sensor will be broken eventually.
2. There could be a big amount of mechanical play in the position of the nocles of the U-joint, so the sensor has to mounted quite far from the shaft.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

It was recommended to us for it to be placed towards the end of the drive shaft that didn't move as much (gearbox end rather than the diff. end).

I wouldn't put it on the universal joint itself, you don't get good mounting opportunities that way.

The one that I did was placed as far up the shaft as it could, but was eventually "misplaced" by a flying blow-up rubber doll.

Don't ask.

The doll got too close to being shafted eh? Mick C

No, it was well and truly shafted. Wrapped around so tightly it had to be cut off the drive shaft.

It's knobbly enough, it should work...

speedometer encoder no good? If the speedo is mechanical perhaps a hall effect sensor could be put inside the speedo case? (since there's already a magnet there)

How about a hall sesnsor, or reluctor on the teeth of the crown (or instead pinion) gear (in the diff) - you'd be less succeptible to road debris inside the diff case.

ABS sensors are another possibility if fitted. would monitoring the reverse lamp give accurate enough direction information?

Bye. Jasen

Don't ask, don't tell?

;-) Rich

In a manner of speaking. :-)

It was my brother-in-law's car, (well before he was officially my brother in law anyway) and it took many, many years before I managed to get the (albeit brief) explanation out of him.

It started after he made changes in the drive train ratio as well as wheel sizes that threw the existing speedo so far out it was useless. He commissioned me to build a digital speedo, so I did, with a magnet on the drive shaft (which is where all this started).

And that's where it stood, till about six months later where he said it "stopped working".

A little casual observation noted the metal arm the pickup sensor was on, was mangled beyond recognition, the cable was pulled apart, and of course, the pickup was no longer near the magnet anyway.

It didn't look like it bottomed out anywhere (the likely problem), so I was at a loss as to what could do this type of damage. So I asked.

A bit of vague non-descript running over a plastic bag resulted.

Yeah, I didn't believe that either, and it was obvious he was trying to hide something. I stopped caring about what did the damage, and instead was now more interested in why he was being so evasive.

Fast forward many years, where after repeated questioning, the subject eventually let up: In an attempt to reduce noise coming in around the gearstick cavity, he stuffed (his words) "a rubber doll" in the hole. Said "rubber doll" came loose, fell down, wrapped around the driveshaft, flapping around killing the magnetic pickup, where it left him stranded by the side of the road till he cut it loose with a knife.

To this day, he still hasn't been clear on the _exact_ nature of the type of "rubber doll", other than it used to belong to his brother. Of course...

And we still rib him about it every so often. :-)

Maybe his brother was "Bud Bundy"?

Unlikely, I know his brother quite well. Ultimately we may never find out. He's being quite evasive about it still, and even immediately afterwards, he said he hadn't removed all of the "rubber doll", and pieces of it were still wrapping around the drive shaft a little later. Since then, he claims to have completely removed it eventually. It is not known if he kept any pieces for keepsakes. (we "ask" but he claims not to).

of

It was a reference to the old Fox TV show, "Married, with Children"

I know, I used to watch it when it was on years ago.

I don't recall either of the brothers mentioning the name "Isis". :-)

Though, it would have been creepy if they did...

Maybe that's the reason he didn't want to tell you what really happened? ;-)

So basically what I'm hearing is if I engineer a magnet on the driveshaft, we have to make sure to mention in the User's Manual not to stuff rubber dolls down holes in the gear shift mechanism.....

Oh, and that Bud Bundy can't ride as a passenger in the cab.

-mpm

Imagine the kind of customers you'd get if you suggest that they DO stuff blowup dolls in the holes. ;-)

I thought Bud was still in jail?