Couple Quick PAS Mounting Questions

Getting ready to mount my PAS on my bike but I have a couple questions

This is the PAS I bought
https://bmsbattery.com/ebike-parts/504-pas-pulse-padel-assistant-sensor-with-12-pcs-magnets-parts.html

Obviously the pic does not show the 12 pole magnet wheel.

Here are pics of the one I have in hand.





Can I mount this on either side of the bottom bracket?
Also does it matter which side of the magnet wheel faces the sensor?
There are no directional arrows on the ring as I have seen one some other wheels.

Yes and yes. There's 4 possible combinations of side and magnet orientation. Occasionally, the sensor is a double hall, which can be handed, which means only one combination will work, but I'm prety sure that yours is a single hall, so two combinations will work.

You can test it first by connecting it and rotating the magnet disc with one hand against the sensor, which you hold in your other - with the wheel off the ground, obviously. I do it by turning the bike upside down. Whatever you do, test it before reassembling the crank.

If you ave a 25mm Hollowtech crank, you need to unscrew the sensor and fix it on the other side of the bracket to reach over the bearing holder.

If you wnt to fit it on the left side of a square taper crank, you need a lcking ring, which costs about $1 from Ebay.

I have just received the exact same PAS and have the exact same questions
Please update us here if you find out how it works.
Here are my theories so far: (none actually tested, the bike is not yet ready)

-The V shaped head of the sensor would be a clue into the orientation (mount it so that the V points in the forward/rotation direction)
If that is true, it would probably mean the unit is meant for non-drive (left) side mount, since then you mount the black plastic part side facing away from the bike (seems logical as it looks nicer).
The cable then comes out at the back of the unit, where it is not exposed to spray from the front wheel. Again sounds logical.

-The magnet wheel; If my assumption about mounting the black plastic part of the sensor facing out is correct, I would expect the same to be true for the magnet wheel. This again looks nicer, and this way the magnets are closer to the hall sensor (no plastic in between) for a stronger signal. Sounds logical right?

My theory:
Meant for Left side mount, plastic part of sensor away from bike, magnet wheel, plastic side away from bike as well.

Then again, this is China, so any of my "logical" assumptions could be incorrect :lol:

The sensor is designed to be used on the drive side because the bottom bracket has a flange on that side to retain the bracket. It would only fit on the other side if you have the old separate cup and cone type BB. You can still fit it on the left side when you have a normal BB, but you need to unscrew the BB a bit on that side and then use a locking ring to retain the sensor bracket or find some other way of retaining the sensor. Some people bend the bracket at right angles and wrap it under the BB, held with a zip-tie. It doesn't matter which way the sensor points, but you have to flip the magnet disc to match it.

The disk has an arrow on it, but I wouldn't go by that. It's very simple to test which direction it works before you re-install the crank, then you can flip the magnet disk in the correct orientation.

Read what I wrote above about handed ones. The one in the picture is not handed (or never has been so far!)

I have a modern cartriged style bottom bracket with a square taper spindle and I have no issues mounting the sensor on either side.

I am sorting through the wiring now and will do some testing to see what it does then make the choice to mount it accordingly

vwhammer said:

I have a modern cartriged style bottom bracket with a square taper spindle and I have no issues mounting the sensor on either side.

Click to expand...

How will you retain the sensor on the left side then?

This pic may help illustrate how it is held in place.

I have had the sensor installed on both sides and it seems to mount just fine.

After I do my test (still messing with wiring) I am hoping to mount it on the drive side so it is hidden better

That's an unusual BB. The left side is normally plain thread without the flange.

That BB type (one separate flanged plastic cup on the non-drive side, and a fixed steel cup on the drive side) is not that unusual for a cartridge bottom bracket. I have the same one on 3 of my bikes.

[strike]Mounting the PAS on either side is fine, although Left side is easier, as it doesnt require complete removal of the BB.

Quick update on mounting this type of PAS.
When mounting on the Left side (non drive):

Arrow of the sensor facing to the front of the bike (Other way around works as well, but this is easier to align and it looks nicer)
Magnet wheel, shiny side out.[/strike]

Edit:
After more testing, I was not able to get the Left side install to work reliably. Sometimes it works, sometimes it doesn't . It seems that the magnets (Shiny side) must directly face the sensor for a good signal. That is not possible on the Left side, because then you need to pedal backwards to activate the motor 8)
It seems this PAS is meant for Drive side only mounting after all. That is unfortunate, because it is trickier to install, and messes up your chainline considerably (something like 7-8mm). That requires adjustment of the front derailleur.

How to install:
remove Left and Right cranks, remove complete BB.
- Mount the sensor under your BB cup flange on the Right (Drive) side, with the black plastic part facing away from the bike.
- Tighten the Right BB cup.
- Mount the magnet wheel with the magnets facing the sensor.
- Mount the chainrings and tighten them
- Check that the magnet wheel (which has been pushed closer to the sensor by tightening the chainrings) does not touch the sensor, if it does: bend the sensor inwards a little with your finger (if you can reach it )

A small complaint about this PAS: The cable is way too short to reach anywhere useful

Well I have managed to get my motor to spin with the throttle but I am not getting anything from the PAS.

All of my setting appear to be correct but I get nothing no matter which direction I go or side I use.

That type of PAS will work OK on the left side. You haveto make sure that the magnet disk is very close to the sensor (ca. 1mm). You can use a rubber spacer cut from an old hanlebr grip or a bit of hose pipe to ensure that it doesn't move back.

vwhammer said:

Well I have managed to get my motor to spin with the throttle but I am not getting anything from the PAS.

All of my setting appear to be correct but I get nothing no matter which direction I go or side I use.

Click to expand...

Did you set your control panel to level 1 or more?

Why didn't you test the PAS before installing, like I suggested above in post #2? That test will show which way it should be installed, or whether it works at all!

Please report back after you tested it.

Myself and another forum membe had a problem with the controller's PAS wiring. Which controller do you have?

I do not have the crank or PAS mounted yet.
I tested it as suggested while off the bike.

I am running thw S12S controller

I've never before known or heard of one one not to work on a S12S as long as you have it on level 1 or more. The ones that didn't work were on the 20 amp controller in the battery holder, where they crossed a couple of wires because they have a 4 wire connector to the PAS, but only 3 wires. Did you check all four combinations of direction and magnet disk orientation? Which PAS do yo have? The double-hall ones are handed.

With it switched on, check that you have 5v between the red and black (or equivalent) wires. Then check between the signal wire and the black to see if it switches when you pass a magnet over it. Again you have to try all four combinations.

The PAS I have is listed in my first post.
I know I had it in level 3 or higher.
I am also pretty sure that I tried every combo but i will tinker with it some more.

I will also check out the wires and see if all that checks out.

Well magically I played with it again and it all works just fine.
For anyone that cares, the part of the sensor that forms a point points to the back of the bike if it is on top for the bottom bracket.
Then the exposed magnets face the sensor.

All of this is mounted on the drive side.

I will get a pic when I actually assemble it so there is no confusion.

If it's not handed, it will work on the left side with the magnet isc flipped. As I said, most are not handed.

I put it all on the non drive side and it would only work pedaling backward.

I also tried flipping the disk on both side and it did nothing.

All tests were with the disk 1-2mm away from the sensor.

I bought the exact same thing. It only works one way. For me, it means I cannot use it, as the magnet disc does not fit under the chainrings.

Hot glue is a beautiful help. Switching the display to reverse PAS mode was also easy.