Gear Sensor for Bafang BBS02 Mid Drive *+ other mid-drives?*

[teslanv]

First off, I would like to tank Tom (tomjasz) for sending me this handy little gadget. Apparently he ordered one from the manufacturer (http://gearsensor.com/) and they asked him to pass some along to a few ES members. Tom was kind enough to offer me one, and I am glad I obliged.

What is it?

It's a sensor that attaches to your shift cable, and effectively kills the motor momentarily when you shift gears. This is especially helpful on the Bafang mid drive kits, since shifting with the drive under power can really torture your drivetrain.

Here is what the sensor looks like out of the box:


This sensor was apparently design specifically for the Bafang kit, as it has the matching waterproof ebrake connector that comes on all the Bafang BBS0x kits.
View attachment 4


As it so happens, I had an unused ebrake connector, since I did not install an ebrake on the right side of my handle bars, since my brake lever is integrated into my trigger shifter. - I previously only had the left (front) brake connector as an ebrake. - If you have both of your ebrake connectors in use, you will need to disconnect one, or cut & tap into one of your ebrake leads.

The Sensor did not come with any instructions, but none were needed after a quick visit to the website, where you can see the sensor attached to the shifter cable.

I pulled the cover plates off to reveal the innards of the sensor.
View attachment 2

The shift cable sleeve terminates with ferrules on either end of the sensor, and the bare shift cable runs inside the sensor, routing around a tiny pully.

The only logical place to locate my sensor was near the head unit of the kit, since both the Bafang's ebrake lead and the sensor cable are less than 8" long.


The most difficult part of the install process was routing my shifter cable through the sensor. I had to disconnect the shift cable from my derailleur, pull out the bare cable from the housing, cut the housing at the location of the sensor, leaving out a length of housing that the sensor would now replace, and then reroute my shift cable. If your shift cable end is frayed, like mine was you will need to cleanly cut it to get it to feed through he multiple ferrules and housing it will have to go back into. I had to shorten some housing sections accordingly. The worst case scenario is that you may need to replace your entire shift cable and housing, which I had done recently when I initially installed the Bafang kit.

In all, it took me about half an hour to install the sensor.

It was able to hide it pretty discreetly near my battery frame bag.


A quick road test went well. The sensor works exactly like an ebrake. If the shifter cable is moving (shifting up or down) it kills the drive instantly. No crunching sprockets or pinging chains.

[edit] After a longer ride with more shifting, I encountered sensitivity issues with the sensor, where it completely kills the drive, until another gear is selected. Not looking good for this accessory at this point...

 

[Tench]

That is an excellent addition to the kit, I can see how it will increase the appeal of the BBS drive as it eliminates one of the main concerns relating to the pedal assist mode and shifting ratios. How much do these sensors cost?

 

[teslanv]

I think they cost about $30???
(This review unit came free from Tomjasz. )

 

[tomjasz]

I have no firm price. I'd be interested in how the programming could be adapted, and will be watching for that advice. If I ever finally overcome the programming caveats. 4 computers in this house, none have windows installed. Grrrrrrrrr.

 

[teslanv]

Just finished a 10 mile ride into work with the gear sensor. - Lots of stops & hills and lots of shifting...

My attitude has changed.

The sensor appears to have sensitivity problems when in certain gears. Occasionally, I will shift and the drive will not reengage. If I then shift again, it will power up again. I can only attribute this to sensitivity issues within the gear sensor, as my drive has never done this previously.
Sixth gear (out of 8 ) is completely dead. no matter what I do, when I am in 6th gear, the drive will not power up. - I would guess that the cable is moving around ever so slightly in sixth gear and that is tripping the kill command in the sensor.
The other little annoyance is that it kills power when downshifting, which I generally didn't do previously when using the "tap the ebrake" technique, so that would take some getting used to, if I were to continue to use the gear sensor.
I will be disconnecting the gear sensor for the ride home. (Just unplugging the connector) to see if it is indeed the problem.

 

[tomjasz]

THAT is a royal PIA! Noted with developer, waiting for an answer.

 

[GearSensor.com]

Hello,

let me first introduce myself. My name is Radim Mraz and I am responsible for GearSensor sales.
I was informed by Thomas, that you have this problem mentioned abouve.
We have done a lot of testing and nothing like this never happened to us.

I have already passed this info to our engineer, he will check it.
But at first I would like to ask you, if you could send an e-mail to: info@gearsensor.com.
In this e-mail I would like to ask you, if you could specify the problem in details, and also I would like to ask you if you could specify to us if your bike has derailleur or internal gear hub? And exact model of shifting system.

I believe that we will find a solution, because something like this never happened to us, and we have done a lot of testing.

Thank you in advance

 

[teslanv]

Email sent.

 

[kevo]

Gearsensor.com,

I am very interested in this working on a SRAM DualDrive 3 speed IGH and 7 speed rear deraileur.
Based on your testing is the 3 speed IGH or the 7 speed deraileur a better candidate?

Very much appreciate the cables compatible with Bafang ebrake connectors.
Any chance of a PAS Throttle kill along the lines of Kepler's circuit?

Thanks in advance,
Kevin

 

[tomjasz]

There are two versions. One for IGH and one for derailleur. Radim informs me they are both fully functional.

 

[teslanv]

Disconnected the sensor for my ride home. Drive engaged perfectly. No dead 6th gear.

I am accustomed to tapping the ebrake when I up-shift, that at this point, I prefer my "learned shifting technique" over the gear sensor. - While the gear sensor mostly does what it claims, it kills the drive indiscriminately, regardless of how much force is being applied to the crank (by motor or human). I find that I can conveniently shift in the dead zones of the drive without even tapping the ebrake, and thus do not lose power at all, and can still shift smoothly.

For someone new to this kit, who has not yet developed their shifting "technique", I can see a market for this gear sensor.

It is not for me, I am sad to say.

 

[Ypedal]

I wonder if the cable tension increases as the gears go up, causing the unit to remain triggered is the reason for your problems.

 

[teslanv]

6th gear for me is a 14T sprocket. If anything, it would be under less tension. And the problem doesn't recur in 7th or 8th gear, which are 12T & 11T respectively.
The only thing I can think of is that in 6th gear, maybe my derailleur isn't quite perfectly on the sprocket and the cable vibrates.

 

[Kepler]

I really like the concept behind this device. It seems quite an investment has been made in developing this device and although failed to work well so far on this actual install, I think it deserves further testing and an explanation on why it didn't work. I have a feeling its going to be a minor setup issue or a faulty unit that has let this review down.

Looking at the picture below, it looks like the gear cable rotates a magnet on a pulley that in turn acts against a hall sensor to provide an output (Just speculation at this point). This seems to be a smart way to transfer the cable's linear movement into a reliable output signal.

I wonder if the cable isn't sitting properly in the plastic groove or perhaps the small pulley is not turning freely. I may be completely off the mark here, but this is the first thing I would be checking.

In regards to using the brake cut off to interrupt the motor power, I personally found the BBS02 delay to be frustrating long. Fine if you are just cruising along but in the real world, you tend to want to have power back as soon as possible after making the gear change. Unfortunately there is no way to tune this delay out even if you have access to the software (Not that I have found anyway).

The better way to interrupt power is by pulling down (or pulling up) the throttle output to around 1.15V. This kills both the PAS and throttle and then recovers power after the change with only a minor delay. Other good thing is that the minor delay is actually tunable with the Bafang software.

I think that Gearsensor could just provide a special Y harness that splits the throttle signal from the head unit. you would then get to keep both your brake sensor inputs also.

Another neat feature would be having the up change and down change power cut selectable. Going down the gears (bigger to smaller) you really don't need to cut the motor unless it is a high powered setup. However up changing is more stressful on the gear system and nearly always benefits from the power cut.

Anyway, this looks to me to be a promising product and i look forward to hearing more about it. I wouldn't mind testing one.

 

[tomjasz]

I really like the concept behind this device. It seems quite an investment has been made in developing this device and although failed to work well so far on this actual install, I think it deserves further testing and an explanation on why it didn't work. I have a feeling its going to be a minor setup issue or a faulty unit that has let this review down.

Looking at the picture below, it looks like the gear cable rotates a magnet on a pulley that in turn acts against a hall sensor to provide an output (Just speculation at this point). This seems to be a smart way to transfer the cable's linear movement into a reliable output signal.

I wonder if the cable isn't sitting properly in the plastic groove or perhaps the small pulley is not turning freely. I may be completely off the mark here, but this is the first thing I would be checking.

In regards to using the brake cut off to interrupt the motor power, I personally found the BBS02 delay to be frustrating long. Fine if you are just cruising along but in the real world, you tend to want to have power back as soon as possible after making the gear change. Unfortunately there is no way to tune this delay out even if you have access to the software (Not that I have found anyway).

The better way to interrupt power is by pulling down (or pulling up) the throttle output to around 1.15V. This kills both the PAS and throttle and then recovers power after the change with only a minor delay. Other good thing is that the minor delay is actually tunable with the Bafang software.



Anyway, this looks to me to be a promising product and i look forward to hearing more about it. I wouldn't mind testing one.

I'm certain Radim would provide a sample given your aplomb with the BBS0x. I was certain I supplied your email address to him.

Tom

 

[tomjasz]

6th gear for me is a 14T sprocket. If anything, it would be under less tension. And the problem doesn't recur in 7th or 8th gear, which are 12T & 11T respectively.
The only thing I can think of is that in 6th gear, maybe my derailleur isn't quite perfectly on the sprocket and the cable vibrates.

No response from gearsensor? But of course they haven't had much of a chance yet... It Seems a shame to agree to test and at first sight of a glitch throw out the device. I think the vendor deserves a better look.

 

[izeman]

hi radim
i'm also still waiting for a response to my mail. i invited you to our forum and the other thread, but w/o the chance to test those devices under changing environments and on different bike it will be difficult for you to rule out all troubles.
i could imagine that the thickness of the shifter cable may influence the results as well. especially the newer derailleurs have very thin cables compared to the older models. they are much thinner than the formerly used brakes wires.
if the switch kills the controller and the power doesn't come back when you expect it this could cause serious troubles with high powered mid drive systems. if i imagine my system loosing power and then applying full power again when i don't expect i'd be frightened.
just give us some units to test and you'll get a lot of feedback to your device - and as i said in mail you have a good chance to multiply your sales.

 

[izeman]

...It's a sensor that attaches to your shift cable, and effectively kills the motor momentarily when you shift gears. This is especially helpful on the Bafang mid drive kits, since shifting with the drive under power can really torture your drivetrain. ...

teslanv: you maybe change your thread's title as this gear sensor can be used for ALL mid drive systems (can you used for all geared systems, but doesn't make sense for hubmotors of course).
this special unit of course was pre-wired for bafang that may be why you chose this title?

 

[tomjasz]

...It's a sensor that attaches to your shift cable, and effectively kills the motor momentarily when you shift gears. This is especially helpful on the Bafang mid drive kits, since shifting with the drive under power can really torture your drivetrain. ...

teslanv: you maybe change your thread's title as this gear sensor can be used for ALL mid drive systems (can you used for all geared systems, but doesn't make sense for hubmotors of course).
this special unit of course was pre-wired for bafang that may be why you chose this title?

A quick read of their web pages indicates it is primarily designed for BBSOx and "MPF drive", it also mentions they are working on other systems.

- MPF drive

- 8Fun cental drive (Bafang)

 

[izeman]

A quick read of their web pages indicates it is primarily designed for BBSOx and "MPF drive", it also mentions they are working on other systems.

so? how does that differ from what i said? it's preconfigured for bafang and can be/may be used for other systems as well. and as this is a forum where many engineers are online to test thing, it's time to try out.

 

[teslanv]

...It's a sensor that attaches to your shift cable, and effectively kills the motor momentarily when you shift gears. This is especially helpful on the Bafang mid drive kits, since shifting with the drive under power can really torture your drivetrain. ...

teslanv: you maybe change your thread's title as this gear sensor can be used for ALL mid drive systems (can you used for all geared systems, but doesn't make sense for hubmotors of course).
this special unit of course was pre-wired for bafang that may be why you chose this title?

Yes, I chose the title based on the fact that the unit I tested had the Bafang style connectors. I suppose one could cut off the connector and add their own compatible one. - It is a three-wire cable.

 

[teslanv]

Gearsensor Response:

I have already received a first idea from our engineer.
He told me, that our GearSensor cut off the motor power just for a very short time and then the motor (drive unit) will restart again when the movement of shifting cabel is finished.
He told me, that it is impossible that GearSensor will cut off the motor power and motor (drive unit) will not restart again (you mentioned that this is the problem, am I right?)

He also told me, that it is possible that when you were shifting from 6th speed to 7th speed, that you maybe you were riding very fast, it means that GearSensor cutted of the motor (drive unit) power but then the motor didnt restart because of higher speed (more than 40km/h or 24,8 MP/H).

Please be sure, that nothing like this never happened to us. Please inform us.

For the record, my drive is set to unlimited speed, and when shifting to 7th or 8th gears, the drive did reengage. - So my drive is not maxed out, speed-wise.

Really I would love to be able to give a great review of this product. (And did on my initial post). But they have some bugs to work out before their product is ready for market.

 

[tomjasz]

this is a forum where many engineers are online to test thing, it's time to try out.

Imagine the difficulty trying to sort out who those appropriate people are. Quite a few contacted me and three wanted to test the device, for free, and didn't have a BBS0x to trial the unit on. Hardly fair and difficult to sort out. Intended as conversation, not criticism.

I apologize if I misunderstood your question about the title. Any comments made by me are made in good faith with no intended sarcasm or criticism.

Tom

 

[tomjasz]

Really I would love to be able to give a great review of this product. (And did on my initial post). But they have some bugs to work out before their product is ready for market.

Perhaps our EU friends are not testing and riding as aggressively? Nary a glitch here but I'm a mild rider with a 36V 350W.

 

[teslanv]

My Response to Gearsensor:

Radim,

If the drive does not restart within a couple seconds of shifting, then I would consider it faulty. I don't think anyone will want to use this sensor if the lag in motor power is that long. In my testing, I gave it at least five seconds before shifting to another gear, which then prompted the drive to start again.

Also, my drive is programmed for "unlimited speed" so I was not exceeding the preset speed limit of the drive. I think I was only going maybe 20 mph (35 km/h) when I had the problems.

I am happy to send this test unit back to you for evaluation and if you want to send me another unit to confirm that the unit I have is faulty, I will test a new sensor.

Let me know what you would like to do or if you have any other advice on how to make this one work properly.

In all of your in-house testing, were you always using new bikes with modern shift cables & shifter? I ask because mine is 10 years old, and may not have the precision shifting that new shifting systems use. - I would suggest you test your sensors on old/used bikes if that is the case. You may well encounter the same problems I am having.