Ok, they produce the magnetic pulse, and provide a sort of kiox display replacement by reading the motor data (they reverse engineered the communications protocol of the kiox display)
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MEGABOBRA: Bosch Smart System Derestriction for Rim Magnet - DIY Project with Support
- Thread starter megabobra
- Start date
- Thread starter
- #242
That's great news Manu. I share a similar feeling with steeling the info. I'm quietly working on some improvements and new features that I'll look to share in the future, but I'll likely withhold the code and/or specifics for exactly that reason.
Looks like they're picking up the mode changes from the controller (switching EMTB to Turbo for example) to turn their device on and off. Don't think there's any other data being drawn from the motor though, eg remaining battery percentage.
Out of interest Alumi, why are you switching?
AlumiPro
Well-known member
I haven’t been able to get the Megabobra to be consistent; I’ve never had a ride with out an error code at some point with it. Which can be dangerous with the type of cliff side tech trails I’m climbing……when an error code occurs assisted power shuts off. I would constantly wonder when it would happen next, which makes the ride not as enjoyable.
I put a sharpie mark on my reed switch to keep track of its position, while slowly rotating it to find its sweet spot with no luck. Also slowly moving the spoke magnet in different positions.
It gets frustrating because I also have a Gen3 S-Works Levo which is derestricted with a simple plug and play unit at the mastermind screen in the top tube that keeps the correct speed and odometer, which I have had zero issues with. I’m frustrated with Bosch not Megabobra, I understand the Megabobra installed on a Race motor with up to date firmware was not a 100% guarantee it would work.
I’m willing to spend a decent amount of $ for a device that is guaranteed to not trigger error codes and give me at least 28mph of assisted power. Hopefully the Speedbox 1.2B works as advertised, it’s essentially doing the same thing as the Megabobra and eplus unit.
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- Thread starter
- #244
I haven’t been able to get the Megabobra to be consistent; I’ve never had a ride with out an error code at some point with it. Which can be dangerous with the type of cliff side tech trails I’m climbing……when an error code occurs assisted power shuts off. I would constantly wonder when it would happen, which makes the ride not as enjoyable.
I put a sharpie mark on my reed switch to keep track of its position, while slowly rotating it to find its sweet spot with no luck. Also slowly moving the spoke magnet in different positions.
It gets frustrating because I also have a Gen3 S-Works Levo which is derestricted with a simple plug and play unit at the mastermind screen in the top tube that keeps the correct speed and odometer, which I have had zero issues with. I’m frustrated with Bosch not Megabobra, I understand the Megabobra installed on a Race motor with up to date firmware was not a 100% guarantee it would work.
I’m willing to spend a decent amount of $ for a device that is guaranteed to not trigger error codes and give me at minimum 28mph. Hopefully the Speedbox 1.2B works as advertised, it’s essentially doing the same thing as the Megabobra and eplus unit.
Understood, appreciate the feedback!
Hi Alumipro,
If you are brave and curious, you could open the electromagnet case and see and measure the resistance of the coil. I made different coils , some didn’t worked …
Maybe share, if they allow that, the installation instructions .
Let us know how this sb works
Thanks
If you are brave and curious, you could open the electromagnet case and see and measure the resistance of the coil. I made different coils , some didn’t worked …
Maybe share, if they allow that, the installation instructions .
Let us know how this sb works
Thanks
- Thread starter
- #246
Preview of one of the new pieces I'm working on. The OLED display and buttons will show the true speed, true distance, reported speed etc, as well as providing the user options to set their own multiplier, change units, wheel circumference etc. It'll be set in a 3Dprinted case to suit either mounting on handlebars or top tube.
Other works in progress: new tiny electromagnet, hall sensor, no LPP.
Other works in progress: new tiny electromagnet, hall sensor, no LPP.
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How will you provide the power?
- Thread starter
- #248
Looking to intercept power going to the handlebar controller.
If you draw too much amps from the LPP port you get this error message (I had it when using a electromagnet of 23ohms if I remember well)
- Thread starter
- #250
Interesting, I never encountered that one.
Are you running your magnet at 12v? Even if so, that'd only be pulling ~ 12v/23ohm = 0.52amp; I thought the LPP was good for 1amp?
Oh sorry 7.8ohm @12V = 1.5
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magnet and reedswitch needs to be far away from other "spinning" metal objects...
- Thread starter
- #253
New coil in the works. Old version on the left, new version on the right. This will be small enough to be fixed directly to the motor, regardless of how close it is to the frame, as it sits within the bounds of the motor case's footprint. Similar to the OLED display, I'll print a small case for the magnet to protect it and the wires.
You also have a voima I recall? Isn't it easier to replace the rim magnet with a rotor magnet to open up more possibilities?
- Thread starter
- #255
Yes I have unit fitted in my Voima. Certainly, if you're able to move away from the rim magnet everything becomes easier for derestriction. I understand you're given the option of rim or rotor magnet with the Voima now, but sadly the earlier versions had rim magnet only.
I assume dealers can change the preference in the motor firmware at any time, but that'd be an interesting conversation to have...
The derestriction for rim magnet is fiddly, but reliable once it's in place. I suspect this is due to the fact that it's not interfering with intercepted signals like the rotor magnet-style devices do. I'm hoping that the changes I'm working on will take out the guess work from installation/setup others had been having trouble with.
MCIwoo
New Member
Well I don't know.. there is no water resistance. The price is good, but I'll probably stick with the commercial chips.
Its definitely possible to convert, people have done it.
Instructions are vague and incomplete though. I'm currently going through this for my incoming voima, plus a wheelsize change for a mullet, will document the steps in the pole forum once it's done.
The magnet, slim speed cable and clip are about £45.
Excited to see the progress on your projects and really appreciate you sharing the 1st gen ‘bobra directions with us.
I have a friend at Bosch and although it is possible to change from an ‘internal’ speed sensor to an ‘external’ speed sensor, the dealer can’t do it, and neither can Bosch.
Only the OEM manufacturer of the bike can do it from their side of the Bosch software.
All the dealer can do is plug your bike in and submit a “configuration change request” and hope the random engineer at the bike company who works on Bosch integration will receive it and be willing to make the change.
Also, the friend confirmed Bosch is following all of these threads so best to keep the code under wraps as long as possible to protect the rider’s ability to derestrict. Bosch really wants to keep us from owning our own motors.
Thanks again megabobra, can’t wait to see the new parts!
- Thread starter
- #260
Little update on the display. Just about happy with the all the functions now. All the typical screens, current speed, max speed, distance (all true values of course), as well as total climb/descent. Additionally, there's a menu for the controls of the megabobra itself; setting the desired multiplier, units (metric/imperial), wheel circumference etc. I'm considering also adding an option to turn on/off distance catch up functionality, ie where the device keeps the trip running after being idle for a minute in order to clock up the true trip distance to the motor. Certainly not a feature I'd use, but some asked for it and it's only a few lines of code.
Some snips below to show comparison of trip distance reported by the bosch display vs the true distance on the megabobra display. Bosch shows 22.1km vs true distance of 31.06km. I'm running a 1.4 multiplier (for max assisted speed = 35kph), so 22.1 * 1.4 = 30.94km, or within 0.3% of what the megabobra shows. I'm happy with this tolerance!
Just waiting on some new cabling before I tidy up the display and install it in its housing. For now, it's attached with velcro
Some snips below to show comparison of trip distance reported by the bosch display vs the true distance on the megabobra display. Bosch shows 22.1km vs true distance of 31.06km. I'm running a 1.4 multiplier (for max assisted speed = 35kph), so 22.1 * 1.4 = 30.94km, or within 0.3% of what the megabobra shows. I'm happy with this tolerance!
Just waiting on some new cabling before I tidy up the display and install it in its housing. For now, it's attached with velcro
We buy but don’t really own it… and “with a click” they can brick it…
AlumiPro
Well-known member
Will you offer the new tiny electromagnet and hall sensor for those who already own your first Gen Megabobra?….provided they are compatible?
- Thread starter
- #263
Hi Alumi,
It's something I've thought about a lot. Yes, I'm happy to send an upgraded coil at no cost to anyone with v1 who's experiencing trouble like you faced. It would just be a plug-in replacement.
As for the wheel pickup sensor, this will be trickier - at best, a hall sensor needs an additional wire core (3-core instead of 2-core) going to the rear wheel, meaning the existing reed sensor plug would be incompatible. I'd be happy to supply the new sensor along with a new female connector to suit, BUT it'd require some soldering at your end to attach the new connector to the megabobra and a code update.
Just noting though that the new-est pickup sensor (call it v2.5 if you will) which sits inside the frame at the motor, rather than at the back wheel, will not be an easy upgrade from v1 to v2 as it requires new hardware. Though, it doesn't offer any advantage over the hall sensor at the back wheel, we live in a world where less visible wiring = better!
I'll reach out directly when I'm in a position to offer the coil/sensor to v1 owners who need it.
AlumiPro
Well-known member
So your new v2 you’re still finishing has no exterior wires outside the motor area?! But it’s designed for the Rim sensor Bosch?!
There are plenty of 2-wire hall sensors. Bosch themselves make one, and it's freely available. Connect between an input pin and ground with a 3k3 pullup to +3.3V (that's what Bosch motors appear to do - it draws ~1mA when magnet is present). Works fine that way with my arduino-based speed display.
- Thread starter
- #266
That's correct.
I've not seen a 2-wire hall sensor before, do you have a link? Are you sure you're not thinking of a reed switch?
Example here (at a LBS chain here is Australia, but they're all over the place)
They are the ones used on pre-Smart System Bosch motors with the spoke magnet. They come in different lengths, and have the nanoMQS plug at the end (the one you can't get a socket for)
- Thread starter
- #268
Gotcha thanks. Those are reed switches, rather than hall effect sensors. Both detect a passing magnet, but the reed switches do so physically and are susceptible to vibration, and can be a bit particular with orientation. Orientation issues are addressed in the one you linked by the screw mount, ensuring it's always facing the way the manufacturer intended.
I had some early vibration issues with the reed switch where it was held in place loosely with a cable tie but could bounce around a little. Securing it firmly sorted the issues.
The hall effect sensors have no moving parts, instead detecting changes in electrical current induced internally by the passing magnet.
Reed switches can definitely work OK, as evidenced by most bike computers and ebike speed sensors, but moving to a hall sensor just removes one more variable when installing the megabobra, making it less sensitive to correct placement.
AlumiPro
Well-known member
I understand you don’t want to give out all the details for good reason. But I am very curious how your V2 would work, keeping everything inside the motor area. Besides the screen wiring of course.
Will you be offering it without the screen option? Or I guess maybe it’ll be good to have the screen for at least set up mode, as I have no interest in having another screen on my bike.
The Bosch 2-wire wheel speed sensor is a hall sensor afaik - it uses a 2-wire hall sensor chip, similar to this one. (I've never taken one apart to check for certain which chip it uses, and they are potted, so it would be hard to see anyway). They are polarity sensitive (which a reed switch isn't) and are used commonly in automotive sensors (Bosch also makes a lot of those)
When I first encountered 2-wire hall sensors I thought they were black magic, but they are definitely a thing.
When I first encountered 2-wire hall sensors I thought they were black magic, but they are definitely a thing.
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