MEGABOBRA: Bosch Smart System Derestriction for Rim Magnet - DIY Project with Support

[Sander]

So if you're running rim magnet, the megabobra is confirmed working up to ~v5 on the motor firmware. After that point there hasn't been much luck.

If you're running rotor magnet, it should work regardless of firmware version.

Hey Megabobra! I'm still running your 1st gen MegaBobra for about 4k now ;-) A friend of mine also rides a Voima, but his motor has issues so it's gonna be replaced under warranty. We swapped his motor with a new one from another bike. Today we're gonna put the Bobra back. So if due to higher software version his Bobra won't work, the only solution is to switch from external to internal? And then "firing" the sensor input on the motor with the Bobra? Cheers Sander.

 

[megabobra]

Hey Megabobra! I'm still running your 1st gen MegaBobra for about 4k now ;-) A friend of mine also rides a Voima, but his motor has issues so it's gonna be replaced under warranty. We swapped his motor with a new one from another bike. Today we're gonna put the Bobra back. So if due to higher software version his Bobra won't work, the only solution is to switch from external to internal? And then "firing" the sensor input on the motor with the Bobra? Cheers Sander.

Hey Sander, ha that's outstanding. Did the motor that's being replaced have the megabobra running on it?

Do you mean switch from Rim to Rotor magnet? If so, yes I think that's safest. BUT let me send you a PM

 

[robbydobs]

I was thinking about this the other day as I took magnet off when chaning the valve.

I think the rim magnet is oriented so north-south is tangential to the wheel.

In which case, I think you'd need two coils, a longer one running up/down (as if coiled around the seapost), one running left/right (like you have already).
The up/down one needs to increase, then decrease and produce a strong field.
The left/right one needs to be weaker and incrase, then flip negative and decrease (as this crosses zero, it represents the rim magnet being perpendicular to the sensor)
These two magnetic fields should then add up to simulate the magnet on the rim passing.

I think this is exactly how the Speedfun rim magnet chip works, as there is space for the up/down coil in the longer raised part of the magnet emulator...

I did email about buying one but they aren't available yet.

I may get the bits and attempt to construct something similar with the megabobra schematic. I think the L9110 already has two outputs, so shouldn't be too hard to add another coil.

 

[megabobra]

Yes I think you're on the right track with this. I'd built up a three axis coil for the reasons you state above, but it was wound in a continuous strand so it wouldn't be possible to fire in sequence or with different power levels.

Again yes correct, you can use the second channel of the L9110 to do so.

Keen to hear how you go!