cloudcover
10 mW
- Joined
- Sep 8, 2009
- Messages
- 30
hi folks -
thanks to the great information on this forum, i have an ebike setup that i absolutely love and that's dramatically increased how frequently i ride my bike. it's a surly big dummy bike with the xtracycle cargo kit and i'm coupling that with a bmc v2-t motor, an infineon controller, and a half-twist throttle. the setup is so versatile that i've really reduced how often i drive the car. very happy about that.
but i have to say that the one thing that bugs me quite a bit is the throttle. i know many people out there like the manual control that a throttle provides, but i'd be much happier with an automated pedal-assist-based approach that doesn't require me to regulate throttle manually -- like the one used in kona's (relatively) new electric bikes (for example, http://www.konaworld.com/bike.cfm?content=ticket).
so i'm hoping that some folks here can maybe help me with this project. i'm happy to be the guinea pig and willing to report results and hopefully help out others.
1. torque sensors
someone referred me to a german company called "thun" that makes a bottom bracket sensor that can measure torque (in addition to cadence and rotational direction). it's their x-cell rt sensor and here's a link to it's technical specs: http://www.thun.de/thun_eng/Datenblatt X-CELL_GB.pdf. i'm told that it runs around 100 euro.
and it seems that kona uses a different torque sensor that they call a "Dutch design TMM sensor." a quick online search led to this page: http://www.idbike.com/tmm-powermanagement.htm. don't know if it's available to retail or what the cost would be, but am happy to pursue that. unlike the thun sensor, this seems to be a unit that mounts to the rear dropout of the bike and measures chain force.
any thoughts on which of the two would be better / more reliable / etc?
2. configuration
i wanted to have some way of controlling how much motor assist is provided at maximum torque. so i was imagining some kind of simple circuit that would have an analog knob (potentiometer?) that would take the output from the torque sensor and modify it to a desired range for sending on to the controller.
an example will probably help here. let's say that we're using the thun sensor, which has an output that varies between 0 - 5V depending on the amount of torque. i don't know what the throttle input range is for the controller, but just for discussion let's say it's 0 - 1V. and let's suppose there's a "amount of assist" knob that we're going to use that has markings from 1-10.
so if i wanted to get more of a workout on a particular day and so desired only a moderate amount of electric assist, i might set the knob to 2 (corresponding to 20% of max motor assist). and that would modify the range of the torque sensor output so that instead of a voltage of 0 - 5V reaching the controller, instead that range gets modified to 0 - 0.2V.
3. the electrical wiring
i have a background in engineering, but it's now of minimal use to me because it's been so long since i've used any of that. so i'd love to get any help i could in figuring out how to mate one of the sensors described above to the controller, to achieve the functionality i mentioned. i'm sure there are things that i haven't thought of but hopefully there are some kind folks out there who're willing to help with this conversation / thread.
thanks!
cc
thanks to the great information on this forum, i have an ebike setup that i absolutely love and that's dramatically increased how frequently i ride my bike. it's a surly big dummy bike with the xtracycle cargo kit and i'm coupling that with a bmc v2-t motor, an infineon controller, and a half-twist throttle. the setup is so versatile that i've really reduced how often i drive the car. very happy about that.
but i have to say that the one thing that bugs me quite a bit is the throttle. i know many people out there like the manual control that a throttle provides, but i'd be much happier with an automated pedal-assist-based approach that doesn't require me to regulate throttle manually -- like the one used in kona's (relatively) new electric bikes (for example, http://www.konaworld.com/bike.cfm?content=ticket).
so i'm hoping that some folks here can maybe help me with this project. i'm happy to be the guinea pig and willing to report results and hopefully help out others.
1. torque sensors
someone referred me to a german company called "thun" that makes a bottom bracket sensor that can measure torque (in addition to cadence and rotational direction). it's their x-cell rt sensor and here's a link to it's technical specs: http://www.thun.de/thun_eng/Datenblatt X-CELL_GB.pdf. i'm told that it runs around 100 euro.
and it seems that kona uses a different torque sensor that they call a "Dutch design TMM sensor." a quick online search led to this page: http://www.idbike.com/tmm-powermanagement.htm. don't know if it's available to retail or what the cost would be, but am happy to pursue that. unlike the thun sensor, this seems to be a unit that mounts to the rear dropout of the bike and measures chain force.
any thoughts on which of the two would be better / more reliable / etc?
2. configuration
i wanted to have some way of controlling how much motor assist is provided at maximum torque. so i was imagining some kind of simple circuit that would have an analog knob (potentiometer?) that would take the output from the torque sensor and modify it to a desired range for sending on to the controller.
an example will probably help here. let's say that we're using the thun sensor, which has an output that varies between 0 - 5V depending on the amount of torque. i don't know what the throttle input range is for the controller, but just for discussion let's say it's 0 - 1V. and let's suppose there's a "amount of assist" knob that we're going to use that has markings from 1-10.
so if i wanted to get more of a workout on a particular day and so desired only a moderate amount of electric assist, i might set the knob to 2 (corresponding to 20% of max motor assist). and that would modify the range of the torque sensor output so that instead of a voltage of 0 - 5V reaching the controller, instead that range gets modified to 0 - 0.2V.
3. the electrical wiring
i have a background in engineering, but it's now of minimal use to me because it's been so long since i've used any of that. so i'd love to get any help i could in figuring out how to mate one of the sensors described above to the controller, to achieve the functionality i mentioned. i'm sure there are things that i haven't thought of but hopefully there are some kind folks out there who're willing to help with this conversation / thread.
thanks!
cc