Giant Twist RS2 pedelec - can't (re)locate cadence sensor

[theabsurdman]

I recently acquired a pair of 10+ year old Giant pedelecs - a Twist Express and a Twist RS2 which are almost identical models except...

The Express can be easily derestricted by relocating its cadence sensor mounted on the rear triangle detecting a magnet affixed to a rear wheel spoke but I can't locate the equivalent on the RS2 wich has no obvious sensor and no spoke magnet!

Presumably the RS2 speed sensing is happening in the motor and there is indeed a white wire coming from the motor which has been designated "speed" in another ES thread. I tried cutting that but it just resulted in an error condition and no power.

I'm wondering if I buy the Twist Express cadence sensor part and try to wire that into the RS2 controller in place of the speed wire coming from the motor might that work to externalise the cadence-sensing.

Any other ideas?

 

[amberwolf]

A cadence sensor reads your pedalling speed. This is not typically used to restrict the speed of the bike.

A speed sensor reads your wheel speed. This *is* typically used to restrict the speed of the bike.

Your RS2 in-motor sensor would have to read wheel speed, because it wouldn't have a way to read the pedal (or chain/sprocket) speed.

If your Express sensor at the rear wheel is reading the chain or sprockets' speed, then it is reading cadence. Otherwise it is reading the wheel speed.


What is the specific, complete change made to the Express to "derestrict" it? Knowing that, it might be possible to do something similar to the RS2.

 

[theabsurdman]

A cadence sensor reads your pedalling speed. This is not typically used to restrict the speed of the bike.

A speed sensor reads your wheel speed. This *is* typically used to restrict the speed of the bike.

Your RS2 in-motor sensor would have to read wheel speed, because it wouldn't have a way to read the pedal (or chain/sprocket) speed.

If your Express sensor at the rear wheel is reading the chain or sprockets' speed, then it is reading cadence. Otherwise it is reading the wheel speed.


What is the specific, complete change made to the Express to "derestrict" it? Knowing that, it might be possible to do something similar to the RS2.

Thanks for responding, yes it's a speed (not cadence) sensor mounted on the rear triangle - I had my terminology mixed-up. On the Twist Express it detects a spoke magnet to determine speed. Derestricting simply involves mounting another magnet on the crank and relocating the sensor to line up with that instead. Since you can't spin the crank as fast as the wheel, the bike always appears to be going slower than it is. The problem with derestricting the RS2 is that there is no external speed sensor because it is in the motor. Presumably the "speed" wire from the motor is reporting back to the controller a series of pulses. I was wondering simply if I could swap the motor-based sensor for the external sensor part from the Twist Express. Or if there is some other way of feeding a slower set of pulses to the controller.

 

[amberwolf]

If it worked with the one, then assuming the other works identically, there should be no problem using a different pulse sensor (even an actual cadence sensor, if it is the one-signal-wire type (which actually has three wires, 5v, signal, ground)) mounted to the cranks.

In this case, you would run the white signal wire from the controller's motor-cable to the crank-mounted sensor, and tap into the 5v and ground that is used to power the hall sensors / speed sensor in the motor (you would leave them still connected to the motor, too).

If things don't operate correctly this way, you can instead tap the 5v and ground from the throttle (if you have one).


Note that if you already have a PAS cadence sensor on the bike, you could try just connecting it in parallel to both the PAS connector on the controller (as normal), and the white signal wire from the controller to the motor (without the white wire being connected to the motor).

 

[theabsurdman]

If it worked with the one, then assuming the other works identically, there should be no problem using a different pulse sensor (even an actual cadence sensor, if it is the one-signal-wire type (which actually has three wires, 5v, signal, ground)) mounted to the cranks.

In this case, you would run the white signal wire from the controller's motor-cable to the crank-mounted sensor, and tap into the 5v and ground that is used to power the hall sensors / speed sensor in the motor (you would leave them still connected to the motor, too).

If things don't operate correctly this way, you can instead tap the 5v and ground from the throttle (if you have one).


Note that if you already have a PAS cadence sensor on the bike, you could try just connecting it in parallel to both the PAS connector on the controller (as normal), and the white signal wire from the controller to the motor (without the white wire being connected to the motor).

Cheers for the tips. I'll do some experiments and report back.

 

[theabsurdman]

I had a look at the controller for the RS2 - see photo below. It's a different controller, differently wired from the Express. What is intriguing is an unused black 2-pin connector to the controller with red and white wires that looks like it could be for a speed sensor.

 

[amberwolf]

Most of the speed sensor inputs, when available on a separate connector, have three wires so that it can provide power to a hall-type speed sensor.

I don't know what that specific connector is for; it could be a number of things, from an ebrake input to speed sensor to speed limiter, to "one-wire" programming connector, etc.

If you measure ground (continuity to battery negative input pin) on one wire, and 5v on the other, it could be any of those things (the 5v could be a pullup or a supply). If there is some other wiring / voltage, then it's unlikely to be a speed sensor input.

 

[E-HP]

intriguing is an unused black 2-pin connector to the controller with red and white wires that looks like it could be for a speed sensor.

hmm not sure what makes it look like a speed sensor; I don't recall seeing that color combo often. Could be for lights.