Reverse by back pedaling - Grin

[offGridDownUnder]

I have read fleeting references to a function of Grin kits where back-pedaling will invoke regen or invoke reverse.

I read that a 2-wire cadence sensor will signal this, and I have the 24-pole sensor Grin sells, and on the SETUP PAS DEVICE screen on my Cycle Analyst (v3) I can see the two signals flipping up and down. The other components are a v5 Z9 Baserunner, a Cycle Analyst with 3.15 firmware, and Shengi SX2 rear hub motor.

I have brake switches that invoke regen (in case that alters the set up).

I have not found a way to invoke motor reversal or regen by pedaling backwards.

I have searched with phrases such as "pedal reverse" here and I don't find any posts that mention it.

Can someone suggest where I can find out more about these?

 

[amberwolf]

AFAIK, there isn't a simple direct way to do this.

By itself the CA can't tell the controller to reverse, because there's no communication to the controller from the CA, just a throttle signal.

The CA can tell when you're backpedalling, and *can* send the "braking" throttle output (max) when you do that. So in this way it can tell a controller that accepts two voltage ranges for throttle input (like the *runners) that it should be doing something other than powering the motor normally in this event.

Normaly that's used to engage regen. Mine is just set to stop driving the motor.

But if the controller can be setup to go into reverse when it receives this throttle input voltage, then the two functions together would do it--but since the CA outputs a fixed voltage when backpedalling (if you have enabled this, otherwise it just ceases outputting nromal throttle and goes to neutral output), you only get a fixed reverse speed.

If your pedal drivetrain does not physically drive the wheel, but instead drives a generator or other load (like a series hybrid), or has a clutch you can disengage between it and the wheel, you can instead setup the reverse-by-button/switch on the *runner, then hold that button and pedals now modulate that exactly like they did when forward, within whatever limitations the controller has for reverse torque, speed, etc.

 

[offGridDownUnder]

I do see references to this from Grin. I've written to tech support asking about it.

I do know (and have demonstrated myself) about reversing by grounding the wire. I may yet do this, but I like to make informed decisions.

Further bulletins as events warrant.

 

[amberwolf]

I poked around the release notes in the CA setup program, and found that the 3.2b1 release says I'm slightly wrong about the backpedal regen, that it uses crank position to modulate the throttle within the regen braking mode throttle output limits (normally 0.8 down to 0.0v). I added the whole file for the latest 3.2b3 release notes in case anything else is useful, and quoted just the relevant part below

(3) 1726 - (New) Back Pedal Position Regen Control

A mode was added to allow regen control similar to a coaster brake by pedaling
backwards, with the regen intensity modulated by how far back the cranks are
rotated.

The parameter 'Back Pedal Regen Poles' has been added to the
settings menu and determines how far back the cranks must be turned to
reach max regen.

The back pedal regen requires either quadrature (2 wire) PAS signals, or
a single wire PAS pulse with a functional FWD/REV signal. The back pedal
regen braking overrides the user throttle. It also clears automatically once
the vehicle has come to a stop.

(4) 1726 - (New) Back Pedal Throttle Modulated Regen

Another option is provided to vary the backpedal regen intensity via the
throttle rather than the backwards pedal position. This mode mimicks the
behavior of ebrake activated proportional regen. A small amount of backwards
pedal motion (set by 'PRgn->EngageSteps') starts regenerative braking at the
ThO->Brake Out voltage, and the user can increase the regen with their throttle.
Any forward motion of the pedals will clear the braking mode.