Using Reverse to Brake

[EliTheIceMan]

I am looking into using the SP4 for a small scooter/skateboard thing (it's hard to describe) that you stand on and ride.  I plan to use the SP4 12" so I have the tire and everything.  I will control the motor wirelessly from a handheld controller that allows the "base" to alter the various signals the motor needs.  It's great that you can already configure the motor extensively with things like acceleration rate, current draw, etc.  To make using the SP4 even an option I need to be able to have electronic brakes only.

I see the regen braking is either on or off, no variability.  So my thought is that I could set the regen to a low value that is my minimum braking level, beyond that, to apply harder brakes, would it be damaging to apply a very light reverse while moving forward?  I highly doubt the brake signal could be PWMed?  (Pulse width modulated, switching on and off with a varying duty cycle to control regen level)

Any thoughts are appreciated.  It's difficult to decide if the SP4 would work without having one to test but a 12" isn't much use to me beyond this project!  Thanks!

PS. Is it is possible to directly control the SP5 via bluetooth SPP link?  I'm going to build a wireless bluetooth controller anyway, it would be cool if I could eliminate the "base" and didn't have to connect anything at all to the SP5.

[GM Canada]

Hi Eli,

Interesting project. I look forward to seeing the results.

One major thing of caution. Regen braking is fine an it saves a lot on wear and tear on the mechanical brakes. But there is a serious issue with it being the only brakes. If for any reason you lose power from the battery you also have zero regen braking. So if you ride until the battery kicks out you will not have any brakes at all.

About the current app. It does not control the motor at all. You can change and save the settings. You can use it to monitor speed, voltage etc while riding. But you cant control it.

As for using reverse to slow down. I don't know how well that would work.It seems that may cause issues but I really don't know. Maybe Alan can enlighten us on that one.

Looks like you have some challenges ahead. Good luck with your project. I hope you succeed as it sounds very interesting.

Gary

[Bikemad]

As for using reverse to slow down. I don't know how well that would work. It seems that may cause issues but I really don't know. Maybe Alan can enlighten us on that one.

I would be slightly hesitant to actually try it out in case it did cause damage to the controller, as I envisage it would be akin to forcing a stalled motor to turn in the wrong direction.
Whilst it might be OK at slow speeds, I'm not so sure it would be a good idea braking quickly from higher speeds.

I just don't like the thought of rolling a bike backwards at speed down a steep hill and then trying to stop it by only applying the throttle. 

Most motor controllers for R/C cars have an inbuilt motor braking function, but I suspect it works differently to simply applying the throttle in reverse.

I wonder if it's possible to use a R/C car brushless/sensorless motor controller:



The controller could easily be operated by a conventional RF Tx/Rx instead of Bluetooth.

A working current of 200A and a burst current of 1000A sounds pretty good to me, and could be a whole lot of fun in conjunction with a Magic Pie!
In fact, I could almost be tempted to try one of these controllers just to find out whether it would actually work. 

It would be interesting to find out what the Magic Pie's maximum rpm would be using this controller and an 8S LiPo pack. 

Alan