To Castle: MMP sensored motor issue

[maverick67]

Please excuse this long post, but I want to make it as clear as possible in the hope that Castle will address the issue. I know the MMP is more or less a discontinued product, but I can't help but think a simple firmware modification is all that's required to improve the following issue:

BACKGROUND: I have tried several different sensored brushless motors with both my MMP and Mamba X (MX), here is a huge difference I've spotted when both ESCs are in Normal Reverse mode. Because there's no on-the-fly drag brake adjustment on the MMP, I like to set a very low drag brake setting (0-10%) and then rely on normal braking when required (ie: use normal reverse mode).

With the MX, when rolling slowly down a slope, with throttle at neutral, vehicle can be slowed down using normal braking multiple times. Throttle input sequence would be: Neutral-Brake-Neutral-Brake etc.... Basically mimics what a driver would do and the expected response in a real car going down a hill.

However, with the MMP in the exact same situation, the above throttle input would result in the first brake application doing the same thing, BUT, then the second brake application onwards would cause the vehicle to go into reverse (I guess a bit like crawler reverse).

From the symptoms, the only conclusion I can draw is that the MX can detect through the sensor cable that the vehicle is rolling down hill and so no matter how many times reverse throttle is applied, only the brakes are applied. In fact, I've found that if the brake setting is set to a level where its insufficient to completely stop the vehicle on the hill, then its actually impossible to engage reverse.

On the other hand, the MMP seems to operate with no regard to the sensor wire which means that ESC has no idea of the actual speed/direction of the vehicle. Therefore, after the first normal brake application, it will just arbitrarily apply reverse power from the second reverse throttle input onwards.

Am I making any sense at all? Can anybody else relate to what I'm saying? Thanks very much!

 

[JohnRobHolmes]

Is the MMP and MMX in double tap reverse mode, or crawler reverse? Both ESCs will wait until the motor is stopped before applying reverse, but the MMX does handle drag/throttle/reverse differently.

 

[maverick67]

Yep both ESCs are using the most basic "with reverse" mode. Even with the MMP, the first brake input does apply the brakes. But the second and onwards engages the reverse regardless of forward speed. I actually used the HH PP 2700kv and 3500kv and a cheap Turnigy motor in the test with the same results. All used a different sensor cable so its not that either. As I said, I can only assume the ESCs interpret the sensor feedback differently.

 

[JohnRobHolmes]

Ah yes. The mmx is double tap when the rig is stopped, whereas the MMP and BLE are double tap to enable reverse. I've always used crawler reverse, as it is more predictable and quicker to prevent a rig from flipping backwards.

 

[maverick67]

Ah yes. The mmx is double tap when the rig is stopped, whereas the MMP and BLE are double tap to enable reverse. I've always used crawler reverse, as it is more predictable and quicker to prevent a rig from flipping backwards.

Thanks JRH for the reply. At least now I know its just an inherent limitation of the MMP and not some setting I stuffed up.

 

[CoolRunning]

Wow, that would have driven me crazy. I can't believe all 'the get a MMP and XYZ motor' malarkey like it was the gold standard on here when the thing would do that! I constantly either tap brakes down a hill to adjust whenever the drag brake isn't handling or add tiny bits of throttle and then brake intermixed for descents and that would likely cause lots of flips and annoyances.

 

[Evo93]

Makes me glad I'm running a brushed motor with my MMP still I guess. Lol.
But my brushed motor doesn't do this so maybe your right and it just needs an update.

 

[JohnRobHolmes]

Wow, that would have driven me crazy. I can't believe all 'the get a MMP and XYZ motor' malarkey like it was the gold standard on here when the thing would do that! I constantly either tap brakes down a hill to adjust whenever the drag brake isn't handling or add tiny bits of throttle and then brake intermixed for descents and that would likely cause lots of flips and annoyances.

To be frank, everybody pretty much uses crawler reverse and learns how to drive it. The forum recommendations aren't malarkey. Double tap reverse being hard to decend with is overlooking the fact that there is a mode specifically called crawler reverse. It's for improving the handling of crawlers.


I would like to point out that the MMP still applies brakes in double tap mode. If your brake amount and drag brake is too weak to stop the motor, it won't go into reverse either. But if it's the second tap and the rig came to a stop, it will begin reverse. The MMX requires double tap too, but resets the double tap count every time the rig moves forward. I personally do not like the MMX double tap after playing with it. It's less predictable on whether it will engage or not. Crawler reverse mode is what I run normally though, and it's always predictable.

 

[maverick67]

As JRH said, I think the best way to describe it is that after the 1st brake application, and if the rig keeps rolling down hill, the MMP does not "reset" which means the second brake/reverse input will ALWAYS make it go into reverse. Great if you like doing forward somersaults, not great if you actually want to control your rig!

The MX is different in that even after applying the brakes, if it senses your rig is still rolling, it will apply the brakes again (and again, and again) and keep doing so until such time your rig is stopped, then it will go into reverse.

I agree with what JRH says about crawler reverse being more predictable, but I still think normal reverse mode can give you smoother control on some descents. In my opinion, the fact that the MMP does not have on the fly drag brake adjustment makes a correctly working normal brake/reverse mode all the more important. Because at least with the MX, you can immediately adjust the drag brake to a level which allows you to make a controlled descent and not really need to use normal braking. With the MMP, you don't have that option.