Connecting 2 mow motors on PCB1.3 for 2.0 chassis?

[romualdas]

Hi,

Anyone has an idea (if it is possible at all) how to properly connect two mow motors (from the shop) to the PCB 1.3 on 3d printer chassis (aka V2)?

Original (V1) chassis has 1 mower motor and it is attached via motor protection circuit to both outputs of MC33926.
At the same time it measures current (via one of the channels) and check for the faults reported by controller.

What would be the approach to connect two mower motors to PCB 1.3?

Option 1: Connecting both mower motors in parallel via P37?
Potentially, MC33926 can supply just enough current as the motor uses ~2.7A and the controller supports 3A/channel (based on https://www.pololu.com/product/1213 ).
As driver has "under-voltage, over-current, and over-temperature protection", probably it wouldn't burn down immediately.
However, I guess that there's purpose why one motor was connected to two channels with one motor setup
Sensing with two motors would be off and not represent actual situation (e.g. mower turns mowing engine off if the power consumption is above 75W for certain time, which wouldn't make sense with 2 motors). Without sensing, it is basically an option 2, with barely capable controller.

Option 2: Using powerful enough controller (or controllers) and go without the feedback
That would be similar to using LM298-type controller. Some intermediate board might be nice.
Little software modification would be required, to drop the checks for the mow motor, but leave for the drive motors, but in general it should work.

Any other options?

Thanks,
Romualdas

 

[bernard]

Hi.
Option1:
Easy but need change in the code to not stop the motor immediatly from PWM255 to 0
Very Dangerous for the driver and motor (if one is totaly stop by obstacle ???????)

Option 2:
Use arduino Nano, 2INA169 and 2 L298N(or equivalent) and connect the PinMotorEnable,PinMotorPWM to the Nano.
The Nano control all by itself ,it is 5V board so be carrefull maybe the feedback need to be reduce to 3.3V if DUE and no levelshifter..

Otption 3:
Connect Motor 2 to normal P37
Cut the 2 junctions between M1OUT1,M1OUT2 and the PCB1.3 and use normal screw to connect motor 1 directly on the Driver.
The JP3 Jumper send the feedback motor 1 sense.
The motor1 have no protection board but it can work without.
Make change in the code to check the 2 sense feedback to stop all if >2A

By

 

[romualdas]

After reading a bit around (not sure if I get things right), here are my thoughts for now.

Option 1 - is probably not the best one, because it is not the motor that has to be protected, but rather motor driver and DC/DC step-down regulator. As I understand this was quite a problem for the PCB v1.2. And if so, the same applies to the option 3 as well.
Option 2 - somehow I doubt that L298N would be sufficient enough as their limit is ~2A. In addition, together with Nano they would take significant space in already crammed PCB box
Option 3 - sounds easy, but doesn't protect the driver from inductive currents, however, I think it should be fairly easy to solder a mini-board with same protection elements as on the PCB,

and attach it in middle between M1OUT1,M1OUT2 and the motor.
Hopefully, the board will fit somehow under the PCB in the PCB box.
Attachment: https://forum.ardumower.de/data/media/kunena/attachments/4472/Protection.PNG/

 

[jussip]

Is there any availabe pins on due/mega? How about connecting two MC33926's paraller so that only senses are in separate pins.
Why option 2 above is using other than MC33296 drivers?
Marotronics shop sell optional 2 motor kit but there's no additional driver with that.

 

[romualdas]

Just my opinion here:
the only missing feature with the PCB 1.3 and 2xDual-MC33296 is the lack of motor protection circuit on for each mow motor driver output, because both driver outputs connected to single driver protection circuit.
Apart of that, one can control:
- PWM, check driver state, enable/disable driver - for both motors simultaneously, but IMO for mow motors that's fine
- check current feedback - for each motor independently with JP3 connected.

As there's not much space in 3d printed ardumower PCB box, personally, I don't want to introduce a lot of new boards and controllers.
I'd prefer not to rewire the the PCB either.
In my case, I just disconnected M1OUT from the PCB and connected to small driver protection circuit, similar to the one on the PCB.
It fits under the PCB in the box and seems to working ok. I have posted more details here .

 

[jussip]

OK, thanks. I didn't fully understand your wiring first. That is probably easiest way to do it, if driver one channel is enough for mowing motor.