MD22 Problem

[olof_n]

Hi!

I have a very strange problem with my new MD22.
First I tried the MD22 with a pair of motors and everything worked fine.
I than replaced the motors with 2 smaller ones (http://www.pololu.com/catalog/product/1107).

After that I get random errors.
Exampels:
If I send a value of 138 to motor 2 motor 1 gets in full reverse and motor 2 have the correct speed (138).
Sometimes everything works ok and then suddenly random errors occurs.
When I read the speed registers they are reporting the correct values (138 motor 2 and 128 motor 1) but the motors are rotating in the wrong way.

I have hooked up a Arduino as in your example (http://www.robot-electronics.co.uk/htm/ ... s.htm#MD22 Dual 50V 5A Motor Driver).
I have capacitors across the + - on the motors.

Do you think my MD22 is broke?

Regards

Olof

[olof_n]

Hi!

I think the moderator can remove my topic.

I have figured out the problem (after 6 hours and alot of testing ).

Problem 1: I used a PC-powersupply. The powersupply seems to have some kind of protection. When the motors have full speed and I stopp the motors the powersupply turn off!
The reason it worked earlier was because the acceleration register was set to 255 instead of 0. The current changed slowly and the powersupply did not turn off.
I have now replaced the supply.

Problem 2: The first things my program do is: set the correct mode, stop the motors and set the acceleration register.
Here something is wrong. The motor register reports 0 (full reverse) but the motors do not rotate.
When I send 138 to the first motor the first register is 138 and the second 0. Motor 1 starts to rotate slowly and the second motor is going full reverse (0).
Bug?

It is not a big problem because I can just send a second command to motor 2.
Sorry for my english it is not my first language.

Regards

Olof

[chris]

Hi Olof,

Problem 1: Switch mode power supplies are far from ideal for a switching H-bridge board, the MD22 was really intended for use with a battery.

Problem 2: As far as I am aware the registers work fine, they should power up at 128 (stop) commands can then be sent as stated in documentation, the default mode is below:

0, (Default Setting) If a value of 0 is written to the mode register then the meaning of the speed registers is literal speeds in the range of:
0 (Full Reverse) 128 (Stop) 255 (Full Forward).