DC motor control using MR C3024 board?

[Robotech]

Hi all, I have been following this forum since i bought my RN1 one month ago. Now, I am thinking of adding wheels to my RN1. Is there anyone can help on how to get DC motor controlled using the RN1 control board?

The Robobasic instruction touches a little on DC motor control using RN1 controller but i just can't figure out how to do it.

I am using tamiya universal gearbox to drive the wheels. Information of the DC motor:
http://www.pololu.com/products/tamiya/0069/

[Pev]

Not sure about DC motors or what speeds you want to do but you could always modify a couple of standard servos for continuous rotation and use those......

This may help

http://www.lynxmotion.com/images/html/smodh2.htm

Pev

[Robotech]

Thanks for your info, Pev.

I am using tamiya universal gearbox : http://www.pololu.com/products/tamiya/0069/

I just receive an e-mail from hitecrobotics on this. They mention only about PWM port. I will try it out then.

The DC motor has only 2 terminals. How is the connection should be? connect to GND and SIGNAL ,igore +5?

How the code should look like? Use PWM command? How to make it rotate in both direction? Varying speed?

Thanks for enlighten me

[Bullit]

I think I would use one of the unused servo ports and a r/c speed control with reverse to control the motor.

[i-Bot]

Interesting question, not quite as simple as I first thought.

Depends also on whether you want to build or buy a solution.

For an off the shelf solution either a speed controller from the servo outputs as suggested by Bullit, or a serial controller similar to the one from Pololu are the probably the easiest.

The servo outputs have the advantage to setting zero for stop. However the servo settings are now speed, and not position, this will cause some interesting challenges when using PTP on group moves.

The serial option would go on the ETX/ERX, but would probably be a little slower.

For a build option then the PWM on the C-3024 can be used. The PWM outputs are only ttl levels, so cannot drive a motor direct. There are 3 PWM outputs, but you will also have to use a couple of other ports to give direction signals.

For an external motor driver you would need a dual H-bridge such as LM298N.

[sippy]

I think it comes down to exactly how you want this motor placed/packaged. Looking at the prices of continuous servos(http://www.active-robots.com/products/motorsandwheels/servo-motors.shtml), they are not much more expensive than the motor you are talking about. This will then give you the control circuitry and h-bridge in a reasonably small package, ready to plug into the existing board pins. This would then mean that the motors control circuitry and motor are reasonably close, you could however be looking for a small presence around the motor and to control it elsewhere, in which case an external control circuitry would be needed.

If however you are looking for a more low level solution as I-bot say's you will need to create your own h-bridge circuit since the pins of the atmel will not be able to deliver enough power( figure 7 in http://www.st.com/stonline/books/pdf/docs/1773.pdf gives an excellent diagram), and possibly a feed back method would be needed too if you are looking to control the motor accurately. Either way you generally need 2 signals as shown in the table of the datasheet that define forward, back, resist movement and free rotate.

Again like i-bot says http://www.pololu.com/products/pololu/0410/ could be a good one for space and ease of integration, but slow since it uses a serial protocol. Depends if you are looking for ease, cost or fun of DIY.

[Robotech]

Thanks guys, you all are so helpful. I think I am going to get a servo modified for continuous rotation.

By the way, how does the control of continuous rotation servo motor differs from the normal servo?

I want to make it rotate in both directions ,stop and vary its speed.

[DerekZahn]

A servo modified for continuous rotation has the mechanical stops in the gear train removed, and also has the potentiometer (which gives position feedback) either disconnected or removed.

You will be able to set the direction and (roughly) speed by telling the servo where to go. Telling it to go to the "center" means stop.

[Robotech]

http://www.youtube.com/watch?v=wMgng2aT ... user%2Ephp

[gdubb2]

Thats GREAT... I love it..

Gary

[Robotech]

Hi all, Robotech is now convertible to wheeled robot!! Just like the transformer. Also, I have made him dance. Enjoy..

The dance:
http://www.youtube.com/watch?v=qQx6G1P4 ... user%2Ephp

The Transformer:
http://www.youtube.com/watch?v=wMgng2aT ... user%2Ephp

This is not the perfect one(the dance) but the only video I managed to take using my friend's digital camera.

[Robotech]

I have removed previous videos on my robotech
New vidoes of better quality:

phpBB [media]

phpBB [media]

phpBB [media]

[joaocunha99]

hi,
you controlled the dc motors with pwm gate or a bridge H.

Could provide the codes.

I wanted to control dc motors with H bridge but with the outputs of the servos. I do not know how.