Society of Robots - Robot Forum

Mechanics and Construction => Mechanics and Construction => Topic started by: Maltaeron on February 22, 2008, 06:18:00 PM

Title: Looking for reasonable bipolar stepper
Post by: Maltaeron on February 22, 2008, 06:18:00 PM

I have a robot that I need to be moved with stepper motors so that it can have fairly exact movements in a clear environment, I am looking for some help with what I did wrong and some steppers to buy that could fit within my current setup with minimal change. If it wouldn't be too expensive, I could rework the whole setup, even to another type of stepper, but I would prefer not two. I have also searched the forum already,  ;)

I set up a circuit on my breadboard with an atmega168 controlling two steppers from an Epson printer via 4 NJM3717 drivers.
Data sheet: www.ortodoxism.ro/datasheets/newjapanradio/ee04004.pdf (http://www.ortodoxism.ro/datasheets/newjapanradio/ee04004.pdf)
I am using the example setup from the data sheet, with I₀ and I₁ connected to one control pin and PHASE an other.

This is my code, the macro PORT_TEST is true if the given pin is on, and false otherwise, hope the code is not undecipherable (I am self taught)

Code: [Select]

void motorStepForward(int i){
static IOPin ioPin;

ioPin = ioPins[i ];

Toggle current, and possibly phase for coil A
PORT_TOGGLE(*ioPin.port, ioPin.pin + 1);
if (!PORT_TEST(*ioPin.port, ioPin.pin + 1)){
PORT_TOGGLE(*ioPin.port, ioPin.pin);
}

//Toggle current, and possibly phase for coil B
PORT_TOGGLE(*ioPin.port, ioPin.pin + 3);
if (!PORT_TEST(*ioPin.port, ioPin.pin + 3)){
PORT_TOGGLE(*ioPin.port, ioPin.pin + 2);
}

}
I got the motors to sort of work; however, there were some very interesting things that I don't think should have occurred.

- Very little torque, next to none
- I could change the direction of the spinning just by manually setting in the new direction (this was actually really fun ;D)
- Some time near the end of my playing testing of the motors, some internal connection broke (no connection between A and A' anymore)

Some other facts:
I powered the motors at different times from unregulated 4.8V and 9.6V, though the drivers I used were meant for 10V to 45V

I am limited to 9.6V, as this robot is for a competition with that as a limit.
There are others on this forum with the same event, Robot Ramble, regulations: https://www.lakesideschool.org/upperschool/community/ScienceOlympiad/rules/RobotRamble.pdf (https://www.lakesideschool.org/upperschool/community/ScienceOlympiad/rules/RobotRamble.pdf)

Thanks,
Mad High school Freshman

Title: Re: Looking for reasonable bipolar stepper
Post by: Admin on March 09, 2008, 10:31:58 AM

Not enough torque means you aren't supplying enough power.

Are the batteries fully charged?

Whats the voltage rating on the steppers?

How much current are they using (check with multimeter)?