Reconn's World Project Log - Stepper Motor Driver

PIC Code, Verified

nospam@example.com (Andrew) — Wed, 05 Jul 2006 22:08:30 -0400

Well, the PIC18F2550 wasn't working for me so I changed to the PIC18F2520.

I don't know why it was giving me problems, but it essentially was not letting me set the clockrate fuses correctly (and I seemed to be missing pieces out of my 18F2550.h file, compared to other people's projects I found on the net.) The only thing I'm really missing is the USB-capability of the 2550, but I wasn't going to use it anyway.

I have completed the PIC code to read from the analog-to-digital converter, as presented in my last post. I have also verified the duty cycle on my GDS-820C oscilloscope.

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Speed Control Dial

nospam@example.com (Andrew) — Wed, 28 Jun 2006 19:37:26 -0400

While the stepper motor could be completely computer-controlled, I'd like to be able to change the speed of the motor by turning a dial. for this i'm using a linear potentiometer from radioshack (10kohm, RadioShack #271-1715.) I'll read the voltage off of the middle pin -- turning the potentiometer will cause this middle-pin voltage to swing from ground to +Vcc (5v in my case). I will read this voltage in via the PIC's analog-to-digital converter and control the motor's speed accordingly.

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Beginning of Stepper Driver

nospam@example.com (Andrew) — Tue, 27 Jun 2006 23:12:21 -0400

So today I started on a pic-based stepper motor interface board. This project is designed to interface with a seperate motor controller circuit for the actual motor control, and monitor the rpm's via a sensor -- creating a nice closed loop system. The feedback will be via a hall effect sensor or led reflective/breakbeam setup. I'm not sure yet. Also, eventually I will make my own motor controller circuit, but right now I'm using the BSD-02 motor controller from Interinar. This controller will let me control a bipolar stepper motor, up to 50V @ 2amps. Pretty nice. I can also full-step, half-step, quarter-step, and eight-step.

System Components:

PIC Microcontroller: I'm using the PIC18F2550 with an Olimex development board. The pic will sent the control signal to the motor driver circuit. The pic will also monitor the feedback circuit to determine the real rpm. Furthermore, the PIC will monitor a potentiometer that will be used for speed control. Additionally the PIC will have a serial interface to a PC to display rpm, and possibly accept settings from.

Potentiometer: the potentiometer will control the rpm of the stepper motor. This setting will be read by the A-to-D on the PIC.

Stepper Motor: I picked up from stepper motors for cheap from my friend John at engineeringhobbyist.com and will be using the PowerMax II stepper motors. These suckers are rated for 1.75A operation. 1.8degree full steps. Model #: P21NSXC-LSS-NS-03.

Stepper Motor Controller: like I said, I'm using the Interinar BSD-02 motor controller, and may roll my own later down the road.