Schedule

Per our Gantt Chart, this week I was supposed to set up the stepper motors. I was able to do some of it, but a lot of this week was focused on the Design Proposal.

Progress This Week

This week, besides working on the design proposal slides, presentation, and report, I was able to obtain the stepper motors and drivers and check whether or not I could interface them with an Arduino Uno. Using an Arduino Uno allows me to isolate variables of not knowing how a RPi works and all the potential interrupts, etc. With an Uno, I can quickly setup the code and check whether the motors and drivers are working. If the RPi doesn’t end up working, we can revert to the Uno code, which can be helpful.

I used these two links as reference:

How To Control a Stepper Motor with A4988 Driver and Arduino

Control Stepper Motor with A4988 Driver Module & Arduino

In writing a simple test and setting up the circuit, there were a few problems. 1) Using a breadboard would pose a significant problem, as when I used it, the connections were unstable, and I have to hold the wires at very specific angles in order for the motor to move. 2) I am currently receiving a “avrdude: stk500_recv(): programmer is not responding” bug, where my sketches are not uploading, even though it worked once. 3) I’m still struggling to understand how to adjust current limit and how that correlates to current draw from the microcontroller GPIO pins.

From the feedback received from the design review proposal, I noticed that someone was concerned about the accuracy of the motor (since resistors are tiny). They mentioned that though the motor can go down to 1/16 step, it might not be enough. And I would like to look more into this. Also during the Q&A, Aarohi mentioned how the parts can weigh down and distort the shape of the gantry. I would like to keep this in mind moving forward.

Next Week’s To-do

Next week, I’m looking to solve the above problems in the following ways:

1) Solder the connections onto a board.

2) Debug, with the help of stack overflow. But potentially swap out the Arduino. Some references say that this might be the issue, which I’m not too convinced by, but still… options/

3) Measure the current from the GPIO pins with a DMM.

I will also be attempting some stepper controller code on the RPi, to test if we will have to use the Arduino. Beyond this, I will also be following the Gantt chart and hopefully setting up the servos. I think we will be using an off the shelf rack and pinion, so there will be less assembly for me to do.