In terms of hardware risks, the stepper motor seems to heat up quite a bit when we hold the motor instead of releasing it after each rotation. However, since we are gaining a significant amount of accuracy, I believe we should keep it for now. Also, previously we had an automatic correction movement on the dispenser when a card was not dispensed. However, the forward-to-backward transition motion might be pulling too much current that it’s disconnecting the Arduino from the Pi. We will try to put capacitors in parallel to load so that we can smooth out the sudden current draw, but for now, we decided to manually fix it, which is fine since the accuracy of the dispenser is still pretty high.
We also made some changes to the software design. We moved over to an asynchronous io and execution model to allow for updates to happen between various components at any time. We also decided to use websockets on the website as it makes it easier for us to send updates from the server to all of the clients. The monetary cost of both of these changes is zero. For the websockets, that does increase the computational intensity of the web server but we are moving that off of the raspberry pi to be hosted on a laptop. Thus, the load on the raspberry pi has actually gone down.
Here’s a photo of the first draft of the website. There are no changes to the schedule.
