Updates to Turntable pages

I am updating my Railroad Turntable page to reflect my change in the design of the motor drive. The changes include:

  • 5 volt NEMA 8 miniature stepper motor instead of much larger 12 volt NEMA 17 motor
  • 18-tooth pulley gear for 4 mm motor shaft instead of 20-tooth gear for 5 mm shaft
  • Recalculation of size of large 3D-printed turntable-side pulley gear

The Turntable Calculations page is also being updated to reflect these changes.

Update coming on UDP-with-echo protocol

I’ve been working on improving the UDP-E or UDP-with-echo protocol I describe here to make it more flexible and to improve reliability. I’m currently testing it with a Raspberry Pi as the controller, and an Arduino UNO plus Ethernet shield as the peripheral. The goal is to create a protocol which will allow the controller to send messages to the peripheral, and the peripheral will echo messages back to the controller if the received messages are verified as valid. The controller will retry sending each message if (a) the echoed message is not received by the controller before a timeout occurs, or (b) the echoed message is received but fails validation tests. This protocol should make communications with the UDP protocol more reliable than one would get with data only with UDP. At the same time, this protocol will accomplish this with much less overhead than using TCP, and with performance much closer to real time. Hopefully I’ll have more to report within the next few weeks.

Revisions coming on “Turntable Calculations”

Looks like I will be making extensive edits to my Turntable Calculations page very soon. I learned this week that the stepper motor I had chosen for my turntable project is not guaranteed to meet the specifications listed on the web page from which I had ordered it. Specifically, the quoted number of steps per revolution can vary wildly from motor to motor from what the web site had originally stated as 513 steps/revolution. They now put it at 516, but comments on their user forum say users have received those motors with a variety of gear ratios. So I can’t rely on the motor I originally chose. More details coming soon.

Switch Machine Controllers page updated

I’ve updated my page on my Switch Machine Controller design, adding more information on how the controller and driver modules are designed to connect together. This includes a design for an Arduino UNO based test setup to verify that multiple Switch Machine Controllers sharing an I2C bus work as expected.

Updated info on Turntables pages

Added some information regarding modeling railroad turntables.

First, I added some back-of-the-envelope calculations to the Railroad Turntable page to verify that the maximum speed of my planned stepper motor will not be exceeded. Also, on the Turntable Calculations page I edited a note regarding Adafruit replacing their 16:1 geared stepper motor with a 64:1 model. As of November 2021 they have reversed that change, so the 16:1 motors are again being sold. Based on the maximum-speed calculations I mentioned above, this is a very good thing. 😉