Unless designed to do so, it’s generally bad when your electronics project bursts into flames. That said, I learned something yesterday (I also need to file away a “Pyrotechnic Clock” for a potential future project).
One of the issues I’ve had with this project is that I don’t really have a good space to work on it where my kids won’t get to it, so I have only sporadically hauled it out of the basement and up to the kitchen counter after the kids are asleep–done a little soldering and packed it all back up and down into the basement.
I think that work-flow really bit me yesterday. Having gone through a few different iterations, and tests with steppers, I found a complete single axis that was about the right size, with a 1204 ball screw, so I decided to buy it. After letting it sit for a while, I started looking through the rest of the system and found that the stepper motor included with it required a 24v power-supply. No big deal. Order a new power supply and wait a few more days. New power supply arrived, and I finally took the time to get back to work on the clock. Unfortunately, it had been quite a while since I reviewed system requirements for the rest of the project–including those printed right on the parts. The metro’s stepper motor shield accepts power supplies from 5V to 12V. Adding in a 24V power supply is a good way to buy a new motor shield. On the bright side, it is immediately apparent that you made a mistake, so the amount of time where you think (falsely) that you’re making progress is minimized.
After I set the electronics on fire, I decided to focus on what parts of the system I still had.
First, remove the 24V stepper motor and see if the 12V motor fits. Answer: Yes. Alright! The resistance of the ball screw is pretty slight, so I don’t anticipate an issue driving it–but what’s the worst that could happen? It catches on fire and my children die a horrible death? Oh yeah…that. I should probably look at heat sink options for stepper motors.
Second, look for ways to mount the limit switches at each end: It looks like there are troughs in the rail that you place hex nuts in, so I can create my own little brackets that mount directly to the rail and hold the switchs.
The troughs are on the top and bottom of the railing, so this will also work for mounting it to the housing.
Finally, it was time to solve the issue of occasionally hauling everything out. I setup a desk in the basement. It’s really true, the simplest solutions can evade you for excessively long times. I find myself occasionally thinking of Jeff Bezos’s story about packing books on the floor of a basement he was renting out in the early days of Amazon, and lamenting to a coworker that they needed knee pads, and the coworker saying, “No, you idiot, we need packing tables.” I find a lot of comfort in that story.