Copal 227 + stepper motor retrofit

[dpwellis]

I've been working on a microcontroller (Arduino)-driven stepper motor replacement for seized synchronous motors.

My first effort was a GE 7-4305 clock radio. It worked great, but there's a lot of space inside that unit. Someone commented it would be hard to fit inside a smaller clock.

Since then, I've worked on slimming down the electronics, and I've successfully retrofitted a little Copal 227 alarm clock with the motor and electronics. The clock was purchased as "for parts" from eBay; as expected, the original motor was stiff and not spinning.

The electronics consists of an Arduino Pro Mini (small and cheap), a DS3231SN-based Real-Time Clock board from Adafruit (<5ppm accuracy), and the ULN2003A stepper motor driver board. I'm putting together a GitHub release of my Arduino sketch and wiring so that other people can reproduce this.

The only part that doesn't fit inside is the USB power supply, so this clock will now have a captive USB tail instead of a mains cord. Then you simply plug it in to a mini USB adapter at the mains outlet.

In addition to the synchronous motor, I also had to replace the glow lamp and the buzzer. (Removing the original buzzer helped make space for the electronics). The glow lamp is replaced by a 5mm orange LED, which gives pretty much an identical effect.

I replaced the buzzer with a small piezo speaker, being fed a very 1990s "pip-pip-pip-pip" 4 kHz alarm signal (also generated by the Arduino). I'm using the original microswitch and alarm mechanism to connect the signal to the speaker.

I'm really pleased by how this all came together!

[Jumblejeff]

Nice work!

Amazing that it all fit inside the Copal 227 clock but the USB power supply.
I would not know where to start a conversion like this, but I find it interesting you made it work.

I do miss the spinning whirlygig sticker in the small opening. That feature really defines these vintage clocks for me.

Thanks for sharing your work and the pictures as well!

[flipoclock]

The whirlygig is a good point, perhaps you can connect a small display to that arduino, to display the spinning whirlygig. Surely that's possible, whether it's practically doable, that's a different story altogether.

[flipoclock]

Very cool that you made this work and that it ends up fitting in the case. Indeed when you are able to remove the original alarm, that will free up some needed space. Some more close up pictures of the whole thing put together would be lovely.

[dpwellis]

Removing the buzzer was a bit of a pain - I had to unscrew the back of the flip mechanism frame since the screw holding the buzzer is behind the flaps. Getting it apart was OK, but reassembling it involved removing the alarm dial (by removing the C-clip) because one screw holding the back of the frame was underneath the dial (I managed to loosen that screw from the side with pliers, but I couldn't get it back in the thread that way.)

Here are some more pictures. The boards aren't mounted; they are held in place by the springiness of the wires packed in to the gap. Because the stepper motor is a little smaller in diameter than the Copal original, there's quite a lot of space overall.

I put the original motor and buzzer in the last picture so you can get a sense of the sizes.

[Mephysto]

Well Done! I've been managing something similar using a servo motor, but your stepper version sounds better. Where may I find your work on github for comparison?

[Johan de Jong]

Very nice job! Could be a nice alternative for clock motors that are really hard to fix or replace (as well as a fun project anyway!).
If you don't mind me asking, can you give a rough estimate of the total cost of the components?

[cyb3rbyte]

Very cool project! Would be nice for clocks with motors that are not as reliable as the Copal-II motors. I’d love a video of how loud it is, compared to a regular flip clock!

Other consideration: would it be possible to shield the components to not make any additional radio interference in a clock radio application?

[dpwellis]

I've put up the basic GitHub page with Arduino code, Fritzing circuit diagram, and STL files for 3D printing gears:
https://github.com/dpwe/StepperFlipClock

I discuss costs in my earlier post:
https://www.flipclockfans.com/forum/...lock-mechanism

but the basic parts (most available through Amazon) are:

Arduino Nano clone ~ $6
28BYJ-48 stepper motor and driver board ~ $3
DS3231 Real Time Clock board ~ $3 (although for this project I ended up using a more expensive, smaller one from Adafruit at about $15)
Piezo buzzer ~ $1
USB power supply ~ $4
10 ft USB mini cable ~ $5
3D printed custom pinion gear ~$4

(these are the per-unit prices, although most of these I bought in packs of 3-5).

So, all in under $30, with room for further cost reduction.

The acoustic noise depends on the mounting. The one I put inside a GE 7-4305 clock radio is very quiet; the one in the Copal 227 makes an audible 0.4 second "hum" (~300 Hz) in time with each minute's click.

The RFI doesn't seem to interfere with the FM radio on the GE clock radio, but I'm sure you could put in more shielding if needed.