So Who Wants To Build The World's Coolest Clock?

A project log for Gummi Worm Clock

I forgot to build something for the Bay Area Maker Faire Bring A Hack event. I started this on April 7th. The Faire is May 16th.

BenchoffBenchoff 04/12/2015 at 07:075 Comments

Before I dig into this, I'm just going to say, no, I'm not going to build this. This is simply an exercise in procrastination. It does look pretty cool, though.

Okay, with the Pi version out to fab, I figured the clock doesn't need that much RAM to drive the display, the Pi version already has a RTC, and we're basically working with shift registers here. For the fuck of it, let's design a version with a microcontroller.

And so a dozen hours were lost.

This version (it's in the github now) features:

There we go, a microcontroller-based RGB Seven-Segment clock that has all the functionality of the Pi version and is completely overengineered for a clock. Does your clock have WiFi? No? Yeah, mine does.

I'm not going to build this. It's insane, impractical, and I'm already spending $200 on the prototype to see if the LED2472 drivers will work. I just made this one because I'm bored.

If anyone wants to make it, go ahead. It might work. Files are in the Git. I'd like to see it made, and you could probably sell a few of them on Tindie with some SEO on Pinterest or something...


esot.eric wrote 04/12/2015 at 22:09 point

For clarity, you mean you're not going to make the AVR version, but you are still going to make the Pi version?

"and every time DST comes around, I need to disconnect the battery in my car, and reconnect it exactly at noon" -- at least you don't have to do it at midnight?

You might've seen, I was inspired by your clock idea and tried to apply it to my LCD project... Similar procrastination-ponderance... Hey there's a "Pro" in procrastination, so whatever comes of it, it's supposed to be good, no?

I wasn't planning to actually code it up, it was mostly proof-of-concept. But I've been thinking, a little bit, about actually doing it, or something like it... Would you be offended by the obvious knock-off? 'cause those gummi-worm-colored segments are pretty-durn-cool looking. (Was thinking about maybe having different color-palettes for different times... Something about the old NES Tetris color-schemes...? not sure).

  Are you sure? yes | no

Benchoff wrote 04/12/2015 at 23:50 point

Yeah, I'm probably not going to make the AVR version. That's just me wanting to design something and procrastinate. I will say that I'm pretty proud of the layout around the microcontroller. That actually has the potential to be a usable design.

And I wouldn't be offended by an obvious knock off at all. That would be great. I would highly recommend that you wait until the Pi version of mine is done to see if these displays can actually be made into a real clock. I have some questions about their brightness and if the current limiting on the LED2472 chip will work like I hope it will

If that works out, I wouldn't be opposed to productizing this. It would be a terrible product unless you can get the price of the displays and drivers down to a few dollars per digit. Those RGB seven segments are *expensive*. Hackaday might have some people going to Shenzhen in a month or two, maybe there's a clone out there.

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esot.eric wrote 04/13/2015 at 00:55 point

Hah! I actually had it in my mind that maybe they made them by sucking out the guts of regular single-color seven-seggers and replacing them with multicolor LEDs... That'd be a bit ridiculous, I suppose :)

Props on the design turnaround-time. Those LED drivers' layouts are elegant. If the AVR-layout's similar, usability-potential should be great. ("procrastination" has such negative connotations, I really think that concept needs to be reevaluated in this society.)

Not sure about the LED chip you're using, I assume it has the same current-output for all LEDs... but worst-case, you might be able to implement something like PWM (with a lot of shifting).

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Benchoff wrote 04/13/2015 at 01:01 point

Here's the chip if you're wondering:

Actually it's not constant current across all LEDs; you can set the current for individual colors. The more I read the datasheet, the more sure I am that this is the best chip for the job.

I probably could implement PWM with this, but for that I would probably have to move to an ARM or Teensy or something. Yeah, a third revision...

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esot.eric wrote 04/13/2015 at 01:12 point

Well, there's an OE for each color, so even if it didn't have individual-color-current you could PWM those OE pins (if the R/G/B LEDs vary in brightness at the same current). But this is all irrelevent, since it handles that.

But, even if you didn't want to use the full-brightness, for other colors, then you could probably shift data in (30MHz!) to simulate PWM *with* these chips... I bet you could do that with an AVR ;p

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