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A project log for blinktronicator

Sixteen different LED colors on a teeny tiny board.

zakqwyzakqwy • 12/21/2015 at 05:01•7 Comments

The board needs a thorough de-fluxing, and it's late and I need to go to bed. But I soldered up the other shift register, along with the other components, and plugged the whole works into a USB port that I've got mounted to the underside of my shelving (hence the odd perspective):

This was unexpected behavior. I plugged the Blinkronicator in just to make sure it didn't release the Magic Blue Smoke (tm). When I touched the back of the board (specifically, a few of the programming pads), it started doing weird things as you can see in the video.

What's going on? I'm guessing I'm picking up 60hz from my house's wiring, and that's running through the MOSI pad to SRCLK on the first shift register. Then ... the ATtiny is doing something too? Keep in mind, I just soldered everything together--no code has been uploaded at this point (or written, for that matter).

Anyhoo, it looks like the shift registers are doing something right, and the LEDs are all lighting up (and appear to be different wavelengths), and nothing caught fire. We'll see what happens when I try to control the display...
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12/20/2015 at 19:37 • 9 comments
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Discussions

alpha_ninja wrote 12/22/2015 at 18:02 • point

You have about 6 more hours....

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zakqwy wrote 12/22/2015 at 19:05 • point

yeah.. Zach ran outta time :-/ but I'm happy with how it turned out! I'll work out a starter program when I get back from Columbus. Also get fresh boards on order so I can scale back the tedium a bit next time..

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alpha_ninja wrote 12/22/2015 at 19:45 • point

Erm, actually, we extended the deadline. 

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zakqwy wrote 12/22/2015 at 19:53 • point

:-)

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Jarrett wrote 12/21/2015 at 06:03 • point

Looks like an open circuit on one of the inputs, probably of one of those shift registers. You see stuff like that when the capacitance of your hand is affecting the voltage of a floating pin.

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zakqwy wrote 12/21/2015 at 14:55 • point

I also noticed that I forgot to install one of the shift registers' bypass caps--I'm sure that doesn't help..

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Eric Hertz wrote 12/22/2015 at 08:31 • point

right, and an unprogrammed AVR usually results in all pins being inputs without pull-ups, so basically floating. Happy coincidence that it helps with early-early testing :)

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