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May 11, 2012
about 2 years ago
What did poor pin 14 ever do to you? PB0 can’t be restrained!
News - On Counting Things
about 2 years ago
Yeah, cycle counting was actually pretty straightforward when I was working for a meter manufacturing company. I’d come in to work to an inbox full of kits to pick and fulfill and assorted random parts bins to go and inventory. I miss the counting scale the most - weigh out 30 or 40 of a small part, then dump the rest on the scale and let it tell you how many you had. The worst part was when the computer asked me to inventory a part that was in a location that had been moved several times over the years, so I would end up killing a half day looking for that one bulky item that everybody kept tripping over.
Tutorial - Testing LEDs with fast-switching tweezers
about 3 years ago
The flip side is that (barring the slightly overkill arduino pro mini), all of this is the sort of jellybean crud that tinkerers tend to have cluttering up their desks anyway.
Yeah, I almost wish I had a SOIC tiny85, but even still the PDIP would tuck in nicely with a CR2032 at the apex of the tweezers. Put it into deep sleep mode after a few minutes (1.8uA!) and put a pin change interrupt on the tweezer pins, it could be reasonably self contained and long lived.
Nah, LEDs are diodes - if you source too much in reverse it’ll break down eventually, but not with the 3v as provided. Look up “charlieplexing” for some interesting tricks this feature makes possible.
Now the neat thing, and I’ve seen it in my designs so I know it works is that rapidly switching a LED on and off like this somehow seems to significantly lower the Vf requirement. I haven’t scoped it up to see if the actual voltage spikes higher than the source through some mechanism. I had RGB LEDs charlieplexing easily (if faintly) as low as 2.1v, while the spec sheet swore up and down that the blue die wouldn’t even light up below about 2.8v.
I’m considering doing this with an ATtiny and some makeshift tweezer probes because I’m a cheap bastard and I have the parts laying around.
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