Good Enough For Testing

A project log for Global View

Persistence of vision is awesome

JarrettJarrett 11/09/2018 at 21:472 Comments

With an entire side done, I can move on from the electronic side for now. With the microcontroller, LED drivers, and all of the LEDs soldered on there, I can work on code and fit it into the mechanical test fixture. 

For some interesting stats:

All 20 blue LEDs full-on is currently drawing almost exactly 70mA at 3.0V. The current setting resistor for the TLC5947 is 1.3kOhm.

Also in keeping with the bodgery-theme, I managed to salvage the microcontroller, driver, and most of the LEDs from the old board. I did have to replace 4 LEDs because they did not survive the transplant. I replaced all of the passives, though, those were toasty.

Code for the PIC is coming along nicely - I think I have a proof of concept that should work almost perfectly. I can't test it until it's in the assembly and spinning, however, so that is next.

The LR44 batteries I intend to use are rated at about 50 ohms at 1.42V, which works out to about 28mA, regardless of how many I stack up in series. That means that I suspect I will probably have to reduce the current limit on the LED driver, or just set it down in software. Hard to say, it's also possible the battery will be able to handle the quick discharge spikes every once in a while.


Jarrett wrote 11/09/2018 at 22:19 point

That's an interesting idea, for sure.

This first version, because I wanted it to be built easily and quickly(hah!), I'm definitely going to go with the LR44s like this:

The intention though, after this is working and solid, is to use a BLDC motor on both poles. The bottom one can spin the disk, while the top one, inverted, can act as a generator for on-board power.

Very much in the future, though! The 3-phase generator will be a cool side-project on its own.

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Ted Yapo wrote 11/09/2018 at 22:01 point

Hmmm...need power on a spinning platform.  What a coil of wire on the PCB (or etched inductive trace) and some magnets around the outside?

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