PortaLED

I was also able to assemble the other PCB, the portable LED circuit thing. It was rather interesting assembling it since I had to go in and fix a few places that didn't reflow well, and I accidentally dumped a ton of flux on the board (didn't realize the flux pen would release so much). After a bit of debugging, the main LED driver seems to work and I am able to program the microcontroller. However, the battery charger doesn't work, or at least charging indicator light doesn't work. I'll need to figure that out later. Also, during my debugging process I lifted a pad somehow and one capacitor is soldered in at an angle now.

Completed board. A bit gunky from the left over flux.

My idea to program the microcontroller with the pads on the bottom of the board turned out to not work so well. It was too difficult to maintain good contact with all the pins without some sort of clamping rig, and for now I just soldered in some pins. I can take them off when I'm happy with the firmware.

Programming header.

This thing is stupidly bright. And hot. Running the LEDs at full power generates quite a bit of heat from the LEDs, and I'll likely limit how long that mode is allowed to run for.

Bright.

Things to do (updated 2/25!):

• Fix charger (seems to work but LED doesn't turn on during charging)
• Add different brightness modes (added 8 brightness modes; thinking about implementing a brightness ramp and shutting down some brightness levels when battery gets lower)
• Add battery low voltage shutdown (code doesn't allow lights to turn on when battery is below a certain level, need to add warning)
• Add battery voltage blink out (done, but code is blocking and a little buggy)
• Design a case (in progress)

All updates 2/25:

I've just written a simple firmware for the light; it now has 8 brightness modes and can display the battery (or VCC in general) voltage. I'm still considering adding more brightness and blinking modes, but for now my focus is designing a nice case for it. (Code at my Github here.)

Reading more into the datasheet of the ATtiny85, I think I've just found my new favorite microcontroller for small projects. It can has 4 PWMable outputs (some can be setup to be opposing pairs with a deadtime generator) and a differential analog input mode with internal 20x gain, and everything else in a normal AVR. The PWM I know isn't that special, but I'm not sure how common the differential input mode is among 8-bit AVRs. Regardless, a cool feature I will want to try out some time.

LED Flash

I was able to come back home for the long weekend and assemble the PCBs I ordered from OSHPark. I designed an LED flash driver and a constant current portable LED light thing (that I really don't know what to call) several weeks ago and only now have the opportunity to put them together.

Some background on why I made these: For EE lab in school we were asked to order free op-amps from TI, and I decided to just get some more free parts while I was at it. I wanted to make a simple LED flash for high-speed photography, and wanted to test out the UCC27324 MOSFET driver. And since I was already using LEDs, why not learn a bit about boost circuits and constant current LED driving with the LM3410 constant current boost LED drivers? All of this is good design practice in the end too.

Back to the LED flash. Here are the PCBs for the flash and constant current driver:

Purple PCBs!

Close-up of the flash.

Here some screenshots from KiCAD:

Schematic

PCB

Super Blue Blood Moon

Super blue blood moon! What a mouthful! On January 31st, 2018, there was the second full moon of the month, the moon was closer to earth than normal, and it just happened to be a lunar eclipse, giving rise to the red moon.

I decided to wake up early in the morning to take some pictures of it with some friends. They turned out pretty well:

This time I managed to capture the red color! I think the compression from Blogger kills the image quality, but you can these photos (along with a few more, all in better quality) and a relatively uninteresting timelapse on my Flickr.