Forrest O. Fab Academy

Week 10. Output Devices

Group work

Characterizing the power consumption of my addressable RBG LED rope.

Power meter showing 5 volts.

LED rope with battery bank and supplied controller, power meter showing 5 volts.

Power meter showing 0.3 amps.

With only a some of the rope lit up, the power meter shows 0.3 amps.

Power meter showing 1.5 amps.

With the rope fully lit up, the the power meter shows 1.5 amps.

Probe setup.

Setup to probe the data line with the Salaea and supplied controller.

5v data signals.

Probe UI showing 5v data signals.

Data signal showing on and off binary data.

Probe UI zoomed in to a data signal.

LED rope animation driven from XIAO.

Using an existing dev board with a level shifter. FastLED working!

Circuit fo_v3

Since the XIAO RP2040 data pins have 3.3v and the LED rope data line needs 5v, I knew that my breakout board needed a level shifter. We added a LevelShifter_Texas_TXB0104DR_SOIC-14 from the fab inventory. We also added a power-only USB connector.

KiCad schematic

fo_v3 KiCad schematic.

KiCad PCB

PCB design. I have to say that the routing is quite satisfying and I can see it being addictive.

📝 Capacitors should be as close as possible to the chip.

Mill V-bit

The USB-C power breakout requires a 0.3mm clearance. We have 0.3mm routing bits, but the Bungard mill started breaking them. After breaking a few, we switched to a v-bit, which worked.

fo_v3

fo_v3 circuit assembled. Better than last time! I'm tempted to encase it in hot glue.

Big thanks to Kris' soldering tips videos. The key tip for me was the surface mount chip order of operations:

  • Put a little solder on one corner pad.
  • Place the chip with tweezers, make sure the rest of the feet are aligned.
  • Melt the one foot into the solder blob, again make sure the rest of the feet are aligned.
  • Solder the opposite corner foot and pad.
  • Do the rest. Go slow.

📝 The level shifter is symmetrical and the data sheet didn't give a clue as to which way the text is printed. The printed dot on the top is closest to pin 1.

fo_v3 to LED rope

XIAO to LED rope working on fo_v3 board. 😅

Next steps

  • Make a light animation to go from 0 → 250 with full brigtness white, to see the real max amps of the LED rope.
  • Connect 6dof sensor and start programming lights reacting the the ball movement.
  • Iterate on the electronics enclosure and light ball design. 🌀

Files