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Just Some Misc Stuff

LED Lantern

LED Lantern

This is a few inches tall and made of acrylic and balsa wood, put together with hot glue. It turned out slightly uneven because of the fact that I didn't have proper tools to cut either balsa or acrylic... It's got an RGB Led in it, and some plastic as a diffuser to look like a flame.

Starlight Ghost Cage

I got this cage on sale at fred myer, put some LEDs on it, and covered the resistors and power jack at the bottom with black fabric. The thin ebay "LED fairy light" wire is a little delicate, so I tied it on with hemp cord. The wire was originally silver which didn't match the black of the cage, so I mixed black acrylic, elmers glue, and one or two drops of soap to make a paint that actually sticks fairly well to the enameled metal. I could have used model paint, but didn't want to deal with it for a decorative piece that won't see much wear.

UART to WBTV converter


Wed 13 Aug 2014

This device is basically a MCP2561 CAN tranciever wired to a rj45 jack. You can use it to talk to WBTV devices, but a normal USB to serial device isn't fast enough to do the high speed timing of WBTV, so some of your messages might get lost unless you have a leonardo or something instead of a converter running a sketch that can do arbitration.

The adapter has a 10k resistor between it's ground and the bus ground so as to prevent any ground loop damage. It's also got a standard barrel jack for if you want to supply power to the bus, with a polyfuse to prevent exceeding the cat5 current limit(600ma).

The whole thing is built point to point using enamel wire. Usually I would use hot glue to reinforce things like that nut this time I tried making a "case" by streching electrical tape over the balsa frame. I used a little hot glue to secure the male header that the wires are plugged into.

WBTV STAGE 2 Protocol RGB light


This is an RGB light made from a food storage jar thing. A cheap ebay DC-DC board converts the input to 9.6V, which powers an arduino pro mini through it's built in LDO. The Arduino recieves commands through WBTV with an mcp2561, and controls a WS2803 18 channel LED driver. The channels are paralelled in 3 groups of 6 for about 120ma per color. The LEDs are the 70 cent 6 pin 3 watt kind, and each color is wired in series, with a resistor on the red(I think it was 10 ohms) to compensate for the lower forward voltage and decrease power dissipation in the chip. The WS2803 is mounted with thermal paste to the back of the heatsink. Yes, I know I could get almost the same brightness with just 1 RGB led at 300ma per channel, but then I'd have to find a driver chip that could do 3x 300ma, and the ws2803 is cheap and common. Plus, the LEDs last longer at lower current, and are easier to heatsink, and also, The LEDs are all rotated 120 degrees from the last one for optimal color mixing.

When it powers up it sends a message to NOTE saying "Send a message to channel XXX to set the start address". The channel is 16 bytes long and generated randomly the first time it starts up using the temperature sensor for entropy.

Because the 6 channels that make up a color are individually controlled, the greyscale depth per color is 6*255=1530 instead of 255, and there's a little bit of color dithering thrown in to increase it a little bit more. WBTV STAGE2 has 16 bit color commands, and the full 1530 levels are used even when fading between 2 8 bit values, for smooth fades even at very dim levels.