RS-485 node control for Arduino

rs-485-arduino-nodes

Wanting to control a split flap display that was not near a computer [Tom] looked to a common solution for communicating over distances not practical for I2C or SPI. He developed his own hardware and packet format using the RS-485 protocol.

This is part of a larger project he has been working on to feed data to a split flap display that he plans to hang on the wall. RS-485 is designed to work over long distances and overcome noise issues. The core of the communications system is the board seen on the left. It uses a MAX1483 chip, a pair of RJ45 jacks for Ethernet cables, and two terminal blocks for power and communications. There are a few nice things about this. The board acts as a pass-through making it easy to chain nodes together, and the data structure is completely independent of the hardware itself. Because of this [Tom] developed his own packet format that will be a bit more resilient than the Arduino networking scheme we looked at the other day.

Halloween Light Show Gets an Upgrade

This is [Dave]‘s second year of putting on a Halloween light show (cache), and his latest production has received some upgrades over last year’s Christmas show. He’s switched from Christmas style bulb lights to high brightness LEDs, and upgraded to 48 channels of control.

The controllers are from Light-O-Rama, and each provides 16 output channels. They communicate over RS-485; the same type of network used for controlling professional theater lights with the DMX512 protocol. The whole thing is powered by a 20 A DC supply from some Chinese retailer.

[Dave]‘s show features light up pumpkins, tombstones, and faces mounted on his house. The lights are coordinated to a list of songs that he plays over an FM transmitter, allowing for cars to tune into the music that’s synced up with the lights.

If  you happen to be in Estacada, OR, you might want to head over to [Dave]‘s and check out the show in person. Otherwise, there’s two videos of the light show after the break.

[Read more...]

USB to RS-232 adapter hacked to use RS485 instead

[André Sarmento] needed to connect a computer to an RS-485 bus. A simple converter can be sourced online, but the only thing he could find locally that was even close was a USB to RS-232 converter. He used that component to craft his own USB to RS-485 bridge.

RS-485 is often used for remote sensors as it provides a method of connecting electronics over long distances. The converter which he started with seems to be encased in a hot-glue-like substance. A bit of time with a torch and he was able to get to the components on the board. There are two stages, one which converts RS-232 to TTL, and the other converts TTL to USB. [André] removed the RS-232 chip and patched his own board (shown on the left) into its TTL lines. He was also able to add a few more configuration options, like using an external power source, and having a few jumper-selected resistor options.

Controllable LEDs spice up the living room

[Sprite_tm] brings us another great hack by lighting up the living room. Unsatisfied with just replacing incandescent bulbs with an LED alternative he went with strips of LEDs to illuminate the length of a wall. Starting with a seven-meter strip of the lights, he cut it down to fourteen pieces in order to make the RGB devices individually controllable. [Sprite_tm] whipped up a design for controller boards using RS-485 to communicate with each, and sourcing an ATtiny2313 for the PWM necessary to generate any color. As you can see in the video above, the finished project is brilliant. Oh, and the Lounge Music as a background is nice too.

The Serpent Mother

serp-mother

The Serpent Mother is certainly an appropriate name for this 168foot long snake fire art installation filled with enough goodies to impress anyone who is into flame effects. [The Flaming Lotus Girls] were allocated $60,000 in May of 2006 to bring this art project to Burning Man. A team of nearly 100 people worked together at a furious pace to pull it off. The collaboration of skill-sets is unfathomable between the metal art, firmware, software, LEDs, and propane design. The primary flames consist of  41 “poofers” along the spine of the serpent each one capable of delivering a 8′ tall flame. Tucked away near the tail is a egg that makes use of methanol and boric acid to create a massive green fireball. When the egg is open nobody is allowed with 150′ of the project. The brain that runs the beast is nothing more than a RS-485 network of humble ATmega8s. The microcontrollers are wired with XLR cable and chatting at a 19200 baud. Max/MSP is used on a laptop to control flame patterns. Here is a enjoyable write-up and video. We particularly enjoy the bit about the strange looks the team got when purchasing 50 stun guns.

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