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The Development Of A Lightweight Wireless Protocol

BANO[Texane] had been thinking about how to monitor the state of his garage door from a remote place. The door itself isn’t around any power outlets, and is a few floors away from where his server would be located in his apartment. This presented a few design challenges – namely, the sensor itself should have a wireless connection to the server, and being low power would be a great idea. This led to the development of a minimalist framework for wireless communication that allows a sensor to run for weeks without a battery swap.

The wireless protocol itself is based on a simple key value pair; each individual sensor, coupled with a NRF905 radio, has passes an address, a key, and a value. There are allowances for checksums and acknowledgement, but as the PDF says, this is a very minimal protocol.

With the software out of the way, [Texane] turned to the hardware. The microcontroller is a simple Arduino clone, paired with a radio and a coin cell on a small board. The micro spends most of its time in a low power state, with the sensor, in this case a reed switch, tied to an interrupt pin.

There was a problem with the power consumption of the radio, though: when the short 17-byte message was transmitting, there was a significant voltage drop. This was okay with a fully charged battery, but with a partially drained coin cell, the possibility of brownouts was high. A big cap in parallel was enough to offset this voltage drop.

It’s still a little expensive for an all-in-one home automation and monitoring system, but developing a functional wireless protocol and the hardware to go with it is no small feat. It’s actually a great piece of kit that [Texane] is sure to find a few uses for.

Koch Lamp is 3D Printed with a Twist

Koch Lamp

[repkid] didn’t set out to build a lamp, but that’s what he ended up with, and what a lamp he built. If the above-pictured shapes look familiar, it’s because you can’t visit Thingiverse without tripping over one of several designs, all based on a fractal better known as the Koch snowflake. Typically, however, these models are intended as vases, but [repkid] saw an opportunity to bring a couple of them together as a housing for his lighting fixture.

Tinkering with an old IKEA dioder wasn’t enough of a challenge, so [repkid] fired up his 3D printer and churned out three smaller Koch vases to serve as “bulbs” for the lamp. Inside, he affixed each LED strip to a laser-cut acrylic housing with clear tape. The three bulbs attach around a wooden base, which also holds a larger, central Koch print at its center. The base also contains a PICAXE 14M2 controller to run the dioder while collecting input from an attached wireless receiver. The final component is a custom control box—comprised of both 3D-printed and laser-cut parts—to provide a 3-dial remote. A simple spin communicates the red, green, and blue values through another PICAXE controller to the transmitter. Swing by his site for a detailed build log and an assortment of progress pictures.

 

The $50 DMX Tester

DMX

Despite being around for about as long as MIDI, DMX, the industry standard for controlling stage lighting and smoke machines, is still an astonishing expensive protocol to work with. Where MIDI can be banged out with a simple microcontroller – with odd bit rate requirements, no less, DMX testers cost hundreds of dollars. Of course this means the market is wide open for a DIY DMX tester, and over on the projects site [Tony] has just the thing.

For the hardware, [Tony] is using few 4×4 matrix keypads for user input, and a character LCD for the display. With this, he can set any of the 512 lighting channels in a DMX setup to any one of the 256 intensity values. Setting a range of channels to any intensity is a snap, with an extremely cut down command protocol. All the processing is handled by an Arduino, which seems more than capable of handling the DMX protocol thanks to the Conceptionetics DMX library.

While it’s not a full-blown lighting console you’d find in the back of a theatre, it’s more than sufficient to test a lighting rig. It also seems pretty simple to use, just the thing if you’re trying to wrap your brain around some theatrical lighting.

Developing the Grillino in 24 Hours

grillino

[Mastro Gippo] hit Shenzhen back in April and organized a challenge for himself: could he develop an electronic device from idea to product in only 24 hours? The result is the Grillino, a simple clone of the Annoy-a-Tron: a small, concealable device that makes chirping sounds at random intervals. It’s name was derived from a mix of the Italian word for a cricket—”grillo”—and, of course, “Arduino.”

Shenzhen was the perfect setting for his experiment, especially because [Mastro Gippo] was in town for the Hacker Camp we mentioned a few months ago. The build is pretty simple, requiring only a microcontroller, a battery, and a piezo speaker. What follows is a detailed journey of dizzying speed through the production process, from bags stuffed full of components, to 3D-printing a test jig, to searching for a PCB manufacturer that could fulfill his order overnight. Video and more below.

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Homemade Alarm System Doesn’t Lack Features

alarm system

To many of us, our garage (or workshop) is probably one of the most important parts of the house. If a burglar broke in, we’d likely be more worried about our tools! [Ron Czapala] decided he needed an alarm system in his garage to keep his stuff safe, so he decided to build one from scratch.

The system makes use of a Parallax 4×4 keypad membrane, a MCP23008 port expander, a Parallax Propeller, a LCD screen, and a few switches to represent future magnetic reed switches located in the door and window.

Using circular buffers, the propeller has several states for monitoring the garage.

  • Not armed — ignore all sensors
  • Armed — system will react to changes in the sensors
  • Exit delay — system has been armed, 45 second countdown has begun to allow you to exit the garage
  • Window trigger — if the window is opened, the alarm will go off immediately (siren and strobe light)
  • Door trigger — alarm will go off in 60 seconds if correct code has not been entered on the keypad

For a complete demonstration, check out the following video where [Ron] explains it all!

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Firmware For Cheap Bluetooth Modules

Ibluetoothf you’ve ever built anything with a microcontroller, some sort of sensor, and a connection to the outside world, you’re probably wondering how those places in China can pump out cheap electronics for a mere percentage of what it costs you to pull a DIY. It’s not just volume – it’s engineering; if something has Bluetooth, you find a Bluetooth module with a built-in microcontroller so you can write firmware to it.

The BC417 is the System on Chip found in the very popular BlueCore4-Ext Bluetooth module featuring 8Mbits of Flash (75% of which is used for Bluetooth related stuff), somewhere around 12 kB of RAM, with everything run in a virtual machine. [pfalcon] wrote an extremely experimental firmware for this device that allows anyone to create a wireless sensor node for peanuts. These devices are almost as cheap as a bare ATMega, so the possibilities are interesting, to say the least.

At this point, the hardest part of putting custom firmware on these devices is programming them. For that, [Elastic Sheep] comes to the rescue with a parallel port to SPI interface. There’s also a firmware dumper and some breakout boards available. These modules are pretty cheap, and the pitch isn’t too bad, so you might be able to etch your own boards should you want to experiment a little.

Thanks [Peter] for sending this in.

Reading Paper Tapes From Scratch!

Home made tape reader

Feeling a little nostalgic? Dying to read some paper ticker tapes? You can do it manually, but that’d take forever! [NeXT] decided to make a little PCB to help him out.

Having searched for paper tape readers for years, and even getting halfway through building the mechanical portion of it in his high-school tech class, [NeXT] decided to take a serious stab at it — and by golly, it works!

The reason he finally decided to go down this route is because you just can’t buy them (well, for cheap), and even the DIY or hobby ones out there are notoriously slow — what better reason to design it from scratch?

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