Another product from our friends at Adafruit! NeoPixels are RGB LEDS which can be controlled by an I2C bus.
What does that mean? As you probably know, an LED is a solid-state light. They are more efficient than bulbs and last much longer. They are available in a variety of colours. By combining red, green, and blue LEDs in a single device we can produce any colour we like.
That leaves us with a final problem: How do we control them? We create different colours by changing how bright each LED is, and this is done using pulse-width modulation. The difficulty with pulse-width modulation is that without specialized chips it's a nuisance, and we need many pins if we want to control more than just one RGB LED. That's where I2C(pronounced I-squared-C) comes in. It's a serial bus, sort of like a telephone system. You hook up two wires from the microcontroller to the LEDs, and they all share the same two wires.
Then you can tell each LED what to do by effectively dialling it on the telephone. With NeoPixels you can hook up more than a hundred RGB LEDs, and control them using even a small microcontroller.
The print so far.
This is our biggest print yet, courtesy Chelsea. It's going to take four days, and 93 meters of filament! It consists of more than six million lines of g-code. A one kilogram spool has roughly 136 meters of filament.
Chelsea next to the lulzbot.
Six million lines!
We are in an amazing age for the electronics hobby. This board from Adafruit has four sensors. Triple-axis accelerometer, gyro, and magnetometer are combined a barometric pressure and temperature sensor. All sensors are on an I2C bus, so even a Trinket microcontroller can access everything on the board.
Adafruit sells this board for $50, but Hackforge happens to be a dealer for them. This means we can get you a discount! Shoot us an email and we’ll add you to our next upcoming group order.
Not everyone knows this, but the access control system at Hackforge is rather unique. Instead of a closed, commercial system we built our own.
Members Randy and Terry are responsible for the latest version of the system. Randy is an expert in python programming, and Terry is an expert in electronics. Together they built a system around a Raspberry Pi. Running Linux, the RFID card reader and a relay control board are connected to the GPIO pins on the Pi.
When it boots, it runs a python script that waits for card numbers sent via serial to the Pi. When it receives a number, it checks the number against an SQL database on the SD card. If it finds the number, one of the GPIO pins is pulled high. This signal tells the relay board in the upper left to turn on its relay. The relay then disconnects power from the maglock on the door, and the person who scanned their card is able to enter.
The Pi rests in a 3D printed case, made using member Amber’s LulzBot. Thanks for the work everyone, Hackforge wouldn’t be the awesome place it is without you!
We can rebuild him.
Hackforge is, appropriately, a place where things are hacked. This UPS battery is old enough that it wasn’t holding a charge. Most people would just replace it — but what’s the fun in that?
Our member Dez took up the challenge, prying open the lid on each cell and refilling the battery with distilled water. This is a picture of the battery on the bench being charged with Dez’s variac. So far, it seems to be working!