code and fabrication resources for physical computing and networking
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Nicolas Villar sent me a sample of the PepperMill, a new sensor board he and Steve Hodges designed at Microsoft Research in Cambridge, UK. It’s a nifty little board. You attach a DC motor and the board can an output voltage when the motor is turned, and analog signals telling you the direction and speed of the motor. It turns a DC motor into a rotary encoder, of sorts.
Coming late to the game, I’m trying out a Bluetooth Mate from SparkFun with an Arduino Lilypad.
Overall, it’s a nice Bluetooth radio to use with microcontrollers. A few thoughts on getting it working:
Matt Mets has written a nice Nikon remote control library for Arduino. I used it to make a motion trigger and intervalometer. It looks like this:
I’m making some changes to this blog. I’ve been unhappy about the fact that all the code is static, not the code I use every day. Instead, I want a nice code repository, so whatever I write on my machine can be published directly, and if I update it, the updates end up here. I would also like syntactical highlighting of the code. And now, ta dah! It’s all done. Here’s what I did, for your reference and my own, because I’ll forget next time I need to update it.
So from now on, new code on this blog will look like this:
void setup() {
Serial.begin(9600);
}
void loop() {
Serial.println("Hello from Tom!");
}
And it’ll all be updated whenever I make changes. Exciting, isn’t it?
Peter Knight works with Massimo and Alex and co. at Tinker.it. He’s written some great AVR code, which is useful in Arduino. For example:
Secret Thermometer takes advantage of the ATMega’s internal thermometer. Turns your ‘328-based Arduino into a thermometer with no extra parts.
Secret Voltmeter same idea, but this reads the internal analog-to-digital converter to tell you the Arduino’s supply voltage. Also works on the ATMega168.
He’s also done Cantarino, a speech synthesis engine; Auduino, a granular sound synthesis engine; a DMX library; and more. Check them all out at the tinker.it code repository.
Shigeru Kobayashi, who made Gainer and Funnel, has made yet another nifty tool for physical computing: physical x wonderfl. It combines Gainer, Funnel, Firmata, Arduino, and Wonderfl.
Making LED displays is fun. There are a a few tools that get used all the time, from row-column scanning to LED driver chips to multplexers and shift registers. This tutorial discusses some of the more popular methods for controlling large amounts of LEDs from a microcontroller, including their various strengths and weaknesses, and how they work. For more on this subject see chapter 14 of “Physical Computing“, where Dan O’Sullivan and I discussed it in more depth. I’ll also include some notes on how to apply these ideas to controlling multiple motors or other high-current loads.
Most microcontroller modules have a limited number of outputs. Even if you use the analog inputs as digital I/O, there are only 19 pins on an Arduino, for example. That’s a fairly typical number for an 8-bit controller, and it seems not nearly enough if you want to control, say, 100 LEDs or more. There are a couple ways around this problem. Without adding any additional hardware, you can make a matrix of your LEDs and control them using row-column scanning. If you want discrete analog control over one output at a time, you can use a multiplexer. For digital control over multiple pins, you could use an addressable latch or a shift register. If you need pseudo-analog control over multiple pins, you could use a PWM driver. There are also several LED driver chips that are designed specifically to control groups of LEDS.
This tutorial will show how to control multiple LED outputs from a microcontroller using a CD4099B addressable latch.
This tutorial will show how to control multiple LED outputs from a microcontroller using a CD4067 analog multiplexer.
This is a stub. More explanation will follow, but for now, here are schematics and code for Arduino.
Parts you’ll need:
This tutorial will show how to control multiple LED outputs from a microcontroller using an STP16C596 shift register. The STP16C596 is similar to the popular 74HC595 shift register, but it’s nicer because it can sink a constant current to the LEDs it’s driving.
This is a stub. More explanation will follow, but for now, here are schematics and code for Arduino.
Parts you’ll need:
