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November 9, 2012 AT 6:00 am

Ratsberry Pi! #piday #raspberrypi @Raspberry_Pi

Here’s yet another really awesome Halloween project we are just discovering now! Really neat project that I’d really like to see in 3D-printed characters! Works lovely to control a bunch of servos with a Pi — check out our tutorial as well! From HariEdo:

I found some squeaky rubber rats at the local dollar store last year. Of course I had to buy ten of them, and then work on some sort of project later. Once I got my Raspberry Pi, I knew I had to combine these into a Hallowe’en decoration project.

Recipe:

  • 2S hobby lipo (2S4P in this configuration) for 7.4V
  • 2x Sparkfun 5V/3.3V breadboard power regulator, modified to remove PTC fuses
  • Raspberry Pi Model B Rev 1
  • Adafruit Pi Cobbler GPIO breakout
  • Adafruit 16 Channel i2c PWM Servo Controller
  • 10x Tower Pro SG92R micro servos (via Adafruit)
  • 20x 5mm Red LEDs
  • 10x 330 Ohm resistors
  • 10x 1 meter Futaba-style servo extensions (via eBay)
  • 10x 6 cm Futaba-style servo extensions (hand assembled)
  • 10x dollar store rat toys
  • 2x solderless breadboards and a few wires
  • USB micro B plug (chopped a USB plug) to power Raspberry Pi
  • Hot Glue to form insulators and standoffs

Check out our Adafruit 16 Channel Servo Driver with Raspberry Pi tutorial for our Servo Driver blow:

ServoDriverHookedUp

Adafruit 16-Channel 12-bit PWM/Servo Driver – I2C interface – PCA9685

You want to make a cool robot, maybe a hexapod walker, or maybe just a piece of art with a lot of moving parts. Or maybe you want to drive a lot of LEDs with precise PWM output. Then you realize that your microcontroller has a limited number of PWM outputs! What now? You could give up OR you could just get this handy PWM and Servo driver breakout.

When we saw this chip, we quickly realized what an excellent add-on this would be. Using only two pins, control 16 free-running PWM outputs! You can even chain up 62 breakouts to control up to 992 PWM outputs (which we would really like to see since it would be glorious)

  • It’s an i2c-controlled PWM driver with a built in clock. That means that, unlike the TLC5940 family, you do not need to continuously send it signal tying up your microcontroller, its completely free running!
  • It is 5V compliant, which means you can control it from a 3.3V microcontroller and still safely drive up to 6V outputs (this is good for when you want to control white or blue LEDs with 3.4+ forward voltages)
  • 6 address select pins so you can wire up to 62 of these on a single i2c bus, a total of 992 outputs – that’s a lot of servos or LEDs
  • Adjustable frequency PWM up to about 1.6 KHz
  • 12-bit resolution for each output – for servos, that means about 4us resolution at 60Hz update rate
  • Configurable push-pull or open-drain output
  • Output enable pin to quickly disable all the outputs

We wrapped up this lovely chip into a breakout board with a couple nice extras

  • Terminal block for power input (or you can use the 0.1″ breakouts on the side)
  • Reverse polarity protection on the terminal block input
  • Green power-good LED
  • 3 pin connectors in groups of 4 so you can plug in 16 servos at once (Servo plugs are slightly wider than 0.1″ so you can only stack 4 next to each other on 0.1″ header
  • “Chain-able” design
  • A spot to place a big capacitor on the V+ line (in case you need it)
  • 220 ohm series resistors on all the output lines to protect them, and to make driving LEDs trivial
  • Solder jumpers for the 6 address select pins

This product comes with a fully tested and assembled breakout as well as 4 pieces of 3×4 male straight header (for servo/LED plugs), a 2-pin terminal block (for power) and a piece of 6-pin 0.1″ header (to plug into a breadboard). A little light soldering will be required to assemble and customize the board by attaching the desired headers but it is a 15 minute task that even a beginner can do. If you want to use right-angle 3×4 headers, we also carry a 4 pack in the shop.


998Each Friday is PiDay here at Adafruit, be sure to check out our posts, tutorials and new Raspberry Pi related products. Have you tried the new “Adafruit Raspberry Pi Educational Linux Distro” ? It’s our tweaked distribution for teaching electronics using the Raspberry Pi. But wait, there’s more! Try our new Raspberry Pi WebIDE! The easiest way to learn programming on a Raspberry Pi.

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