Electronics and MicroControllers

Power Diagram

PowerDiaPic

The hexapod uses two LiPo batteries; one 8 cell battery to power the servos and one 3 cell battery for logic. Since there are 18 servos, we suspect the battery will have to be changed reasonably often. To bump these down to voltages that our shields can handle, we have DC-DC converters. The Arduino Mega operates in a higher voltage range, so it's supplied with 7.5V; the servo motors, on the other hand, run off 4.8-6V, so that circuit runs on a 5V output. The motor line has a relay controlled by the Arduino Mega so the servo motors won't get power until the "brain" is on. It also includes an E-Stop that will shut off only the motors, in case something goes wrong.

Adafruit Servo Shield

Purchase page: https://www.adafruit.com/product/1411
Adafruit guide: https://learn.adafruit.com/adafruit-16-channel-pwm-slash-servo-shield/overview

Setup

Soldering

Board Picture
We probably want to solder header pins onto the 16 servo connection pins with PWM, V+, and GND pins for each servo.

We also are going to want to solder a power connector onto the board's V+ and GND pins on the left of the board(see picture).

Wiring

In order to use the board with an arduino, you need to connect it to the following pins:

3v and 5v arduino power pins for pwm and i2c chips
SDL/SDA I2C pins on the arduino
to control servos, you need seperate power from a power supply to the shield's V+ and GND

We also talked about utilizing both this shield and an IO expansion board. In order to do this, one possible option is to stack the IO expansion board and the arduino and then use wires to connect up the servo shield separately in order to get access to everything.