Quadrocopter

Quadrocopter
[[{{{image}}}|border|frameless|220px|center]]
Primary Contact	{{{primary}}}
Created	10/08/2011
Completed	{{{completeddate}}}
Dormant	{{{dormantdate}}}
Version	{{{version}}}
Members	'RepRap' Matt
Manufacturer	{{{manufacturer}}}
Model	{{{model}}}
Location	[[{{{location}}}]]
GitHub / Repo	{{{repo}}}
Status	Research
Type	Undefined
Live Status	{{{livestatus}}}
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"A quadrotor, also called a quadrotor helicopter or quadrocopter, is an aircraft that is lifted and propelled by four rotors."

I've been flying model helicopter on/off for a few years and have now started to build a Quadcopter. As this is my first quadcopter I'm going to try and detail as much as I can here, some of this is likely just to be a bunch of random notes and not make a lot of sense to any one else, but as always I'm happy to explain if you can catch me at hackspace. --'RepRap' Matt 15:33, 15 August 2011 (BST)

Parts List

Quick breakdown of the parts i intend to use in my first build

Electronic system components

Break down of part that need connecting to the mbed

Important bits

• IMU (2pins) I2C
  • both wii IMU (WMP&NC) and ALLINONE IMU are I2C based
• Spektrum satellite (1 pin) USART
  • Saves so many pins :) can also use same pin to bind
• ESC outputs (4 pins) PWM
  • standard servo outputs
• nRF24L01+ (6 pins) SPI
  • using for telemetry and possible command link
  • could replace with "XRF wireless module" which is USART and needs just 2 pins and a lot less code £11.88 each

Later options

• Ultrasonic Rangefinder (1 pin) ADC
  • pointing down for altitude hold
• IR rangefinders (4pin) ADC
  • pointing out for obstacle avoidance
• GPS (1 pin) USART
  • UAV, nuff said
• Pan tilt camera mount (2 pins) PWM
  • FPV, have small 1.2ghz spy camera, might not be up to much quality but way cool!
• Battery voltage sens (1 pin) ADC
  • must protect LiPo's!!!
• Curent sens (1 Pin ADC
  • Only have 6 ADC pins so this might not happen
• MAX7456 OSD (6 pins) SPI
  • could share 3 SPI with nRF24 if can switch between both fast enough, both are used for telemetry mind but nRF24 might also be flight commands, OSD could be done on ground station.
• MiniM RGB LED's (2 pins) I2C
  • these can share the I2C bus with the IMU but they are 5v devices so may need LLC
• Data logger, SD or USB
  • SD needs SPI (3 pins & CS) could also share with nRF24 & OSD, USB needs 2 pins but they are dedicated so no cost

mbed pin assignment

Possible mbed pin layout and connection

Spektrum Satellite protocol

Breakdown of the serial protocol use by the Spektrum Satellite receivers.

I have a Spekturm DX7 transmitter which i use to fly my trex450 and my blade mSR. the Spektrum uses a 2.4ghz signal rather than the older 35mhz or 75mhz FM signals. On the tre450 i have an AR7000 receiver, one of features of this and other Spektrum receivers is the use of satellite receivers as seen in the picture to the left, theres satellite receivers are use to help maintain a solid signal between the TX/RX, usual located in a different location on the air frame in case the signal to the main antenna is disrupted. Now interestingly the data is sent between the two using a 3 wire cable using basic serial! For my quadrocopter this is great news as it means i can just plug the satellite straight into the MCU and read the serial data to get the TX data.

I found hobbyking do a range of Spektrum compatible receivers under the name OrangeRX, i have order a 6ch receiver and a satellite receiver for use in the quadcopter.

The satellite receivers run at 3.3v so if used with and arduino would requirer some protect against the normal 5v logic.

The serial link is standard 8n1 @ 115200baud (but i have seen mention of 125000 baud on some forums, need to investigate) it sends 16 bytes of data at 22ms intervals. The first 2 bytes are frame data, the following pairs of bytes contain the channel data.

It is also possible to bind the RX by pulsing the data line just after the RX powers up, need to send between 3 and 6 pulses each between 116us & 120us in length.

• Rcgroups threads [1] [2]
• posible first two byte break down [3]
• Some useful arduino code [4]
• bind example sketch [5]
• ardupilot, spektrum to ppm [6]

wii IMU

First IMU will be using sensors from the motion plus and the nunchuck

• http://snzgoo.blogspot.com/ usefull stuff in WM+ calibration

ALLINONE IMU

Second generation IMU using all I2C sensor board for eBay

This boras has the following:-

• HMC5883L Triple Axis Magnetometer
• BMA180   Triple Axis Accelerometer
• BMP085   Barometric Pressure Sensor
• ITG3200  Triple-Axis Digital-Output Gyro
• Build in ultra low noise linear LDO voltage regulator.
• Dimensions 30x16mm
• I2C all sensors connected to I2C bus.
• Designed for 3.3V logic level

There is also a version with a UBLOX Neo-6Q/M GPS receiver already attached

eBay store [7] RCgroups thread [8]

Links

Huge unsorted list of links to random bits of useful information