DIY CNC mill first 3-axis run drawing G-code from Inkscape

Quadcopter kit project

Santa pushed the boat out this year and, completely unprompted, gave me a quadcopter kit for Christmas :)

The kit included an airframe, battery, motors, propellors and motor control electronics. The airframe is a CSL X600

In the box were a load of bagged bolts, screws, aluminium section and cut glass-fibre board (?) and absolutely NO instructions.

I found a 'guide' here, a time lapse video here both of which helped to work out how this thing goes together as the design seems to have had some tweaks since the seller website was put up, so looking at the pictures there can be confusing.


The quadcopter is basically assembled in four parts:
1. The central chassis
2. The arms and motor mounts
3. The landing gear
4. Mounting the electronics and motors on the chassis and arms

I started with the central chassis and added the arms, working my way through the bits so I knew what fitted where. The process involved a bit of trial and a lot of error, but below is a pictorial build log...

This plate is the TOP of the quadcopter - here it is upside-down for fitting

Arms mounted

Arms - note that they have a top and bottom side. The tiny hole on the far right shows the bottom of the outer end of the arm - that hole is used by the tension spring in each landing leg

Folded arms

The bottom two plates - make sure that the arms can still fold once this plate is installed!

Motor mount and brushless motor

Motor fixing - use the round-head bolts supplied in the kit and ignore the counter-sunk screws that come with the motor

Landing gear - note this config looks different to the selling website pics

Landing gear spring

Landing gear in action

Out of all the bits supplied with the motor and prop, heres what I think you need...

Assembled prop

Finished build with electronics fitted

 Now to wait for a shiny new Spektrum radio set to arrive in the post...

Design for a robot vacuum

My dog makes lots of hair. Seriously, you can hoover the kitchen and five minutes later there's fluff all over. I want a robotic vacuum to keep it under control, but I'm not willing to spend £300+ on a roomba

So I'm going to build one.

Maybe.

First issue I can see is navigation - there are a lot of posts and designs that use ultrasonic sensors, IR, GPS :) and all kinds of expensive, fiddly kit that needs a hefty processor to calculate position ...

Well, my kitchen has a tiled floor. Surely I can use that grid for really simple navigation with no floating point maths or stats, all running on an 8-bit microcontroller of choice?

My intitial thoughts are:

Two bog-standard DC motors driving differential steering and forward/backward motion. This should allow the robot to swivel on the spot.

Three light sensors mounted on the underside of the robot will pick up the lines of the grout and determine if the robot is staying straight on the grid line, and detect when it crosses another line.

A bumper sensor (basically a switch) to detect when the robot hits an obstacle

Oh, and a modified hand-held hoover...

Possibly a charging dock also...

Mantis-a-like CNC milling machine - update

I've been working on the Mantis CNC build recently to get the X-Y table up and running. Previously, I'd posted the design. I was working on a motor driver board based on an ATMEGA328P running the Arduino bootloader and three L293 motor driver chips. After a few months on-again-off-again (I/O pun) work on the board I gave up trying to get it working :( Instead I bought 3x Easy Driver boards.

These are really easy to use - just two pins are used to step the motor and tell it which direction to turn. They support bi-polar (4,6 and 8 wire steppers) motors and have a trim pot for varying the current supply.


So I wired an Easy Driver running on a PC PSU 12V supply into an Airpax stepper motor that I found a pair of on Ebay. It made a few noises and tick-tocked, but spectacularly failed to spin. I suspect these motors need more voltage/current to run. Oh well. In my box-o-junk I had a stepper from a 99p Ebay printer. Wiring that up and tweaking the step speed gave good results so I fitted this motor to the X-axis drive shaft on my mill. Now we're in business:

Triple axis accelerometer and gyro - MPU-6050

I splurged some hard-earned Amazon vouchers on toys this month, including a motion sensing break-out board from Sparkfun (via Proto-PIC in the UK).

The MPU-6050 chip is made by Invensense and its blurb says:

The MPU-6050 incorporates InvenSense’s MotionFusion™ and run-time calibration firmware that enables manufacturers to eliminate the costly and complex selection, qualification, and system level integration of discrete devices in motion-enabled products, and guarantees that sensor fusion algorithms and calibration procedures deliver optimal performance for consumers.

Basically this means the chip has some fairly sophisticated processing on-board that handles things like sensor fusion. It does some useful stuff like calculating the overall direction of motion regardless of the chip's own rotation - this saves a lot of heavy floating-point calculations, which is good for integrating with Arduino and microcontroller systems. The accelerometer data can be read using an I2C bus (the linky is a library that builds on the Arduino Wire lib)

The breakout board is fairly simple to use - connect VDD to +3V3, GND to ground (duh) and the I2C pins (SDA and SCL) to the microcontroller I2C pins (A4 and A5 for most Arduinos/ATMEGA chips). The one 'gotcha' I found was that VIO needs to be connected to a reference voltage for the I2C logic to work... connecting this up to +3V3 seemed to work OK for me.

A note of caution - the chip is a 3V3 (3.3V) device so use a level shifter (or voltage divider) if using a 5V microcontroller... I'm using an Arduino mini pro 3V3 and a 3V3 FTDI USB to serial board for uploading sketches. Here's my test rig:

The rig is running off a LiPo battery on the right. The red board is the MPU-6050 accelerometer, the blue board is an Arduino Mini Pro and on the left is a graphical LCD from Adafruit (with a funky RGB backlight). The display is showing acceleration (in x, y and z) on the top row and rotation angle underneath. The circles show the amount of acceleration in each axis (bigger = more).

Software for the Arduino was acquired from here for the MPU-6050 and here for the graphical LCD . A few bodges and Pritstick code let me grab data from the MPU-6050 and push it onto the display. Note that the graphics code slows the whole system down to around 5-10 Hz. The serial only demos are much faster!

What next? Well, aside from building a balancing robot, I'm going to try to make an inertial navigation system... we'll see if its worth reporting on!

Remote weather station using Raspberry Pi and Arduino

To make the weather station actually useful, the sensors need to go outside. Running a cable to the Raspberry Pi wasn't a good option, so I dug out a pair of XRF serial radio modules to handle sending the weather data over wireless.

An ATMEGA328 chip is used to run Arduino code that pulls raw data from the sensors and pushes the processed weather data over the serial radio link.

Outdoors module for the weather station

The ATMEGA chip sits on a custom board (actually its an Arduino shield prototyping board) that includes a power regulator for the 3V3 rail (for the XRF and sensors) and breaks out headers for the XRF module and sensors. At the moment its connected up with jumper cables, but the intent is to remote the sensors in a box that can have free air movement, whilst the processor, radio and battery sit in a snug, dry box.

The weather data comes from a BMP085 temperature and pressure sensor, a humidity sensor and a light-dependent resistor. More sensors (rain gauge, wind speed and direction) can be added with some code mods.

At the moment the system is mains powered; there is a battery holder for 1xAA rechargeable. The intent was to use a solar source to top up the battery and to use a buck booster to raise the 1.2V battery output to 5V for the ATMEGA chip. Battery life without solar top-up is around 5 hours... not good for the UK in winter! I'm using a low-power mode that only fires up the ATMEGA chip every 8 seconds (using the watchdog timer function) - the system waits 5 minutes between transmitting data. This is an attempt to eek out the power, but I think the honking 3V3 regulator and always-on-XRF are sapping the battery juice. I intend to play with a LiPo battery to see if we can get better performance... the original design intent allowed an output pin from the ATMEGA to drive the XRF such that it could be powered up only when needed to send data over the wireless.

Code to follow...

Live embedded Cosm graphs

As a minor bonus to the Cosm service, I found you can create an embeddable graph for your data to stick in any website...

Behold the current air pressure in Liss, live!

:)