Cheap sensor evaluation for Arduino/Pi

The Plan

Last year I designed and built a custom IMU Arduino shield containing an accelerometer, gyroscope, digital compass and pressure sensor for my Aeroquad. The shield worked well, but I was quite surprised at the price of the various sensors.  What was even more intriguing was the difference in price between well known brands and imported ebay alternatives, did they work as well ? Or are they cheap copies not worth the price ?

With a number of projects in mind that require some of these sensors I decided to test a selection from difference sources to see if the price made much difference...

The Sensors

All of the sensors  are I2C so fairly easy to use and I have experience of writing/fixing Arduino libraries for these types of sensor.

So far the collection includes;

10 Degree Of Freedom boards

•  Unbranded (GY-80?) - £6.70 ebay China
• L3G4200D - Digital gyro
• ADXL345 - Digital accelerometer
• HMV5883L - Digital compass
• BMP085 - Barometric pressure

6 Degrees Of Freedom boards

• Sparkfun 6DOF -£45 from Hobbytronics.co.uk
• ITG3200 - Digital gyro
• ADX345 - Digital accelerometer
• GY521 - £3.20 from ebay China
• MPU6050 - Digital gyro and accelerometer
• Unbranded - £2.50 from ebay China
• MPU6050 - Digital gyro and accelerometer

Individual breakout boards

• Sparkfun HMC5883L breakout
• HMC5883L - Digital Compass
• GY271 - £1.90 from ebay China
• HMC5883L - Digital Compass
• Sparkfun BMP085 breakout - £13 from Proto-pic.co.uk
• BMP085 - Barometric pressure
• CJ-M32 - £2.65 from ebay China
• BMP085 - Pressure sensor
• MMA7660 - £2.50 from ebay China
• MMA7660 - Digital Accelerometer

First impressions

Overall the boards are well made; although the Sparkfun boards are obviously of a higher quality than the ebay versions.  The main difference is the support and documentation offered by the main stream vendors (e.g. Sparkfun, AdaFruit).  They have good websites with lots of examples and documentation, with the ebay purchased boards you are usually on your own.

10DOF breakout board

I have started using the unbranded 10DOF board and its gyro (L3G4200D).  There was no documentation with the board, but I did find an on old Arduino library that needed updating to 1.5 before it would work.  I also found an excellent library on the AdaFruit site for a similar board which filled in the missing pieces.  I will place the source on GitHub when its finished.

More to follow.....