/tanduino

Tanduino is an Arduino based project to replace the analog "tandem" inclinometer + compass with a digital one.

Primary LanguageArduinoBSD 3-Clause "New" or "Revised" LicenseBSD-3-Clause

Tanduino

Tanduino

Tanduino is an Arduino based project aimed to mimic the analog "tandem" inclinometer + compass.

User guide

  • Power the device with a DC 3.3V to 9V battery.
  • Turn on and off the device with the rocking switch.
  • Push the temporary button to start the capturing procedure, you will hear a short chirp, hold the device as stable as possible. A second short chirp will be emitted once satisfactory values are read and the laser will go off. If you hear a long chirp push the temporary button again and try to hold the device more steadily.
  • Maintain the temporary button pushed during more than 2s to enter in raw mode (for calibration purposes).
  • When the laser diode is on don't look at it directly in the eye.
  • The backlight level can be adjusted by rotating the 10KΩ trimmer resistor with a screwdriver.
  • The laser power can be adjusted by rotating the 10Ω trimmer resistor with a screwdriver.

The compass is tilt compensated by the accelerometer.

The device must be recalibrated each time the hardware design is modified. Particularly if you decide to use a different battery format (4xAA instead of 1x9V for instance).

Ratings

  • Heading precision: ±0.1º
  • Pitch precision: ±0.1º
  • Power consumption*:
    • hold state: 41mW
    • unhold state: 149mW

*Measured with the lowest backlight level and a regular laser power at 20ºC.

Developer guide

Software design

Calibration

After any hardware change (PCB, enclosure, battery etc.), the magnetometer needs to be calibrated. This tutorial is a good start:

Advanced hard and soft iron magnetometer calibration for dummies

...

Dependencies

Electronic design

Electronic design

Hardware list

  • Arduino Pro Mini ATmega328 8MHz 3.3V
  • Triple Axis Digital Compass HMC5883L
  • Triple Axis Accelerometer ADXL345
  • 84*48 LCD Display PCD8544
  • 5mW 650nm 3V red laser diode
  • Rocker on/off button
  • Temporary push button
  • 10kΩ resistor and 100nF ceramic capacitor for push button debouncing
  • 470kΩ and 1MΩ resistors to divide battery voltage sensing
  • 10kΩ trimmer resistor to adjust display's backlight
  • 10Ω trimmer resistor to adjust laser power
  • LT1521 3.3V 300mA voltage regulator and 1µF electrolitic capacitor
  • Piezo flat speaker
  • Autotransformer (boost piezo voltage)