M
O
WAY
Title
: mOway Beginner Manual
Rev
: v2.1.3 – March 2011
Page
16
of
65
www.moway-robot.com
3.3.8.
Accelerometer
An accelerometer is a device that measures acceleration and the gravity induced
forces: the movement and rotation. There are many types of accelerometers, most of
them based on piezoelectric crystals, but their size is too big. Because of that, it was
tried to design a small device in the field of microelectronics, which might improve the
applicability. Then, the MEMS (Microelectromechanical Systems) accelerometers were
created.
An easy way to create an accelerometer is measuring changes in a capacitor.
Capacitors can work as sensors or as actuators. In the case of mOway, it is a capacitive
accelerometer, which consists of two capacitors displaced in differential mode whose
electrical capacity changes as the acceleration varies.
By measuring X, Y, Z axes of the MMA7455L accelerometer from
FREESCALE Semiconductor, it is possible to know if mOway is correctly positioned,
inverted or tilted.
3.3.9.
Battery level
The robot has a LiPo cell battery rechargeable. For proper operation of the
microcontroller, the battery is connected to one of its analog inputs through a splitter.
Thus, with a reading of the ADC battery level can be measured.
3.3.10.
Front LED
The front LED is a white LED placed on the front side of mOway. The output of
the OSRAM LW A6SG LED is connected to a digital output of the microcontroller.
3.3.11.
Top two-color LED
This double indicator and the light sensor share the same opening on the top part
of the robot. They are connected to two microcontroller digital outputs
5
.
5
Please note that since they share the same opening as the light sensor it is fundamental to switch
them off when wanting to perform a light intensity reading.
