Velleman EDU02 - Manual (Page 25)

25 www.vellemanprojects.com
How it works: The solar cell provides the
supply voltage for the microcontroller. Once the
controller receives 2VDC it starts running its
internal program. The zener diode and the 470
ohm resistor make sure the supply voltage of
the controller never goes beyond 2.4V, even in
bright sunlight. A too high voltage can damage
the device. The voltage generated by the solar
cell is also divided by two by means of two
equal resistors (4K7) and fed to the analog
input of the controller.
Even in bright sunlight, the input receives no
more than 4.5/2 = 2.25VDC.
The internal software ‘measures’ the voltage at
the input and compares it to the previous level.
When it detects a sudden change (i.e. When
the beam is interrupted or someone casts a
shadow on the solar cell ), it generates a sound
trough the piezo.
SOLAR CELL
ZD1
2V4 +
BUZ1
PIEZO
R1
4K7
R2
4K7
R3
470
VD
D
2
VS
S
7
GP3/MCLR/VPP
8
GP2/T0CLKI/FOSC4
3
GP1/ICSPCLK
4
GP0/ICSPDAT 5
IC1
PIC10F220
Required parts: Solar cell, microcontroller (µC), 2x 4K7 resistor (yellow, purple, red, gold),
470 ohm resistor, (yellow, purple, brown, gold), 2V4 zener diode, piezo sounder, wire.
P P
4
4
4