Velleman EDU02 - Manual (Page 27)

27 www.vellemanprojects.com
How it works: When the sun shines, the
voltage generated by the solar cell will be
higher than the voltage of the batteries, so a
current will flow from the solar cell to the
batteries. This current will charge the
batteries. The BAT85 diode prevents
discharging of the batteries trough the solar
cell in low light conditions. The base of the
transistor is tied to ground (-) by means of the
4K7 resistor. This causes the transistor to
turn on and supply power to the µcontroller.
The controller will behave identical to project
2, so the led will flash. However, note that the
base of the transistor is also tied to the (+) of
the solar cell, so as long as the sun shines,
the base of the transistor is kept high enough
to prevent turn-on of the transistor, so the led
remains off at daytime.
Required parts: Solar cell, microcontroller (µC), 4K7 resistor (yellow, purple, red, gold), 100
ohm resistor, (brown, black, brown, gold), BAT85 diode, BC557 transistor, battery holder for
two AAA batteries, two AAA 1.2V rechargeable batteries, wire jumpers, red led.
SO
LA
R
C
E
LL
VD
D
2
VS
S
7
GP3/MCLR/VPP
8
GP2/T0CLKI/FOSC4 3
GP1/ICSPCLK 4
GP0/ICSPDAT 5
IC1 PIC10F200-I/PG
D1
BAT85
R1
4K7
BC557
R2
100
Red led