I developed this project in order to learn more about PIC microcontrollers,
especially with PIC16F84. This torch has 10 Leds conected to 5 port
A pins, each pin has 2 leds of the same colour conected to it :
2 red, 2 green, 2 blue, 2 white and 2 UV. So they are grouped in
pairs of the same colour, and each of these pairs is contolled with
a transistor working in switching mode. Transistors are used to
avoid overloading the microcontroller's ports, because each port
can sink a maximum of 20 ma and it's not enough to feed each pair
of leds, which needs 40 ma. Each color intensity is regulated controlling
the duty cycle of a 40hz square signal that activates Q2N222A transistor
base. This means that that modulating the width of each pulse will
chage birghtness of the leds. In fact it works as a software pulse
width modulator (PWM). The intensity of the light and its consumption
is proportional to the number of LEDs that are ON and each one's
duty cicle:
All LEDs ON |
100% Duty
Cicle |
0,160 A |
All LEDs ON |
50% Duty Cicle |
0,080 A |
All LEDs ON |
1% Duty Cicle |
0,001 A |
Red LEDs ON |
100% Duty
Cicle |
0,048 A |
Green LEDs
ON |
100% Duty
Cicle |
0,028 A |
Blue LEDs
ON |
100% Duty
Cicle |
0,025 A |
White LEDs
ON |
100% Duty
Cicle |
0,040 A |
UV LEDs ON |
100% Duty
Cicle |
0,024
A
|
As you can see one of the most important adavantatges of this torch
is the low current consumption compared to conventional torches:
all energy is converted to light. Another advantadge is that It
can make any colour you want, you only have to configure the right
RGB W-UV combination. It has other functions like a blinkning configurable
frequency, and an option to save your favorite RGB W-UV color into
EPROM and therefore restore it at a later date. All this funcitons
are controlled only with 2 buttons.
As
chasis I used a torch wich I bought for 2 Euros in the supermarket.
These are some pictures of Cleverlamp:
|