Transcript Solar Powered LED Blinds

Solar Powered LED
Blinds
Group 28: Austin Estes and Kerr Oliva
TA: Katherine O’Kane
Introduction
• The solar powered LED blinds provides a less costly
method of allowing a consumer to harvest the sun’s
energy.
• The solar panels on the blinds are directed towards the
sun by a microcontroller and electric motor. A battery,
which is charged by the solar panels, provides power to
the microcontroller, electric motor, and RGB LEDs.
Objectives
1. Allow user to determine color of ten RGB LEDs to add an
accent light to a room during the night
2. Automate blind rotation through use of a motor for the best
solar power production
3. Power the system through a Li-Ion battery charged by solar
panels
System Overview
• Hardware
•
Solar panel array
•
Charge controller circuit
•
Rechargeable battery
•
Microcontroller
•
Motor driver
•
LED circuit
• Software
•
Microcontroller programmed to turn the blinds and turn the LEDs on and off at the correct
frequency
Solar Panels
Charge Controller
Block Diagram: Power
Transistor Current
Mirror (BJT)
RGB LEDs
Li-ion Battery
Voltage
Regulation
Microcontroller
Voltage
Regulation
Motor Driver
Electric Motor
Photoresistor
Microcontroller
Motor Driver
Block Diagram: Signals
Transistor Current
Mirror (BJT)
User Inputs
Review of Original Design
• Solar Panel Array
•
•
Original
•
27 panels in series of 3 with 9 parallel lines
•
Rated for 18 V and 0.63 A (11.34 W)
•
Cost: $ 133.65 (4.95/unit)
New
•
12 panels in series of 3 with 4 parallel lines
•
Rated for 18 V and 0.664A (11.952 W)
•
Cost: $ 39.48 (3.29/unit)
Review of Original Design
• RGB LED Circuit
•
•
Original
•
30 RGB LEDS
•
1k Ω potentiometer
New
•
10 RGB LEDS
•
500 Ω potentiometer
Power Circuitry
• Solar Panel Array
•
Each solar panel produces 6 V and 0.166 A
•
The array produces 18 V and 0.664 A
• Charge Controller
•
The charge controller decreases the voltage from the solar panel
array, increasing the current that is sent into the battery.
•
Outputs 12.3 V and 1.32 A
• Rechargeable Battery
•
Charging voltage of 12.6 V
•
Rated output of 11.1 V and 5.7 A
•
In ideal conditions, the battery would charge in 6.6 Ah/1.32 A = 5 hours
Solar Panel Array
Three Solar
Panels in Series
Full Sun
Light Overcast
Percent Change
Series 1
18.50 V
15.21 V
17.78%
Series 2
19.28 V
16.57 V
14.06%
Series 3
19.15 V
16.24 V
15.20%
Series 4
18.75 V
15.43V
17.71%
Average Value
18.92 V
15.86 V
16.17%
Charge Controller
Circuit
•
LT 3652 IC
•
Programmed to have a battery
float voltage of 12.3 V and
charging current of 1.32 A
Voltage output of charge controller
Current output of charge controller
Motor Driver
• H-Bridge
•
Takes in select bits that decide the direction to apply current through a DC motor.
•
Allows for the microcontroller to easily control when the motor is active and which direction the
motor will turn.
• Current Limiter
•
The current limiter limits the amount of current that the motor draws.
•
This was done as a precaution in case the motor stalls, that way the motor won’t draw more
current than it can handle and possibly start a fire.
H-Bridge Chip
•
SN754410
•
VCC1: Chip power
•
VCC2: Power that is output to the
motor
•
1_2EN: Enable
•
#A: Select bit for the output #Y
•
#Y: Attached to either terminal of the
motor, outputs VCC2
Current Limiter Circuit
Microcontroller and H-Bridge Testing
•
•
The microcontroller’s interaction with the H-Bridge was tested first
using a simple loop of outputs to make the motor turn back and forth.
Next, we tested that the microcontroller would turn the motor different
amounts depending on the voltage value it read from the
photoresistor.
•
While testing the photoresistor with the microcontroller and motor, we were never
able to get the microcontroller to turn the motor different amounts depending on
what the voltage across the photoresistor was.
RGB LED Circuit
•
Powered through initial switch-transistor
•
Enabled by an op-amp
•
Driven by a current mirror
•
Each color given their own current mirror
to limit current
•
Current mirror biased to draw 0.2 A of
current
•
Addition of potentiometer allows for
variation of color
Current mirror for
red LED
Current mirror for
green LED
Current mirror for
blue LED
Switch-transistor
RGB LED Circuit
Op-amp
Transistor Measurements
Switch Transistor
Current Mirror Transistors
LED
Theoretical
Measured
Red
0.2 A
0.172 A
1.89 %
Green
0.2 A
0.172 A
9.44 V
0.63 %
Blue
0.2 A
0.173 A
7.95 V
9.66 %
Transistor
Terminal
Theoretical
Voltage
Measured
Voltage
Percent
Error
Base
9.5 V
9.32 V
Collector
9.5 V
Emitter
8.8 V
Microcontroller
Programming
•
Switches control what the
microcontroller activates
•
Motor
•
•
The microcontroller takes
voltage readings from a
photoresistor in order to
find where the maximum
light intensity is.
RGB LEDs
•
The microcontroller
applies a square wave
through an op-amp to a
transistor in order to flash
the LEDs at 60 Hz.
Automate Motor
Signal
LED Signal
Flash LEDs
Turn Blinds Using Motor One
Direction
-Check if light is increasing or
decreasing
-Increasing: Continue turning
-Decreasing: Stop turning and
check other direction
Turn Blinds In Other Direction
-Check if light is increasing or
decreasing
-Increasing: Continue turning
-Decreasing: Stop turning,
local max has been found
Wait for 15 minutes while
checking if the Automate
Motor Signal has changed
state
Microcontroller Programming Flowchart
High/True
Low/False
Microcontroller
Output
•
We expected 5 V ± 0.25 V (5 %
deviation)
•
Multimeter measurement shows
output of 4.8 V at I/O pin for
LED and motor enable signals
•
4 % error
Successes and Challenges
• Fully functional RGB LED circuit working in conjunction with microcontroller
•
Circuitry components not operating as expected (ex: switches & transistors)
• Motor driver circuit receiving input from microcontroller
•
Photoresistor sampling not correctly signaling arduino
• Time management
•
Debugging of subsystems took longer than anticipated
• Debugging of microcontroller
•
Initial ATmega328P burned
• Soldering
Conclusion
• Our solar powered LED blinds had three main modules, the power circuit, the
motor driver, and the LED circuit.
• We recommend using a lower voltage than 11.1 V to power the RGB LED
circuit.
• The microcontroller’s motor programming is not completely functional and still
needs debugging.
• The charging circuit needs to be tested fully in order to determine if it is safe
to charge a Li-Ion battery.
Thank You