Light-controlled Comfort Umbrella

Billy Byun, Marcus Cain, Lee Ferber, Rasesh Joshi

Table of content

• Executive Summary and Background

• Project Timeline: Goals and Tasks

• Design: State Diagram, Mechanical, and Electrical

• Light-to-Voltage: Phototransistor Circuit and Op-amps

• The Controller: PICAXE

• Voltage-to-Rotation: Motor Circuit and H-bridge

• Technological Challenges and Learning

• Conclusion, Cost, References, and NGs

Executive Summary and Background

Project Timeline

Design: Mechanical

Product: Mechanical

Open the flap layer until 50<L<70

Design: State Diagram

• Too cold• Little sun-

light

If L < 50

• The 'Com-fort' Zone

100< L <150• Too hot

• Too much sunlight

If L > 200

Close the flap layer until 50<L<70

- Four critical values in the feedback system.. Wide?- Sensitivity vs. Oscillation (Noise)

- Hysteresis & Deadband..System with Memory

- L: Intensity of the Light under the Umbrella.. Relative !

sensitivity

Design: State Diagram

Phototransistor(Light-to-Cur-

rent)

2 Op-amps(Current-to-

Voltage & Gain)

PICAXEH-bridge (Two –way rotation)

Gear Motor

Design: Electrical

Light-to-Voltage: Phototransistor Circuit and Op-amps

Light-to-Voltage: Phototransistor Circuit and Op-amps

• Phototransistor Circuit Demonstration

The Controller: PICAXE8M2

The Controller: PICAXE18M2

Note: if the H-bridge connects +VDC toR1 and GND to R2 at the same time or+VDC to R3 and GND to R4 at the same time,It shortens the battery. Hence..

Voltage-to-Rotation: Motor Circuit and H-bridge

Voltage-to-Rotation: H-bridge

Resistor 1 Resistor 2 Resistor 3 Resistor 4

Forward VDC VDC GND GND

Reverse GND GND VDC VDC

Halt GND GND GND GND

Voltage-to-Rotation: H-bridge

Motor Circuit Demonstration

Voltage-to-Rotation: Power-Ground Board

• Current Divider with two 15 Ohms resistors

Components

Final Demonstration

• http://www.youtube.com/watch?v=kHai--hbqNA&feature=g-upl

Technical Challenges and Learning

• Oscillations (H-Bridge)Single power supply -> Capacitor and Serial in-Ground• Oscillations (Phototransistor Circuit) -> Wider range• Oscillations (Noise) -> Larger Umbrella and Curtain• Speed of the rotation: Current Divider• Photodiode with reverse bias configuration -> Pho-

totransistor• Soldering -> Debug!

Reference

• http://www.johnloomis.org/ece445/topics/egginc/pt_char.html

• http://www.robotroom.com/BipolarHBridge.html• http://en.wikipedia.org/wiki/Hysteresis• http://en.wikipedia.org/wiki/Phototransistor#Other_modes_o

f_operation

Take 0 – Youtube NGs

• NG1 : http://youtu.be/2Ko6o740K6k• NG2: http://youtu.be/_-qF7b6f4oU