ETRO_296_Final_Presentation
- 1. I. NIGHTLIGHT ANALOG AND DIGITAL CIRCUIT Fig.1 Nightlight analog circuit Fig.2 Nightlight digital circuit By Wagner Nunes
- 2. A. Light Depended Resistor (LDR) Fig. 3 Example of LDR component Fig. 4 Example of the LDR function in the exponential decay graphic Fig. 7 Example of an LDR when resistance increases Fig. 6 Example of an LDR when resistance decreases Fig.5 Example of the electrons in the valence band jumping to the conduction band • The LDR is made of a semiconductor material that is layered on an insulating material such as ceramic.
- 3. B. The Comparator • 1) The Logic: – If (V-) > (V+) => Vout ≈ GND or “0” low (-saturation) – If (V+) < (V-) => Vout ≈ +Vcc or “1” high (+saturation) Fig. 8 Example of a comparator output “0” Fig. 9 Example of a comparator output “1”
- 4. C. Function of the NPN Bipolar Junction Transistor (BJT) as a Switch • NPN (N stands for negative charge and P stands for positive charge or hole) • BJT(bipolar junction transistor ) is because it involves both of these types of charger. Fig. 11 Example of a transistor tuning the LED onFig. 10 the three regions of a NPN transistor
- 5. 1) Cut - Off Region Conditions : • Input base current IB= 0 • VBE < 0.7v • Output collector current IC= 0 • Base – Collector junction BC is reversed biased • Base – Emitter junction BE is reversed biased • Maximum collector VCE= VCC Fig. 12 Example of cut - off region conditions
- 6. 1) Saturation Region Conditions • Input base current (IB) connected to VCC • VBE > 0.7v • Max collector current IC= VCC/RC • Base – Collector junction BC is forward biased • Base – Emitter junction BE is forward biased • VCE= 0 (ideal saturation) Fig. 13 Example of saturation region conditions
- 7. Calculation for the collector resistor ( ) , base current ( ) , and base resistor( ) IC = 20mA(datasheet) VCE (Sat ) = 0.2V(datasheet) bDC (direct current gain) = 60(datasheet) IC = bDc ´ IB -VCC + IC RC +VLED +VCE(Sat) = 0 -6V + 20mA ´ RC + 3.4V + 0.2V = 0 -2.4V + 20mA ´ RC = 0 RC = 2.4V 20mA =120W IB = IC bDC = 333mA RB = 6V - 0.7V 333mA =16KW IB RB RC
- 8. D. LED (light emitting diode) Fig. 12 Example of the barrier potential Fig. 14 Example of current in forward direction on a diode Fig. 15 Energy released by the electron of a single photon. Fig.13 An LED will begin to emit light when the on-voltage is exceeded. Fig. 11 Example of a blue 5mm LED
- 9. Calculation for energy released by the electron of a single photon. h (Plank 's constant) = 6.626 ´10-34 J / s C(Coulomb) = 6. 25´1018 e- c (Speed of light) = 3´108 m / s l (called lambda or wavelength) u ( frequency) eV (electron volts) lu = c u = c l = 3´108 m / s 470 ´10-9 m = 640 ´1012 s-1 E( photon) = hu = (6. 626 ´10-34 J / s)´ (640 ´1012 s-1 ) = 423´110-21 J E(eV ) = E( photon) ´1Coulomb = (423´10-21 J)´ (6.25´1018 e- ) = 2. 6eV
- 11. II. NIGHTLIGHT DIGITAL CIRCUIT VERSION – BASIC OPERATION • Arduino Function: – There is no analog output on Arduino. Instead it is a digital output (on or off). – If the output is half of the time on and half of the time off, it is said to be 50% duty cycle. – Duty cycle is the percentage of time that the output is on. The output can be 30%, 20%, 10% duty cycle, or any percentage from 0 – 100%. – The Arduino has a technic called pulse width modulation (PMW) that makes its output work as analog.
- 12. Arduino Function: • In the nightlight device, it allows the LED to fade in and out going from 0 to 255 (8 bits = as a default resolution) value repeating in a loop. • 0 correspond to 0 volts and 255 to 5 volts and any value in between are proportional to those voltages. • Then theses values are sent to the PWM pin (PWM Pins 3, 5, 6, 9, 10, 11) thus fading the LED in and out. 28
- 13. Arduino Function – Pulse Width Modulation Fig.18 Example of pulse width modulation
- 14. 1) Formula for Duty Cycle: DutyCycle= TH T ´100% Voltage per step (analogWrite( )) : x=0 ® 255 xsteps how many volts xsteps = x steps 5V 255 steps =19.6mV per step how many volts= x 5V 255 æ è ç ö ø ÷ =
- 15. E. Arduino Function: • This “function call” passes the read value (argument) from the inputs (A0 to A5) to the function in the library and its return an integer, which is from 0 to 1023 (10 bits = ) as a default resolution). • 0 corresponds to 0V and 1023 to 5V. 210
- 16. formula to calculate the voltages per step on the input read x = 0 ®1023 xsteps how many volts xsteps = x steps 5V 1024 steps = 4.88mV per step how many volts= x 5V 1024 æ è ç ö ø ÷ =
- 17. Appendix C Flowchart for the Digital Circuit
- 18. III. NIGHTLIGHT ANALOG CIRCUIT VERSION VS. NIGHTLIGHT DIGITAL CIRCUIT VERSION NIGHTLIGHT ANALOG CIRCUIT VERSION NIGHTLIGHT DIGITAL CIRCUIT VERSION I spent more time with the digital circuit than the analog one because of my familiarity with it. I improved my lack of skills with Arduino the analog circuit required more space on the board than the digital one due to more parts used.
- 19. V. COST TO BUILD AND OPERATE NIGHTLIGHT ANALOG CIRCUIT NIGHTLIGHT DIGITAL CIRCUIT costs about $5.70 costs about $26.38, approximately five times more (because of the Arduino ) + Arduino can be used for other applications because it is programmable. Running on 6V (Maui Electric Company), 8 hours per day, the cost is $1.20 per month. Running on 6V battery, 8 hours per day, the cost is $11 per month.
- 20. Conclusion • As a result, this project spiked my interest even more in electronics hardware, software, and more about technology in general. Consequently, after my associate degree in the ECET, my next academic goal is to earn a bachelor’s degree, become an electronic computer engineer, and perhaps to earn a master degree so I can teach electronics at a university.