Download File - WA Powers

10/23/2014
Diode IV Curve
Experiment
LabVIEW Graphical Representations
Andrew Powers, Hubert Walkowski, Cole Leether
WENTWORTH INSTITUTE OF TECHNOLOGY
Abstract:
A LabVIEW simulation was run in order to see how an electrical signal
flowed to four different LED lights. A bread board circuit was set up and using
LabVIEW as a function control and also graphical output simulator, voltage was
run through the system. Once the system reached a certain current, the LEDs
would start to glow. Once they glowed completely, depending on the inputs on
the LabVIEW interface, graphical outputs of diode IV characteristics and change in
voltage with respect to current were gathered. From this lab, it is now known that
each of the four LED lights showed similar trends of blue, yellow, green, and red
IV characteristics, where blue took the most voltage to turn on at 2.47 bolts, then
green at 1.7 volts, and green and red turned on at 1 volt. Also, the red LED has the
highest voltage with respect to current. This all shows that the red LED takes the
longest to turn on.
Synopsis:
When lighting an LED, each color has a particular IV characteristic. Because
of this, voltage and current of each color LED differ. By using LabVIEW, it visually
shows the characteristics of each color LED with the IV characteristic graphs. Also,
voltage versus current graphs were created by LabVIEW to show the rate of
voltage change with respect to the current through the system. With both of
these graphical outputs, the voltage it takes to turn on each color LED was
understood.
Apparatus:
The electrical components used to construct the circuit consisted of a
power source, a voltage output reader, various colored diodes, a 1k resistor, a
bread board and the required test leads to connect the components into a circuit.
The below image expresses the complete set up of all the above listed
electrical components. The only aspect of the test equipment left out is the
computer in which LabVIEW was projected on giving us the various diode IV
curves as expressed in the below graphs.
The below figure explains the orientation of the resistor and diode in the
circuit used to run the testing for the diode IV curves.
(Vd)
Results:
Equations
I=
𝑉𝑑 − 𝑉𝐷𝑀𝑀
𝑅
R = resistor (1000 ohms)
I = current
Vd = alternating supplied voltage
VDMM = voltage read from the DMM reading
The LabVIEW block diagram
IV characteristics
Red IV
Green IV
Yellow IV
Blue IV
dV/dI
Red dV/dI
Green dV/dI
Yellow dV/dI
Blue dV/dI
Discussion of Graphical Results:
Red Diode – On the IV curve, the current did not change significantly until the
voltage reading reached 1.45 Volts. After this point, the curve became steeper
due to the current increasing at a higher rate than the voltage reading. The slope
of this IV graph changes slower than the rest of the graphs. This is shown by the
curve on the dV/dI graph for the red diode, which decreases slope and eventually
becomes horizontal, indicating a larger change in current compared to voltage.
Green Diode – On the IV curve, the current did not change significantly until the
voltage reading reached 1.7 Volts. After this point, the curve’s steepness
increases exponentially due to the current increasing at a significantly higher rate
than the voltage reading. The IV graph for this diode has a slope that increases
quicker than that of the red diode. This is shown by the curve on the dV/dI graph
for the green diode, which has a large decrease in slope as voltage increases, and
eventually becomes horizontal, indicating the higher change in current compared
to voltage.
Yellow Diode – Similar to the green diode’s IV curve, the current did not change
significantly until the voltage reading reached 1.7 Volts. After this point, the curve
became steeper due to the current increasing at a significantly higher rate than
the voltage reading. The slope of the yellow diode’s IV curve increased faster than
that of the green diode. The relationship between the change in voltage and
current is shown by the curve on the dV/dI graph, which decreases slope and
eventually becomes horizontal, again, indicating that the current changes at a
higher rate than that of voltage.
Blue Diode – On the IV curve, the current did not change significantly until the
voltage reading reached 2.4 Volts. After this point, the curve became steeper due
to the current increasing at a higher rate than the voltage reading. The slope of
this graph increases faster than that of the red diode IV curve, but not as fast as
the IV graph of the green diode. This is shown by the curve on the dV/dI graph for
this diode, which decreases slope and eventually becomes horizontal, indicating a
higher rate of change in current than voltage.
Conclusions:
All of the IV curves showed the same trend in that a specific amount of
voltage was required to turn on the specific diodes. The red diode activated at
1.45 volts, the green diode at 1.7 volts, yellow diode was 1.75 volts and the blue
diode activated at 2.4 volts. These voltages relate to the below table which
expresses the voltage drops for various colored diodes. The exact voltage values
do not measure up perfectly, but the experimental trend matches the theoretical
trend expressed in the below table. The red diode required the least voltage, then
green, yellow, and finally the blue diode required the highest voltage to turn on.
All of the IV slopes exponentially increased. The rate in which current increased
ranging from lowest to the highest was the red, blue, green and yellow diode
according to the graphs.
The second set of graphs are the rates of change of voltage over current.
The rate of change in current is greater than the rate of change of the voltage
resulting in the exponential downwards slope, and eventual leveling, of the
graphs.
In the end our data concluded that voltage does drop across a
diode/resistor electrical circuit.
Conventional LEDs are made from a variety of inorganic semiconductor materials. The
following table shows the available colors with wavelength range, voltage drop and material:
Color
Wavelength
[nm]
Voltage drop
[ΔV]
Infrared
λ > 760
ΔV < 1.63
Red
610 < λ < 760
1.63 < ΔV <
2.03
Orange
590 < λ < 610
2.03 < ΔV <
2.10
Semiconductor material
Gallium arsenide (GaAs)
Aluminium gallium arsenide (AlGaAs)
Aluminium gallium arsenide (AlGaAs)
Gallium arsenide phosphide (GaAsP)
Aluminium gallium indium phosphide (AlGaInP)
Gallium(III) phosphide (GaP)
Gallium arsenide phosphide (GaAsP)
Aluminium gallium indium phosphide (AlGaInP)
Gallium(III) phosphide (GaP)
Yellow
570 < λ < 590
2.10 < ΔV <
2.18
Green
500 < λ < 570
1.9[70] < ΔV <
4.0
Blue
450 < λ < 500
2.48 < ΔV <
3.7
Violet
400 < λ < 450
2.76 < ΔV <
4.0
Gallium arsenide phosphide (GaAsP)
Aluminium gallium indium phosphide (AlGaInP)
Gallium(III) phosphide (GaP)
Traditional green:
Gallium(III) phosphide (GaP)
Aluminium gallium indium phosphide (AlGaInP)
Aluminium gallium phosphide (AlGaP)
Pure green:
Indium gallium nitride (InGaN) / Gallium(III)
nitride (GaN)
Zinc selenide (ZnSe)
Indium gallium nitride (InGaN)
Silicon carbide (SiC) as substrate
Silicon (Si) as substrate—under development
Indium gallium nitride (InGaN)
Dual blue/red LEDs,
blue with red phosphor,
or white with purple plastic
Diamond (235 nm)[71]
Boron nitride (215 nm)[72][73]
Aluminium nitride (AlN) (210 nm)[74]
Ultraviolet λ < 400
3.1 < ΔV < 4.4
Aluminium gallium nitride (AlGaN)
Aluminium gallium indium nitride (AlGaInN)—
down to 210 nm[75]
Blue with one or two phosphor layers:
yellow with red, orange or pink phosphor added
Pink
Multiple types ΔV ~ 3.3[76]
afterwards,
or white phosphors with pink pigment or dye
over top.[77]
White
Broad spectrum ΔV = 3.5
Blue/UV diode with yellow phosphor
Purple
Multiple types
2.48 < ΔV <
3.7