Core Concept

Overview

Summary

Instructions

Parts List

  • myDAQ
  • 1 Red LED
  • 1 Green LED
  • 1 Blue LED
  • 1 White LED
  • 1 220 ohm Resister

Learn It

1 LED IV Curve

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Build a series circuit from your Red LED and 220 ohm resistor with
AO0 acting as the power supply.You may follow the wiring diagram in
Figure 1. Wire AI0+ to the node that connects the LED and
resister, wire AI0- to ground (AGND).

2 LED IV Curve

Open and run the Lumens.vi in the “Lumens” folder, navigate to the “IV Curve” tab on the front panel and click “Get IV Curve” in order to run the voltage test to get a voltage versus current curve for your Red LED. Flip the LED around in the circuit so that the cathode is tied to AO0 and the Anode is connected to the resistor, click the “Get IV Curve” button a second time and observe the results.

Explain the difference in the curves for different colors. Explain the difference between real and ideal LED curves.

3 LED IV Curve

Replace the Red LED with the Blue one in your circuit in the proper orientation and click “Get IV Curve” once again. Examine the differences in the two curves. Repeat this for every LED.

Where on the plot do you think an Infrared LED IV curve would fall? Ultra Violet?
Explain the inefficiencies of this circuit. How much power is lost when the LED is off? How much power is lost when it is on?

1 LED PWM

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Click on the “PWM Control” tab then click on the “Start PWM” button and
examine the analog output waveform going to the LED. Vary the “Duty Cycle” control and observe how the graph data and brightness of the LED change.
Reduce the frequency control until the LEDs blinking becomes noticeable
take note of that frequency.

2 LED PWM

Change the LED you are using and repeat the process of varying the frequency and duty cycle of
the analog output signal. Keeping the frequency the same, take note of which color LED looks brighter at different duty cycles.

What do you see with the same duty cycle and frequency on different color LEDs? Why is this happening?

3 LED PWM

Explore the Block diagram, the architecture is a Producer Consumer where user interaction information is collected from the front panel in the producer loop while the myDAQ’s
generation and acquisition functions are handled in the consumer loop. Observe how
information is sent between the loops and how each loop is stopped.

Using what you observed in this portion of the module and your understanding of colors, explain how you would gain different colors using the Red Green and Blue LEDs.



Bootstrap Slider

Build It

Click on the hardware that you have to get specific instructions.

Resources