1. PWM? K. A. Connor Mobile Studio Project
Center for Mobile Hands-On STEM
SMART LIGHTING Engineering Research Center
ECSE Department
Rensselaer Polytechnic Institute

2. Outline Overview Outcomes Activities Tasks Materials & Supplies
References/Resources
Nomenclature
Questions
18 September September 2018

3. Overview Take light apart and put it back together
Observe the colors from standard ‘white’ light bulbs using a diffraction grating
Observe the pixel colors in LCD display using magnifying lens or microscope
Generate at least 3 colors of light using LEDs
Use color mixing app or program to show possibilities & importance of amount of each color
Use PWM to control intensity of light
Use 3 PWM systems to control relative intensity of red, green, blue & white (other colors too)
18 September September 2018

4. Tasks Participants will
Identify activities, concepts, etc. appropriate for 5th grade students
Identify STEM related outcomes that can be addressed using activities, concepts, etc.
Develop outreach activities for 5th grade students.
18 September September 2018

5. Diffraction Grating
Set up three clamp on lamps with incandescent, CFL & LED bulbs
Observe color spectra using diffraction grating slide
Technique
Observations
Describe (Draw?) the similarities & differences in the light observed from the three bulbs
18 September September 2018

6. Spectra
18 September September 2018

7. What do Humans See?
18 September September 2018

8. Magnifying Lens
Observe RGB color pixels in LCD using a magnifying lens (microscope)
18 September September 2018

9. Stickie
Light a series of LEDs using a CR2032 coin battery (red, green, blue, white, yellow, orange …)
Try each in turn – note polarity
Try two or more at once – conclusions?
Complete Stickie
Attach LED to battery with tape
Add strong magnet to coin
Attach with tape
See where it sticks
18 September September 2018

10. Mobile Studio Frequency Control – set from 1Hz to 1kHz
Duty Cycle – set from 0% to 100%
Output voltage range: off is 0V and on is 3.3V (uses digital levels)
18 September September 2018

11. Mobile Studio Plug in Mobile Studio
Connect PWM1 and digital GND to 10Ω resistor in series with LED
Turn on PWM software
Select 1Hz and 50% duty cycle
Try different frequencies and duty cycles
Select 120Hz (frequency of most common bulbs) and vary duty cycle from 0% to 100%
Observe average voltage with DC voltmeter
What is PWM?
0.1Hz and then count seconds for each duty cycle?
18 September September 2018

12. Analog Discovery
Frequency Control – set from 0 to 10 times 10A where A is power of 10
Duty Cycle – set from 0% to 100%
Start – to begin
Output voltage range: off is 0V and on is 3.3V; voltage is 1.65V when Start is not selected
18 September September 2018

13. Analog Discovery Plug in Digilent Analog Discovery
Connect Yellow (AWG1) and Black (GND) wires to 10Ω resistor in series with LED
Turn on ADAP software and select PWM
Select 1Hz and 50% duty cycle and start
Try different frequencies and duty cycles
Select 120Hz (frequency of most common bulbs) and vary duty cycle from 0% to 100%
Observe average voltage with DC voltmeter
What is PWM?
0.1Hz and then count seconds for each duty cycle?
18 September September 2018

14. RGB Light Bulb Install RGB bulb with remote Explore controls
Observe light
18 September September 2018

15. RGB PWM Combine three LED Mobile Studio or Analog Discovery Setups
Each group controls a color in the 3 color LED
Explore how to make white light of different intensities
18 September September 2018

16. BOM? Bill of Materials Diffraction grating slide
Magnifying glass or microscope
Incandescent, CFL, LED bulbs with clamp on lamps
Bright LEDs (Red, Green, Blue, Yellow, Orange, White … separately and in RGB package)
CR2032 Coin Batteries
¼” Neodymium Iron Boron Magnets
Analog Discovery or Mobile Studio
Resistors (10Ω, 100Ω, 500Ω, 1kΩ)
Protoboard & jumper wires
Three color bulb with remote, LED touch lamp
Solar cell
Inexpensive multi-meter
BOM?
18 September September 2018

17. References/Resources or
18 September September 2018

18. Nomenclature PWM LED Diffraction Voltage Current Resistance Pixel RGB
LCD
CFL
Incandescent
Neodymium Iron Boron Magnets
Solar Cell
Multi-meter
18 September September 2018

19. New Visions Outreach Goals/Outcomes Content Level …
18 September September 2018

20. Questions
Start with separating colors from light bulbs and possibly LCD monitors, using diffraction slides
Divide colors and show one can make white from RGB or something.
Measure average with DC voltmeter
Eveready desk lamp PWM
Lights and motors? AD Board cannot drive motor.
High efficiency LED operation – pick the correct resistor.
5x5 array of 3 color LEDs, driven by audio amps. Takes about 5W each. Maybe 4x4 with 5x5 white LEDs to give flexibility
Small box to be ‘stage’ or office or something
Do stickies to show how to make colors with LEDs
Show how levels of each color can be controlled on average. Compare with commercial bulb.
18 September September 2018