This is a presentation on a project I completed as a freshman as part of the "Computers, Instuments, and Data Acquisition Techniques" course taught by Dr. Bob Kremens of RIT.

1. STAMP-based
Lightmeter
Christopher Tomkins-Tinch
ThroughTheKeyboard.com

2. The Sensor

3. TSL230
Light to
Frequency
Converter

4. How is the TSL230
Used?
• The TSL230 outputs a square-wave
pulse train with a frequency
proportional to light intensity
• These pulses can be counted to determine the
frequency output by the TSL230 in a given
amount of time. From this, the relative
intensity can be determined.

5. TSL230 Functional
Diagram

6. TSL230 Output
Frequency

7. The
Microcontroller

8. Basic
STAMP
BS2e
Programmable
BASIC-running
microcontroller

9. How is the
STAMP BS2e used?
• The STAMP • The STAMP regulates
interfaces with and power for the TSL230
reads in output from -- 9V source to 5V
the sensor, and sets supply
the sensitivity
multiplier • The STAMP handles
user input via buttons
• The STAMP outputs
the data to the LCD • The STAMP handles
processing of
radiometric data and
light intensity
calibration

10. BASIC STAMP BS2e
Overview
• 64 Bytes RAM (not much!)
• Temporary space to store program
variables at runtime
• 16KB EEPROM
• Non-volatile space to store program,
constants, long-term data
• 16 Channels I/O
• Programmable over RS232 (serial)

11. STAMP BS2e Schematic

12. The Display

13. LCD
AppMod
2x8 Character
LCD Module with
4 input buttons

14. LCD AppMod Schematic

15. The Schematic

16. Lightmeter Schematic

17. The Program

18. Rough Overview of
Lightmeter BASIC program
• Initialize LCD
• Set sensitivity multiplier of TSL230
sensor to 1x scaling
• Count pulses on input pin for 1 second
• Convert count value to ASCII string
• Output ASCII string to LCD screen

19. Rough Overview of
Lightmeter BASIC program
• 80% RAM usage (approx)
• 25% EEPROM usage (approx)
• 400 Lines in length (approx)

20. Build Materials

21. Build Materials
• 6cm x 6.8cm Main Circuit Board
• 4.4cm x 1.8cm Sensor Circuit Board
• 30 awg solid wire
• 24 pin DIP socket
• 8 pin DIP socket
• 3 pin Molex header -- for onboard
programming over serial

22. The Case

23. Serpac
Enclosure
3.65”
x
7.20”
x
1.26”

24. Serpac Case Dimensions

25. Modifications
to Serpac Case
• 4cm x 2.4cm cutout for LCD
• 1cm x 1cm cutout for 8-pin DIP socket
to hold sensor

26. Results

27. Results
• Current reading is approximately
given in units of μW/cm2
• The lightmeter can distinguish light
sources of varying brightness quite
well
• The LCD screen correctly outputs the
COUNT value

28. Possible Improvements
• User input via buttons
• On/off switch -- quite the oversight!
• Calibrate sensor output to known light
source
• Output useful data -- radiometric,
photographic, etc.
• Futher case modifications -- button holes,
etc.
• More secure mounting of internal
components

29. Approximate
Production Cost
• BASIC STAMP BS2e - $50
• LCD AppMod - $15
• TSL230 - $5
• Serpac Enclosure - $11
• Wire, buttons, connectors, misc.
materials - $9
• Total - about $90

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61. Special Thanks to
Dr. Robert Kremens
of the RIT CIS Laboratory for Image Algorithms and Systems
For his advice, guidance, and supplies