Detection Circuit ENGR 1182.03Pre Lab

TrimPot Is a potentiometer (variable resistor)

By varying the resistor, it creates a variable voltage source Total resistance (Pin 1 to Pin 3) = 10 k ohms Resistance at Pin 2 varies by turning the small adjustment screw ( 0 to +5V on Pin 2)

Is used to calibrate the Binary Voltmeter circuit

Pins 1 2 3

+5 V

1 0 K

P O T

13

2

Schematic

+5 V

+5 V +5 V

1 0 K

P O T

13

2

P C B 2

Bina ry Voltm e te r

6

2 1

75 14

4 3

8 9 10 11 12 13

D7

(MS

B)

+5V

+5V

D6

V I

nput

Gnd

+5V

+5V

D5

D4

D3

D2

D1

D0

(LS

B)

D 7 D 6

D 5

D 4

D 3

D 2

D 1

D 0

SHORTW IRE

B in a r y V o ltm e te r C a lib r a tio n C ir c u it

L EDs

0 to +5 V OL T S

BINA RY DISPL A Y

DMM

Fluorescein Detection CircuitThe detection circuit performs four

functions:

Fluorescein excitation (with a blue LED)

Fluorescein emission detection (green light photodetector)

Converts fluorescence signal from analog to digital

Displays a binary coded value 0-255 that is proportional to the amount of fluorescein in the detection well

Fluorescein Detection

photodetector

blue LED

Acrylic chip

detection well

em

issio

n

excitation

Side view where Acrylic chip is sitting on top of the DAD

Optical ComponentsLight Emitting Diode (LED) Emits light proportional to current through diode Two uses of LED:

Blue LED – Fluorescein excitation Red and Green LEDS are used to display

the “Binary Number” at the output of the Binary Voltmeter

LEDs are polarity dependent, the short wire has negative terminal whereas the longer wire has positive.

Photodetector Resistance that varies with incident

light Sensitive to specific wavelength

(Green) Fluorescein emission detection EXTREMELY SENSITIVE TO POLARITY!

Negative terminal

D 1

Shor tW ire

Fluorescein Detection Circuit Fluorescein Detection Circuit

Diode 2 wires Integrated Circuit

ADC0804

Photo-Transistor3 wires

DAD

Analog vs. Digital

Learning Objectives of Lab

Students will learn about – Electronic circuit components Building the binary voltmeter circuit from a schematic drawing Troubleshooting electronic circuits Binary numbers and binary-decimal conversion