Download Fluorescein Detection Circuit

Detection Circuit
ENGR 1182.03
Pre 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
3
+5V
10K
2
1
POT
Pins
123
Schematic
Binary Voltmeter Calibration Circuit
DMM
2
1
+5V
4
3
+5V
+5V
+5V
+5V
+5V
PCB2
10K
Gnd
D1
D2
D0 (LSB)
14
13
12
D3
11
10
D5
D6
D4
9
8
7
6
5
3
+5V
D7 (MSB)
V Input
Binary Voltmeter
2
POT
1
LEDs
D7 D6 D5 D4
SHORT
WIRE
0 to +5 VOLTS
D3 D2 D1 D0
Fluorescein Detection Circuit
The 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
detection well
Acrylic chip
Side view where Acrylic
chip is sitting on top of the
DAD
blue LED
photodetector
Optical Components
Light 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!
D1
Short
Wire
Negative
terminal
Fluorescein Detection Circuit
Fluorescein Detection
Circuit
DAD
Diode
2 wires
PhotoTransistor
3 wires
Integrated Circuit
ADC0804
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