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Variable Pressure Detector
The document outlines the design of a variable pressure detector using a variable capacitor as a pressure switch, incorporating both analog and digital components for pressure detection and time display. It details various electronic circuits including a Wien bridge oscillator, active rectifiers, and a monostable multivibrator, alongside resistor and capacitor configurations necessary for operation. Additionally, it describes the integration of display and counting circuits to indicate pressure levels visually.
Variable Pressure Detector
- 1. Variable Pressure Detector ECET270 Andy Schnobrich
- 2. Overview This projectutilizes a variable capacitor as a pressure switch. The analog portion of the circuit is used to detect how much the switch is depressed. The digital portion of the circuit is used to Display the time that the switch is depressed and to display the current pressure level.
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- 4. The Peak Detectorand Voltage Comparator Circuit +15V 15V 741 2 3 7 4 6 Vin (13.90°)V @5.86kHz D1 1N914 C1 .47F R1 10k IDC +15V 15V 741 2 3 7 4 6 R1 150k R2 150k R3 680 VLED VCC ILED V3 V1
- 5. The RC WheatstoneBridge and The Instrumentation Amplifier +15V 15V 741 2 3 7 4 6 C1 70pF R1 56k R2 100k C2 60.5pF FROM THE WEIN BRIDGE OSCILLATOR VOUT2VOUT1 +15V 15V 741 2 3 7 4 6 +15V 15V 741 2 3 7 4 6 +15V 15V 741 2 3 7 4 6 R2 12.1k R1 10k VOUT1 VOUT2 Vy Vx VOUT1 VOUT2 VOUT R2 12.1k R2 12.1k R2 12.1k R2 12.1k R2 12.1k
- 6. The Second OrderActive Band Pass Filter +15V 15V 741 2 3 7 4 6 +15V 15V 741 2 3 7 4 6 R1 12.1k RA 12k 33k C1 0.0033F C2 0.0033F R2 12.1k R3 12.1k TATION ER VOUT 330 RB 0 2 4 6 8 10 12 14 16 18 250 2250 4250 6250 8250 10250 Vout_pp(V) frequency (Hz) Frequency Response
- 7. The Active RectifierCircuit +15V 15V 741 2 3 7 4 6 +15V 15V 741 2 3 7 4 6D1 1N914 D2 1N914 R2 12.1k R1 12.1k R3 12.1k R5 12k +15V 15V 741 2 3 7 4 6 VOUT VIN R4 10k
- 8. The Active PeakDetector and Voltage Comparator Circuits +15V 15V 741 2 3 7 4 6 +15V 15V 741 2 3 7 4 6 +15V 15V 741 2 3 7 4 6 R3 100k R2 100k R1 100k R6 680 R5 680 R4 680 LED3 RED LED2 YELLOW LED1 GREEN VOUT1 VREF1 3.9V 15mA VREF2 6.3V VREF3 10.2V VOUT2 VOUT3 VOUT4 15V 15V 15V 15mA 15mA
- 9. The Transistor Drivers,and Passive Low Pass Filters R3 100k? R2 100k? R1 100k? VREF1 VREF2 VREF3 VOUT2 15V 15V 15V R5 680 2N3903 RC2 1k 5V C2 22F VOUT5 VOUT1 R4 680 2N3903 RC1 1k 5V C1 22F VOUT4 VOUT3 R6 680 2N3903 RC3 1k 5V C3 22F VOUT6 FROM ACTIVE PEAK DETECTOR RB2 22k RB1 22k RB3 1k Normal 1st Level 2nd Level 3rd Level 0V 0V 0V 0V FROM ACTIVE PEAK DETECTOR VOUT1 VOUT2 VOUT3 -13V -13V -13V +13V +13V +13V 0VVOUT6 0VVOUT5 0VVOUT4 +5V +5V +5V
- 10. The Monostable Multivibrator, and555 Square Wave Oscilator Circuits VOUT4 Q4: 2N3904 5V SN74121 2 3 4 5 6 7 14 13 12 11 10 9 8 1 5V NC NC NC NC NC NC OUTPUT RB4 6.8k RC4 1k Cext 0.1F RT 150k VOUT7 1 3 2 4 8 7 6 5 RB 1M RA 100k C1 0.068FC2 0.01FOUTPUT +5V LM555
- 11. The Counter, Decoder,and Display Circuits 74190 FROM 555 TIMER FROM 1/3 PRESSURE TRANSISTOR SWITCH FROM MONOSTABLE MULTIVIBRATOR 74190 74190 7446 a b c d e f d R1 220 R7 220 . . . . 7446 a b c d e f d R8 220 R14 220 . . . . 7446 a b c d e f d R16 220 R22 220 . . . . R15 220 RCO RCO CLK CLK 1/10's place 1's place 10's place
- 12. The Pressure DisplayCircuit 7 1 2 6 7446 8 16 vcc 13 12 11 10 9 15 14 a b c d e f g R's 220 . . . . R's 220 a b c d e f 20 10 7 8 9 19 18 17 16 vcc . . . . PLD FULL 2/3 1/3 FROM TRANSISTOR DRIVERS MSB LSB