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TOUCH ME NOTTOUCH ME NOT
TOUCH ACTIVATED SWITCHTOUCH ACTIVATED SWITCH
Sharon AbrahamSharon Abraham311311
Criteria & Chosen CircuitCriteria & Chosen Circuit
Possible to build Possible to build Physical CircuitPhysical Circuit
Parts learnt about in Parts learnt about in classclass
Simple enough to Simple enough to model and model and understandunderstand
Learn about real Learn about real circuit developmentcircuit development
Get A in classGet A in class
Chose Touch Chose Touch Activated SwitchActivated Switch
Meets criteriaMeets criteria
Interesting Interesting conceptsconcepts
CircuitCircuit
C4
470p
M1
BSS138/FAI
V15Vdc
V25Vdc
U5A74HC14
1 2
14
M2
BSS138/FAI
U5A74HC14
1 2
14
M1
BSS138/FAI
V25Vdc
R6
47
Sink
Source
Touch ButtonR4100k
R5
47k
R6
47
U1A
74HC14
12
R7100KSET = 0.5
R115k
R2470k
R32.2k
R8
47k
Q1
Q2N2907A
D1D1N4148
C1.1
C20.0022
C30.1
U2A
74HC14
12
U3A
74HC14
12
U4A
74HC14
12
Problems / ChangesProblems / Changes
Circuit had both Circuit had both source and sinksource and sink
How to model human How to model human touchtouch
Removed one piece – Removed one piece – used only sinkused only sink
Modeled as capacitor Modeled as capacitor and pulse voltage and pulse voltage sourcesource
Final Circuit ModelFinal Circuit Model
R4100k
R5
47k
R6
V5
TD =
TF = 1nPW = .05mPER = .1m
V1 = 0.1
TR = 1n
V2 = 0
U1A
74HC14
12
R7100KSET = 0.5
R115k
R2470k
R32.2k
R8
47k
Q1
Q2N2907A
D1D1N4148
C1.1
C20.0022
C30.1
U2A 74HC14
12
U3A74HC14
12
U4A
74HC14
12
C4
470p
V
V
M1
BSS138/FAI
V15Vdc
V25Vdc
U5A74HC14
1 2
14
M2
BSS138/FAI
V45Vdc
R1110k
C5.1m
SimulationSimulation
Time
0s 20us 40us 60us 80us 100us 120us 140us 160us 180us 200usV(C5:2) V(R6:1)
-2.0V
0V
2.0V
4.0V
6.0V
Human Body CapacitanceHuman Body Capacitance
R4100k
R5
47k
R6
47
V5
TD =
TF = 1nPW = .05mPER = .1m
V1 = 0.1
TR = 1n
V2 = 0
U1A
74HC14
12
R7100KSET = 0.5
R115k
R2470k
R32.2k
R8
47k
Q1
Q2N2907A
D1D1N4148
C1.1
C20.0022
C30.1
U2A 74HC14
12
U3A74HC14
12
U4A
74HC14
12
C4
470p
M1
BSS138/FAI
V15Vdc
V25Vdc
U5A74HC14
1 2
14
M2
BSS138/FAI
V45Vdc
R1110k
C5.1m
Sizable Capacitance ChangeSizable Capacitance ChangeEnvironmental FactorsEnvironmental Factors
AnalysisAnalysis
OscillatorOscillator
20 kHz20 kHz
Shmitt TriggersShmitt Triggers
Rails – Voltage Rails – Voltage sourcessources
R5
47k
U1A
74HC14
12
R32.2k
C20.0022
U2A 74HC14
12
U3A74HC14
12
U4A
74HC14
12
C4
470p
V
OscillatorOscillator
Time
0s 20us 40us 60us 80us 100us 120us 140us 160us 180us 200usV(R5:1)
-4.0V
0V
4.0V
8.0V
High ResistanceHigh Resistance
Zero CurrentZero Current
R4100k
R5
47k
R6
47
V5
TD =
TF = 1nPW = .05mPER = .1m
V1 = 0.0
TR = 1n
V2 = 0
U1A
74HC14
12
R7100KSET = 0.5
R115k
R2470k
R32.2k
R8
47k
Q1
Q2N2907A
D1D1N4148
C1.1
C20.0022
C30.1
U2A 74HC14
12
U3A74HC14
12
U4A
74HC14
12
C4
470p
M1
BSS138/FAI
V15Vdc
V25Vdc
U5A74HC14
1 2
14
M2
BSS138/FAI
V45Vdc
R1110k
C51f
R4100k
R5
47k
R6
47
V5
TD =
TF = 1nPW = .05mPER = .1m
V1 = 0.0
TR = 1n
V2 = 0
U1A
74HC14
12
R7100KSET = 0.5
R115k
R2470k
R32.2k
R8
47k
Q1
Q2N2907A
D1D1N4148
C1.1
C20.0022
C30.1
U2A 74HC14
12
U3A74HC14
12
U4A
74HC14
12
C4
470p
M1
BSS138/FAI
V15Vdc
V25Vdc
U5A74HC14
1 2
14
M2
BSS138/FAI
V45Vdc
R1110k
C51f
Transistor – Transistor –
Diode – Only positive voltageDiode – Only positive voltage
Amplifies SignalAmplifies Signal
R4100k
R5
47k
R6
47
V5
TD =
TF = 1nPW = .05mPER = .1m
V1 = 0.0
TR = 1n
V2 = 0
U1A
74HC14
12
R7100KSET = 0.5
R115k
R2470k
R32.2k
R8
47k
Q1
Q2N2907A
D1D1N4148
C1.1
C20.0022
C30.1
U2A 74HC14
12
U3A74HC14
12
U4A
74HC14
12
C4
470p
M1
BSS138/FAI
V15Vdc
V25Vdc
U5A74HC14
1 2
14
M2
BSS138/FAI
V45Vdc
R1110k
C51f
Time
0s 20us 40us 60us 80us 100us 120us 140us 160us 180us 200usV(R6:2) V(C3:1) V(C1:2)
-5V
0V
5V
10V
ConclusionConclusion
Circuit works as was expectedCircuit works as was expected
Uses ModificationsUses Modifications
Elevator buttonsElevator buttons
Pool sensorPool sensor
Touch activated lampTouch activated lamp
- Addition of Flip Flops- Addition of Flip Flops
Alarm SystemAlarm System
- Output load is a siren- Output load is a siren