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