Eyelid Motion Monitor

Instructor: Adi Hanuka

By: Alon Berger Maor Itzhak

11.6.2014

Spring Semester 2014

1. Quick Review of the Last Presentation

2. What We Planned To Do• Problems Encountered & Consequences

3. Our Progress So Far

4. What’s Next

Outline

First “Intuition” of the signal

Plans for Future Experiments

Last Time

Main effects:◦ Amplifies only the change from the reference

voltage

Side effects:◦ Amplitude – Frequency dependence ◦ Transient response

AC Effects

Test Points

Hall Probe

Amp

Coupling

A to D

A B C D

Analog Card

1. Frequency Dependence of Hall Sensor (Inductor Experiment)

2. Frequency Dependence of the System:2.A: Motorized Experiment on test point A2.C: Motorized Experiment on test point C2.D: Motorized Experiment on test point D

3. Experiment on Glasses

Experiments

Goals: ◦ Understand the probe’s dependence on frequency◦ Is there capacitance in the probe?

SetUp:◦ Hall probe circuit◦ Inductor circuit

1. Inductor Experiment

Results:

1. Inductor Experiment

0 20 40 60 80 10060

65

70

75

80

85

90

Hall Detector Output Voltage

Middle of Inductor

Edge of Inductor

Frequency [Hz]

Volt

age P

P [

mV

]Noise Amplitude:16mV

Measurement Error: 2mV

Conclusion:

◦ The output amplitude is constant and independent of the frequency

◦ The hall sensor is not equipped with a built-in capacitor

1. Inductor Experiment

Goal: Understanding the Probe’s response to blink like motion in different frequencies

Setup: ◦ Hall probe circuit◦ A magnet attached to a pole, controlled by a

motor performing a periodical arced motion◦ Magnet: Class = N50, Dimensions = 3x0.65mm

A

2.A: Motorized Arm Experiment

Video Demonstration

◦ Low Frequency Behavior (4Hz)

◦ High Frequency Behavior (8Hz)

2.A: Motorized Arm Experiment

2Hz:◦ Constant peak◦ Two pulses

per period

6Hz:◦ Two pulses

per period◦ Different height

each pulse◦ Same height

each period

2.A: Motorized Arm ExperimentT = 0.5 sec

T = 0.166 sec

Technical Difficulties: The system is not compatible with frequencies

over 4Hz

Difficulties with keeping a fixed distance between the pole and the hall probe

Inability to set a fixed aperture for the pole’s motion

Difficulties with measuring the distance between the pole and the magnet in a sufficient scale

2.A: Motorized Arm Experiment

Results: Near-field effects:

2.A: Motorized Arm Experiment

Results: The peak amplitude is constant over the frequency.

2.A: Motorized Arm Experiment

0 1 2 3 4 5 6 7 8 92.5

2.55

2.6

2.65

2.7

2.75

2.8

Peak Amplitudes

First Peak Second Peak

Frequency [Hz]

Volt

age [

V]

A new setup is required

Temporary Solution : Circular motion

New setup (*video demonstration):

◦ Hall probe circuit

◦ New pole

◦ A magnet (class N50, 3x0.65mm) attached to a pole, controlled by a motor performing fully circular motion

2.A: Motorized Arm Experiment

Results: Amplitude◦ Expected: constant

2.A: Motorized Arm Experiment

0 0.5 1 1.5 2 2.5 32.3

2.4

2.5

2.6

2.7

2.8

2.9

3

Signal's Peak

Frequency [Hz]

Sig

nal's P

eak [

V]

Results: Pulse’s Width◦ Expected:

2.A: Motorized Arm Experiment

0 0.5 1 1.5 2 2.5 3 3.5 4 4.50

10

20

30

40

50

60

70

80

90

R² = 0.999527100194315

Pulse's Width

Period [Sec]

Wid

th [

mSec]

Conclusions:

Amplitude is constant regardless of the frequency

Near field effects

Width proportional to T (Period Time)

Better setup is still required

2.A: Motorized Arm Experiment

2.C: Motorized Arm Experiment

Goal: Understand the output of the analog card

Set up: Same magnet, motor & pole.◦ Analog card positioned in front◦ Upper Sensor connected to scope

Tested 11 frequencies up to 2.8Hz

C

Results:

2.C: Motorized Arm Experiment

(Frequency = 0.2Hz)

Expected effect of the Analog Card:◦ Transfer Function

2.C: Motorized Arm Experiment

Results: Amplitude

2.C: Motorized Arm Experiment

0 0.5 1 1.5 2 2.5 30

1

2

3

4

5

6

Amplitudes

Positive PeaksNegative PeaksReference Voltage

Frequency [Hz]

Volt

age A

mplitu

de [

V]

0 1 2 3 4 50

20

40

60

80

100

120

140

R² = 0.998938674264566

Width of Positive Pulse

T [sec]

Wid

th [

msec]

Results: Pulse Width◦ Expected:

2.C: Motorized Arm Experiment

Conclusions and points to note:

Frequency Response (Transfer Function) effects

Unexpected descent in the positive peak amplitude

Negative Peaks are an indication of velocity!

Is the pulse width actually that interesting?

2.C: Motorized Arm Experiment

Goal: Understanding the output signal of the whole system

Set up: Same motor & pole.◦ Analog card positioned in front of the pole while

connected to the digital card

Tested 11 frequencies up to 2.8Hz

2.D: Motorized Arm Experiment

D

Results:

2.D: Motorized Arm Experiment

(Frequency = 0.5Hz)

Conclusions:◦ Digitization of the signal – discrete voltage values

◦ Same frequency dependence as point C

◦ Points C, D – same signal

◦ Change in y axis’s scale

2.D: Motorized Arm Experiment

Digital (Test Point D) Analog (Test Point C)

Goal:◦ Observation of response of the whole system to

controlled blinks◦ Comparison of blinks and arched motion setup

Experiment process – Controlled blinks:◦ 5 slow blinks◦ 5 fast blinks◦ 5 very fast blinks

3. Preliminary Experiments With Glasses

Results:◦ In fast successive blinks, amplitude rises

◦ Unexpected effects (horns)

Depends on the position of the probe?

3. Preliminary Experiments With Glasses

(Upper Sensor)(Lower Sensor)

Eye shuts Eye opens

New Idea: Bend the Sensors?

Reduces risk of passing the probe!◦ Graph: Eye closure followed by eye opening◦ Blue line: Bent sensor. Red line: Original

New Idea: Bend the Sensors?

Signal changes drastically with the position of the glasses

Slight changes to the position of the probes affect the signal dramatically

Conclusions

Amplitude Dependence on Frequency:◦ In Hall Probe: None◦ In Analog Card:

Transfer Function Decreases as a result of an additional effect

Width: What can we learn from it?

Effects of the Capacitors in the Analog Card:Changes to the Signal Shape

Signal after A/D: Consistent with output of Analog Card

Position of Glasses: CRUCIAL for obtaining expected results

Bending the probes: A good idea to investigate

Summary

We believe we know what signal to expect

It’s time to collect data from patients◦ Learn about the variance between them

Find a mathematical model

New glasses are needed:◦ Most up-to-date analog card scheme◦ Bent probes◦ Better positioned and more comfortable

What’s Next

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