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Choose-your-own-adventure Lab Name: ______________________________

BME305 Lab 8

11/23/2015

Objective: Build and test a circuit to solve one of the following design challenges Skills learned: Circuit design from a problem statement Deliverables: Follow these guidelines to generate a lab report. Turn in to Nick in Ford B100 by 5pm on Friday, 12/4.

1. Choose one of the following design challenges:

a. When you contract a muscle, there is mechanical vibration within the tissue resulting in audible noise. Use

phonomyography (https://en.wikipedia.org/wiki/Phonomyography) to measure the noise. Filter and amplify the

interesting part of the data. Connect the output of the circuit to your speaker and record an audio file of what your

muscle sounds like when flexing. Rectify your signal and see if it can be used to control the Pong game.

b. Apply electrodes to either side of your bicep (or forearm, palm, or other thick muscly area). Create a frequency

response of the impedance between the two electrodes (so one electrode is attached to A1, the other to Ch1 and a

resistor to ground). This is a method of measuring your bioelectrical impedance

(https://en.wikipedia.org/wiki/Bioelectrical_impedance_analysis) and a one-dimensional version of electrical

impedance tomography (https://en.wikipedia.org/wiki/Electrical_impedance_tomography) (a cool example is at

http://www.chrisharrison.net/index.php/Research/Tomo using the http://www.analog.com/media/en/technical-

documentation/data-sheets/AD5933.pdf). Use the frequency response to determine the impedance of the tissue, and

see how much it changes when you flex the muscle. Write your code to compute the impedance as fast as possible, and

normalize it to a number between 0 and 5. See if it can be used to control the Pong game.

c. Stick some electrodes to your forehead and try to measure your EEG at that location

(https://en.wikipedia.org/wiki/Electroencephalography). Try to pick a spot that limits (or build a circuit to filter out)

EMG noise (or, if you can’t identify the EEG, see if you can pick up the EMG from the muscles under the skin). Filter and

amplify the interesting part of the data. Rectify the output of the circuit and see if it can be used to control the Pong

game.

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2. For your report:

a. If necessary, research your problem a little. Cite any interesting solutions or circuit diagrams you find.

b. Build the sensor and first stage of your circuit. Create an FFT with no activation and an FFT with activation to see where

the interesting frequencies are.

c. Build your circuit and tune the gains and cutoff frequencies. Draw the circuit diagram of your final design and label all

component values and frequencies of interest.

d. Create a spectrogram of your signal, demonstrating where the signal lies in frequency space when active.

e. Use LTSpice to simulate your filter and amplifier. Attach the circuit diagram and a frequency analysis.

f. Rectify the signal and try to play the new Pong game posted on Canvas.

g. Write, no more than a page,

i. a description of the physiological signal you are trying to measure

ii. how the signal is measured

iii. how the signal is filtered and amplified, and why the amount and frequencies you used

iv. what type of device the signal could be used in

v. how the setup could be improved (more sensors? better positioning?)

3. Get a sticker here for demonstrating your circuit -> ⃝