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2017 January 19

Project ideas for freshman design seminar

Filed under: freshman design seminar — gasstationwithoutpumps @ 09:47
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I haven’t blogged much about the freshman design seminar lately.  So far, I’ve had the students take the training to use the drill press and scroll saw in the (rather limited) Baskin School of Engineering Fab Lab, and had them look for projects they might be interested in doing.  At one point, before the quarter started, I looked into using the Neptune software from Boston University (which I found out about at the iGEM Jamboree) for designing and building low-cost microfluidic systems, but the software was nowhere near ready for use by freshmen, and I did not have the time get all the pieces figured out and working with the somewhat different hardware tools we had available. So, as in previous years, I’ll be counting on the students to come up with a couple of projects that they are interested in and capable of making a good start on.  This is only a 2-unit class, so they only have 6 hours a week on it, 3 of which are in class.

I assigned them the task of finding interesting projects they would want to work on and providing links to web pages about the projects. I think that they may have been overly influenced by an example I brought up in class, but there seems to be a fairly large group interested in an EMG-controlled prosthesis.  That’s a bit ambitious for a 2-unit freshman course, but we could do an EMG, we could do some simple programming for servo motors (I think that more sophisticated motor control would take more time than we have), and we could probably get an already designed hand printed or laser-cut.

Here are some of the project ideas they’ve come up with, grouped by student, in their own words—I’ve not even fixed the typos:

Vernier has a simple (but kind of expensive) EKG sensor that records the electrical events happening within the heart. This sensor uses a digital control unit as well as an EKG sensor. Also, we would need some additional software help.
Vernier also has a project that is an LED color mixer that uses digital control unit. This will have the ability to shine red, blue, and green light, any of which can be shone individually or with other lights.

Similarly to the EKG sensor, Vernier has a blood pressure sensor that calculates blood pressure. Vernier uses a blood pressure sensor and digital control unit in order to carry out the experiment. This device has a cuff that is placed on the upper arm to in order to pressurize the arteries. The sensor monitors the pressure in units of mm Hg.
I thought this website was interesting as they have links to interesting DIY lab equipment such as the micro centrifuge.,_open-source_hardware
This website was has a large amount of open source hardware for science and also 3D printed equipment

From that website, I found
which was a DIY microscope

and also
for a DIY Bioprinter

[Later, from the same student:],_open-source_hardware
This website was has a large amount of open source experiments and DIYs

and I’d like to do an Arduino robotic arm project

-This would be my number one choice for a project to design. This post in particular doesn’t have a whole lot of specifics as to what parts were used, and how they built it, but it does have a brief explanation of how it works. [The student doesn’t say what the project is, but it seems to be an EMG-controlled RC car.]
-The  basics of an EMG and how they work. Materials and a quick blurb about cost vs learning. It would actually cost more to buy the components and build it ourselves than it would be to just buy a pre-built MyoWare. That being said, the learning experience is important.
-Again, pretty basic idea, but this site seems to have more about the coding and signaling from the EMG to the RC car
-Just the basic ideas behind an EMG and possible research applications

A free 3d printable prosthetic hand off of thingiverse.

This is a page detailing how to create a simple EMG.

Attached is also an extensive paper on making a myoelectric prosthetic hand. [attachment from email is not included here—there is a reason the assignment required links, not attachments]

How to build a CNC machine
Remote webcam — could be placed on robot
Wind turbine generator

This is a blood pressure diagnostic devise.
We can work on sensors, and it seems like a freshmen project.
Let me know what you think.  [Not a valid link, so I have no idea what the student is talking about.]
So I saw this, and I noticed the price. But if we could make the individual parts our self, and at the same time learn to implement human movement into a devise such as this it would be awesome. The correlation of movements are what interest me in this project.
Please let me know what you think. [The model arm to imitate a human arm is indeed pricey, as are all Pasco products.]

I’m interested in building nerve controlled prosthetic limb.(EMG)

This is a link that somewhat describes EMG with lots of article links at the bottom.

Homemade Electrocardiograph/ Will ONLY cost about $10/ Will take about 2-3 weeks/ Code available in a zip file. 

exiii HACKberry

3D Printed Bionic Arm/ costs about $200/ Open sourced/ Developed as a cheaper alternative to prosthetics/ Site has tutorials from assembling to programming. 
Response from a different student:
The Homemade ECG really seems like a cool project, but there was a warning about how it was dangerous because to try it someone has to attach the sensors to their chest. 

I like the HACKberry prostetic hand. We would need to choose a specific part out of it that we want to work on since it is a big project, I think. 

I would like to focus on learning how to program the hand to open and close. Also, I would love to learn how to design and construct it.

for this project, I want to work on making a functional mechanic hand.

I would like to make a foot-glove massager with an insert in between the big toe and the second toe using some of the concepts found at these links:

If it’s possible I’d like the glove to be able to massage the foot as if it was “kneading”/”squeezing” the foot.
The idea would be to help people (old or young) with bunions in their foot. You can read more about this foot problem here:

2012 August 31

EMG video

Filed under: Circuits course — gasstationwithoutpumps @ 10:38
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I just got pointed to a video that seems relevant to the EMG/EKG lab:

For those without the patience to watch a 76-second video, it shows the use of 20 EMG channels from skin electrodes being used to control musical instruments (mostly percussion).  It probably takes some practice to be able to control each of the muscles independently with enough precision to play music, as the muscles involved are mostly large ones.

This video might be a good one to show as an introduction to the EMG/EKG lab.

2012 July 14

EMG and EKG works

I decided to try the instrumentation amplifier again, doing an electromyograph, rather than an electrocardiogram.  The principle is the same, but you get the signal from a muscle other than the heart.  I chose to use my left biceps, because it can be conveniently close to the breadboard to the left of my laptop.

Electrode placement for electromyograph readings from the biceps. The purple lead on the elbow goes to the virtual ground, the green and yellow leads to the instrumentation amplifier inputs.

The circuit is a very simple one, taking advantage of the off-the-shelf ina126  instrumentation amplifier:

Schematic for the EMG circuit. The op amp is used to create a virtual ground halfway between the power rails. The instrumentation amplifier is set to have a gain of 103 using the Rgain resistor. [UPDATE 2012 July 14 21:04: I noticed a bug in the schematic—all capacitors are 4.7µF not 47µF (not that it matters much).]

With my arm relaxed, I get about 40mV of noise at the amplifier—mainly 60Hz and 1.080 MHz, the frequency of the strongest local AM radio station. I can get rid of the AM radio signal by putting a 4.7 µF capacitor on the output of the instrumentation amplifier, but this does not remove the 60Hz noise.

When I tense the biceps, I get low frequency signals—spikes about 10 msec long and about 0.2v high. Given that the gain is about a hundred, the signals from the electrodes must be about 2 mV.  I ran off of batteries initially, to avoid problems with noise from the wall wart, but after I got it working, I tried a 5v wall wart (with a 100Ω resistor and 470µF capacitor, to remove the worst of the ripple from the power supply), and it worked fine also.

Here we can see a couple of pulses with the muscle tensed. The scale is 0.2V per division vertically and 10msec per division horizontally, so the two pulses in the center are about 0.12 V high and 16msec apart.

Having had this success with EMG signals, I decides to try electrocardiogram signals also (ECG or EKG). Most of the info on the web is about 12-lead EKG systems, but I want to use only 3 wires. I found a nice reference intended for nurses that describes where to place electrodes for 3-lead, 5-lead, and 12-lead systems. I tried using the MCL1 setup in Figure 4.3

Placement of EKG electrodes for modified central lead (MCL1), copied from Figure 4.3 of An ECG Primer by Nursecom Educational Technologies (without permission).  The text says that the ground electrode can be anywhere on the body, so I left it on my left elbow.

Interestingly, the ECG Primer refers to any pair of electrodes as a “lead”, which does not match usual electrical engineering usage (in which a “lead” is a wire and corresponds to a single electrode).

With the MCL1 placement of the electrodes (in the hollow below the left shoulder and between the ribs just to the right of the sternum), I was able to get EKG signals.  The depolarization pulses are about 50mV (which means about 500 µV at the electrodes), but the background noise is still bothersome.  I added a very simple RC low-pass filter between Vout and the oscilloscope (3.9kΩ and 4.7µF), and reduced the noise to less than 5mV, while still getting 40–50mV depolarization peaks. Replacing Rgain with a 100Ω resistor increase the spikes to about 300 mV.

With a little more amplification and a slightly lower-pass filter, this should be good enough to feed into an Arduino ADC, and test out the data logging program my son has been writing.

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