Noisebridge - User contributions [en]

Pulse Necklace 16Sept2009

2009-09-18T08:04:49Z

Chung-Hay:

=Pulse Choker Hack Notes, Sept 16th, 2009=

==New Stencil==

Our new stencil is here! It supports 5 independent control lines, with 7 LEDs total. We are still using the silver conductive paint, and the white mesh fabric (although the new mesh "organdy" is stiffer than the old mesh). We used paper as the backing during the painting step, but this turned out to be a mistake - pealing up the stencil was fine, but when we pealed up the mech fabric from the paper, over half of the paint went with the paper rather than staying with the fabric. This created several visible areas of lack of paint, which the multimeter confirmed as non-conductive spots (and the multimeter also confirmed that the paper has fully conductive traces, what a waste). We had to re-touch the paint job by hand.

On the up side, we had only a little bit of bleed, and once we removed the backing no traces were shorting with each other.

In the future, we should use a non-absorbent backing such as plastic to prevent this problem.

After all the touch-ups, we measured the resisitivity of each trace. Placing the stencil in an upside-down 'T' manner ( around neck __||||||__ around neck ), going from left to right, we had the following readings in ohms:

30, 14 or 60, 11, 41 on power line to the left, 34 on power line to the right, 21, 15

If we want the LEDs to be completely isoluminant, we need to account for the fact that different colored LEDs have different current needs and the differences in the above resistances.

==Progress on Wiring==

We had some serious trouble soldering headers unto the lower end of the display, so we switched plans. Instead, we hot glued a peice of thick paper to the traces (for stability and to prevent twisting, etc), and then soldered stranded wire to each of the paint traces. This worked well in 5/6 cases, the 6th case it seems that the hot glue somehow absorbed into the fabric and was preventing a proper solder connection - we had to move that solder connection up to an area without the glue.

Then we soldered LEDs to the other end of the paint traces, and resistors to the small stranded wires (500 ohm for single LED ones, 270 ohm for outside dual LED ones). A little shrink wrap to protect the resistors, and we're almost done.

==Out of Time==

But we ran out of time to finish the prototype tonight - we still need to wire it into the electronics, write code to support 5 LEDs, and see if the ECG stuff is still working after a month of down-time. We will meet again next Wednesday, and thence forth we'll meet on Thursdays as that will work out better for Chung-Hay due to wed night assignment deadlines.

==Pictures==

Pulse Necklace 12Aug2009

2009-08-13T04:37:35Z

Chung-Hay: /* 2-lead Open ECG Circuit */

=Pulse Choker Hack Notes Aug 12th, 2009=

==2-lead Open ECG Circuit==

We have received the [http://www.open-ecg-project.org/tiki-index.php?page=Small+2-Lead+ECG tiny little red board], and wired it up on a bread board, put on some Red Dots, and it works! We were able to observe 1V signal spikes in time with hearts.

However, one of the electrodes really did have to be over the heart. Moving to the other side of the chest or up to pendant location still worked, but signal was about 1/4 the size. Neck and arm electrodes showed nothing. We did get clear, beautiful signals from heart beat just below the pect and eye blink just outside the eye though.

We had a long discussion about how to proceed next - whether to try optical stuff again, or to try to work forward on ECG, or what else we could do.

We looked at stethoscopes (they are cheap, like $5, at Amazon), and that made us think again of acoustic techniques. Could we have a differential acoustic solution, involving two microphones, one of which is like a stethoscope and picks up your internal noises, and the other is external and provides a "reference" that you subtract from the first signal in order to cancel out background noises? We'd need to tackle some signal processing, perhaps using triangulation to separate out external sounds from internally generated sounds like heart beat and vocalization. Need a good common-mode-rejection op-amp but placement might be really tricky, since even just having the sound waves out of phase would make it totally broken. Maybe active noise canceling stuff could be useful too? Eric will look into this idea.

Chung-Hay did some research into neck-positioned optical solutions, and didn't find much. She did find a [https://www.noisebridge.net/images/5/59/Branche04-SensorPulseMilitaryHelmet.pdf paper] in IEEE on a military helmet with an optical blood-oxygen sensor. They claimed that forehead was the best location (better than chin, jaw, nape of neck). Forehead still wasn't as good as finger, but it was close.

We took a hacking break for some conductive body paint awesomeness - [http://www.youtube.com/watch?v=IObPkUFq0hg Humanthesizer]

Eric purchased a [http://www.numetrex.com/webapp/store/Shopping/product/STRP numetrex Fabric Chest Strap], which hopefully will allow us to use ECG without having to use those super painful Red Dots on chest hairs again ;-).

Pulse Necklace 12Aug2009

2009-08-13T04:32:10Z

Chung-Hay: /* 2-lead Open ECG Circuit */

=Pulse Choker Hack Notes Aug 12th, 2009=

==2-lead Open ECG Circuit==

We have received the [http://www.open-ecg-project.org/tiki-index.php?page=Small+2-Lead+ECG tiny little red board], and wired it up on a bread board, put on some Red Dots, and it works! We were able to observe 1V signal spikes in time with hearts.

However, one of the electrodes really did have to be over the heart. Moving to the other side of the chest or up to pendant location still worked, but signal was about 1/4 the size. Neck and arm electrodes showed nothing. We did get clear, beautiful signals from heart beat just below the pect and eye blink just outside the eye though.

We had a long discussion about how to proceed next - whether to try optical stuff again, or to try to work forward on ECG, or what else we could do.

We looked at stethoscopes (they are cheap, like $5, at Amazon), and that made us think again of acoustic techniques. Could we have a differential acoustic solution, involving two microphones, one of which is like a stethoscope and picks up your internal noises, and the other is external and provides a "reference" that you subtract from the first signal in order to cancel out background noises? Need a good common-mode-rejection op-amp but placement might be really tricky, since even just having the sound waves out of phase would make it totally broken. Maybe active noise canceling stuff could be useful too? Eric will look into this idea.

Chung-Hay did some research into neck-positioned optical solutions, and didn't find much. She did find a [https://www.noisebridge.net/images/5/59/Branche04-SensorPulseMilitaryHelmet.pdf paper] in IEEE on a military helmet with an optical blood-oxygen sensor. They claimed that forehead was the best location (better than chin, jaw, nape of neck). Forehead still wasn't as good as finger, but it was close.

We took a hacking break for some conductive body paint awesomeness - [http://www.youtube.com/watch?v=IObPkUFq0hg Humanthesizer]

Eric purchased a [http://www.numetrex.com/webapp/store/Shopping/product/STRP numetrex Fabric Chest Strap], which hopefully will allow us to use ECG without having to use those super painful Red Dots on chest hairs again ;-).

Pulse Necklace 12Aug2009

2009-08-13T04:30:54Z

Chung-Hay: /* 2-lead Open ECG Circuit */

=Pulse Choker Hack Notes Aug 12th, 2009=

==2-lead Open ECG Circuit==

We have received the [http://www.open-ecg-project.org/tiki-index.php?page=Small+2-Lead+ECG tiny little red board], and wired it up on a bread board, put on some Red Dots, and it works! We were able to observe 1V signal spikes in time with hearts.

However, one of the electrodes really did have to be over the heart. Moving to the other side of the chest or up to pendant location still worked, but signal was about 1/4 the size. Neck and arm electrodes showed nothing.

We were pleased by how clear the electrical signals from heart beat just below the pect and eye blink just outside the eye were.

We had a long discussion about how to proceed next - whether to try optical stuff again, or to try to work forward on ECG, or what else we could do.

We looked at stethoscopes (they are cheap, like $5, at Amazon), and that made us think again of acoustic techniques. Could we have a differential acoustic solution, involving two microphones, one of which is like a stethoscope and picks up your internal noises, and the other is external and provides a "reference" that you subtract from the first signal in order to cancel out background noises? Need a good common-mode-rejection op-amp but placement might be really tricky, since even just having the sound waves out of phase would make it totally broken. Maybe active noise canceling stuff could be useful too? Eric will look into this idea.

Chung-Hay did some research into neck-positioned optical solutions, and didn't find much. She did find a [https://www.noisebridge.net/images/5/59/Branche04-SensorPulseMilitaryHelmet.pdf paper] in IEEE on a military helmet with an optical blood-oxygen sensor. They claimed that forehead was the best location (better than chin, jaw, nape of neck). Forehead still wasn't as good as finger, but it was close.

We took a hacking break for some conductive body paint awesomeness - [http://www.youtube.com/watch?v=IObPkUFq0hg Humanthesizer]

Eric purchased a [http://www.numetrex.com/webapp/store/Shopping/product/STRP numetrex Fabric Chest Strap], which hopefully will allow us to use ECG without having to use those super painful Red Dots on chest hairs again ;-).

Pulse Necklace 12Aug2009

2009-08-13T04:24:39Z

Chung-Hay: /* 2-lead Open ECG Circuit */

=Pulse Choker Hack Notes Aug 12th, 2009=

==2-lead Open ECG Circuit==

We have received the [http://www.open-ecg-project.org/tiki-index.php?page=Small+2-Lead+ECG tiny little red board], and wired it up on a bread board, put on some Red Dots, and it works! We were able to observe 1V signal spikes in time with hearts.

However, one of the electrodes really did have to be over the heart. Moving to the other side of the chest or up to pendant location still worked, but signal was about 1/4 the size. Neck and arm electrodes showed nothing.

We had a long discussion about how to proceed next - whether to try optical stuff again, or to try to work forward on ECG, or what else we could do.

We looked at stethoscopes (they are cheap, like $5, at Amazon), and that made us think again of acoustic techniques. Could we have a differential acoustic solution, involving two microphones, one of which is like a stethoscope and picks up your internal noises, and the other is external and provides a "reference" that you subtract from the first signal in order to cancel out background noises? Need a good common-mode-rejection op-amp but placement might be really tricky, since even just having the sound waves out of phase would make it totally broken. Maybe active noise canceling stuff could be useful too? Eric will look into this idea.

Chung-Hay did some research into neck-positioned optical solutions, and didn't find much. She did find a [https://www.noisebridge.net/images/5/59/Branche04-SensorPulseMilitaryHelmet.pdf paper] in IEEE on a military helmet with an optical blood-oxygen sensor. They claimed that forehead was the best location (better than chin, jaw, nape of neck). Forehead still wasn't as good as finger, but it was close.

We took a hacking break for some conductive body paint awesomeness - [http://www.youtube.com/watch?v=IObPkUFq0hg Humanthesizer]

Pulse Necklace 12Aug2009

2009-08-13T04:23:29Z

Chung-Hay: /* 2-lead Open ECG Circuit */

=Pulse Choker Hack Notes Aug 12th, 2009=

==2-lead Open ECG Circuit==

We have received the [http://www.open-ecg-project.org/tiki-index.php?page=Small+2-Lead+ECG tiny little red board], and wired it up on a bread board, put on some Red Dots, and it works! We were able to observe 1V signal spikes in time with hearts.

However, one of the electrodes really did have to be over the heart. Moving to the other side of the chest or up to pendant location still worked, but signal was about 1/4 the size. Neck and arm electrodes showed nothing.

We had a long discussion about how to proceed next - whether to try optical stuff again, or to try to work forward on ECG, or what else we could do.

We looked at stethoscopes (they are cheap, like $5, at Amazon), and that made us think again of acoustic techniques. Could we have a differential acoustic solution, involving two microphones, one of which is like a stethoscope and picks up your internal noises, and the other is external and provides a "reference" that you subtract from the first signal in order to cancel out background noises? Need a good common-mode-rejection op-amp but placement might be really tricky, since even just having the sound waves out of phase would make it totally broken. Maybe active noise canceling stuff could be useful too? Eric will look into this idea.

Chung-Hay did some research into neck-positioned optical solutions, and didn't find much. She did find a [https://www.noisebridge.net/images/5/59/Branche04-SensorPulseMilitaryHelmet.pdf paper] in IEEE on a military helmet with an optical blood-oxygen sensor. They claimed that forehead was the best location (better than chin, jaw, nape of neck). Forehead still wasn't as good as finger, but it was close.

We too a hacking break for some conductive body paint awesomeness - [http://www.youtube.com/watch?v=IObPkUFq0hg Humanthesizer]

Pulse Necklace 12Aug2009

2009-08-13T04:12:39Z

Chung-Hay:

=Pulse Choker Hack Notes Aug 12th, 2009=

==2-lead Open ECG Circuit==

We have received the [http://www.open-ecg-project.org/tiki-index.php?page=Small+2-Lead+ECG tiny little red board], and wired it up on a bread board, put on some Red Dots, and it works! We were able to observe 1V signal spikes in time with hearts.

However, one of the electrodes really did have to be over the heart. Moving to the other side of the chest or up to pendant location still worked, but signal was about 1/4 the size. Neck and arm electrodes showed nothing.

We had a long discussion about how to proceed next - whether to try optical stuff again, or to try to work forward on ECG, or what else we could do.

We looked at stethoscopes (they are cheap, like $5, at Amazon), and that made us think again of acoustic techniques. Could we have a differential acoustic solution, involving two microphones, one of which is like a stethoscope and picks up your internal noises, and the other is external and provides a "reference" that you subtract from the first signal in order to cancel out background noises? Need a good common-mode-rejection op-amp but placement might be really tricky, since even just having the sound waves out of phase would make it totally broken. Maybe active noise canceling stuff could be useful too? Eric will look into this idea.

Chung-Hay did some research into neck-positioned optical solutions, and didn't find much. She did find a [https://www.noisebridge.net/images/5/59/Branche04-SensorPulseMilitaryHelmet.pdf paper] in IEEE on a military helmet with an optical blood-oxygen sensor. They claimed that forehead was the best location (better than chin, jaw, nape of neck). Forehead still wasn't as good as finger, but it was close.

File:Branche04-SensorPulseMilitaryHelmet.pdf

2009-08-13T04:09:57Z

Chung-Hay: IEEE Paper looking at potential places on a military helmet for placing a pulse oximeter. They found the forehead to yield signals fairly similar to that of the finger, which was not the case for the other locations - chin, jaw, nape (back of upper neck).

IEEE Paper looking at potential places on a military helmet for placing a pulse oximeter. They found the forehead to yield signals fairly similar to that of the finger, which was not the case for the other locations - chin, jaw, nape (back of upper neck).