Pulse Necklace

From Noisebridge
Revision as of 11:14, 20 August 2009 by Cmaier (Talk | contribs)

Jump to: navigation, search

A choker (tight necklace) which measures your heartbeat (pulse) and shows it to others via a set of LEDs. It may also optionally communicate the same info to the wearer via a vibrator. Although theoretically heart rate should be known via senses intrinsic to humans, in practice it is actually quite difficult to know, and I think there are many interesting social interactions that pulse-display could trigger.

Currently Eric Boyd and Chung-Hay are working on this device.


Design Thoughts


Generally all commercial ones a just little electrocardiogram units.

From http://en.wikipedia.org/wiki/Electrocardiography :

"An electrocardiogram is obtained by measuring electrical potential between various points of the body using a biomedical instrumentation amplifier. A lead records the electrical signals of the heart from a particular combination of recording electrodes which are placed at specific points on the patient's body."

However, for this project I think the best solution may be optical. There is apparently a small change in the optical properties of your skin with your blood pressure, meaning that pulse can be observed by an optical sensor pressed against your skin. I have a working "pulse watch" which uses this principle.

Display: Initially, only to people other than the wearer, via a string of LEDs inside the choker. I imagine the pulsing centered on the LED in the center, and going out to all, then coming back in, similar to how some star trek (?) lights worked when the computer talked. There may also be a lone vibrator, which could be used to signal to the wearer a variety of things (like pulse, but also time or low battery etc). Although this is really stretching the definition of "display", the device might also log data for later retrieval via USB.

Armature: Choker, plus it is likely that it will have to have a pendant hanging from it, which would contain the circuit and battery. The vibrator might also be in the pendant. The hard part of the armature will be how to wire the LEDs in a "soft" way (no ribbon cables around our necks!). Also, the optical sensor will have to be held against the neck even while the neck moves, you breathe, etc - that might be tricky. We have experimented with conductive thread with crimp beads, but they are very difficult to use, and end up being more fragile than is really acceptable. We are presently investigating silk-screening conductive paint, and flexible PCBs are possible armature ideas.

Electronics: For prototype, arduino and probably a small op-amp circuit modeled on the circuit inside the watch. To make it wearable, we'll probably have to use an attiny or other similarly super small device.

Prior Art

I already have a set of chokers with surface mount LEDs inside (I've shown this at prior meetings during show and tell). I am unsure of how the LEDs are wired - it's possible that they are all controlled from the same wire, in which case the device will not be able to display as above, and instead will simply flash. I got the chokers from Rebeccas for only $2.15 each, so if they are suitable they make great kit components.

Reverse engineering the choker's flexible PCB:

Lights: 1-12, counted from the batteries
  (Only lights 1, 3, 5, 6, 7, 8, 10, 12 are populated)
Pins: 1-6, counted from the big ground of the batteries nearest the ribbon cable

Schematic Reverse Engineer:
Pin 1: V+ for all lights
Pin 2: V- for 1, 3, 5
Pin 3: V- for 2, 4
Pin 4: V- for 6, 8
Pin 5: V- for 7, 9, 11
Pin 6: V- for 10, 12

Apparently the LEDs are very easy to fry, since both green and pink choker now have many non-functional LEDs

I've done some google searches, but I haven't been able to find anything like this. There are some pulse-sensing watches, for instance Chinavasion: Exercise Watch - pulse + calorie reader or see some reviews at Heart Rate Monitors. These devices almost universally have a small display, but I think a haptic solution could be greatly superior.


You can see in the image a small heart on the left side of the display. When it's sensing your pulse, this heart blinks with your pulse, which is super cool. The sensor is under my index finger on the right hand side. You need to just touch the sensor - if you press hard, that destroys the signals (presumably because the pressure makes it so your skin doesn't respond to the pressure of your blood and instead just responds to the pressure of your hold...)

Technicolor Dreamcoat

Cmaier 09:56, 20 August 2009 (PDT)
added references Cmaier 10:37, 20 August 2009 (PDT)
added reference, minor formatting Cmaier 10:45, 20 August 2009 (PDT)
minor edits Cmaier 10:46, 20 August 2009 (PDT) and Cmaier 11:14, 20 August 2009 (PDT)

Just some thoughts I had, but now it needs to be made Prior Art immediately (If you talk with the lanista of the Circus Maximus about a possible engagement, you need to be super careful that you, or your ideas, don't stay there inadvertently and get fed to the lions without you getting paid):

It would be ultra cool to wear a Technicolor Dreamcoat costume at Burning Man studded with a network of blinkenlights, where the blinking color patterns of your costume would give information about your heartbeat, blood chemistry, and more ...

On the Technicolor Dreamcoat, each blinkenlight is attached to its own microcontroller that, in turn, is also attached to an array of sensors (starting with an infrared LED and a sensor for heartbeat and pulse oximetry, but by no means ending there), and with the microcontrollers communicating with each other (and maybe wirelessly with other costumes or a Central Scrutinizer). A network of sensor studded processor nodes means that you have a lot of redundancy to separate the wheat (the signal[s] you're interested in) from the chaff (artefacts due to you moving around, external interference, or some wardrobe malfunction), and a lot of distributed processing power, so you don't really need quite as efficient algorithms as if you put all your processing power in one place - death of the big hunkin' DSP board by a thousand arduinos (yes, you'd have to come up with distributable algorithms, but I've heard rumors that all the web weenies who want to join the cloud computing bandwagon are already trying this, anyhow).

For starters (since I neither have the time nor the $$$ to afford really cool sensors and write complex programs), it would be nice to just have the microcontroller (or maybe CPLD or some such) nodes with the blinkenlights, talking to each other in such way that they play the Game of Life, would fit nicely into this years' Burning Man theme of "Evolution". In fact, I already bought two white jumpsuits, put some LEDs on order, and did some inquiries how to get stuff from DigiKey real fast. The missing bits are conductive thread or equivalent, and a way to build a lot of PCBs and program chips on them fast.

Of course, for more than one reason, a patient gown would be more suitable for such a kind of Technicolor Dreamcoat - cum - biosensor array - cum - distributed processing - cum - wireless Burning Man costume: The patient gown leaves the butt exposed.

Hack Notes

June 24th, 2009

July 1st, 2009

July 8st, 2009

July 15th, 2009

Circuit Research, July 21st, 2009

July 22th, 2009

Custom Stencil Design Research, July 28th, 2009

July 29th, 2009

August 2nd, 2009

August 5th, 2009

August 12th, 2009

August 16th, 2009

Lessons Learned Along the Way

Lessons on Conductive Paint

Lessons on Paint Thinning

Personal tools