Punch Sensor Prototype

[Dr_Awesome]

Hi guys, I built a prototype for a punch sensor for my latest blog post.

The sensor itself sucked, but it was enough to show it could be done right with a little more work.

Last time we had an Austin throwdown, I had a blast on the mat, but there were zero strikers there. I will really need at least one or two more strikers to come out next time, because my goal will be to get a next generation up and working by then, and I want to take some data from people I don't actively train with.

The video:

The blog entry:
http://theamazingdoctorawesome.blogs...prototype.html

[W. Rabbit]

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Dude, you had me at "sucking electrons" and piezoelectric transducers. I had this very project on my list a couple years ago...some other project swallowed up my time.

You can make this baby wireless with very little redesign. Would you mind posting a circuit diagram?

http://www.springerlink.com/content/u384l21733741424/

[Dr_Awesome]

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Dude, you had me at "sucking electrons" and piezoelectric transducers. I had this very project on my list a couple years ago...some other project swallowed up my time.

You can make this baby wireless with very little redesign. Would you mind posting a circuit diagram?

http://www.springerlink.com/content/u384l21733741424/

Cool. Thanks. Obviously, I need to get one that works well first, but that's a good idea. Here is a hastily drawn circuit diagram. Should you ever pick up a project like this, I will be happy to send you the program I used to plot it out and make the calculations (nothing fancy, but it works). just send me a message and I'll email it to you.

[Dr_Awesome]

/subscribe

Dude, you had me at "sucking electrons" and piezoelectric transducers. I had this very project on my list a couple years ago...some other project swallowed up my time.

You can make this baby wireless with very little redesign. Would you mind posting a circuit diagram?

http://www.springerlink.com/content/u384l21733741424/

[W. Rabbit]

I had a couple of thoughts.

First, LEDs!

Second, I noticed all your graphs were in the time domain, but you are generating AC in the frequency domain (crystals!).

What is the Ardruino's sample rate for analog in? If it's not high enough and without other components you could be losing information. I doubt it's being lost on the dummy side of the circuit. :)

[hungryjoe]

Century Martial Arts had a sensor integrated into a bag around twenty years ago. I don't remember seeing it in a catalog. My instructor at the time worked there, so perhaps it was a prototype.

Being off target just a bit changed the reading dramatically.

[Dr_Awesome]

I had a couple of thoughts.

First, LEDs!

Second, I noticed all your graphs were in the time domain, but you are generating AC in the frequency domain (crystals!).

What is the Ardruino's sample rate for analog in? If it's not high enough and without other components you could be losing information. I doubt it's being lost on the dummy side of the circuit. :)

[Dr_Awesome]

I had a couple of thoughts.
What is the Ardruino's sample rate for analog in? If it's not high enough and without other components you could be losing information. I doubt it's being lost on the dummy side of the circuit. :)

[Dr_Awesome]

Century Martial Arts had a sensor integrated into a bag around twenty years ago. I don't remember seeing it in a catalog. My instructor at the time worked there, so perhaps it was a prototype.

Being off target just a bit changed the reading dramatically.

I've seen a few other different, either in the form of gloves or targets, and they almost always measure "force" which makes no sense to me. "Force" is easy to measure (your bathroom scale is an excellent force meter), but a punch has a very rich force curve over time, and whether they measure it by "peak force" or "total force" it still doesn't tell you anything important about a punch. Someone could easily lean on you and apply more "force" than you would feel with a knockout punch. Do you remember what those sensors did if you leaned on them or just pushed them with your hands? Did it end up teaching you to just push really hard after impact each time?

Directionality is a tough issue to deal with, which was why I tried using three sensors in parallel, but it is tough to make them identical when you do it by hand.

I really cannot stress how much you need to measure both energy and momentum for it to make any sense...

[hungryjoe]

I've seen a few other different, either in the form of gloves or targets, and they almost always measure "force" which makes no sense to me. "Force" is easy to measure (your bathroom scale is an excellent force meter), but a punch has a very rich force curve over time, and whether they measure it by "peak force" or "total force" it still doesn't tell you anything important about a punch. Someone could easily lean on you and apply more "force" than you would feel with a knockout punch. Do you remember what those sensors did if you leaned on them or just pushed them with your hands? Did it end up teaching you to just push really hard after impact each time?

Directionality is a tough issue to deal with, which was why I tried using three sensors in parallel, but it is tough to make them identical when you do it by hand.

I really cannot stress how much you need to measure both energy and momentum for it to make any sense...

Point being, F=ma equals nothing if you're not on target.

Enjoying the read. Looks as though you're moving forward.

[cereus]

So tell me, as an MA noob and borderline Luddite (through laziness if I'm honest), what exactly would you like your punch sensor to tell us that other sensors don't?

[Dr_Awesome]

So tell me, as an MA noob and borderline Luddite (through laziness if I'm honest), what exactly would you like your punch sensor to tell us that other sensors don't?

Momentum Transfer and energy transfer.

Momentum transfer tells you how much you push your opponent (or parts of your opponent, like his head or his hands or the air in his lungs).

Energy transfer is associated with structural damage to the local tissue and pain.

Most sensors measure "force" because it is easy to measure, and in colloquial english the word "force" sounds like an awesome things to measure for a punch, but the actual physical quantity is not helpful to us unless we plot the whole curve over time and then translate that curve into momentum and energy.

I tried to spell out some of these distinctions in a prior blog entry here:
http://theamazingdoctorawesome.blogs...our-fists.html

[W. Rabbit]

You can try digitizing using an ADC, and feed the Arduino digital in values from that in instead of analog current/voltage directly from the sensor.

http://www.maximintegrated.com/app-n...ex.mvp/id/3775

[hungryjoe]

Dr_Awesome,

Are you using an accelerometer chip in your setup?

[cereus]

Now that it's been spelled out to me I am very interested in seeing where this goes. I never felt like force ever gave a clear picture.

Can you give examples of what punches (perhaps to which targets) might require more "push" or "snap". I haven't done any striking for the past 10 years and tkd from 8-14 didn't really give me any real education in the matter.