Cheap DIY motion capture.

[flysouth]

Now you can get all those poses for your characters at a very low cost.... :mrgreen:

http://hackaday.com/2016/09/13/bewegungsfelder-is-a-wireless-imu-motion-capturing-system/

If anybody is actualy interested in this I can assist. I have done designs with these modules in the past.

[deathbravo]

interesting project. thanks for the recommendation.

[chriscalef]

@flysouth I am very interested! Have you experimented with these units? I've been thinking somebody should be doing exactly this for years but I never went there myself, so glad to hear somebody else did! Love it when that happens! :-)

Thanks for the link!

[flysouth]

@chriscalef - I have used these units but not for doing motion capture.

[chriscalef]

Right on.

Well, I downloaded, built and ran the c# project from github, no problems there. And I found many sources for the MPU6050 units, some of them getting down to less than $2 each!

I'm a little confused about the rest of the pictured hardware, however, and am not experienced at the circuit construction / arduino end of things at all. Clearly you need a wifi chip for each one, and then some other stuff. I didn't look exhaustively but so far haven't found the guide for building his sensors. Any idea what the rest of the parts are and how they might go together?

[flysouth]

The ESP8266 is a WIFI module. It can be controlled using 'AT' style commands from an Arduino or PC.

You can also download the ESP8266 SDK and program it directly, then you dont need the Arduino which I think they are doing.

The ESP8266 is a very capable device. It comes standard with a built in web server too. It has firmware that allows it to be programmed in Python etc.

So it can be configured as a server or client and it is fairly cheap.

The movement sensor is connected to the ESP8266 using an I2c bus.

In the code they define the pins as:

// SDA on GPIO4
#define I2C_SDA_MUX PERIPHS_IO_MUX_GPIO4_U
#define I2C_SDA_FUNC FUNC_GPIO4
#define I2C_SDA_PIN 4

// SCK on GPIO5
#define I2C_SCK_MUX PERIPHS_IO_MUX_GPIO5_U
#define I2C_SCK_FUNC FUNC_GPIO5
#define I2C_SCK_PIN 5

[flysouth]

Just to add to the above...

SDA & SCK (SCL or SCLK) are the names of the pins on the I2C bus. So if you find the datasheet for the MPU6050 board that you want to use there will be an SDA & SCK pin on it. Those pins would be connected to GPIO4 & GPIO5 on the ESP8266 module.

If you search for the ESP8266 you will find that there are various PCB's that you can purchase. Some have more pins and others. Just make sure the one you use has GPIO4 & GPIO5 on it

Datasheet for MPU6050: https://www.cdiweb.com/datasheets/invensense/MPU-6050_DataSheet_V3%204.pdf

Of course the diagram I have shown is if you connected the MPU6050 IC to the WIFI module. Unless you make your own PCB you would need to see which pins are being used on the MPU6050 PCB you purchase

I hope this helps

[chriscalef]

Wow, okay, so take it slow with me here for a second...

In terms of the chips themselves, if I'm satisfied with a slow boat from China it looks like here's an example of where I could find the MPU:

https://www.aliexpress.com/item/GY-521-MPU-6050-MPU6050-Module-3-Axis-analog-gyro-sensors-3-Axis-Accelerometer-Module/32340949017.html

And here's a potential 8266 source:

http://www.gearbest.com/transmitters-receivers-module/pp_227650.html?currency=USD&gclid=CJ7mjpzuks8CFYllfgodEqAKlQ

There are many options but it looks pretty easy to end up with both of those for under five bucks.

However, what else do I need then? Apparently some perf board that I'd cut up into little squares... (total novice here, sorry). And then I'm not sure what the white board is that they've attached the 8266 to, but I'm not seeing any chips I can buy that come with that, yet.

And then, a couple of resistors and those two buttons - don't know what they're used for but they're probably important.

And, any guesses as to how this little bad boy would be powered? I don't see any wires leading to a battery pack, so maybe he's got a little button battery sandwiched between the two squares of perf board? Any idea how I'd figure out how much power I'd need for this little rig? I might also be tempted to run wires from a wearable battery pack, just because button batteries are so evil (we don't have little kids but I've heard terrible stories online about what happens when they get eaten). :-0

Oh, and then last question, do you suppose my typical home comcast router would be able to juggle twenty or so wifi signals all streaming UDP data to my PC, or would I need a fancier wifi router?

Oh yeah, and then _really_ the last question, ;) how do you go about programming these things? I guess he's got the drivers included in his github project, but how do I go about transferring them from my PC to each unit? USB cable with an end to match those pins, I guess?

Thanks again for bringing this up and bearing with my ignorance! I do have a friend nearby who can help me with the physical manufacturing aspects if I can figure out the technical details.

This is exciting stuff! I've seen accelerometer based mocap suits going for well into the five digits, I'm very much liking the sound of a low three digit competitor to that!

[flysouth]

The white board looks like it might be an Arduino shield. You dont need that if you are happy to solder wires or pins into the ESP8266.

The docs for the ESP8266 are poor but if you google it you will find a lot of info because it has a very large fan base.

Take a look at this page: http://hackaday.com/2015/03/18/how-to-directly-program-an-inexpensive-esp8266-wifi-module/

To program it you need a USB to TTL converter here: https://www.adafruit.com/product/954 or search for USB to TTL on alliexpree. Look for the one that does 5v and 3.3v. Note that the ESP8266 works on 3.3V so make sure you use that setting on USB to TTL converter

Buttons and resistor for reset.

Put this "ESP8266 to MPU-6050 circuit" into Google an you get this... http://www.esp8266-projects.com/2015/12/mailbag-mpu6050-module-i2c-driver-init.html

SOmething you might have noticed on the first link in this post. There is a way to make the ESP8266 work using an Arduino setup. Then you will find plenty of code to connect a MPU-6050 to an Arduino. That means all the code is done already... just a thought.

You will need to use a 3.3v votage regulator to power the circuit. You could then use a small 9v battery to power everything. I am not sure how long it would last, I have not tested it with a small battery.

Who can help you with manufacturing... I could maybe help with that, let me know what you have in mind

Regarding the router I dont know for sure but I think it will work.

[chriscalef]

Huh, okay. Thanks for the info!

Arduino shield sounds useful, I'm into doing less work whenever possible. :-)

Can't allow this project to creep onto the front burner right now, but I'll definitely pick up at least a sample kit and see if I can get anywhere. Thanks again for your help!

[chriscalef]

Okay, well, just for the record, I got all crazy and ordered three of these:

http://www.miniinthebox.com/the-latest-mpu-6050-6000-6-axis-gyro-accelerometer-module_p4348915.html

And then three of these:

http://www.banggood.com/ESP8266-ESP-12E-Remote-Serial-Port-WIFI-Transceiver-Wireless-Module-p-980984.html

Will report back when they arrive, and look into the other parts in the meantime.