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Author Topic: Accelerometer/gyro data to serial port using bluetooth.  (Read 4579 times)

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Offline SerasTopic starter

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Accelerometer/gyro data to serial port using bluetooth.
« on: November 30, 2014, 05:15:44 PM »
Hi I am looking for a way to send accelerometer/gyro data via Bluetooth. My thoughts so far are to use an RFduino and something along the lines of a MPU-6050 but since I am on a limited size factor (somewhere along the lines of the outermost bit of a thumb) I do not want to use breakout boards. Here is an example of what I want to achieve but without using the breakout boards (or at least get the finished product really tiny):

(Any help on the matter would mean a lot to me, thanks in advance  ;D)
I still haven't bought any electronics so I am still not limited to anything so if you have a better idea please tell me.
/Seras
« Last Edit: November 30, 2014, 05:17:39 PM by Seras »

Offline Gertlex

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Re: Accelerometer/gyro data to serial port using bluetooth.
« Reply #1 on: December 01, 2014, 07:48:31 PM »
I haven't looked at how small the bluetooth adapters out there get, but I think they get on the order of the size of my last thumb section... I could see an approximately thumb tip sized sandwich of mpu6050 breakout | custom perfboard with basic MCU chip | bluetooth chip/board.

Other than that, I don't have a specific idea in mind, but am instead probing at your requirements to see how flexible they are...

Is bluetooth a requirement? I've had so-so results using bluetooth in practice, but also haven't personally used any wireless solutions of the size you're after.

What are you planning to do to power this small wireless IMU setup?
I

Offline SerasTopic starter

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Re: Accelerometer/gyro data to serial port using bluetooth.
« Reply #2 on: December 02, 2014, 01:05:19 PM »
I haven't looked at how small the bluetooth adapters out there get, but I think they get on the order of the size of my last thumb section... I could see an approximately thumb tip sized sandwich of mpu6050 breakout | custom perfboard with basic MCU chip | bluetooth chip/board.

Other than that, I don't have a specific idea in mind, but am instead probing at your requirements to see how flexible they are...

Is bluetooth a requirement? I've had so-so results using bluetooth in practice, but also haven't personally used any wireless solutions of the size you're after.

What are you planning to do to power this small wireless IMU setup?

"The RFduino has Bluetooth 4.0 Low Energy built-in"

And it is pretty small so the only problem is to get an accelerometer on it and with its 7 io's it should be able to handle the signals from an mpu-6050 parallel?

Edit: Forgot the "What are you planning to do to power this small wireless IMU setup?" question.
I dunno just a small battery of at least 150 mAh would probably suffice for 3 hours run time?
« Last Edit: December 02, 2014, 01:09:55 PM by Seras »

Offline Gertlex

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Re: Accelerometer/gyro data to serial port using bluetooth.
« Reply #3 on: December 02, 2014, 03:20:53 PM »
Whoops. I completely missed that your image showed the RFDuino on the left. (I assumed it was just the layout for an MPU6050 breakout, and that you had pulled the image from a seller's site...)  I also wasn't aware the RFDuino wasn't just yet another Arduino form-factor board, heh.

Seems straight forward to just put one on top of the other, possibly with double-sided foam tape, and then solder the resistors/wires where they're needed.  I do this sort of thing commonly with my own projects.

Not sure if you can directly put, e.g. a 1S Lipo powering the RFDuino. If you can't, one solution might be this small board.

I'm not aware of a smaller MPU6050 breakout, unfortunately. But its .8" length seems like it shouldn't be too bad.
I

Offline SerasTopic starter

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Re: Accelerometer/gyro data to serial port using bluetooth.
« Reply #4 on: December 02, 2014, 03:29:57 PM »
How do you know where a resistor etc. is needed? And do you think it would be better
/easier to use serial data? (programming wise?)

Edit: Also it says this about the RFduino:
Low Supply Voltage   1.9V
Typical Supply Voltage   3V
High Supply Voltage   3.6V
« Last Edit: December 02, 2014, 03:35:13 PM by Seras »

Offline Gertlex

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Re: Accelerometer/gyro data to serial port using bluetooth.
« Reply #5 on: December 03, 2014, 10:31:51 AM »
Resistors for what?

Your interface would be:
MPU6050 --i2c--> RFDuino --???--> Primary data recording device.

You can't communicate with the MPU6050 via serial, as far as I know. You would almost definitely use this library on the RFDuino, which manages the i2c to the MPU6050 for you: https://github.com/jrowberg/i2cdevlib/tree/master/Arduino/MPU6050

Looks like if you use a LiPo, you would need a regulator such as the one I linked in my previous post, since LiPos get up to 4.2 V when fully charged. If you can find a LiFePo4 battery of the desired form factor (I couldn't find one on ebay/hobbyking just now), that would allow you to directly power the RFDuino. The power input limits on the MPU6050 may also need to be considered.
I

 


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