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CleverHand - EMG

Modular & portable high-density dry sEMG acquisition devices

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Robotic prostheses are highly sophisticated devices, which imply very expensive components to provide acceptable performances. Consequently, it is almost impossible to find effective hand prostheses for less than tens of thousands of euros. To tackle this issue, we are designing the "Clever Hand", a low-cost alternative for high-density electromyography (EMG).

Requirements:

ConstraintStatusComment
WearablehammerWifi feature in progress
>16 channelsheavy_check_markUp to 128 channels (16x8)
>2kHz bandwidthheavy_check_markUp to 2.5kHz
>=16 bits resolutionheavy_check_markUp to 24bits
Bipolar/Monopolarheavy_check_mark
Modularheavy_check_mark1 to 16 modules by bus
Affordableheavy_check_mark<15€ per module
Opensourceheavy_check_mark

Other features:

  • 8 onboard electrodes
  • Flexible ADC-electrodes rooting
  • 1 shared ext. electrode
  • 4 RGB LEDs
  • Ethernet & USB (& soon WiFi) interface

  • SPI selection trick

    Aightech11/23/2022 at 11:27 0 comments

    SPI buses are very fast however the number of wires needed increases with the number of modules connected to the bus. In this project, we are limited by the number of connections as we cannot afford to have 3+16 lines just for communication.

    A solution would be to create an addressing system to select a module on fewer buses. A standard addressing system requires a hard-coded address for each module. It could be done with pads to solder on each board to set their individual address. Unfortunately, this system is not very modular as it forces each module to be "differentiated".

    A solution I came up with after chatting with my father is :

    Addressing the module by their order on the bus.

    The addressing system works on 4 wires. Each module read the 4 bits address present on the 4 wires and then increments by one the address for the following module. Each module is activated only if they read 0xF (0b1111, 15). Indeed, when the module tries to increment 0xf, it activates a carry bit connected to the chip select of the chip!

    Here a schematics providing a visual explanation of the system:

  • LEDs testing

    Aightech11/23/2022 at 10:01 0 comments

  • First versions

    Aightech11/20/2022 at 12:14 0 comments

    Some pictures of the previous iterations of this project

    From very simple analogue OpAmp circuits I designed to amplify a single EMG signal, I went to create modular multichannel digital devices!

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