Hardware

BrainAccess hardware is exclusively based on dry-contact electrodes.

The electrodes have been developed to be optimal in terms of size, signal quality and comfort. They feature 12 gold-plated spikes, each spike is spring-loaded allowing for the electrode to conform to the curvature of the head, therefore, increasing the comfort when compared to standard dry-contact electrodes. The back of the electrode is shielded to ensure maximum isolation from external noise sources. For EEG measurements where there is no hair, gold-plated pad electrodes are used instead of spike electrodes for improved contact and comfort.

BrainAccess electroencephalographs are wireless, lightweight, battery-powered devices in order to make them truly portable devices that can be used in different environments. They feature multi-channel EEG inputs with a common reference channel and also additional data inputs such as the accelerometer. They offer active noise suppression and come with shielded mini cables to minimize the effects of the surrounding environment. Multiple electroencephalographs can be connected to the same computer for multi-user experiments and applications. Multiple electroencephalographs can be synchronized in time-sensitive applications.

BrainAccess headwear offers usage flexibility, BrainAccess CAP is available in different sizes and with a different number of electrodes. The CAP follows the standard 10-20 system with a large number of available mounting positions for electrodes.

BrainAccess MINI

BrainAccess MIDI

BrainAccess CAP

BrainAccess MINI

The BrainAccess MINI is a 8-channel electroencephalograph with a common reference channel.

Its compact size, Bluetooth connectivity and long battery life make it a truly portable device.

Overview

USB Bluetooth adapter

The device comes with a USB Bluetooth 4.2 adapter, which is used to communicate and stream data to the computer from BrainAccess MINI. If preferred, a different Bluetooth adapter such as an integrated Bluetooth adapter in a laptop may be used instead.

Power switch

Press and hold a push-button for a couple of seconds to turn the device on/off. Power LED will be lit when powered on.

Charging port

The device's battery can be charged via a micro-USB port using standard 5V chargers such as mobile phone chargers with a micro-USB plug. The charger should be capable of providing at least 800 mA of current. Do not use the device when charging with chargers powered from grid electricity due to safety reasons and potentially 50/60 Hz noise affecting the signals. The device can be used when charging from a power bank though.

Power LED

It is a red-colored LED that indicates when the device is powered on. If the power LED starts blinking, it indicates that the battery level is below <10% and needs charging soon.

Connection LED

It is a blue-colored LED that indicates when a Bluetooth connection is established between a computer and the device.

EEG inputs

These inputs should be connected to electrodes that measure EEG activity with respect to the reference electrode.

Reference input

An input that should be connected to a common reference electrode. In BrainAccess Kit setups it is typically an electrode placed at the Fp1 location. The connection is denoted as 'R' on the device.

Bias input

An input that should be connected to a bias electrode. In BrainAccess Kit setups it is typically an electrode placed at the Fp1 location. The connection is denoted as 'B' on the device. It is a driven bias that which reduces the common mode noise such as noise coming from the grid electricity. The bias signal is derived from any of the EEG inputs which can be chosen in software. They are denoted as `bias feedback channels' in software. Use only channels/electrodes that have good quality signals for bias feedback.

Digital input

The device has an additional digital input that is sampled at the same rate as EEG signals and is treated as an additional input channel in software. It can be used for connecting external sensors or for synchronizing multiple BrainAccess MINI devices. The digital input is internally pulled high and is driven low when input contacts are closed. An external switch or open-collector/open-drain circuits can be used to close the digital input contacts and drive the digital signal low.

Accelerometer

The device has an integrated 3-axis accelerometer. It can be used for example to record any body/head movements when it is attached to the EEG cap. The accelerometer data comes as 3 additional input channels in the software.

Velcro tape attachment

A velcro tape can be found at the bottom of the device that can be used to attach it to the BrainAccess CAP.

Set-up

If not connected, connect the electrodes to the BrainAccess MINI EEG inputs.
Press the power push button and hold for a couple of seconds, the power light should be lit-up indicating the BrainAccess MINI has turned on. If not, the battery might be empty — charge it first.

For Microsoft Windows users:

Plug in the provided Bluetooth adapter to your computer, the drivers should install automatically. Skip this step if using an integrated or some other installed Bluetooth adapter.
Find BrainAccess MINI on the list of available Bluetooth devices and connect to it.
Go to “Bluetooth & other devices” settings, under the “Related settings” section click on “More Bluetooth options”. A new window will pop up, select the “COM Ports” tab and look for a port with an “outgoing” direction. Note down this COM port as you will need it when connecting to the BrainAccess MINI.
Follow the BrainAccess software installation instructions and set up here to start recording EEG data.

For linux users:

Plug-in Bluetooth adapter. Skip this step using an integrated Bluetooth adapter. Connect to the device via Bluetooth. If using Ubuntu/GNOME, this can be done through the GNOME Control Center, or using the bluetoothctl or bluez tools.
Install the bluez-utils package (Ubuntu/Debian: sudo apt install bluez-utils)
Enter the following command: sudo rfcomm bind , where:is the port you will enter into the application to connect to the device (/dev/). By default, you should use rfcomm0is the Bluetooth address of the device (example: B8:F0:09:AA:28:6A) Example command: sudo rfcomm bind rfcomm0 B8:F0:09:AA:28:6A (replace this address with your device address) This step has to be repeated every time the PC is restarted.
Once finished, you can do sudo rfcomm unbind to remove the port and free it for usage by another EEG device.
Follow the BrainAccess software installation instructions and set up here to start recording EEG data.

Specifications

Specifications of BrainAccess MINI electroencephalograph.

Connectivity
Type	Bluetooth 4.2
Range	up to 10m (using the provided Bluetooth adapter)
EEG Input Channels
Number of channels	8 + common reference channel
Sampling frequency	250 Hz
Input resolution	24 bits
Analog gain values	1, 2, 4, 6, 12, 24
Input voltage range	4500 mV / gain value (w.r.t. reference channel)
Input connector	Ultra-mini RF coaxial connector
Digital Input Channel
Type	internally pulled-up, driven low by closing the input contacts
Sampling frequency	250Hz
Connector	JST right-angle, 2 mm pitch, cable with a plug also provided
Accelerometer
Number of axis	3
Sampling frequency	50Hz (resampled to 250Hz in software)
Range	+/-2g
Resolution	10 bits
Battery
Type	Li-Po
Capacity	1500 mAh
Operating time	up to 6 hours (continuous streaming, all channels turned on)
Charging time	2 hours
Charger input	5V 800 mA min (charger not included)
Charger connector	micro-usb
Mechanical
Mass	70g
Dimensions	68x50x21 mm

BrainAccess MIDI