In summer 2016, we met to build a low-cost brain-computer interface that you could plug into your phone. We want everyone interested in BCI technology to be able to try it out.
Two months later, we premiered the world’s first £20 BCI at EMF camp as ‘smartphone-BCI’.
As of summer 2017, we have:
- a simple, two electrode EEG kit that amplifies neural signals, and modulates them for input to an audio jack;
- a basic Android diagnostic app;
- an SSVEP Unity text entry app.
The v0.1 circuit reads a bipolar EEG signal and sends the signal out along an audio cable, for use in a smartphone, tablet, laptop, etc.
EEG signals are difficult to work with as they are very faint, and easily interfered with by other signals, including muscle movements and mains electricity – both of which are much more powerful. Also, the interesting frequencies range between 4Hz to 32Hz (depending on the intended use), but a smartphone sound card will filter out all signals below 20Hz.
Thus, the v0.1 circuit:
- amplifies the signals that comes from the electrodes, boosting them from the microvolt to the millivolt range;
- uses amplitude modulation to add a 1kHz carrier tone, allowing the signal to bypass the 20Hz high-pass filter behind the phone’s audio jack.