Biofeedback development with HAL-4 EEG
The SW I develop can register and save brainwaves (and optionally hearth pulses) using 4 channels and Egely Wheel 'bioenergy detector' (see photo below) pulses (made from one of the two event switch channels) plus the free event switch.
While measuring or replaying, brainwave impulses and spectrum map can be seen in windows, together with the rotation speed of the wheel.
Saved screen from EEG registration
Original HAL PCB scanned:
Basic HAL 80C31controller EPROM and DOS measuring SW with source
Third party SW for HAL from BYTE Magazin issues
Modifying HAL-4 (cf. Tech. Manual):
1. Simply changing R25 (47 ohm) to e.g. 120 ohm decreases (and balances)
power drain and still enough to drive LED1 and TIL111 opto coupler (as I use it now).
2. 9V battery can be omitted (like all well-educated mice have done it;-))):
connect green phone cable (from Pin 2, TX, not used) to DTR (Pin 20) of serial connector. It's important to put a diode (open direction from serial connector to HAL) before the green cable to protect HAL from negative volts
(RS-232 works using +/- voltages, practically +/-12 V on PCs). If DTR is active and pulled up to +12 Volts, it ensures the required current (< 20 mA) for the 7805 regulator (HAL's 'opto-separated part' to the PC) and drives
MAX232. For this, also connect the 3rd pin (to green cable) of the phone jack to the 9V battery connector (pin 1 or 4) instead of the battery.
It's also important that the original demo software WILL NOT work, after this change the source code must be modified and recompiled to ensure the usage of the DTR line.
I haven't done it myself, I re-write the code in Delphi for using it under
Windows and to add some features (samples store to file for registration, etc.)
and extra HW (Egely Wheel) to one
event switch port.
3. I expanded the bandwith (low freq. to 1 Hz, about high to 25 Hz by modifying RC elements of the filters) and have changed EPROM SW of 80C31 to 9600 Baud transmit rate and made some oversampling to 128 samples per sec.