This is a collection of resources on biopotential measurement
and next generation human-computer interfacing.

• Biofeedback Device Schematics
• Portable Biofeedback Devices
• Biopotential Measurement Theory
• Digital Signal Processing Theory
• Biofeedback/Neurofeedback Theory
• Brainwave Entrainment Resources
• Human Computer Interfacing Resources
• Affective Computing Resources
• Context-Aware Computing Resources
• Electromagnetics Resources
• ESP and PSI Resources

Biofeedback Device Schematics

• EEG - Electroencephalograph Schematics
• ECG - Electrocardiogram Schematics
• EMG - Electromyrograph Schematics
• GSR - Galvanic Skin Response Schematics
• Respiration Monitor Schematics
• Mind Machine (Light and Sound) Schematics
• Other Miscellaneous Schematics

EEG - Electroencephalograph Schematics

• Biosemi
  
  
  • Amplifiers for bioelectric events: a design with a minimal number of parts - This article includes a schematic for a low-noise multi-channel EEG that uses only 3 op-amps, 6 resistors, and two capacitors per channel. Frequency response is 0.2-40 Hz and CMMR is 136 dB.

  • A Low-Noise, Low Power Multichannel Amplifier Design - This article includes a schematic for an 8-channel EEG. Frequency response is 0.1-100 Hz and CMMR is 80 dB. Multiple modules can be connected to make a 32-channel EEG.
  
  
• Brainmaster
  
  
  • Brainmaster Schematics - These are Tom Collura's freeware build specs for the Brainmaster EEG. These specs are based on the Motorola 68HC11EVBU evaluation board which is no longer available and difficult to find. I have heard that Axiom 68HC11 boards can be used as an alternative. The amplifier is based on AD620 instrumentation amps and OP90 op-amps. Frequency response is 1.7-34 Hz and CMMR is 110 dB. Unfortunately the firmware and PC software is no longer available.

  
  
• OpenEEG Project - This is a project to develop a low-cost EEG for < $100. There is a discussion group about this project here.
  
  
  • ModularEEG - This design is a 2-channel EEG with RS232 PC interface. It uses an AT90S4433 microcontroller for ADC and a differential amp based on INA114 instrumentation amps and TLC277 op-amps. The input stage is modeled after (or influenced by) the Biosemi designs, with some modifications. Data is sent to the PC over the RS232 data lines (RX/TX). This is the most recent and sophisticated of the OpenEEG designs.

  • RS232EEG - This is an older version of a 2-channel EEG with RS232 PC interface. It uses an AT90S4433 microcontroller for ADC and a differential amp based on INA114 instrumentation amps and TLC272 op-amps. Data is sent to the PC over the RS232 data lines (RX/TX). The firmware rom image and source code are included in the download file.

  • ComEEG - This is a lower cost 1-channel EEG with RS232 PC interface. This one uses no microcontroller, it sends pulses to the PC over the RS232 handshake lines (RTS/CTS). It uses a differential amp based on INA114 instrumentation amps and OPA2604 op-amps. ADC is implemented with 555 timers. It includes a 7555 timer for calibration circuit. The PC must be run in DOS only mode to disable interrupts in order to achieve proper timing.

  • ComADC - This is another low cost 1-channel EEG with RS232 PC interface. It also uses no microcontroller and sends pulses to the PC over the RS232 handshake lines (RTS/CTS). There is no differential amp, signals are fed into a 555 timer based PWM circuit. The PC must be run in DOS only mode to disable interrupts in order to achieve proper timing.

  • GamePortEEG - This is another low cost EEG that sends signals to the PC via the game port. It uses a differential amplifier. There doesn't seem to be much info about this design.

  • Joerg's Home Page - This is Joerg Hansman's home page for download of the OpenEEG schematics and firmware. Joerg is the designer of all of this fancy OpenEEG hardware.

  • Design of a multi-purpose biofeedback machine - This document describes an multi-parameter biofeedback system based on a Texas Instruments MSP430F149 microcontroller and ADS1252 analog/digital converters. There are no schematics in this document.

  • ElectricGuru EEG Software - This is Rob Sachs' Windows software that uses FFT to do spectral analysis of the EEG data. It apparently works with the RS232EEG and ModularEEG designs above. This is binary executable only, the source code is not available.

  • Eagle Layout Software - You need this software to look at the OpenEEG schematics above. Low volume orders of boards can be done at PCBexpress, they accept Eagle format CAD files.

  • Atmel DevTools - These are the development tools for Atmel AVR 8-bit RISC microcontrollers. Atmel microcontrollers and flash tools can be ordered online from Digikey. They also have most of the instrumentation amps, operational amps, and other parts. A schematic for a programmer's cable is here if you want to make your own.
  
  
• Circuit Cellar
  
  
  • HAL-4 EEG - Circuit Cellar designed a low cost EEG using the ubiquitous 8031 microcontroller. The amp section is built using six TL084 op-amps. Singals are digitized using ADC08008 A/D converters. Frequency response is 4-20 Hz and the firmware is set up with 64 Hz sampling. There used to be a kit for sale at Creative Concepts, but it's no longer available. Apparently the original PCB design file was lost. There is a manual that shows the schematics, and there is a newsgroup for HAL-4 fans. Some people have improved on this design to achieve better band width and sampling rates.
  
  
• Other EEG Schematics
  
  
  • Meissner Research - Jim Meissner improved on the HAL-4 design and was able to achieve better frequency band width and sampling rates. He used a 68HC11 board from New Micros. There are tons of free development tools and info about 68HC11 on the web. Jim posted his EEG firmware source and some sample EEG recorded data here. Jim also invented the Brain State Synchronizer and some interesting meditation speakers.

  • Bernd Porr - Here's an EEG preamp and filter circuit that uses AMP01 instrumentation amp and NE5532 op-amps. He uses a TIL111 opto-coupler. He also has an interesting Java-based EEG viewer that connects to a C++ server via socket connections.

  • Two-channel data logger for quantitative EEG recording while driving - This document describes a 2-channel portable EEG built using an 87C552 microcontroller and AD620 instrumentation amps. Band width is 0.1-40 Hz, sampling is 128 Hz, and it does 10-bit resolution A/D conversion. There are no schematics in this document. There is another document describing this system here.

  • How to Build a Lie Detector, Brain Wave Monitor and Other Secret Parapsychological Electronics Projects - This book has plans for a simple EEG that uses 741C and N5556 (signetics) op-amps. The brain wave signals feed into an audio tone generator, and thresholds can be set with a potentiometer. It also has an auxilliary output for a chart recorder. The book seems to be out of print, but the plans and schematics are here.

  • A CMOS IC for Portable EEG Acquisition Systems - This short document describes the design of a an EEG into a single CMOS IC that consumes 520 uA power. This single IC contains 16 instrumentation amplifiers, analog multiplexer, programmable gain amplifier, auto-calibration circuitry, and a digital computer interface.

ECG - Electrocardiogram Schematics

• Electrocardiogram Amplifier - This document contains schematics for an EKG amplifier using AD621 instrumentation amp and LM6484 op-amps. Another circuit shows addition of a common ground. There is a circuit for evaluation of common mode rejection ratio (CMMR). It further describes how to add a low-pass butterworth filter using MF4 switched capacitor, and how to digitize the EKG signals using ADC0848.

• Scientific American: Home is where the ECG is - This article from "The Amateur Scientist" column describes how to build an ECG using just an AD624 instrumentation amp, 5 resistors, and 4 capacitors, and a potentiometer for "zero adjust".

• Sima's ECG Project Page - This is a good description of Sima's experimentation with the simple ECG described in the above Scientific American article. He includes a revised schematic, and provides more detail on safety, grounding, and noise reduction. Sima used the Pico Technologies DrDAQ data logger to digitize the ECG signals and chart them on a PC.

• EKG Happy - This page describes a home brew EKG system. It includes a schematic for an EKG amplifier using TL082 op-amp, diagrams showing how to wire the leads, and some notes on safety considerations.

• Electrocardiogram Lab - These are student lab instructions from an EE course. They include a schematic for an ECG that uses an AD620 instrumentation amp and 741 op-amps, and discusses adding a low-pass and high-pass filters.

• Texas Instruments ECG Schematic - The data sheet for the Burr-Brown (Texas Instruments) INA121 instrumentation amp includes a schematic for an ECG amplifier with right-leg drive. It also has schematics for low-pass and high-pass filters, galvanic isolation, and multiplexed-input data acquistion.

• Real Time Portable Heart Monitoring Using Lown Power DSP - This docment describes an ECG system that uses a TMS320C5410 DSP to do real-time analysis of ECG signals. It describes how the DSP is used to do QRS complex detection using an adaptive threshold technique. The portable system has small keypad, LCD, and audio output, and also an RS232 interface for connection to a PC. There are no schematics, just block diagrams.

• Portable System for High Resolution ECG Mapping - This document describes a multi-channel portable ECG with parallel port connection to a PC. It's a brief document with not much technical information.

• Lego Mindstorms ECG Sensor - Lego has changed a lot since my childhood days. Now they have lego bricks containing programmable microcontrollers. This page describes a lego ECG sensor. It includes schematics, cabling info, and shows photos of the ECG circuitry attached to lego bricks. There is also a program called MindScope which downloads ECG data from the lego brick and charts it on a PC. I think the big kids are enjoying mindstorms more than the little ones.

• Optical Heart Monitoring - This page describes projects that measure pulse using light transmitted and reflected through the finger. One method uses a super bright LED, light penetrating the finger is detected by a TSL230 light to frequency converter. Another methods uses an infrared LED, light is detected with a PIN photo diode.

• ChipCenter Question: Heart Monitor - This is a response to a question submitted to ChipCenter on how to make a heart monitor. It talks about instrumentation amplifier choices, isolation methods, and usage of 60 Hz notch filters. It has links to some useful technical briefings and data sheets, but all of the links are broken, so I have included fixed links below:
  • Design a 60Hz Notch Filter with the UAF42
  • Low-Power, Low-Voltage IC Choices for ECG System Requirements
  • Very Low Voltage, Micropower Amplifiers: Choosing and using them
  • Isolation_Amps_Hike_Accuracy_and_Reliability
  • AD620 Data Sheet
  • AD627 Data Sheet
  • INA121 Data Sheet
  • ISO107 Data Sheet

EMG - Electromyrograph Schematics

• Self Contained Electromyograph
• Chip Epstein's EMG on a shoestring

GSR - Galvanic Skin Response Schematics

• E-Meter GSR Meter Schematics
• Huidmeter GSR Schematics
• The Galvactivator Glove
• Lego Mindstorms Galvanic Skin Response Sensor
• MIT Cricket GSR Sensor
• Lie Detector Circuit (GSR)
• Simple Lie Detector (GSR)

Respiration Monitor Schematics

• Venthesizer Respiration Monitor

Mind Machine (Light and Sound) Schematics

• Brain Wave Machine
• Build Your Own Light and Sound Machine
• The Brain Wave Lab
• PCM MindWave
• Mind PICkLer Light and Sound Machine
• The Flicker
• Mind Machine Bibliography

Other Miscellaneous Schematics

• MIT Thinking Tags
• Digital Step Pedometer Schematic
• Float Tank Construction Plans

Portable Biofeedback Devices

• Sensors for Biopotential Measurement
• Mobile Biofeedback Monitors
• Portable Neurofeedback Devices
• Clinical/Research Instrumentation

Sensors for Biopotential Measurement

• Electrodes
  • The Electrode Store
  • Etrode Electrodes
  • Medtronic Electrodes
  • Neuromedical Supplies Online Catalog
  • Flextrodes Pasteless Electrodes
  • QuickCap EEG Positioning System
  • Electro-Cap International
  • Biosemi EEG Active Electrodes
  • J&J Neuroamp EEG Active Electrodes

• Cardio Sensors
  • ADI Instruments Pulse Transducer
  • ADI Instruments Cardio Microphone
  • Vernier EKG Sensor
  • Vernier Exercise Heart Rate Monitor
  • Biopac Cardio Sensors

• Respiration Sensors
  • ADI Instruments Respiratory Belt Transducer
  • Vernier Respiration Monitor Belt
  • Biopac Respiratory Effort Transducer

• GSR and Temp Sensors
  • ADI Instruments Skin Temperature Probe
  • Thermochron Temperature Logging iButton
  • Biopac GSR and Temp Sensors

• Other Sensors
  • Harvard Biocience
  • Thought Technology Intelligent Sensors
  • SLP Physiological Sensors
  • Sleepmate Sensors
  • Skill Technologies Real-Time Motion Analysis
  • The Motion Monitor
  • MicroStrain VirtualCorset
  • Aura 6000/Coggins Camera

• Amplifiers
  • ADI Instruments Bio Amp
  • ADI Instruments GSR Amplifier
  • Double Differential Surface EMG Pre-amplifier
  • Vernier Instrumentation Amplifier
  • Analog Devices Instrumentation Amplifiers
  • Texas Instruments (Burr-Brown) Instrumentation Amplifiers

• Sensor Interfaces
  • Vernier Sensor Interfaces
  • AnyWear Sensor Interfaces
  • Biopac Sensor Interfaces
  • TI Calculator Interfaces/Sensors

• Data Acquisition
  • National Instruments (LabView)
  • MathWorks (Matlab)
  • Scientific Solutions (Labmaster)
  • Instrutech
  • Axon Instruments
  • Dataq
  • B&B Electronics
  • Prairie Digital
  • PicoTech PC Based Oscilloscopes

• Opto-Isolators
  • Scimar RS232 Opto-Isolators
  • Patton RS232 Opto-Isolator
  • Isocom Optocouplers
  • Infineon Optocouplers
  • Agilent Optocoupler Design Center
  • Fairchild Optocouplers
  • NEC Opto-Electronics Devices
  • Sharp Opto-Electronics Devices
  • Phototransistor Isolation

Mobile Biofeedback Monitors

• Polar Heart Monitors
• Medical Product Review Heart Monitors
• Creative Health Products Heart Monitors
• Elemaya Heart and Emotion
• Omron Blood Pressure Monitors
• A&D LifeSource Blood Pressure Monitors
• MyoMonitor Portable EMG System
• ThoughtStream GSR Monitor
• GSR2 Temp and GSR Monitor
• FitSense Speedometer
• Minitor AR-5 Wrist Monitor
• SmartShirt Sensors
• VivoMetrics LifeShirt
• Wearable Polysomnograph
• Wearable Sensor Patches for Physiological Monitoring
• Televital Real-Time Physiological Monitoring Over the Internet

Portable Neurofeedback Devices

• Brainmaster - 2-Channel, 1.6-40 Hz ($975-$1225)
• Lexicor POD - 2-Channel, 0.5-32 Hz ($992)
• Lexicor NRS-2D - 2-Channel, 0.5-32 Hz ($1295)
• WaveRider CEO - 1-Channel, 0.5-40 Hz ($545)
• WaveRider Jr - 2-Channel, 0.5-40 Hz ($950)
• WaveRider Pro - 4-Channel, 0.5-40 Hz ($1700)
• ProComp - 8-Channel (2 EEG), 0-40 Hz ($3500)
• NeuroDyne RealTimeEEG - 2-channel, 4-18 Hz ($1900)
• Aleph1 EEG Analyser - 1-Channel, 4-30 Hz (1400 GPB)
• MOE Aplha Detector Plus - 1-Channel, 4-16 Hz ($295)
• MOE EEG3 - 1-Channel, 1-30 Hz ($534)
• Alpha Theta Trainer - 1-Channel, 4-12 Hz ($1595)
• Biofeedback Instruments P665 - 1-Channel, 2-40 Hz ($725)
• E2 Personal Neurofitness Trainer - 1-Channel, 4-20 Hz, ($725)
• CEO Cognitive Efficiency Organizer - 1-Channel, 2-40Hz ($600)
• CyberLink - 3-channel (EEG/EOG/EMG) ($1995)
• IBVA Brainwave Visual Analyzer - 1-2 Channel, 0-60Hz ($1300-$2300)
• Mind Mirror III - 2-Channel, 0.75-38 Hz ($3500)
• Neurofile NT Mobil - 24-Channel
• EPAS 24/32 - 24-32-Channel
• BioControl Systems
• Oxford Portable EEG

Clinical/Research Instrumentation

• Biosemi
• Cephalon
• CTF Systems
• Grass Telefactor
• Guger Technologies
• Neuralynx
• Neuroscan
• Psylab
• ADI Instruments

Biopotential Measurement Theory

• Biopotential Measurement Theory
• EEG Signal Measurement
• ECG Measurement
• EMG Measurement
• GSR Measurement
• Respiration Measurement

Biopotential Measurement Theory

• Fundamentals of Electrophysiological Monitoring
• Handbook of Medical Informatics
• Real Time Holter Monitoring of Biomedical Signals
• High Quality Recording of Bioelectric Events: Interference Reduction Theory
• Bioelectronics Project Laboratory: Reference Handouts
• The Nyquist Frequency Fable
• Very Low Voltage, Micropower Amplifiers: Choosing and using them
• The Isolation Mode Rejection Ratio in Bioelectric Amplifiers
• A System Designer's Guide to Isolation Devices
• Electromagnetic Interference and Patient Isolation
• Patient Isolation in Multichannel Bioelectric Recordings
• Applications of Opto Couplers
• Design a 60Hz Notch Filter with the UAF42
• The configuration of the power supply in battery-powered front-ends
• Surface Electrodes for Biopotential Measurement
• Low-cost Active Electrode Improves the Resolution in Biopotential Recordings
• Resources for Sensors, Measurements, Instrumentation and related Sciences
• System for Collecting and Processing Bio-Metric Signals in Natural Situations
• Bio-Engineering Animations