MAX86141-Based NIR-HEG
We’ve been working continuously for over a year and a half—since well before the release of HEGduino V1—to develop a compact, state-of-the-art, open hardware solution for home NIR-HEG biofeedback. HEGduino V2 is an original design that brings you low-cost, intuitive home brain training and research-grade cerebral blood-flow monitoring. This new device also lets us incorporate Heart Rate Variability (HRV) training and can even monitor breathing and skin temperature.
HEGduino V2 comes in a comfortable. easy-to-use headset with support for wireless operation and battery power. The components are breakout boards that let you detach them from the headset to tinker with or replace easily.
Technical Specifications
- Sensor: MAX86141 pulse oximeter ADC
- 2x4096 SPS simultaneous sensing with two high-sensitivity BPW34S photodiodes
- 19-bit resolution
- Hardware ambient cancellation and error detection
- Fully customizable LED routines, power usage, sampling rates, etc.
- Hardware & Software IIR filters for AC power and high-frequency noise ensures a high-quality signal
- Two IR LEDs and one Red LED for HEG/FNIRS and oximetry
- Microcontroller: ESP32 breakout board
- 32 bit, 4 MB, 240 MHz dual-core ESP32 microcontroller with rechargeable battery support
- Wi-Fi, BT/BLE, and USB connectivity
- Fully customizable firmware via Arduino and Espressif IDEs
- Free web software and tools to use your HEG on any device with no installs necessary.
Comparisons
| HEGduino V2 | HEGduino V1 | Mendi | Peanut nIRHEG | |
|---|---|---|---|---|
| Cost (USD) | $80 | $60 | $300-$500 | $495-$895 |
| Resolution (bits) | 19 | 16 (12-15 actual) | Not public | 21 Bit |
| Sampling Rate (max) | 4096x2 SPS | 860 SPS (120 sps actual) | Not public | ~2000 SPS? |
| Monitor Heart Rate and Breathing? | Yes | No | No | No |
| Monitor Temperature? | Yes | No | No | No |
| Software | Mobile or Desktop | Mobile or Desktop | Mobile | Desktop |
| Open Hardware? | Yes | Yes | No | No |
| Open Software? | Yes | Yes | No | Obsolete |
What Is HEG?
HEG stands for Hemoencephalography, which just means "monitoring blood flow in the brain." It is complementary to Electroencephalography (EEG), which involves monitoring the brain’s electrical signals. HEG—or, more broadly, Functional Near Infrared Spectroscopy (FNIRS)—is increasingly recognized as an essential source of information about brain activity and brain health. For our purposes, it assists with breathing exercises and obtaining essential feedback on how well our brain is circulating blood and energy.
Live brain-pulse data from the HEG. (You can do HRV and HEG training simultaneously!)
HEGduino V2’s easy-to-use software will help you get started with home brain training as quickly as possible, and its uncompromising hackability will allow you to explore the science and engineering readily. And there’s more on the way! We have additional projects in the works for 2021, including the FreeEEG32, which will be launching soon on Crowd Supply, and which will dovetail nicely with the work around HEGduino V2.
We are continuing to develop more affordable hardware so that we can eventually make multi-sensor, multi-modal BCIs feasible for students, out-of-pocket researchers, and anyone else who wants to learn more about their brains and themselves.
Software
We are partnering with the open source (GPLv3) Brains@Play general Brain-Computer Interface (BCI) platform to develop neurofeedback experiences for home use. This platform will allow student developers to get involved with creating their own standalone brain applications or by contributing to our main feature set. We are working to become a hub for lots of exciting, community-driven, brain-controlled content.
Among other features, our new platform supports multiple simultaneous users, remote-streaming, GPU-accelerated real-time signal analysis and visualization, and various types of concurrent hardware streams, including EEG, HEG, and streams from novel devices like Neosensory. We are even testing support for eye and face tracking and, possibly, for some kinds of brain implants! Our framework is opening the door to endless possibilities.
The following alphas are currently available:
Additionally, biofeedback therapists can access HEGduino v2 using the BioEra software.
Original HEG software (left) vs. the new 100% open source Brains@Play platform (right).
Support & Documentation
HEGduino is an open science project dedicated to making brain technology more widely accessible. Schematics, design files, firmware, software, and a whitepaper are all available on our GitHub repository. You can learn more about us on the HEG Alpha webpage. And, if you have a question, please feel free to reach out using the Ask a technical question form on our campaign page. This is an open project, so let’s find ways to work together!
Manufacturing Plan
Our PCBs will be fabricated and assembled by PCBWay, after which they’ll be sent to us for testing and headband assembly. The HEGduino v1 campaign gave us plenty of practice, and we’re excited to continue optimizing and scaling this process. We will ensure that every device works consistently before packaging them up and shipping them to Crowd Supply. That way, you can jump right into training and experimentation rather than spending your time debugging hardware.
Fulfillment & Logistics
We expect to have all HEGduino V2 products manufactured, tested, packaged, and on their way to Crowd Supply’s fulfillment partner within eight weeks of hitting our funding goal. To allow time for shipping logistics (and to give ourselves a bit of a buffer) we’re estimating a ship date of approximately three months after the end of the campaign. Orders will be subject to taxes and shipping fees based on the location of the backer. If you have more questions about shipping, please take a look at the Ordering, paying, and shipping section of the Crowd Supply guide.
Note: The LiPo battery product is only available to US backers. Sorry about that!
Repair Policy
We are continuing our policy of offering free repairs for as long as we have materials available with which to replace broken parts. There may be occasional delays in our supply chain, but we will do our best to ensure that you have a good experience with our products while they continue to improve!
Risks & Challenges
This is a grassroots project. I’ve had many wonderful mentors and contributors—and I’ve even (slowly) managed to assemble a small team—but I built most of HEGduino myself, from scratch, while volunteering the vast majority of my time. At this point, we’re quite familiar with the various pitfalls that surround this area of work, and we know how to avoid them. With your continued support, we’re ready to tackle even bigger problems! Help us get HEGduino V2 out into the world and establish ourselves as a force of nature in the BCI space! We can’t do it without you.
