- Why Electromyograpy?
- There are already EMG systems, right?
- How does FlexVolt compare to other low-cost EMG devices?
- Is it safe?
- Is FlexVolt a medical device?
Why Electromyography with the FlexVolt?
It all started back in college with a desire to alter human-machine interaction. We’ve been following cutting edge development, from electrode patches to eye tracking to full motion tracking (think kinect) and looking for a way to contribute. Looking at current hurdles in prosthetics design and control gave us the answer. We could use the most intuitive system we have – the electrical signals sent to our muscles – to control anything, from a prosthetic limb to a computer mouse to a remote controlled vehicle. What started as a desire for alternative human-machine-interfaces has led us to a device that may be more applicable to education in science and medicine, and home physical therapy and fitness monitoring.
Aren’t there already systems for measuring these signals?
Electromyography is not new, but the currently available systems are expensive and usually only seen in medical centers or research laboratories. With the FlexVolt, we are breaking that barrier and making electromyography accessible to everyone for under $100. The FlexVolt is our first attempt at reaching a loftier goal – making biomedical technology affordable and available to everybody. This goal requires two pushes: The first is designing and producing affordable systems. With the FlexVolt, our approach is using Kickstarter to build enough of a support base to take advantage of bulk discounts on component purchase and assembly. What would cost ~$300-500 for a single unit can cost ~$50 for 250 units! The second push is in making the analysis tools and software algorithms required to make sense of biomedical measurements open source. We will make all software we develop open source, and foster a developer’s forum to crowd-source software improvements.
How does FlexVolt compare to other low-cost EMG sensors?
This question comes up a lot, with the most likely other low-cost sensor being the muscle sensor from Advancer Technologies, which is a great sensor, but significantly different from FlexVolt. Here’s a breakdown:
| Feature | Advancer Sensor | FlexVolt Hacker | Flexbolt Bluetooth |
| Form | bare PCB – easier for hacking into your existing product, but requires additional parts and soldering | Arduino Shield – plug into an Arduino to add EMG capabilities to any Arduino project | Machined plastic enclosure – A polished consumer device |
|---|---|---|---|
| Measurement Channels | 1 | 2-4 | 2-8 |
| Power | not included, requires V+/V-, requires soldering | not included, uses Arduino | Li-Ion battery, ~10 hour life |
| Analog Measurement | not included, requires soldering | not included, uses Arduino analog inputs | 10-bit ADC included |
| Ease Of Use | requires soldering and additional components | uses Arduino: load Arduino code and plug it in | Power on, pair Bluetooth, and connect |
| Cost | $26 | $60 (2CH), $95 (4CH) | $115 (2CH), $150 (4CH), $215 (8CH) |
Is it Safe?
FlexVolt USB device will implement isolation and current limiting circuitry, to protect you in the event of unlikely power anomalies bypassing your computer’s surge protection abilities. Any time you connect an electronic device to house power and to yourself, this is an important question! Most USB ports are designed to limit current at 300-500 millamps, and the ports will disconnect attached devices if any shorts are detected. That said, it is still a good idea to provide current limiting circuits in the electronic device itself. We plan to use a USB terminator with ESD protection. This IC will shunt all surges to ground at the USB cable entrance. We will also implement ESD/overvoltage shunts on the sensing side.
Will FlexVolt Devices be certified as medical devices?
No. Our goal is to make an affordable device to support uses in home monitoring and education. FlexVolt will be safe (see above FAQ about safety), but we do not currently plan to spend the time and money necessary to certify FlexVolt as a medical device. What does this mean? Insurance companies are not likely to pay for FlexVolts but because we have made FlexVolt inexpensive, buying out-of-pocket is less of a hurdle. The next consideration is that doctors may not be willing to recommend using FlexVolts; while some may not, we know it is not uncommon for physical therapists to recommend home-use devices “off-the-books” or “out-of-pocket” because they are inexpensive and effective, like FlexVolt.