Muscle Twitch Sensor Alarm
The client has motor neuron disease and is mostly paralysed but with some muscle movement. The client needed a method of alerting carers whenever his eye tracking communication system is not functioning.
The Mechanomyography (MMG) twitch sensor is a small device that can be placed on a client’s muscle to detect subtle muscle twitches. It measures intentional twitches and after several consecutive twitches, an alarm will sound. The twitch sensor is suitable for clients that are mostly paralysed, such that any movement detected by the sensor was primarily from the muscle it is attached to, rather than the bulk motion of the client.
The twitch sensor consists of a small, cheap, and relatively inexpensive 3 axis accelerometer. It is controlled by an Arduino Nano (or equivalent) and connected to a buzzer/alarm.
The Challenge
The client has motor neuron disease and is mostly paralysed but with some muscle movement. The client needed a method of alerting carers whenever his eye tracking communication system is not functioning.
A blink sensor was considered but it was not successful because the IR sensor is very sensitive to proximity to the eye and required significant calibration and adjustment each time it was positioned on the client. It was decided that this was too much of a burden on the client’s carers and this idea was abandoned.
Electromyography (EMG) were considered. These require special contact pads to ensure a good reading with the muscle. Three contact pads are required and are placed on specific places on the muscle. They require a special sensor to interpret the reading from the pads. This set up would be more expensive in the long run and it was not certain whether the probes would be sensitive enough to record the clients very subtle cheek movements. Additionally, the client wished to use their cheek muscle, so the three pads was not expected to work very well with a relatively small facial muscle.
The solution
Details of the solution provided in the link below. It contains the code and the design files:
1814 Bespoke Alarm Report – Twitch Sensor
The Mechanomyography (MMG) twitch sensor is a small device that can be placed on a client’s muscle to detect subtle muscle twitches. It measures intentional twitches and after several consecutive twitches, an alarm will sound. The twitch sensor is suitable for clients that are mostly paralysed, such that any movement detected by the sensor was primarily from the muscle it is attached to, rather than the bulk motion of the client.
The twitch sensor consists of a small, cheap, and relatively inexpensive 3 axis accelerometer. It is controlled by an Arduino Nano (or equivalent) and connected to a buzzer/alarm.
The benefit
The client is now able to alert his carer’s that he needs attention even when his eye tracking communication system is down. Prior to this, the client had no alternative means of raising an alarm, which resulted in long periods of waiting for attention and caused discomfort and safety concerns for the client.
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