Skip to content

How to design an Arduino-based EMG monitor

The fast pace in technology development has brought innovations in Bioengineering. These innovations have also given rise to many software-based devices. The devices can help control the current patterns of human activity. The medical field is by far the leading consumer of these devices. The demand for such equipment is so high. The high demand it has prompted several companies to develop new designs. They are also developing designs for their products in the reaction. Companies such as Rayming PCB & Assembly have developed a modernized product line design to meet their consumers’ demands. Their new device is a lightweight EMG monitoring system. They have unique designs that we can explicitly use in hospitals or other medical facilities. Medical professionals continuously monitor a patient’s heart rate and blood pressure levels. It is easy to know what jobs using EMG sensor, you can do.

What is an EMG sensor?

An EMG sensor is a small device used to monitor the electrical activity of muscles. Medical professionals use this device to help diagnose patients suffering from muscular pains. The frequency of electrical impulses generated by the muscle can tell the physician a lot about how injured the patient’s muscles are. This will inform what type of therapy they may need to accelerate their recovery process.

Historically, physicians have been monitoring muscle activity through direct contact. They use electrodes placed on the patient’s skin. Such methods have provided accurate readings during the monitoring process. But they are highly invasive and time-consuming. This made such methods unsuitable for long-term monitoring and treatment.

For this reason, medical professionals decided to use ultrasound to help track muscle activity. Medical professionals can see a live ultrasound feed on the track. This allows them to directly assess the muscle movements of their patients from a safe distance. This made monitoring patients’ muscle activities much easier. It also significantly improved their recovery process in most cases.

Types of EMG sensors

EMG sensors use one of two methods to monitor muscle activity. You may design them to pick up ambient signals from the patient’s muscles or have electrodes embedded into them. We usually pick up the ambient signals using a combination of the surface. Additionally, we apply fine-wire-based electrodes directly onto the patient’s skin. Then, The EMG sensor picks up the signal, which the medical professional may hold. They may also attach it to a wearable device such as a holster-like strap.

1. sEMG sensors 

We can also refer to it as the surface EMG sensor. These sensors can pick up the electrical activity from muscles and tendons within an entire body. We do this type of monitoring by covering a patient’s entire body with electrodes while placed in a prone position. The result is that we can covertly monitor the entire patient’s movement when fully clothed. The advantages of using the sEMG sensor are lightweight and very portable. They are also easy to use by medical professionals. Several professionals are conducting numerous research on this type of EMG sensor. They are much easier to troubleshoot when problems arise. The main drawbacks of sEMG sensors are that they have limited life cycles. This is in comparison to other types. If ripped off the patient’s skin, they are easily damaged and rendered useless.

2. Intramuscular EMG

Physicians usually place these are EMG sensors directly into a patient’s muscle. They monitor the muscle movements on such a close level. It helps them tell when there is an increase or decrease in blood flow to certain areas of the patient’s muscle. They use this type in patients with acute or chronic wounds and injuries. They also use it for other related conditions for which long-term monitoring of the patient is necessary. This type of monitoring allows medical professionals to assess the condition accurately. It also helps them track and progress of the patient’s healing process.

3. Deep Tendon EMG

We often refer to this type of EMG sensor as muscle biopsy. It is similar to the sEMG in many ways. The only major difference is that this type monitors mainly tendons. The deep tendon EMG has been around for longer than the sEMG. It is more reliable in terms of quality and accuracy when compared to other types of EMG sensors. The main drawback of this type of EMG is that it needs a very highly trained medical professional to apply and monitor it. This makes the monitoring process of patients in an acute state extremely difficult.

4. Intracortical EMG

This type monitors signals from the cortical neurons within a patient’s brain. These sensors are usually applied to the brain’s motor cortex using a craniotomy. We can also apply their other surgical procedures. It allows doctors access to the area underneath where they can apply the sensor directly onto the part of the cortex. We use this sensor mainly to monitor and detect changes in a patient’s motor skills. It primarily applies to patients whose injuries may be too extensive for sEMG sensors to detect accurately.

How EMG sensor work

If you was to learn how to make EMG sensor, you first need to understand how it works. An EMG sensor is a small, lightweight (usually less than 1.6 ounces) piece of medical equipment placed on the patient’s skin. We typically connect the EMG sensor monitor to the patient. We use a cable that connects to the patient’s computer or a specialized package that connects directly to the patient’s computer. This format enables the monitoring of usable data from multiple patients at once. It also offers an easy way for users to exchange data from one set of monitors to another.

The EMG sensor works by getting close to the patient. Since it is small and light, we can easily place it on the patient’s skin. Once connected to the patient’s computer, any change in the electrical activity of muscles triggers an alert signal. So, we can send it via email or through a wireless application at home. The EMG monitor then provides medical professionals with crucial information. The information can help them make critical medical decisions in their patients’ best interests.

We can make an EMG monitor using different components. It can consist of a kit that allows users to monitor a few muscles in the patient at once. We may also design other monitors to monitor many muscles simultaneously. Usually, the larger the area we monitor, the more complex and expensive the design.

These devices generally consist of medical-grade plastic that is lightweight and durable.

Software Interface of Arduino-based EMG sensor

A software interface is a computer code that facilitates various hardware devices. An example of this would be the interface between a computer and an internet security system. With many commercially available products such as Arduino, we must make the interface case-by-case.

For example, one may want to connect to an EMG (electromyogram) sensor. They may also not connect it to other bio-telemetry sensors that do not offer standard protocols. These are protocols required for easy integration with standard programs on the market today.

We can sample the Arduino analog input using the analogRead function of Arduino. We can use the Arduino to read the signals from the EMG sensor and send them to a PC for processing and analysis. The apparatus used in this project is a simple EMG amplifier circuit that they built and amplified for use with an Arduino (Arduino). The amplifier amplifies the received signals 100 times. This easily transforms them into a digital format that software can record and process. The ADC (Analog to Digital Converter) is the device that converts an analog signal into a digital format. The ADC uses a series of switches to measure the voltage coming from the sensors. Then flip it into binary values displayed on a PC screen. We need to install the driver for our Arduino board to have a functional connection with the computer.

The Interface Circuitry

One can make the interface circuitry for the Arduino of 16 pins, as shown in the figure. We use the first eight pins to connect the Arduino to the PC.

We use a voltage divider circuit to measure voltage. This is the voltage coming from two previously connected sensors and amplified multiple times (100 ×). In our case, we will be using two sensors to reproduce a signal that can track whether a person is in pain. We will use the first sensor to track the rotation of the thumb, and the second sensor will monitor the movement of the index finger. We use the voltage divider circuit to ensure that we can measure any change in output value that is coming from our amplified sensors. This circuit is a very simple but effective way that helps us capture a signal that we can easily process by using Arduino software.

We can connect the Arduino to the PC using a USB cable. The board has a built-in power supply that uses the 5V pin to power the circuit and charge the battery. We will also have to connect a small motor to create real-time results. Then we can use it to simulate a finger movement and track if it has caused any movement in our thumb’s joints and muscles. The Arduino provides us with processing information from the sensors to send it to our computer.

Electrical Safety

We must handle all electrical equipment, including medical devices, with care and caution. When dealing with high voltage electronics, there is always a risk of electric shock that any exposed part of the device can cause.

We should always turn off the electrical connections when not using them. In this situation, we connect the Arduino board to the computer via a USB cable to transmit and receive data over a computer network. When we don’t need this data, we can disconnect it.

When working with any electrical devices, be sure to use protective equipment such as rubber boots and rubber gloves. This ensures that the user remains safe from any possible electric shock while handling the equipment. You should always keep any exposed wires on the device from the user’s body during operation to avoid possible electric shocks. The general rule for working with any electrical device is to avoid touching the exposed wires with the body. Ensure that you use protective equipment whenever needed.

Safety is essential when working with high-power devices such as an EMG sensor. This device delivers a large amount of electrical current. So we must handle it carefully. It helps us avoid possible contact burns or any other harmful effects from improperly handling this equipment. It is essential that the user read all safety warnings before using this equipment. They should always follow all of the manufacturer’s safety precautions.

Essential components

Connecting Wires & Jumper wires: If a servo motor is in use, you should also power the Arduino. The Arduino cannot power the motors directly but only send power through a power supply circuit. Similarly, if you use a small motor, you should power it using a separate power supply.

9V batteries: Using 9V batteries to power the Arduino is not efficient. It is inefficient, especially when powering it with a battery charger and a DC source from an external source such as a wall socket.

A 3-lead connecting cable: We use this for connecting the circuit to a PC. You will need 13 cm of cable for each connection.

52mm electrode pads: These are electrodes attached to the skin. They consist of conductive gel and offer a reliable connection to external electrical equipment.

AD8226-based EMG sensor: It is one of the most common EMG amplifiers used in EMG sensor projects. This device can amplify and convert the EMG signals from the electrodes.

Arduino UNO: This is an Arduino board that we can use in various projects. It is one of the most popular and easiest boards in building projects based on hardware.

Arduino IDE: This program file allows the programming of Arduino to use a graphical user interface. The IDE’s code editor also provides syntax highlighting and auto-commenting tools for any code written by the user.

Arduino code: We then upload this code onto an Arduino board.

Interfacing EMG Muscular Signal Sensor with Arduino

We use EMG sensors to monitor muscular activity in humans and animals. Data is continuously acquired from the sensors by a computer. You can then process it and interpret it into helpful information.

This process involves processing signals from the electrodes. Then, you amplify them before translating them into a form that another system or machine can understand. This form of data is also called an EMG signal, muscle signal, or muscle event.

1. Electrode Connection 

We apply the electrode pads to the skin of a subject. Then, we must connect these electrodes to the EMG sensor through a connecting wire. We frequently do this by placing one of the electrodes between two metal contacts placed on the EMG sensor circuit itself. The connecting wire is then attached to these metal contacts. This completes the circuit. It allows for the reading of EMG signals by the sensor.

Yellow electrode:

This reference electrode allows the Arduino to determine which electrodes we are using. We place this electrode on the skin between two other electrodes and act as a reference point. You must also connect it to the sensor’s power supply to get a stable reading.

Red electrode:

We use this electrode to measure the activity of the muscle. You must place it over a muscle and connect it to an amplifier via a wire. The amplifier amplifies the signal and sends it to the sensor.

Green electrode:

This is another reference electrode that acts as a reference point for the Arduino. You do not need to apply it over any muscle since it does not record muscular activity. Also, you do not need to connect it to the power supply since this will not affect its performance.

2. Power Supply Connection

We also connect the power supply for the electrodes and the amplifier to the Arduino board. This allows for signals generated by the Arduino board and sent to the sensor via the connecting wires.

3. Motor Connection

We connect the motor to a power supply to provide a steady flow of electrical current. We can adjust the current speed by adjusting the power supply’s voltage or by adjusting the resistance between its two terminals. To prevent the wrong movement while sending electricity through it, you need to adjust the resistance.

How to code a EMG sensor 

“The Arduino UNO” is an Arduino board that we can use to build a prototype of an EMG sensor. The Arduino board has a built-in circuit that can read the values coming from the sensors and then process them using the software.

Reading the data straight from the sensors allows for quick evaluation of processed information. This removes all kinds of delays. To do so, we need to connect our circuit to our computer via USB cable and upload a program onto the Arduino. Programmers usually write this program specifically to adapt to any other purpose easily. We can find the provided code under the tab “Code.”

A significant challenge of using EMG sensor Arduino is that it requires a large amount of knowledge. You also need a lot of experience with the program and its environment to get the most out of it. Compared to other ready-made hardware, Arduino offers us a lot more control over its internal components. They are completely open-source. Another advantage of using Arduino is building complex projects. We use it primarily for more advanced projects and applications. 

What does an EMG sensor do

“Muscle activity” controls one or more muscles to produce the desired effect. For example, speaking, lifting, or kicking. We measure it by recording the electrical activity generated by a muscle. One can do this by tracking the resulting change in electrical potential present in a muscle.

1. Muscle activation and electrical potential change

Muscle activation refers to the movement, or contraction, of a muscle. Several factors including: can cause this movement

Muscle force is the amount of force applied to a muscle. You must increase muscle force by making the muscle work harder or decreasing its resistance. One can reduce the resistance through relaxation of the muscle or by lengthening its antagonistic muscles.

Some muscles have an inherent property that causes them to contract when stretched. We refer to this as a reflex action, and it is a common phenomenon present in human beings and animals.

A muscle can exert force to overcome the external resistance exposed to while contracting. This resulting force has an inverse relation with the square of the muscle tension.

Muscle contraction and relaxation are both affected by signals sent from other parts of the body, such as:

2. Muscle action potentials

When a muscle contraction occurs, the muscle activates and then relaxes. The body sends electrical signals from the muscle to the nerves surrounding it during this time. These signals contain information about muscle contraction and pass it on to other body parts. The atrial and ventricular nerves are responsible for sending these signals. However, not all muscles have a direct nerve connection to them. For example, many nerves that connect directly to other body parts, such as the spinal cord or brain, supply many muscles in the body.

3. Recording EMG signals

We can use several methods to measure the electrical activity of a muscle. These methods range in price, complexity, and precision. The most basic way of measuring muscle activity is by placing electrodes on it or around it. We connect these electrodes to an amplifier. Then, a computer reads the resulting signal. This method is common in hospitals and laboratories due to its relatively low cost, ease of use, and accuracy.

4. Processing EMG signals

We can measure and record muscle activation in real-time. The EMG muscle sensor ensures that we do it with a relatively high level of precision. However, these measurements cannot accurately evaluate the muscle actions themselves. This is where the processing of these signals comes into play. We can process the data in several ways depending on the type of activity that we are recording.

The above techniques use numerical methods to evaluate each signal. So they tend to be more complicated and less effective than other techniques.

Conclusion

EMG sensor is a potential solution for human movement and speech recognition. The main advantage of this system is the accuracy of the measurement. Human movement and we can measure speech with a high level of precision. Also, this system is relatively inexpensive. It makes it an attractive choice compared to other available systems and methods. Wearable EMG sensors are also a cost-effective solution for monitoring respiratory function. We use these sensors throughout the respiratory system. They can provide valuable information to the user on respiratory status.

The EMG sensor proves to be a valuable tool for researchers. It helps collect knowledge. It also provides new insight into improving human movement and optimizing speech recognition.