Hello learners! Welcome to the introduction of the round PCBs, where we are going to discuss the round PCBs in detail. This is specially designed for articles for beginners as well as for intermediate skills in printed circuit boards. PCBs are the backbone of any circuit, and it is crucial to understand the type and application of the circuit and its PCB in detail before starting to work on it.
If you are going to buy crucial products like PCBs, always choose the best option that has positive reviews and a great experience. The best option for this is PCBWay.com, which has a great variety of PCBs, electronic components, equipment, and services. They have a vast variety of PCB services that range from high-speed PCBs to optical module PCBs, semiconductor tests, aerospace PCB circuit boards, and many other fields in different shapes, including round PCBs.
The best thing is that they provide the fastest services, and ordering online is easy here. Go to PCBWay.com and click on the PCB instant quote. They will ask for different parameters that you have to fill according to your circuit. Choose the build time and add it to the cart. You can find the detailed process on their website.
In this article, we’ll see the basic introduction of round PCBs. We’ll see the definition of round PCBs and understand how they are different from the other shapes. After that, we’ll see its manufacturing in detail and will see different phases of manufacturing. We’ll also have a look at their application. Let’s start learning.
The PCBs are present in different shapes and sizes and are customized by keeping different parameters in mind such as the scope, type, and working of the circuit. Usually, people have seen rectangular or square PCBs but one must know that round PCBs bring flexibility and functionality in the design and features of the circuits. To easily understand these, let's have a look at their introduction:
"Round PCBs are different from rectangular or square PCBs in terms of shape and applications and these bring factors like space utilization in circuits and provide better performance in different scenarios."
These PCBs introduce signal integrity in the high-frequency circuits because the components are tightly packed in the curved traces and as a result, better performance is gained. The difference is the presence of the curves in the round PCBs that have multiple advantages in the circuits.
Just like other PCBs, the manufacturing of the round PCBs involves different steps and special techniques are applied in these steps. Let’s have a look at these steps:
A PCB design software is used to get started with the design process of round PCBs. it creates the schematic and layout of the circuit. In the case of round PCBs, great care and attention are required because of the curves. The route tracing and component placement are different from the rectangular or square PCBs.
Once the round PCBs are designed, the process of Gerber file generation is carried out. This file has multiple instructions and information regarding the design and some of them are listed below:
The Garber file just discussed is used for the creation process of the photomasks. These are the essential photographic films that have patterns related to the different layers in the round PCBs. A large sheet of laminated material such as the FR4 is cut into the designed panel. A feature of this panel is, that it is pre-drilled with the registration hole so that it may be aligned with the design.
A photosensitive film (photoresist) is put to the copper foil in the laminate panel's inner layers.
The photomasks for these layers expose the required patterns to ultraviolet (UV) light. The exposed photoresist hardens, leaving the unexposed portions soft. The panel is then processed, eliminating any unexposed photoresist. This leaves the copper traces exposed. The visible copper is chemically etched away, leaving the inner layers with the appropriate circuit designs.
The design is now get ready with different processes such as the lamination of the surface and then drilling the holes according to the design. If the design consists of different panels then all of these are aligned together to get the best output. Once the panel is ready, the imaging and etching of the outer layer are carried out to create the final product in terms of design.
The PCBs are then passed through the process of platting. Here, a thin layer of the conducting material is applied to the required arrears to provide conductivity. Usually, this layer is copper because of its best-conducting characteristics.
Once the copper (or any other material) is traced on the round PCBs, a solder mask is applied to the PCB so that the traces may be protected against oxidation. In the end, the silkscreen is applied to the PCBs to add more details.
The applications of the round PCBs are the same as the traditional ones but they play a crucial role in improving factors such as performance and space constraints. Here are some advantages that you must know:
The consumer electrics are changing day by day. Smart technologies have made these electronics smaller and more stylish. The round PCBs help to get better performance in the smaller space. For instance, these are used in smartwatches, fitness trackers, and related wearables where the round shape fits into the device easily.
The medical devices are becoming smaller and smarter. For instance, the large X-ray machines, or blood pressure measuring devices are smaller now and are used as wearables. The round PCBs are used here because of their round curves and smart shape to fit in these devices.
The round PCBs are not only smart but are more appealing in their looks. The automotive industry requires circuits that not only provide better performance but also look more stylish. Some automotive instrument clusters and control panels always prefer round PCBs because of their look.
As a result, we have understood the round PCBs in detail in this article. We started with the introduction to the round PCBs and then saw how these PCBs are designed and ready to work. We saw why these are better in performance and in the end, we discussed how to get the best PCBs from PCBWay.com. I hope all the points are clear now and if you want to know more, you can contact us.
Hey students! Welcome to another episode of the MQ gas sensor series. Today, we are interested to learn about the high-performance sensor that is used to detect the presence of benzene gas. This is the MQ138 gas sensor and it instantly detects the target gas because it has tin dioxide as the sensing element. Usually, it can detect multiple gases and is considered as the Volatile organic compounds (VOC) sensor but the most significant target gas of this sensor is benzene therefore, we’ll pay attention towards the discussion of the benzene detection through this sensor. Many features of this sensor resemble other members of the MQ gas sensor series and we’ll read its basic features and specifications in detail.
In this article, we’ll initiate the discussion with the basic introduction of this sensor where we’ll also see its basic components and their purpose. After that, we’ll show you the datasheet elements that will be helpful to understand its technical specifications. You will also see the working principle, physical dimensions and applications of this sensor in different fields as well so stay with us.
Let’s start with the first topic:
The MQ138 is a member of the MQ gas sensor series that is specialised for the detection of benzene gas around it. It works on low voltages and uses tin oxide as the sensing element that is readily available to detect any leakage of the benzene gas in the surrounding air. Mainly, it follows the chemiresistor which is defined as:
"The chemiresistor of an element refers to the mechanism in which its electrical resistance changes when it absorbs the surrounding gas."
The sensing element of MQ138 absorbs the target gas and the change in the concentration is indicated through the analogue values of the sensor.
We know that benzene is used in multiple industries as a fuel as well as for chemical reactions but exposure to this gas is hazardous for humans. If accidentally inhaled for a short time, it can cause the issue issues like dizziness, and headaches and long-term inhalation is even more dangerous and can also cause cancer. These are the points that make the presence of benzene gas sensor systems such as with MQ138 compulsory at such places.
Let’s see the components of this sensor to know its details:
There is a small ceramic tube-like piece of alumina (AL2O3) that works as the mechanical support to the sensing element. This ceramic tube has excellent thermal stability as well as resistance to the electrical current therefore, this does not cause any change in the electrical resistance of the sensing element but only provides the mechanical strength. This results in the uniform absorption of the target gas on the evenly spread sensing element it.
The heart of the MQ138 is the sensing element that is made of tin oxide (SnO2). This is present evenly on the ceramic tube and ready to react with the benzene gas if gas is leaked into the air. Tin oxide has less conductivity to the clean air as compared to the air mixed with benzene therefore it is used as the sensing element in such sensors.
The heating sensor plays a crucial role in sensors like MQ138 because it maintains the required temperature to stimulate the optimum performance of the temperature. This consists of a heating coil made of nichrome wire and gradually increases the temperature of the sensing element. This is a crucial process and whenever the sensor is turned on, the heater circuit gets the 5V power and starts its work.
The circuit of the sensor is delicate and requires protection from outward agencies such as dirt particles in the air. This is done by a perforated metallic cap that covers the whole sensor. It acts like a filter that only allows the gas to pass through it and as a result, the system may perform best for a long time.
Moreover, the whole body of the sensor is made with plastic or bakelite material. The sensor modules have a large base that has multiple items on it such as the power LED, pins, etc but the sensor alone has a relatively simpler structure and the base has pins for the direct connection in the circuit.
Prior to employing any device, it is essential to review the device's datasheet so we are discussing some crucial points from the datasheet of the MQ138 benzene gas sensor:
The MQ gas sensor series has simple and fundamental features and I am highlighting the most basic features of the MQ138 sensor from its datasheet:
The table given below shows the specifications of the MQ138 benzene gas sensor:
Specification |
Value |
Size |
32mm X 22mm X 27mm (L x W x H) |
Main Chip |
LM393 |
Operating Voltage |
DC 5V |
Heating Voltage |
5 ± 0.2V (AC·DC) |
Working Current |
180mA |
Circuit Voltage |
DC5V (Max DC 24V) |
Load Resistance |
10KΩ (adjustable) |
Test Concentration Range |
1-100ppm |
Clean Air Voltage |
< 1.5V |
Sensitivity |
> 3% |
Response Time |
< 1S (3-5 minute warm-up, theory preheating time 48 hours) |
The labels of the image given above are explained below:
If you want to learn more about the datasheet of this sensor in detail then you must see the link that is provided here:
Till now, we have been discussing the pins and their features at many points but for ease of learning, here is a table that shows the pins, their name, and precise descriptions that will help you to understand this sensor’s pin details:
Pin Label |
Description |
H (Heater) |
It connects to one side of the resistor that limits the current flowing through the internal heating coil. |
GND (Ground) |
It connects to the ground terminal of the power supply. |
A |
It connects to the circuit voltage. Pins A and B are interchangeable. |
B |
Connects to the circuit voltage. |
OUT (Output) |
Analog output pin that provides a voltage signal. |
Package Type |
Description |
Through-hole Modules |
These modules have pins that extend through holes on a PCB and are soldered on the other side. |
Surface Mount Modules (SMD) |
These modules are soldered directly onto the surface of a PCB using solder paste and a reflow oven. |
Grove Modules |
These come with a standardized connector format and are pre-assembled modules for easy integration in the circuit with microcontroller platforms such as Arduino. |
Multiple other options can be used in place of the MQ138 benzene gas sensor. Some important names in this regard are listed below:
Always buy sensitive devices like M138 from the well-reputed source and some of such examples are given below:
Just like the simple structure, the MQ138 benzene gas sensor has the simple way to work. As mentioned before, it follows the chemisterisitor and the details of this are shared in the following points:
As soon as the sensor is powered on, the heating circuit starts it work. It requires 20-25 seconds from the preheating and gradually, the temperature of the sensor reaches 300 Celsius.
At this temperature, the tin oxide is readily available for the reaction and it starts reacting with the surrounding air (assume it is clean air). At this point, the oxygen ions start accumulating on the surface of the sensing element. This results in an increase in the electrical resistance. These values are sent through the analogue pin.
The sensor is ready to detect any target gas around it.
When the target gas is leaked into the air, the oxygen ions from the depletion region react with it and start melting. This results in a decrease in the electrical resistance.
The change in the electrical resistance is indicated on the analogue pin and sent to any output device.
If the threshold value is set through the potentiometer then when the analogue values reach it, the sensor shows the digital output on the digital pin and this results in the indication of this gas on output gas without any need of a microcontroller.
The higher the concentration of target gas around the sensor the more is the magnitude of the analogue value.
Package Type |
Estimated Length (mm) |
Estimated Width (mm) |
Estimated Height (mm) |
Through-hole Modules |
20 - 40 |
15 - 25 |
10 - 20 |
Surface Mount Modules (SMD) |
5 - 15 |
3 - 10 |
2 - 5 |
Industrial Leak Detection
Occupational Safety Monitoring
Air Quality Monitoring
Environmental Remediation
Indoor Air Quality Monitoring (limited)
Personal Safety Devices (specialized)
Hence, today, we have seen the detailed information about the MQ138 benzene gas sensor. Our exploration commenced with a fundamental introduction, followed by an examination of the essential components comprising this sensor. We also understood the basic points from the datasheet of this sensor and then moved towards the working principle and through the steps, we understood the detail of how it detects the target gas. In the end, we saw the packages, dimensions, and applications of this sensor. I trust that I covered all the points and if you want to know more, you can ask in the comment section.