What Types of Sensors Can I Use in My PCB?

August 19, 2019 Cadence PCB Solutions

Set of gas sensors and infrared sensors

 

IoT devices, mobile devices, industrial equipment, environmental sensor networks…  the list of applications for different types of sensors seems endless. The market for sensors is continuing to grow to satisfy these demands and more. In these days where everything in our lives can be connected to our phones, it is almost expected that new consumer products with some level of connectivity will also interact with the environment or the user with sensors.

There are plenty of other applications that demand the use of sensors outside of consumer IoT devices. New developments in manufacturing and other industries are causing traditional tasks to become heavily data-dependent. This is where sensors networks become important for gathering data from the environment, manufacturing assets and other equipment, and even the workers themselves. This data can then be transmitted to a base station where it can be analyzed.

As the connectivity between end users, the environment, and other devices grows over time, PCB designers have to consider creative ways to design new products that enable this connectivity through the use of a broad array of sensors. With the right design techniques and choices of different sensors, you can create new products that interface with the analog world at all levels. 

How To Select Sensors

Selecting sensors for use in new connected products is about more than considering the phenomena you need to measure. You’ll need to consider the environment where the product is deployed and how the product will be used when determining which types of sensors and the specific sensors you need in your device.

The design and functionality requirements for your device are the first place to start considering which sensors your device needs to operate. Different types of sensors have different levels of accuracy, limit of detection, measurement range, form factor, power requirements, and breadth of capabilities. You’ll need to balance the required capabilities with your device’s mechanical footprint and enclosure when selecting sensors to include in your design.

As an example, if you are creating a wearable environmental monitor for use in a factory, you’ll need to balance the required level of accuracy and measurement range with the requirement to keep the device small enough to be worn. If your monitor needs to detect specific noxious gases, you don’t need to detect down to ppb levels if unsafe exposure reaches high ppm levels. In general, sensors with a lower limit of detection will also carry a greater cost, which becomes important if your device will be produced with high volume.

Some Design Considerations for Different Types of Sensors

Sensors are designed to interface with the analog world, thus the signals they collect are output as analog data. However, if this information is to be processed and transferred to a base station, or stored in a memory module, the analog output from a sensor needs to be converted to a digital signal. This means you will need to use standard mixed signal design and routing techniques to ensure signal integrity throughout your device.

 

Passive analog components on a green PCB

Your sensors will need some supporting analog circuitry

 

Power integrity is also an important consideration when working with any mobile device that includes sensors as these devices will likely run off batteries. Power integrity problems like ground bounce and ringing on a power bus can change the operating point of digital ICs in your board and corrupt converted data. These problems can also affect the accuracy of your sensor readings

Applications for Different Types of Sensors

Different types of sensors have their place in different applications, and the list of sensors you need to include is dictated by what you need to measure. The electronic sensors industry has taken great pains to design systems that provide detection of a long list of physical phenomena, ranging from electromechanical vibrations to chemical and biological measurements.

When you work with the right design software, you’ll have the capabilities you need to satisfy basic electrical and mechanical requirements in your device while incorporating the sensors and other functionality you want. Here are some ideas for different types of sensors you can use in your next sensor module or mobile/IoT device:

Infrared Sensors for Thermal Monitoring and Imaging

The simplest sensor for detecting infrared light is a photodiode. This sensor is easy to include in any PCB and allows quick detection of infrared light from a point source. For weak optical signals, avalanche photodiodes can be used to provide some gain, providing more reliable detection of infrared or visible light.

When it comes to thermal imaging, you’ll need to use a CCD in your PCB as the array of discrete photosensitive pixels provides the spatial resolution required to form an image. This provides thermal monitoring over a large field of view. Contrast this with a photodiode, which has lower sensitivity and can only be used to detect light from a single point.

Learn more about working with infrared sensors and photodiodes.

 

CCDs as types of sensors for infrared light detection

This CCD will be sensitive to infrared light

 

Vibration Monitoring

In manufacturing and other areas of industry, vibrations in different pieces of equipment can affect the quality of products produced at a factory, or they act as an indicator of mechanical problems that require immediate maintenance. These vibrations cannot always be detected by touch, nor can they be easily distinguished with the human ear. Monitoring vibration over a range of frequencies becomes very important for monitoring different pieces of heavy equipment.

Piezoelectric sensors and transducers are ideal for monitoring these vibrations over a range of frequencies. If deployed in a manufacturing environment, these sensor modules must be designed to meet more stringent mechanical demands compared to most consumer-grade devices.

Piezoelectric sensors are also useful for monitoring chemical or biological agents when driven near one of their resonance frequencies. A slight mechanical load applied to a piezoelectric element will shift the resonance frequencies and driving amplitude, which can be easily detected using analog signal processing circuits.

Learn more about piezoelectric sensors for vibration measurements.

Wireless Sensor Networks

Environmental, infrastructure, and safety in factories can be monitored remotely using wireless sensor networks. These networks of small embedded devices typically include a small number of sensors and wireless connectivity over WiFi, Zigbee, Bluetooth, or other wireless protocol. Data that is gathered and processed with a small microcontroller can then be passed to a base station over a wireless protocol, allowing real-time monitoring of important environmental information over a broad area.

One important design aspect for wireless sensor networks is the network topology that will be used to connect sensors into a single network. There are a number of protocols and topologies that can be implemented in a wireless sensor network. For a widespread sensor network, a mesh topology may be most useful, especially if the sensors are embedded in a mobile device.

Read more about PCB design for wireless sensor networks..

Embedded Automotive Sensors

Your car is already a large electromechanical computer that includes a large number of internal sensors to ensure the vehicle operates at peak performance. As cars become more connected to each other and to the internet, automotive designers will continue expanding the range of sensing capabilities in vehicles. This is especially important for autonomous vehicles, which need to gather a large amount of information from the nearby environment and other vehicles in order to operate safely.

Infotainment systems and the wealth of performance data that can be gathered from vehicles with embedded sensors require wireless connectivity to metropolitan area networks (MANs). This means infotainment designers will need to create systems that can collect this data and transmit it over the internet via a MAN. This all needs to happen wirelessly. The network of sensors within modern vehicles also requires its own topology and protocol to operate properly.

Read more about new developments in automotive sensors and connectivity.

 

Low noise PCB power supply

Disassembled differential pressure sensor

 

Sensors for Medical IoT Devices

Designing PCBs for use in medical devices brings its own set of standards and design requirements, depending on how these sensors will be used in patients. In addition to the safety aspects of designing medical devices, your options for sensors in these devices will be limited by form factor and signal integrity requirements. Data gathered with these devices will inevitably need to be processed with an external system and stored in a patient’s file, so connectivity becomes an important consideration in these devices.

Read more about design and routing topologies for medical IoT devices.

Cadence Brings Layout and Analysis Together for Sensor Module Design

Once the sensors on your board collect important measurements and the data is processed, you need to get the data off the board and onto a computer for analysis. This is where some kind of connectivity between your sensor unit and an external base station or directly to a computer is required. This can include USB connectivity, DB9 or a similar connection, Ethernet, or a wireless protocol.

This connectivity between sensors, mobile devices, other computers, and the PCBs that support sensor modules forms the foundation of the IoT revolution. You can create new devices that include the sensor modules you need alongside connectivity capabilities with the right PCB design and analysis software.

 

3D layout in OrCAD

You can create beautiful 3D layouts like this in OrCAD from Cadence

 

Cadence offers a full suite of PCB design and analysis tools that are adaptable to any application, including high speed and mixed signal design and simulation. The PCB layout and routing tools in OrCAD are your entry into the world of design for products that integrate many types of sensors. You’ll have access to a complete electronics design and analysis solution when you work with Cadence’s full suite of industry-standard design tools.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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