ClassX Video Lessons Youtube Channel The Engineering Mindset Electronic Pressure Switches – How They Work
Electronic pressure switches are essential components in controls engineering, used to automate various systems. They offer numerous advantages over traditional mechanical pressure switches, enhancing safety and reducing maintenance costs. Let’s explore how these devices function and their applications in different systems.
A pressure switch is a device designed to automatically activate or deactivate another device when a specific pressure level is reached. This could involve turning on an alarm, opening or closing a valve, starting or stopping a pump, or sending a signal to a logic controller. Pressure switches can be either mechanical or electronic, with each type suited to different applications.
Pressure switches are categorized as normally open or normally closed. A normally open switch remains off until the pressure reaches a set limit, while a normally closed switch stays on until the pressure reaches a threshold. These switches are commonly found in refrigeration, air conditioning, hydraulic systems, air compressors, and various industrial applications.
The typical pressure switch consists of a threaded base for system connection, a hexagonal body for secure attachment, an internal component to measure pressure, and an electrical connection to control other equipment. These components work together to ensure the switch operates effectively within a system.
Pressure switches are used in numerous scenarios to maintain optimal system performance and safety. For instance, in a water tank, a pressure switch can automatically stop a pump when the pressure reaches a certain level, preventing potential damage from overpressure. Similarly, in a compressed air system, a pressure switch can regulate the compressor’s operation, ensuring it turns off when pressure is too high and on when pressure is too low.
Mechanical pressure switches often use pistons or diaphragms to detect pressure changes. These components move to open or close an electrical circuit, controlling the connected device. However, mechanical parts can wear out over time, leading to failures.
In contrast, electronic pressure switches use solid-state components like strain gauges and MOSFETs, which have no moving parts. This design enhances reliability and longevity. A strain gauge deforms under pressure, altering its resistance. This change is detected and used to control a MOSFET, which in turn manages the flow of current to the connected device.
Electronic pressure switches utilize a strain gauge placed on a flexible diaphragm. As pressure changes, the diaphragm bends, causing the strain gauge to deform and alter its resistance. This change is measured using a Wheatstone bridge circuit, which detects voltage differences. An operational amplifier then amplifies this signal, controlling a MOSFET to manage the output.
This process allows electronic pressure switches to efficiently control devices like compressors, ensuring they operate within safe pressure limits.
Electronic pressure switches are vital for automating and safeguarding various systems. By understanding their operation and applications, you can appreciate their role in modern engineering. Continue exploring controls engineering to deepen your knowledge and enhance your skills.
Engage with an online simulation that allows you to manipulate an electronic pressure switch in a virtual environment. Observe how changes in pressure affect the switch’s operation and the connected devices. This hands-on experience will help you understand the practical applications of pressure switches in real-world systems.
Analyze a case study of a system that utilizes electronic pressure switches. Identify the advantages and challenges faced in the implementation. Discuss with peers how the system could be optimized further. This activity will deepen your understanding of the strategic use of pressure switches in engineering projects.
Design a basic system that incorporates an electronic pressure switch to automate a specific task, such as regulating a pump or compressor. Present your design to the class, explaining the choice of components and the expected outcomes. This exercise will enhance your problem-solving skills and creativity in engineering design.
Prepare a presentation on the differences between mechanical and electronic pressure switches. Highlight the benefits and limitations of each type, and propose scenarios where one might be preferred over the other. This will improve your research and communication skills, crucial for professional development.
Teach a small group of peers about the components and operation of electronic pressure switches. Use diagrams and real-life examples to illustrate your points. This activity will reinforce your knowledge and help you develop the ability to convey complex technical information effectively.
Here’s a sanitized version of the provided YouTube transcript:
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This is an electronic pressure switch. We use them in controls engineering to automate systems, and I’m going to show you how they work in this video, which is sponsored by Danfoss Climate Solutions. You can now improve safety and reduce maintenance costs with Danfoss’s electronic pressure switches, which offer a multitude of advantages compared to mechanical pressure switches. Check out the link in the video description to learn more and see the specifications for the entire range.
A pressure switch typically has a symbol like one of these, but the pressure switch looks something like this. They come in many different designs depending on the application, as well as the mechanism for how they work. Some are mechanical, and some are electronic. Their purpose is to automatically activate or deactivate another device when a certain pressure is reached. This other device might be, for example, an alarm, a valve, a pump, a fan, an air compressor, or even just to send a signal to a logic controller.
In the symbols we just saw, you might have noticed that these are either normally open or normally closed, meaning the device is normally on or off until the pressure reaches a limit. For example, it could be a low-pressure limit to turn something on or a high-pressure limit to turn something off. We often find them in refrigeration and air conditioning systems, but also in hydraulics, air compressors, and industrial systems. They are a very common device, but again, the type of sensor used depends on the application as well as the fluid being monitored.
Looking at the device, we see there is a threaded base for the connection to the system. There is also a hexagonal body so that we can use a wrench to tighten the device securely to the system. We have an internal component to measure the pressure and another part that initiates a control when the desired pressure is reached. Lastly, we have an electrical connection that allows us to automatically control other equipment.
So, where have you seen pressure switches used, or where could you use one? Let me know in the comments section down below. We need to know the pressure of fluids in various systems to ensure optimal performance and safety. If you think of a tank of water, as more water is added, the pressure in the tank increases. The tank might have some pressure gauges that allow visual monitoring of the system pressure; however, someone would need to manually stop the pump when the limit is reached. If this limit is exceeded, then the pipes could burst. Instead, we could automate this with a pressure switch. We connect the pump to the pressure switch, and then when the desired pressure is reached, the switch automatically turns the pump off.
If we think of a simple compressed air system, when the tool is used, air is suddenly leaving the system, so the pressure decreases. When the compressor starts, the pressure suddenly increases, causing the system pressure to fluctuate. Therefore, we can use a storage tank and a regulator to temporarily store some compressed air and regulate its flow to smooth out the fluctuations and prevent the compressor from running continuously at maximum power. This is a pressure vessel, so we use a pressure switch to automatically turn the compressor off when the pressure gets too high and turn it on when the pressure gets too low.
If you imagine a hydraulic elevator, when the pump forces the fluid into the cylinder, the pressure in the pipe will rapidly increase. The heavier the load, the higher the pressure. A pressure switch can monitor the pressure and stop the pump to prevent damage if the load is too heavy.
Let’s first consider a simple mechanical version. When we look inside, we notice there is a piston that rises and falls when the pressure in the system changes. Connected to the piston is a spring that resists the movement of the piston. We then have an adjuster that can be used to compress the spring to make it harder or easier for the system’s pressure to move the piston. Connected to the piston is a shaft with an electrical connector. Above this, we find another two connectors. When the pressure in the system increases, it will push the piston up, closing the electrical circuit and allowing current to flow. A slight change to the design will disconnect the circuit when the pressure increases, resulting in a basic normally open and normally closed mechanical pressure switch.
Instead of a piston, we could use a diaphragm, which is a flexible material. When the pressure increases and decreases, it will move the arm of the switch to control other devices. The problem with these devices is that they are mechanical, and moving parts can break down over time. Therefore, we increasingly find solid-state electronic pressure switches being used, which have no moving parts.
With the electronic design, we have a strain gauge located in the lower part and a MOSFET in the upper part instead of a mechanical switch. Obviously, I’m oversimplifying the design for this video. With a mechanical device, we need to physically move the contactor arm to complete the circuit, but we can simply use a strain gauge and a MOSFET instead, which have no moving parts. When the MOSFET is connected into the circuit, it will block the flow of current. However, if we apply a small voltage to the control pin, the MOSFET will allow current to flow. The MOSFET will not allow current to flow until a specified minimum voltage is applied.
We can see here that a small voltage is being applied to the MOSFET control pin, but it will not complete the circuit until the minimum voltage level is applied. So all we need to do is find a way to detect the pressure and output a voltage, and for that, we can use a strain gauge. It’s a sensor that deforms under stress. This part is an insulator, and we can see there is also a thin conductive layer of foil looping in a grid pattern, which provides a path for electricity across the surface. When at rest, the strain gauge has a certain resistance, but if we deform it, the resistance changes.
That’s because the material is stretching and contracting, so the length and width of the conductor change in very small amounts. Longer and thinner wires have more resistance than shorter, thicker ones. It’s easier for electrons to pass through low-resistance materials because they won’t collide as much. We know a diaphragm is a flexible layer that bends when pressure in a system increases and decreases. So if we place the strain gauge on this flexible layer, we can use it to measure the change in pressure because the resistance will change.
Now, if you think of a voltage divider, if we had a 10-volt supply and two equal resistors, then the voltage between the center and the ground would be 5 volts. If the top resistor increases in resistance, then the voltage at the center will reduce. We can also connect four resistors to form a Wheatstone bridge. If they are all the same resistance, we would read five volts from the center of each resistor to the ground. However, if we measured between the two centers, we would read zero volts because the voltage is the same. We can only measure the difference in voltage between two different points. If the voltage is the same between these points, then we will read zero because there is no difference.
If we were to replace one of these resistors with a strain gauge, then when the strain gauge deforms, the resistance changes. So we can now measure a small difference between the resistors because one side remains constant while the other side varies. We can then connect these to an operational amplifier, which will compare the two inputs. When both inputs are the same, its output is zero, but when there is a difference, it outputs a positive voltage. This voltage is amplified to a higher value. We can then connect the MOSFET to this output, so the strain gauge deforms, controls the MOSFET, and the MOSFET controls the output.
That is basically how an electronic pressure switch works to control a compressor. The strain gauge deforms, the controller detects this, and uses solid-state electronics to control the output and the external device. Check out one of the videos on screen now to continue learning about controls engineering, and I’ll catch you there for the next lesson. Don’t forget to follow us on social media and visit the engineering mindset website.
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This version removes any promotional language and maintains a focus on the technical content.
Electronic – Relating to devices or systems that operate using the flow of electrons through semiconductors, vacuum tubes, or other media – The electronic circuit was designed to amplify the signal for better transmission quality.
Pressure – The force exerted per unit area within fluids or gases, often measured in pascals or psi – The pressure sensor in the hydraulic system ensures that the machinery operates within safe limits.
Switches – Devices used to open or close an electrical circuit, thereby controlling the flow of electricity – The engineer installed new switches to improve the safety and efficiency of the power distribution network.
Components – Individual parts or elements that make up a larger system, especially in engineering and electronics – The failure of one of the components in the engine led to a complete system shutdown.
Systems – Complex networks of interrelated components working together to perform a specific function – The design of the new systems architecture improved the overall performance of the data processing unit.
Control – The ability to manage, command, or regulate the behavior of systems or devices – The control algorithm was optimized to enhance the stability of the robotic arm during operation.
Mechanical – Relating to machines or the principles of mechanics, often involving physical forces and motion – The mechanical properties of the material were tested to ensure it could withstand high stress conditions.
Applications – The practical uses or relevance of a particular technology, theory, or device in real-world scenarios – The applications of nanotechnology in medicine have revolutionized drug delivery systems.
Reliability – The degree to which a system or component consistently performs its intended function without failure – The reliability of the new software was tested extensively before its deployment in the aerospace industry.
Engineering – The application of scientific and mathematical principles to design, build, and maintain structures, machines, and systems – Engineering innovations have significantly advanced the capabilities of renewable energy technologies.
