The Kynix Blog

CCD image sensors still remain preferable in some specialised application.Today I would like to talk something about CMOS image sensor technology. As the development of image sensor,CMOS technology is widely used in most machine vision applications.What's excited,perhaps as the concepts behind industry 4.0 become adopted more broadly--the need for mre capable vision systems has grown sharply. This is a video of CCD vs CMOS sensors Catalog   Historical and modern CMOS Improve productivity, support high bandwidth   readout Inherent flexible available About the high resolution Design the right products Conclusion FAQ Machine vision systems use images to gather information on a system or process and to then make decisions based on the image captured.While such systems are dependent upon lighting and software,the camera-and the image sensor within it-is the key component in the overall operation of the system,as well as the ability to improve manufacturing quality and increase productivity.At a high-level,a typical machine vision application involves som combinaton of basic measurement,counting or inspection functions.Objects may be assessed to confirm the number of objects present,to determine the number and size of features or their quality level.So machine vision could be used to not only determine that the proper number of holes have been drilled into an item, but also to verify the spacing and shape of each hole. Similarly, the location of an object may be determined in order for it to be picked up by a robot arm or to determine whether a feature is in the correct place. Other functions include reading a barcode, performing character recognition or measuring the level of a fluid.So machine vision could be used to not only determine that the proper number of holes have been drilled into an item, but also to verify the spacing and shape of each hole. Similarly, the location of an object may be determined in order for it to be picked up by a robot arm or to determine whether a feature is in the correct place. Other functions include reading a barcode, performing character recognition or measuring the level of a fluid.   Historical and modern CMOS Historically, machine vision systems have required CCD image sensors because of their high image quality and performance.  Today, however, CMOS image sensors have jumped to the forefront for many machine vision applications. Advances in CMOS pixel design have made the imaging quality available from this platform sufficient for a variety of different end uses.Modern CMOS image sensor platforms, such as that used in ON Semiconductor’s PYTHON family, are based on a global shutter pixel design that enables the capture of moving objects without the introduction of motion artefacts. In-pixel correlated double sampling provides low readout noise, while on-chip fixed pattern noise correction helps preserve image quality. Combined with a 10bit A/D converter and a dynamic range of 60dB, these features allow machine vision systems to leverage the intrinsic advantages of a CMOS platform in their operation.   Improve productivity, support high bandwidth readout With many machine vision applications looking to operate at ever higher speeds in order to increase productivity, image sensors must support high bandwidth readout. The output architecture of the CMOS platform enables this as additional digital outputs can be added to increase the available bandwidth. For example, the use of up to 32 separate LVDS outputs enables high resolution PYTHON devices to realise bandwidths that exceed those of modern computer interfaces, including 10Gbit Ethernet or USB 3.1. The ability to output at up to 80frame/s from a 25Mpixel device is well beyond the capabilities of standard CCD designs. Inherent flexible available The inherent flexibility available in CMOS output designs allows the frame rate to be further increased when operating in Region of Interest (ROI) mode, where only a portion of the image sensor array is read out. With proper design considerations, the speed increase when operating in this manner can scale by both the x and y dimensions of the ROI, enabling faster frame rates than can be realised when using a more standard CMOS output design, which only scales the x dimension. Consider the frame rates from the PYTHON 5000 image sensor compared to theoretical frame rates from a similar 5Mpixel sensor using a standard CMOS output. At full resolution, both designs would provide approximately 100frame/s, but when reading out a 1280 x 720 pixel ROI, the the PYTHON device’s frame rate increases to almost 600frame/s, while the standard output design would increase to only 300frame/s. This can be an important differentiator.    About the high resolution While high resolution can provide finer detail, this must be balanced by making sure that too much information is not captured, which would slow data processing. In addition to having the right number of pixels, they need to be in the appropriate aspect ratio for the application. For example, an aspect ratios of 1:1 is often used in pick and place applications to maximise image capture across the full field of view. Different spectral sensitivities, such as colour, monochrome and extended near infrared (NIR), may also be required to optimise the imaging system for the application. In order to do this, a camera manufacturer will look for an integrated family of image sensor products that includes multiple resolution nodes and colour options to support a portfolio of products.The PYTHON family has more than 40 options, with resolutions ranging from VGA to more than 25Mpixel. These devices are available in multiple configurations, including monochrome, Bayer Color and extended NIR sensitivities. Selected devices are available in low-power configurations or with removable tape to protect the image sensor during the camera assembly process.   Design the right products Avent Silica offers a range of evaluation kits to help designers understand the performance available from the PYTHON family of image sensors.These kits include an image sensor,the appropriate sensor headboard,FPGA evaluation board and software and accessories.The Flexible design also allows the evaluation hardware to be use with other PYTHON devices by purchasing additional image sensors.After identifying the most appropriate image sensor, designers then need to consider the remainder of the camera design. Complementary products from ON Semiconductor include embedded boards, power and signal chain components that allow engineers to choose between modular solutions and the flexibility of a discrete design. If a machine vision system needs to be brought to market quickly, it may not be possible to build it from the ground up. For those applications, Avnet Silica products such as the PYTHON-1300-C camera module. Based on the PYTHON 1300 colour image sensor and featuring a 0.5in SXGA CMOS image sensor with a resolution of 1280 x 1024 pixels, the module can be combined with Avnet Silica’s MicroZed Embedded Vision Carrier Card and the Smart Vision Development Kit to provide a complete hardware design, leaving the designer to only write the application software.\ Conclusion Because of the combination of image quality,bandwidth,image flexiblity and configuration flexiblity available from MOS image sensors has accelerated adoption of this technology in machine vision applications.What's celebrating,The imaging capabilities of such devices has ushered in a new level of performance and functionality for industrial imaging and CMOS sensor based imaging is now suitable for use in almost every type of design.   FAQ   1. How does a CMOS image sensor work? Unlike CCD sensors that use high-voltage analog circuits, CMOS sensors employ a smaller digital circuitry that uses less power, and are in principle free from smear (vertical white streak in the image taken under bright light) and blooming (corruption of images such as white spots).   2. Which sensor is better CCD or CMOS? CMOS sensors have thousands. This means that CMOS cameras can read out incredibly fast, even 100X faster than a comparable CCD. For long-exposure applications that is not so important, but it is especially important for video cameras.   3. Is CMOS a full frame sensor? "Full frame" is a description of sensor size, sort of... "CMOS" is a name for semiconductor technology used to make sensors. So, they are definitely different, and not comparable.   4.What is CMOS sensor type? A CMOS sensor is an electronic chip that converts photons to electrons for digital processing. CMOS (complementary metal oxide semiconductor) sensors are used to create images in digital cameras, digital video cameras and digital CCTV cameras.   5. What is the function of image sensor? An image sensor is a device that allows the camera to convert photons – that is, light – into electrical signals that can be interpreted by the device. The first digital cameras used charge-coupled devices, facilitating movement of the electrical charge through the device so it could be modulated.   6. What is difference between CCD and CMOS? The biggest difference is that CCD sensors create high quality images with low noise (grain). CMOS images tend to be higher in noise. CCD sensors are more sensitive to light. CMOS sensors need more light to create a low noise image at proper exposure.   7. What CCD means? Charged Coupled Device. Stands for "Charged Coupled Device." CCDs are sensors used in digital cameras and video cameras to record still and moving images. The CCD captures light and converts it to digital data that is recorded by the camera. For this reason, a CCD is often considered the digital version of film.     8. What is CCD and CMOS? CCD (charge coupled device) and CMOS (complementary metal oxide semiconductor) image sensors are two different technologies for capturing images digitally. Each has unique strengths and weaknesses giving advantages in different applications.   9. Is CMOS sensor good? CMOS sensors traditionally have lower quality, lower resolution and lower sensitivity. CMOS sensors are just now improving to the point where they reach near parity with CCD devices in some applications. CMOS cameras are usually less expensive and have great battery life.   10. How does a CCD work? Fundamentally, a charge coupled device (CCD) is an integrated circuit etched onto a silicon surface forming light sensitive elements called pixels. Photons incident on this surface generate charge that can be read by electronics and turned into a digital copy of the light patterns falling on the device.  

SummaryRihito Kuroda, a researcher at Tohoku University in Japan who develops UV imagers in his lab said“There's important information hidden in the UV,”. However, this information has been difficult to capture; silicon doesn't absorb ultraviolet wavelengths very well, and other semiconductors that play well with ultraviolet light make slow imagers with low frame rates. But that’s about to change. This week at the International Electron Devices Meeting in San Francisco, two research groups presented ultrathin, flexible UV sensor designs they hope will help make these devices more widespread.  UV images reveal spots that presage rot on mushrooms, dark lines along flower petals that guide insects to nectar, and clouds of acetone in water. And with their relatively short wavelengths, UV sensors could be well suited to more precise navigation for flying swarms of tiny drones. The research aimed at making UV sensors from specially formulated paperA group from King Abdullah University of Science and Technology in Saudi Arabia presented their research aimed at making UV sensors from specially formulated paper. Electrical engineering student Chun-Ho Lin explained that it’s difficult to make flexible UV sensors because they heat up under the high-energy rays. Typical flexible substrates, like plastic and paper, can’t wick away that heat quickly enough. He and other electrical engineers in Jr-Hau He’s lab made thermally conductive, UV-sensitive paper by combining boron nitride nanosheets with cellulose fibers. Flexible sensors made from this formulation can take the heat, withstanding temperatures up to 200 degrees Celsius. What’s more, they are blind to wavelengths above the deep UV band.Other researchers are sticking with silicon, but using graphene to help it along. Yang Xu, an electrical engineer at Zhejiang University in China, says there are good reasons to work with silicon, even though in its native state it is a strong reflector of UV rays. Silicon photodetectors can work quickly, enabling higher frame rates, and they can draw on a vast manufacturing infrastructure. Xu says his philosophy is, “Why not help silicon do better?” With that in mind, his team is pairing the semiconductor with graphene, which absorbs UV light like a champ. To make flexible silicon-graphene UV photodetectors, the Zhejiang University group uses etching and rubber stamps to transfer ultrathin silicon microstructures to a flexible plastic substrate, then coats the silicon with graphene and adds electrodes. This photodetector is blind to visible light, because the silicon layer is just 20 nanometers thick and cannot absorb it. This ultrathin device is flexible and performs as well as state-of-the-art UV photo detectors, says Xu. His lab is currently working on shrinking the size of the photodetectors to improve their resolution. 

SummaryHappy new year! The year of 2017 has become a past tense,whatever you experienced in the last year,let's celebrate the 2018's coming together ! Today I would like to show you a power projects about the high power voltage current  bridge driver using IR2153&IGBT. Project PhotoThis is a high power voltage current half bridge driver. About IGBT and IR2153IGBT based alf bridge board has been designed for multiple applications,like induction heater driver,tesla coil driver,DC-DC converters,SMPS etc. High current and high voltage IGBTs are used to serve high power requirements. IGBT NGTB40N120FL2WG from ON semi and IR2153 from Infineon semiconductor are important parts of the circuit, IR2153 is a gate driver IC including inbuilt oscillator, 40A/1200V IGBT can handle large current.  Gate driver circuit works with 15V DC and load supply 60V DC to 400V DC.  The IR2153D(S) are an improved version of the Popular IR2155 and IR2151 gate driver ICs, and incorporate a high voltage half-bridge gate driver with a front end oscillator similar to the industry standard CMO 555 timer. The IR2153 provides more functionality and is easier to use than previous ICs. A shutdown feature has been designed into the CT pin, so that both gate driver outputs can be disabled using a low voltage control signal. In addition, the gate driver output pulse widths are the same once the rising under voltage lockout threshold on VCC has been reached, resulting in a more stable profile of frequency vs time at startup. Noise immunity has been improved significantly, both by lowering the peak di/dt of the gate drivers, and by increasing the under voltage lockout hysteresis to 1V. Finally, special attention has been played to maximizing the latch immunity of the device, and providing comprehensive ESD protection on all pins.Oscillation frequency adjustable by onboard Trimmer potentiometer, frequency spans approx. 12 KHz to 100 KHz, duty cycle 50%. Note: Please take appropriate precautions as this power supply uses lethal voltages! Features Load Supply 60V to 400V DCGate Driver Supply 15V DCFrequency Span 12 KHz to 100 KHz, Other frequency range possible, alter R5, PR1, C8Duty Cycle Approx. 50%PR1: Trimmer Potentiometer to set the frequencyCN3: Logic Supply 15V DCCN1: Supply DC InputCN2 : L1 Load SchematicTesla Coil ExampleParts List  Connections Note 1: The circuit is provided with few extra components which may be used as per application requirement other components can be omitted as stated in BOM 2: Frequency span is determined by CT Capacitor (C8) and Trimmer Pot value, refer to datasheet for appropriate value for required frequency span. C8 1Kpf, R5=7k5 and PR1=50K provide frequency span 12 kHz to 100 kHz. 3:  Other Mosfet or IGBT can be used as per your current and voltage requirement. 4: This board also can be used as half bridge driver using IR2101/IR2104 and Mosfet, Header CN3 Pin1 HIN, Pin2 LIN, Omit following components R5, PR1, C8 to use IR2101/IR2105 5: IGBTs require large size heat sink. 

SummaryRecently the designers found a approach to improve speed,cost and linearity of A-D conversion--Using  ‘voltage-to-frequency converters’(VFCs) to perform A-D conversions in data acquisition systems that require strict monotonic response,high resolution and reuced noise and moderate speed.The VFC produces a pluse train with frequency proportional to the input voltage.Then a microcontroller or logic converts fre quency into a number by opening a gate for a fixed amount of time and counting how many.However,this approach is not perfect.the main drawback is that to increase speed, designers have to run the VFC at high frequency, which deteriorates linearity.   Design Ideathe design idea of this aproach reverses things.A circuit converts input voltage into a proportional time interval;then,the micro uses that interval to count pulses coming from its internal clock.The results are impressive:1.Good linearity as the voltage-to-period converter runs at low frequency2.Faster A-to-D conversion due to the high value of the clock frequency3.Potentially simpler program or logic, as it only has to count clock pulses, gated by the circuit4.Low priceCircuit and Voltage IssueThe key is that increasing the count frequency does not affect linearity of the A-to-D conversion, while increasing the frequency of the VFC always means worse linearity.Just see the following picture: This picture is a circuit about modified VFC,where the input voltage VIN and the reference voltage VREF swap their roles. The R1-R2 network shifts the input voltage so it is always more positive than the reference voltage and maintain proper operating conditions. The circuit uses all switches of the 4066 part: two in parallel build S1 to reduce the effect of imperfect switch flatness on linearity, one switch goes for S2, and the last switch is part of the start-up circuit, paralleling CINT, and controlled by the logic during initialization.As the input voltage changes from 0 to 5V, the output period changes from 78 to 578µs. Integration capacitor CINT and the threshold level of the one-shot’s Schmitt input do not participate in the period vs voltage relation.Filling the period with 10MHz clock pulses generates numbers from 780 to 5780 – one count per millivolt. Linearity is one count or ±0.02%, which is not a surprise when the maximum frequency is only 12.8kHz. The maximum time of the A-to-D conversion is 578µs. This is 8.65 times faster compared to the case of a 1MHz VFC, where it would take 5,000µs to count 5,000 pulses of 1µs. The interface program is short and simple.Calibration involves some back and forth due to the shift of the input voltage: adjust sensitivity to 100µs/V using the trim-pot of the one-shot. The nominal duration of the one-shot pulse is 26µs. Cancel the 780 count offset in the controller.The following table  shows that the V-to-P approach is significantly better than the V-to-F one (Refs 3, 4). Surprisingly, no chip-maker offers this type of converter.

SummaryIf you have follow the informations of sensor,you will know that sensors are always in a state of rapid progress.Now I will state a few things to prove it in the following.Sensor,also called Transducer, is a kind of detection device,it can receive the measured information and then output them according to a certain rule or other needed form to meet the transport, handling,storage,recording,displaying and controlling of imformation,etc. Know more about it,you can read the article : Most Comprehensive Sicence Popularizing of Sensor (detection device) Researchers created quantum control technique for quantum sensorsAs we all known,there is a common problem that designers are harder to deal with quantum sensing devices. How,University of Sydney researchers have sloved this trouble associated with this super-sensitive tech. They have created quantum control techniques in collaboration with Johns Hopkins Applied Physics Laboratory and Dartmouth College. This development will allow next-gen ultra-sensitive sensors to identify small signals and reject unwanted background noise.By applying the right quantum controls to a qubit-based sensor,the team adjust its response in a way  that guarantees the best possible exclusion of the background clutter—that is, the other voices in the room. In order to obtain and analyze signals, measurement protocols are set in place. Over the years, these protocols have lagged behind the advancement of electronic devices. The disparity has led to a phenomenon known as “spectral leakage,” which occurs when quantum sensors return unclear results.What's more, the new control protocols have reduced spectral leakage by several orders of magnitude by using improved sensor hardware. All the approach is relevant to nearly any quantum sensing application and can also be applied to quantum computing as it provides a way help identify sources of hardware error.‘quantum control techniques' is a major advance in how to operate quantum sensors.  New sensors uses for effective control of enviroment pollutionEnviromental pollution issue are always paid great attention by human being as the development of all the world. A team from the Faculty of Physics of Lomonosov Moscow State University has suggested using porous silicon nanowire arrays in highly sensitive gas sensors which may be used both for effective control of environment pollution levels and for the monitoring of air composition in closed spaces,from classrooms to space stations.According to researchers, these devices will be able to detect the presence of toxic and non-toxic gas molecules in the air at room temperature.Each sensor consists of an array of 10 micron long organized silicon nanowires with diameters ranging from 100 to 200 nm. Each nanowire has porous crystalline structure. The size of silicon crystals and pores between them in individual nanowire, varies from three to five nanometers.ey can be obtained by means of a cheap method of metal-assisted chemical etching. It is based on selective chemical etching, i.e. partial removal of surface layer from a bulk crystalline silicon with the use of metal nanoparticles as a catalyst. Moreover, the procedure is quick—at least 100 elements can be produced in a lab within just one hour.Such porous nanowires have huge specific surface area due to which their physical and chemical properties are extremely sensitive to molecular environment. It was also found out that the obtained samples exhibited an effective photoluminescence in the red spectrum region at room temperature. What's important,this gas sensors based on porous nanowires both work at home temperatures and also are reusable, because the all observed effects were completely reversible. Military sensor systems collect accurate informationCollecting accurate user and environmental information such as enemy's location,survive shock, vibration, moisture plays an important role in military system. Deployment complaints about the platform aside, Lockheed Martin’s Electro-Optical Targeting System (EOTS) for the F-35 Lightning II is a high-performance, lightweight, multi-function sensing solution for precision air-to-air and air-to-surface targeting (Figure 4). Integrated into the aircraft fuselage with a rugged sapphire viewport, the device talks to the aircraft via a fiber-optic interface.Presented as the first sensor to combine forward-looking and infrared search along with track functionality, EOTS enables situational awareness and precision delivery of laser and GPS-guided weapons. Advanced EOTS, the next iteration, will incorporate enhancements and upgrades like short-wave infrared, high-definition television, and an infrared marker.Today’s military sensors must operate well on their own, and function as part of a combined-arms approach with an interlaced network of sensing, to detect threats of any nature from any direction. One such way to address this is with a battlefield awareness solution like 3D Advanced Warning System (3DAWS) from BAE Systems, which can provide universal threat detection to an aircrew with a layered countermeasure defense.The modular and expandable system can integrate with fixed- and rotary-wing aircraft and countermeasure systems, with the flexibility to work with existing radar or laser warning systems. The core of the 3DAWS suite is the passively-cued, semi-active radio frequency 3D Tracker element, which serves as an adjunct to current and future passive threat detection systems. 

 This article is a brief introduction to contactor.  Catalog  I. What is a Contactor?II. Differences Between Contactor and RelaysIII. Contactor Working PrincipleIV. About Arc SuppressionFAQ I. What is a Contactor? As an essential part of the motor control gear, the most widespread switching device used in a starter is the a,c. airbrake contactor which consists of contact assemblies actuated by electromagnetic action. An operating coil is enclosed by the magnetic yoke, as well as when energized attracts an armature to which is attached a set of moving contacts which make with a set of stationary contacts. Modern contractors use a silver alloy contact tip, normally silver–cadmium oxide or silver–tin oxide alloy attached to a brass or copper backing strip. The choice of tip material is critical and is normally established after many types of tests.  Note: The rating of the contactor depends on the size, shape, and material of the contacts and on the efficiency of the arc extinction method used. An electrical contactor is an electromagnetic switch similar to a relay. It is a switch that can be controlled with the current/pulse to switch over an electrically powered circuit. II. Differences Between Contactor and Relays Let me put forward a basic question firstly:If you see in industrial control panels, both relays and contractors are used for the same purpose, so why different names? Both of them perform the same task. The relay is usually used in low voltage paths such as switching tube-light or small LEDs. The contactor is used in electrical circuits of industrial motors or other heavy applications. So, the difference is from an application point of view. The basic working principle is the same for both. The relay behaves similarly to how a contractor works. If you want to switch circuits with high voltages, use contactors and if you want to switch light voltages then the relay is ready for you.  It is important to note here the difference between protection and switching. A relay is a protection device whereas a contactor cannot assure you about protection. The relay can differentiate between normal & abnormal conditions and give command accordingly which contactor cannot. Switching means to break and make a circuit and a contactor is mainly used for that purpose. III. Contactor Working Principle When the contactor coil is de-energized, gravity or a spring returns the electromagnet core to its initial position and opens the contacts. For contactors energized with alternating current, a small part of the core is surrounded by a shading coil, which slightly delays the magnetic flux in the core. The following video will help you understand the working principle of contactor more intuitively:  IV. About Arc Suppression Most motor control contactors at low voltages (600 volts and less) are air brake contactors; air at atmospheric pressure surrounds the contacts and extinguishes the arc when interrupting the circuit. Modern medium-voltage AC motor controllers use vacuum contactors. High voltage AC contactors (greater than 1,000 volts) may use a vacuum or an inert gas around the contacts. High voltage DC contactors (greater than 600V) still rely on air within specially designed arc-chutes to break the arc energy. High-voltage electric locomotives may be isolated from their overhead supply by roof-mounted circuit breakers actuated by compressed air; the same air supply may be used to "blow out" any arc that forms.Without adequate contact protection, the occurrence of electric current arcing causes significant degradation of the contacts, which suffer significant damage. An electrical arc occurs between the two contact points (electrodes) when they transition from a closed to an open (break arc) or from an open to a closed (make arc). The break arc is typically more energetic and thus more destructive. Without adequate contact protection, the occurrence of electric current arcing causes significant degradation of the contacts, which suffer significant damage. An electrical arc occurs between the two contact points (electrodes) when they transition from a closed to an open (break arc) or from an open to a closed (make arc). The break arc is typically more energetic and thus more destructive.FAQ 1. What is the main function of contactor?Function of contactor, generally used for connected and disconnected of electric current supply. Usually in use for applications: motors, heater, lighting or electric power distribution. 2. Why do we need contactors?Contactors are used for high power applications. They allow a lower voltage and current to switch a much higher power circuit, so they are generally larger and more heavy-duty than control relays, enabling them to switch higher power loads on and off for many thousands of cycles. 3. How a contactor is wired?Break your circuit, L N E through your contactor. Link a permanent live and a neutral from your supply to your coil (Al + A2) then use your switch feed to your photocell from A1, and switch the wire to the switched phase of your contactor load. This should now open when light, close when dark. 4. What is NO and NC In Contactor?Normally Open (NO) and Normally Closed (NC) terms refer to type of dry contact or wet contact. Put very simply, a Normally Open sensor will have no current when in a normal state but when it enters an alarm state it will have +5V applied to the circuit. 5. How many types of contactors are there?The contacts are classified as power contact, auxiliary contact, and contact spring. There are two types of power contact; stationary contact and movable contact. The material used for the contacts has stable arc resistance and high welding resistance. 6. Why contactor is used?Contactors are used for high power applications. They allow a lower voltage and current to switch a much higher power circuit, so they are generally larger and more heavy-duty than control relays, enabling them to switch higher power loads on and off for many thousands of cycles 7. What is the difference between a relay and a contactor?A contactor joins 2 poles together, without a common circuit between them, while a relay has a common contact that connects to a neutral position. Additionally, contactors are commonly rated for up to 1000V, while relays are usually rated to only 250V. 8. What are the types of contactors?There are different types of contacts in a contactor, and they are; auxiliary contact, power contact, and contact spring. The power contact has two types that are; stationary and movable contact. Material for making contacts must have a high welding resistance and stable arc resistance. 9. What are the three major parts of a contactor or relay?There are three major parts of a contactor or relay: the coil, mechanical linkage and contacts. The coil is used to create a magnetic field and is rated based on voltage (24 V, 120 V, 208/204 V, 480 V). The mechanical linkage connects the armature to the contacts when the coil is energized, completing the circuit. 10. How contactor is connected?A contactor is typically controlled by a circuit which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 230-volt motor switch. Unlike general-purpose relays, contactors are designed to be directly connected to high-current load devices.