Monthly Archives: May 2018

What Are PhotoRelays?

Classification of relays include two main groups—contact type or electromechanical relays and contactless type or semiconductor relays. While sub-groups of the mechanical type include signal relays and power relays, those of the contactless type include the solid-state relays and photorelays.

Solid-state relays generally use semiconductor photo triacs, phototransistors, or photo thyristors as the output device, and such relays are limited to AC loads alone. On the other hand, photorelays preferably use MOSFETs as the output device that is capable of handling both AC and DC loads. Photorelays are mainly used as replacements for signal relays.

Photorelays are available mainly in two packages—the frame type in an SO6 package, and the substrate type in an S-VSON package. Both packages use a PDA chip and a MOSFET chip encased in epoxy resin for a hermetic seal.

As evinced by the name, a photorelay contains an LED to emit light when current passes through the diode. The emitted light crosses the isolation boundary to fall on the light sensor of the PDA chip, which in turn, powers and drives the gate of the MOSFET. This turns the MOSFET on, and allows AC/DC current flow through the power terminals of the MOSFET.

Compared to the electromechanical signal relays that the photorelays replace, the miniaturization of the mounting area offers a huge advantage in real-estate recovery. For instance, Toshiba is replacing large size packages such as SOP, SSOP, and USOP with miniature packages such as the VSON and S-VSON types. Replacing with photorelays contributes greatly to the miniaturization of the device.

As photorelays have no moving parts to fail, they are more reliable than the mechanical relays they replace. The basic operation of the photorelay involves LED light triggering the photodiode array, which then drives the MOSFET. Mechanical relays, on the other hand, suffer from wear and tear induced degradation. Photorelays are maintenance free, as they do not have contacts.

Since an LED drives the photorelay, the drive circuit can be relatively simple when compared with the drive circuit that a mechanical relay requires—a buffer transistor to boost the microcomputer output. The output pin of a microcomputer can easily drive a photorelay, as this is equivalent to driving an LED by the microcomputer, requiring very low currents of 3 to 5 mA maximum. Designers only need to consider the LED lifetime.

Mechanical relays suffer from chattering or bouncing—contacts connecting and disconnecting rapidly before finally settling down. In high-speed electronic devices, this chattering can cause misreading of the relay status. Moreover, every mechanical relay requires an additional diode to take care of high voltage generation from back electromotive forces. Photorelays do not suffer from chattering or back EMF forces.

Unless connected to the cold side of a circuit, mechanical relays have a shorter lifespan, as they arc when their contacts open when connected to a high voltage. On the other hand, it does not matter for the photorelay whether it connects to the hot or the cold side.

However, unlike the mechanical relay, photorelays cannot offer normally closed contacts without power being applied to the LED.

Progress in the World of Internet of Things

Although many in the electronics field lambast the Internet of Things (IoT) as an inappropriate or inadequate acronym, IoT is a space to huge to be confined to these narrow adjectives. In reality, IoT requires a blanket description, as it covers a vast arena. Problems arise from compartmentalization and although various spaces such as industrial and medical have established a big head start, others have yet to launch their true separate identities.

For the electronics designer this means taking the general palette of IoT features and functionalities and tailoring them specifically to the application at hand. The designer must be knowledgeable about state-of-the-art technologies such as those required for cloud connectivity, wireless design infrastructure, interface ergonomics, and internal power management. The designer must be familiar with the methods of manifesting them in their design, as these may be critical aspects.

For instance, there are several suggestions for scaling the IoT from smart factories to smart homes. Although there are blueprints for pollution reduction, city traffic management, and electrical energy distribution, the purveyors of industrial-grade operating systems do not yet have a detailed plan for the smart home.

According to Wei Tong, Product Marketing Manager of Dialog Semiconductors, wearable technologies can do far more than simply functioning as personal items. Using Bluetooth, a communications standard protocol, wearable devices can connect to a larger network, allowing them to communicate with other devices via beacons and sensors, thereby manifesting the larger Internet of Things.

However, despite the birth of the phrase “the Internet of Things” 18 years ago, and the first connected IoT device 35 years ago, consumers are yet to adopt wearable IoT in mass quantities. According to Nick Davis, this is due to two factors—first, ease of use, or lack thereof, and second, lacking the purpose or serving the wrong purpose.

For instance, take the case of “smart” light bulbs. Some are easy to connect to and control with smartphones, while others give users a hard time. According to Nick Davis, once people face such difficulties, they tend to give up on the entire IoT and smart device concept.

Another example Nick Davis gives is that of a smart toaster or smart refrigerator and the purpose they serve. According to Nick, most companies have not done proper market research into the actual requirement of people who use toasters and refrigerators, and what the consumers expect in such smart devices. However, several new products on the market are potentially useful to designers.

Another example of wrong purpose is the video sunglasses from Snap, the parent company of Snapchat. These are basic sunglasses with a video camera attached. They allow users to capture and post videos more easily to Snapchat. According to Nick, Snap is stuck with hundreds of thousands of their unsold spectacles. Apparently, Snap did not realize that people are not very keen on walking around taking videos with their eyewear.

Despite such debacles above, newer products are appearing on the market that help designers achieve better energy-efficient IoT products, voice recognition engines, and flexible and smart motor-control options that are also lightweight and compact.

Nano-Diamonds Help Prevent Lithium Battery Fires

Last year, airline flights banned Samsung Galaxy Note 7s because of its battery-related fires and explosions. Scientists researching the source of the runway beat buildup found the culprit to be small dendrites forming between the anode and cathode of the battery. A materials specialist from the Drexel University at Philadelphia has proposed a low-cost easy solution to preclude dendrite formation.

According to Drexel professor Yury Gogotsi, this simply requires mixing nanodiamonds with the regular lithium-ion electrolyte at one percent concentration. Gogotsi discovered the method along with a doctoral candidate from Tsinghua University at Beijing. However, Gogotsi found it rather easier to confirm that the nanodiamond additive works, than getting Samsung and several other OEMs and Li-ion battery producers to follow the concept.

Gogotsi had to use internal financial support from Drexel for proving the concept. They are now trying to interest industrial partners for funding to characterize the process in more detail. Specifically, they have yet to determine the amount of nanodiamonds necessary to add to the electrolyte for particular applications.

As Li-ion battery technology is already expensive, it is possible that cost-conscious manufacturers are wary of increasing the cost of batteries because of the addition of diamonds of the nanodiamonds. However, according to Gogotsi, the concern is rather unfounded, as, contrary to popular belief, nanodiamonds are not expensive, but cheap to manufacture. Moreover, they can be easily created from waste materials.

Gogotsi suggests a very simple method of manufacturing nanodiamonds. According to him, this is possible using expired explosives—otherwise expensive to dispose of—and exploding them in a sealed chamber. The coating on the walls of the chamber will have more than 50% nanodiamonds with a typical size of 5 nanometers. This is similar to Superman making diamonds from coal in the popular comic books. The presence of nanodiamonds in the electrolyte of a Lithium-ion battery prevents the formation of dendrites that create shorts resulting in runaway heat build-up and subsequent fires.

Although Gogotsi uses nanodiamonds in his lab, the process for creating them came from Russia. Three separate laboratories in Russia independently perfected the technique, which was kept very secret.

A description of the process finally emerged from a publication from the Los Alamos National Lab, and worldwide people use the technique to turn waste into marketable products. These hard-to-dispose-of waste products include the expired C4. Several manufacturers use nanodiamonds widely in their products. These include medical coatings, industrial abrasives, and magnetic field measuring electronic sensors.

According to Gogotsi and his team, the nanodiamonds work as an additive to the electrolyte to co-deposit with lithium ions, and produces dendrite-free deposits of lithium. This is because lithium prefers to adsorb onto the nanodiamond surfaces leading to a uniform deposit of lithium arrays. This uniform deposition of lithium enhances the cycling performance of the electrolyte, leading to a stable cycling of lithium.

As the nanodiamond co-deposition significantly alters the plating behavior of lithium, the process offers a promising method of suppressing the growth of lithium dendrites in batteries using the lithium metal.

What is Better for Quality — Visual or Machine Inspection?

Although the human eye is a wonderfully complex instrument, it has its limitations. For instance, when inspecting objects on the production line, human eye cannot compete with machine vision, as the latter is not only faster, but also accurate to a larger extent.

The human eye works in tandem with the brain, allowing us to realize our surroundings. We can recognize things within split seconds, even with their exact shape varying. We can analyze our environment keenly, and although we have a wide field of view under normal conditions, our vision is flexible enough to allow us to focus very sharply on particular areas of interest. As humans learned to survive under different environments and stimuli, the ability of the eye gradually evolved over the millennia.

However, in adapting to our environments and circumstances, our visual capabilities are limited to the natural world. For instance, we have only two eyes, as stereoscopic vision is adequate. We do not need to see moving objects in detail, as the perception of movement is enough. We are sensitive to only a limited portion of the light spectrum, and unable to adjust to glare and reflections, which impede our ability to focus on certain properties of an object for a long time, mainly their size and color. Not only are we quite subjective to perception and storing of images, but our eyes are incapable of making accurate measurements. Therefore, our eyes are not the ideal instruments for verifying product quality.

Automatic inspection and analysis, based on imaging or machine vision, surpasses the performance of the human eye. Machine vision can be more accurate for reliable product inspection, and it is possible to combine it with different technologies to ensure highest quality in production environments.

For instance, in a fast-paced production environment, where long-term reliability is essential, the human eye cannot inspect 20 products moving every second, and where errors detection requires an accuracy of 0.02 square millimeters. Manual inspection with a whole team of people may be attempted, but this would go against the objectivity of inspection. Engineers solve the problem with machine vision. They have six cameras observing the fast moving products. As the cameras use polarized light with strobed exposure and very short shutter speeds, they create extremely sharp images on which the defects stand out perfectly. Computers use special software to search for the defects within 50 milliseconds, and the system can continue to do this for 24 hours a day for every day.

Our eye is capable of learning. We can spot anomalies or defects in products, and recognize it as a defect, although we have never seen the defect before. For instance, we recognize a scratch on a surface as a defect, and know it should not be there. Therefore, we have exceptional interpretative abilities, and for a long time, the human eye was almost unbeatable in this area.

However, machine vision technology is advancing, and in many cases, it is able to rival our interpretative abilities. Although this requires fast computers and self-learning vision algorithms, these are easily available. Therefore, machine vision is catching up fast with the capabilities of the human eye.

Stepper Motors with Higher Efficiency

Stepper Motors are essentially open loop systems working efficiently when required to produce torque. However, when the motor faces low torque situations, its efficiency falls drastically. By simply closing the current loop, it is possible to make the entire system operate more efficiently.

Users find them to be economical as stepper motors offer the advantages of excellent positioning with their simplicity. This feature makes them highly popular for use In general automation tasks such as positioning, indexing, inserting, feeding, and more. Now, with closed loop operations, users are finding stepper motors equally adequate for applications involving force and torque control.

Optimizing the operational performance requires users to understand certain characteristics of stepper motors. Traditionally, users operate stepper motors in open loop control. That means the drive electronics has no feedback regarding the torque the motor has to handle at any time. Therefore, the drivers continuously supply full load current even when the motor has no load to drive. The excess load current heats up the motor, reducing the efficiency of the system.

Such operation of stepper motors in open loop systems tends to classify them as inefficient devices because of the loss of power involved. However, this is not true, as stepper motors are highly efficient when called upon to deliver torque, only losing their operational efficiency when not driving a load. The problem is readily solved by providing a feedback to control the amount of current the motor actually requires for handling the present load.

Manufacturers have noticed the benefits of closed loop operation and offer integrated motors that produce higher torque, greater throughput, faster acceleration rates, reduced noise, and higher operational efficiency. These motors have a built-in closed loop system to reduce the input current to the motor automatically as the load reduces.

Such closed loop systems commonly employ a feedback device, usually an incremental encoder, for monitoring the error between the present shaft position as against its commanded position. The drive electronics runs algorithms to control motor current dynamically based on the error information from the feedback device.

The above process tends to reduce the overall current consumption, thereby saving power over conventional open loop stepper motor systems and improving the efficiency of the system greatly. The improvement is readily demonstrated by comparing the power consumption between two stepper motors, one operating in open loop and the other in a closed loop system.

A comparison of power consumption between the two motor systems driving identical loads shows the closed loop system will consume only a third of the power taken in by the traditional open loop stepper motor system for doing the same work. This proves the closing of the current loop results in the stepper motor operating with less power, improved efficiency, and lower costs. This also results in lower downtime, as there is a drastic reduction in motor heating.

Closed loop systems offer additional benefits apart from higher energy efficiency. A stepper motor operating in a closed loop offers faster acceleration and greater throughput because of the higher peak torque it generates—nearly 1.5 times its rated holding torque. The motor also runs more quietly.

Why Panic Buttons are Going Wireless

Panic buttons or emergency stop switches are extremely important for protecting workers, machinery, and products from catastrophic failures. Traditionally, manufacturers include them with their machinery, and most are hard-wired. However, things are changing and now, these red emergency switches are finally going wireless.

When a machine malfunctions, or a critical incident occurs, operators often have to press these last resort switches to bring the system or the entire machine to a halt quickly and safely. Hence, these switches are aptly called E-stop, emergency, or panic switches. Operating these switches brings the machine or the system to a halt and prevents serious damage to products or the machine itself, as well as preventing injury to workers.

The importance of the emergency stop button is evident from a report from OSHA or Occupational Safety and Health Organization. According to this report, more than 5000 US workers were injured fatally in 2015 in industrial accidents.

Ever since the second industrial revolution, manufacturers have hard-wired E-stops in their machines as a standard solution to shut them down in case of emergency. Usually, manufacturers placed these emergency switches well apart from the usual on/off and other switches the machines normally carry on their control panels, making it easier for the operator to identify and hit them to stop the machine. With the E-switches being functionally so important, it is understandable manufacturers were reluctant to make them wireless. However, a wireless E-stop device would allow the worker to shut the machine down without even having to go near it, improving the safety factor.

The tech company, Laird PLC, of London, has seemingly realized the additional benefit of a wireless E-stop button, and has evolved the Safe-E-Stop. It is possible to incorporate the Safe-E-Stop with the existing hard-wired emergency stop system already involved with production systems such as assembly lines. This improves the on-the-job safety, as an individual operator or a group can immediately shut down a machine in the production line, without having to hit the hard-wired E-stop button physically.

The emergency might involve the closest machine-mounted E-stop button in the same danger zone. Therefore, the operator rushing in to operate such an emergency button could face a hazard and increase the response time for arresting the emergency.

Laird PLC has developed a wireless personal safety solution rated at SIL 3 as an answer to the above problem. The Rockwell Automation distributors market the Safe-E-Stop from Laird making it available through the Encompass partner program of Rockwell Automation.

Users can have continuous status indication on LED and LED readouts on the Safe-E-Stop system. They can use the IP/Ethernet port on the MSD or Machine Safety Device for reporting the status of the wireless E-stops actuated to personnel in charge of operations. It is possible to link as many as five PSDs or Personal Safety Devices to the MSD simultaneously. This allows multiple operators to collaborate or work independently to supervise the operation. Activation of an E-stop on any linked PSD causes the MSD to issue a stop command and notify all other PSDs immediately of the stop condition.

Computer Vision & Robotics in Farming

Robots are helping several industries ease labor concerns. This is increasingly so in today’s industrial environment, where the workforce is aging and work output decreasing for lack of efficiency. This includes agricultural fields in both the US and Europe, where the introduction of robots in fieldwork is helping to reduce current labor concerns. New farming standards brought on by natural and chemical resources is increasing the need for precision work, and robots and new technology is helping to alleviate that.

According to Dan Harburg, the design of traditional robots allowed them to perform only specific tasks repeatedly. Dan is with Anterra Capital, an agriculture technology venture capital firm from Amsterdam. According to Dan, robots for agricultural applications must be more flexible than those in automotive manufacturing plants are, as the former need to deal with the natural variation in outdoor environment and food products.

Accordingly, Anterra Capital considers investing in three major category areas in agriculture related to seeding and weeding, harvesting, and environmental control. Dan envisages each of these major categories would benefit from the introduction of advanced technology and robotics.

For instance, farmers get a two-fold benefit from spraying and weeding robots. First, these robots reduce the labor necessary for eliminating such mundane tasks. Second, by precise targeting of crops, the robots bring down the quantity of pesticides necessary to be sprayed. This allows farmers to save on labor costs and produce safer, healthier crops at the same time. For instance, see and spray robots from Blue River reduce agrochemical use by about 90%, as they use computer vision for targeting weeds.

Different technology companies have developed spray robotics. One among them is the Blue River Technology, a farm robotics start-up specializing in spray and weeding robots. According to Blue River, its tractors operate at 6-8 mph, covering 8-12 rows of crops simultaneously. Advanced vision systems on the tractors enable them to differentiate weeds from crops to provide direct targeting as it passes over them.

Autonomous robots from Naio Technologies use laser and camera guidance systems for navigating between rows of fruit s and vegetables autonomously, identifying different types of weeds. Oz, the robot from Naio, runs on four electric engines, working continuously for three hours before needing a battery recharge. Not needing human supervision, Oz follows rows of crops on the plot autonomously, to remove all weeds.

PlantTape, from Spain, offers a plant-transplanting robot that can plant seeds. The robot fully integrates the system of sowing, germination, and nursery care. This brings much higher efficiency as compared to that from conventional transplanting methods. The robot creates trays of tape for holding soil and seeds, with each tray holding nearly 900 plants. While pulling the tape from the tray, the automated robot tractor cuts the tape around each plant as it places the plant accurately in the soil. Farmers use PlantTape robots for planting tomatoes, onions, celery, cauliflowers, broccoli, and lettuces.

Although automation in harvesting crops is common, the variation in size, height, and color of the plants compounds the problem. They also require light pressure and touch for delicate picking. Vacuum suction robotic arms help in this area.

Raspberry Pi Drives the Oton Glass

Imagine standing in front of several road signs but unable to locate the one you want, because they are all written in a foreign language. This is the job for the OTON GLASS, a device to capture the image, translate it to a language of your choice, and read it to you in your ear. Not only will this help travelers abroad, but also help people with poor vision and those suffering from dyslexia.

Oton Glass is the effort of Keisuke Shimakage, who says he was inspired to develop the device by his father’s dyslexia. Keisuke got together a team of engineers and designers from the Media Creation Research Department at the Institute of Advanced Media Arts and Sciences, Japan, and started on the project.

At the heart of the Oton Glass is a Raspberry Pi 3 (RBPi3), along with two tiny cameras, and an earphone. One camera resides on the inside of a spectacle frame, tracking the user’s eyes. As soon as it detects the user blinking with no eyeball movement, another camera on the outside of the frame captures the image of whatever the user is looking at. The RBPi3 then processes the image, running it through an optical character recognition program. If there are any written words in the image, the RBPi3 coverts them to speech, and plays it through the earphone into the user’s ear.

Although the initial prototype of the Oton Glass was slow in capturing and replaying the text into audio, the team was able to cut down the time from 15 seconds to a mere 3 seconds in their second prototype.

The team designed the case in CAD software and 3-D printed it to be able to test it in real life situations. With feedback from dyslexic users, they were able to upgrade the device further.

At present, the Oton Glass is doing the rounds at several trade and tech shows throughout Japan, and is ready for public distribution. Trial is underway with models of the device at the Nippon Keihan Library, Kobe Eye Centre, and the Japan Blind Party Association. The Oton Glass has won the runner-up prize for the James Dyson Award of 2016. It has also generated huge attention at several other award shows and in the media.

In front of the inside camera of the Oton Glass is a lens with a half mirror that reflects the eye of the user, which the camera tracks for movements. The outer camera waits for a trigger from the blink of a still eye resulting from the wearer reading something, and captures the image and passes it to the RBPi3.

The RBPi3 uses an optical character recognition software to filter out any characters in the image. It then uses artificial voice technology to change the words into sounds, whose meaning the user can understand. If the Oton Glass is unable to recognize some characters, it sends them to a remote server to decipher. This allows the Oton Glass to translate anything that the user sees. The device combines camera-to-glasses and looks very much like normal glasses.

What Are Super-Junction MOSFETs?

Switching power-conversion systems such as switching power supplies and power factor controllers increasingly demand higher energy efficiencies. For such energy-conscious designers, super-junction MOSFETs are a favored solution, as the technology allows smaller die sizes when considering key parameters such as on-resistance. This leads to an increase in current density while enabling designers to reduce circuit size. With increasing market adoption of this new technology goes up, other challenges are coming to the fore, mainly the requirement for improved noise performance.

High-end power supplies for equipment such as LED lighting, LCD TVs, notebook power adapters, medical power supplies, and tablet power supplies require reduced electromagnetic noise emission. Designers prefer using resonant switching topologies such as the LLC converter with zero-voltage switching, as these have inherently low electromagnetic emissions. Super-junction transistors in the primary side switching in an LLC circuit helps designers achieve a compact and energy-efficient power supply.

Compared to conventional planar silicon MOSFETs, the super-junction MOSFET has significantly lower conduction loss for a give die size. Additionally, architecture of the latter device allows lower gate charges and capacitances, leading to lower switching losses compared to conventional silicon transistors.

Fabricators used a multi-epitaxial process for structuring the early super-junction devices. They doped the N-region richly allowing a much lower on-resistance compared to conventional planar transistors. They adapted the P-type region bounding the N-channel to achieve the desired breakdown voltage.

The multi-epitaxial processes resulted in the N- and P-type structures being dimensionally larger than ideal and led to an associated impact on overall device size. The nature of the multi-epitaxial fabrication also restricted engineering the N-region to minimize on-resistance. Therefore, fabricators now use single-epitaxial fabrication processes such as deep trench filling to optimize the aspect ratios of N- and P-regions to minimize the on-resistance while also reducing the size of the MOSFET.

For instance, the single epitaxial fabrication process allows DTMOS IV family of Toshiba’s fourth-generation super-junction MOSFETs to achieve a 27% reduction in device pitch, while also reducing the on-resistance by 30% for each die area. Similarly, Toshiba’s DTMOS V, based on deep trench process, has further improvements at the cell structure level.

Thanks to the single-epitaxial process, the super-junction MOSFETs can deliver more stable performance when faced with temperature changes. Power converters with conventional MOSFETs are noted for reduced efficiencies at higher operating temperatures, which the super-junction MOSFETs are able to counter. For instance, super-junction MOSFETs show a12% lower on-resistance at 150°C.

Power converters using the fifth-generation super-junction DTMOS V devices can now deliver low-noise performance along with superior switching performance. A modified gate structure and patterning helps to achieve this, resulting in an increase in the reverse transfer capacitance between the gate and drain of the device.

How to Select Current Sensors?

To select an appropriate AC current sensor for an application, you must know the operational frequency range and the current rating the sensor will encounter. Additional considerations that you will need to decide are the type of the sensor, its mounting (through-hole or surface mount), turns ratio, and the overall dimensions.

Sensor type refers to a sensor only configuration, where a conductor integral to the application forms the primary. Another type could be a complete current transformer where the primary is included as a winding. Engineers typically use current sensors to measure and control the load current in control circuits, safety circuits, and power supplies. Power supplies usually require accurate control of current, and this requires sensing the magnitude of the current accurately.

Irrespective of whether you are using the sensor or transformer, the highest flux density handled is dependent on the worst-case current and frequency faced by the device. However, note that exceeding 2000 Gauss will mean most AC current sensors output will be non-linear. Therefore, the current through the sensor and its output voltage will no longer remain proportional, as the magnetic core of the sensor saturates at very high flux densities. To keep the flux density below the saturation limit, it is necessary to use higher secondary turns.

For instance, in wire-through-the-hole style of current transformers, looping additional primary turns through the hole can dramatically reduce the turns ratio, provided the wire diameter and the hole size permit. Increasing the primary turns allows the use of a higher input current transformer to provide higher output voltage across the terminating resistor on the secondary.

Manufacturers of current transformers offer online tools to help designers select the right current sensor or current transformer for specific application conditions. Initially, the user has to select the type of sensor—a transformer or a sensor only. The next selection is the preferred mounting style—SMT or Through-hole. The online tool also requires other parameters such as the maximum sensed current expected in amperes, the input frequency in kHz, the duty cycle of the primary current waveform as a percentage, and the desired output voltage corresponding to the expected maximum input current.

The tool then calculates the required terminating resistance based on the maximum input current, the number of secondary turns and the output voltage—basing the calculations on a single-turn primary. Next, the tool calculates the maximum flux density of the secondary, making sure it does not exceed 2000 Gauss. It does this by taking into account the output voltage, the duty cycle, secondary turns, and the frequency of operation.

The result lists all part numbers of the manufacturer that meet these input conditions, typically including a graph of the output voltage versus the sensed current for the calculated terminating resistance.

To select an appropriate current sense transformer for your application, you require knowledge of the maximum current, frequency, and duty cycle of the sensed current, including the output voltage you require. Using this information, the online selector tools will provide you with the appropriate terminating resistor value and a list of current sensors that meet the conditions of the application.