Monthly Archives: January 2021

What is Industrial Connectivity?

Engineers include any component involved in the path of delivering control signals or power for doing useful work as part of industrial connectivity. Typically, components such as terminal blocks, connectors, motor starters, and relays are part of industrial connectivity.

Engineers divide industrial connectors into four categories depending on the environments in which they operate—commercial, industrial, military, and hermetic. Commercial applications do not consider temperature and atmosphere as critical operating factors affecting performance. Industrial applications require connectors capable of handling more rugged environments involving hazards such as sand, dust, physical jarring, vibration, corrosion, and thermal shock.

Most general connectors use low-cost materials to merely maintain electrical continuity. However, designers have a large variety of materials from which to choose for making connectors. These include brass, beryllium copper, nickel-silver alloys, gold, gold-over-silver, gold-over-nickel, silver, nickel, rhodium, rhodium-over-nickel, and tin.

No wire preparation is necessary for use in terminal blocks. The user only needs to strip the insulation and install the wire using a screwdriver. One can use a wide range of wire sizes with terminals that provide an easy way to hookup wires from different components, ensuring fast connection/disconnection during troubleshooting and maintenance.

Manufacturers make terminal bodies from a copper alloy with the same expansion coefficient as the wire it connects. This prevents uneven expansion from causing loosening between the connector screws and the wire, avoiding an increase in contact resistance. Using similar metals also avoids corrosion, usually with two different metals in contact, as a result of electrolytic action between them.

SSRs or Solid-State Relays control load currents passing through them. For this, they use power transistors, SCRs, or silicon-controlled rectifiers, or TRIACs as switching devices. Engineers use isolation mechanisms such as optoisolators, reed-relays, and transformers for coupling input signals to the switching devices to control them.

To reduce the voltage transients and spikes that load-current interruptions typically generate, engineers use zero-crossing detectors and snubber circuits, incorporating them within solid-state relays.

Semiconductor switches generate significant amounts of waste power, and engineers must minimize their operating temperature using heat sinks attached to solid-state relays. SSRs can operate in rapid on/off cycles that would wear out conventional electromechanical relays quickly.

Electromechanical relays physically open and close electrical contacts for operating other devices. In general, they cost much less than equivalent electronic switches. They also have some inherent advantages over solid-state devices. For instance, the input circuit in electromechanical relays is electrically isolated from the output circuits, and one relay can have more than one output circuit, each electrically isolated from the others.

Furthermore, the contact resistance offered by electromechanical relays is substantially lower than that offered by a solid-state relay of a similar rating. The contact capacitance is lower as well, benefitting high-frequency circuits. Compared to solid-state relays, electromechanical relays are far less sensitive to transients and spikes, not turning on as frequently as SSRs do. Brief shorts and overloads also damage electromechanical relays to a far less extent than the damage they cause to SSRs.

Improved manufacturing technology is now making available electromechanical relays in small packages suitable automated soldering for PCB mounting and surface mounting.

IoT and DIP Switches

Pre-configuring equipment helps in many ways. In the field, the ability to pre-configure functionality eases installation procedures, helps in diagnostics, and reduces downtime. DIP switches are very popular for pre-configuring devices and an increase in their demand is accelerating the flexibility in their design.

Although designers nowadays prefer to use re-programmable memories and software menus in equipment, DIP switches customizing the behavior of electronic devices was have always been present. DIP switches present an easy-to-use method for changing the functionality that anyone even without software knowledge can use. An added advantage of DIP switches over software menus is the former allows change even when the equipment has no power.

Engineers developed the DIP switch in the 1970s, and their usefulness remains relevant even after five decades, for instance, for changing the modality of a video game or for fine-tuning the operation of a machine on the shop floor. Now, engineers are finding new uses for this proven technology in innovative applications such as the IoT or Internet of Things.

Depending on present requirements, manufacturers now present a large variety of DIP switches for modern applications. It is now easy to find surface mount versions of DIP switches, with SPST or single pole single throw, SPDT or single pole double throw configurations, or multi-pole single and double throw options. Piano type side actuated DIP switches, side DIP switches, and DIP switches in sealed and unsealed versions are also available readily off the shelf.

Originally, DIP switches were a stack of manually operated electric switches available in a compact DIP or dual-in-line package with pins. The configuration of the pins of a DIP switch was the same as that of an IC with leads, which made it easy for a designer to incorporate in the printed circuit board. It was usual for each switch to have two rows of pins, one on each side. The distance between the rows was 0.3”, while the pitch or gap between adjacent pins was 0.1”. By taking advantage of the same mounting technique as that of an IC, the DIP switch provided a compact switching mechanism that designers could place directly on the PCB.

By stacking DIP switches side by side, the designer could add as many switches to the circuit as necessary. The versatility of the DIP switch lay in the numerous configurations achievable. For instance, it is possible to generate an incredible 256 combinations from an eight-position DIP switch. Each switch can assume one of two ways, and an eight switches combination can assume one of 256 ways (2 to the eight power).

Earlier, digital electronics mostly used eight bits to a byte, which made the eight-position DIP switch more of a standard at the time. With advancements, digital electronics now encompasses 8, 16, 32, 64, 128, and even 256 bits, generating a great demand for DIP switches with new designs.

DIP switches are easier for the user as they offer a visual indication of the present setup.  For manufacturers, DIP switches make it easier to customize their production, at the same time, allowing the user to make changes as necessary.

Sensor Technologies for Air Quality Monitoring

Although air is all around us, we breathe it in every minute, and our lives depend on it, yet we pay very little attention to the quality of air, unless when facing a problem. Whether it is indoors or outdoors, poor air quality can affect our health and well-being significantly. Two levels of air pollution measurement are significant here.

One is the presence of small PM2.5 or Particulate Matters measuring less than 2.5 microns in size—one micron being one-micrometer equal to one-millionth of a meter or one-thousandth of a millimeter. The other is the presence of VOCs or Volatile Organic Compounds.

Combustion processes emit PM2.5 type of pollutants, for instance, by fires burning in fireplaces and lit candles within the house. Cleaning textiles, furniture, and supplies can emit VOCs. Engineers and scientists are working on improving sensing technologies to enable monitoring PM2.5 and sensing VOC by personal air quality monitoring systems for improving the health and well-being of the people.

According to the WHO, PM2.5 enters our lungs easily causing serious health problems such as chronic and acute respiratory diseases, asthma, lung cancer, heart diseases, and stroke. A recent study by Harvard University links PM2.5 exposure to sensitivity to viral diseases such as SARS-CoV-2.

While one does receive averaged or consolidated data from official air quality monitoring stations, that data is for the outdoor environment only. For indoor air pollution monitoring, a portable air quality measuring device, also known as a dosimeter, is more appropriate—especially when incorporated within a wearable or a smartphone. So far, PM2.5 sensors were too large for mobile devices. Bosch Sensortec now has sensors that make it possible to incorporate them into personal devices.

The Bosch PM2.5 technology offers sensors small enough to incorporate within wearables and smartphones for measuring the daily exposure of a person to PM. The person can see data and trends of local pollution levels to which they are exposing themselves, and take appropriate actions to minimize their exposure for improving their health and well-being.

BreezoMeter uses PM2.5 sensor technology from Bosch Sensortec to make PM2.5 Dosimeters. They also offer an app for the Dosimeter that collates local data measured by the Bosch PM2.5 sensor and the air pollution data from the BreezoMeter to calculate and display the personal daily PM exposure.

Conventionally, PM sensors rely on a fan to draw air through a cell, where optical arrangements count the particulate matter and calculate the concentration per unit of volume. This arrangement requires the sensor to be the size of a matchbox, incapable of incorporating within a smartphone.

PM2.5 sensor technology that Bosch Sensortec has developed functions on natural ambient airflow. The principle is rather like a camera, with three lasers integrated behind a glass cover. To prevent damage to the user, Bosch uses Class 1 lasers that are eye-safe. The entire arrangement is flat enough like a smartphone camera is, making it easier to incorporate within one, and using only 0.2% of the volume of air that other solutions on the market typically use.

Wireless Charging for Drones

Drones face a significant operating challenge—their limited battery capacity places a constraint on their flight time. More flexible and efficient recharging solutions can address this issue. A 4-year old startup, WiBotic, now has funding to explore this avenue. WiBotic designs and manufactures solutions to charge robot and drone batteries.

WiBotic offers power optimization and wireless charging solutions for mobile, aerial, marine, and industrial robots. Their Adaptive Matching technology is a new method for inductive power transfer. The company is providing power levels necessary for charging flying devices such as drones.

Software libraries monitor battery charge parameters in detail for providing optimization solutions. Combined with wireless charging hardware, the strategic deployment of these software features helps with the optimization of drone uptime. Wireless charging solutions from WiBotic also schedule the recharge, allowing multiple drones to charge from the same transmitter at various times.

Nikola Tesla was the first to demonstrate, in the late nineteenth century, the use of electromagnetic fields as a source of electricity transfer without wires. Although engineers are aware of the wireless methodology, the design of an entire system consisting of transmitters and receivers, their locations, and maximizing their efficiency is a complex challenge requiring specific skills. Most wireless power transfer systems use inductive coupling or magnetic resonance with their individual strengths and weaknesses.

Inductive coupling is the most common method, usually found on consumer devices. However, they are efficient only when the transmitter and the receiver antennas are close together. Therefore, this method is not suitable for drones and robots as they cannot position themselves so that their inductive systems are close enough to provide a reliable power transfer.

The technology of magnetic resonance is one of the latest providing more flexibility in positioning. Most magnetic resonance systems have a special area for delivering power with maximum efficiency. If the robot or the drone stops in this area only briefly or remains off-center, the charging efficiency reduces, and the charging time increases.

WiBotic technology incorporates the best of both systems and operates on the strengths of both resonant and inductive systems. They have a patented Adaptive Matching system to constantly monitor relative antenna positions, while dynamically adjusting both hardware and firmware parameters for maintaining maximum efficiency. This ensures delivery of high-power levels and reliable charging, even when several centimeters of angular, horizontal, or vertical offsets separate the transmitter and the receiver.

For drones, the WiBotic wireless charging station is a square platform of about 3 ft x 3 ft. It has an intelligent induction plate that determines the type of battery the drone has and establishes the proper charging parameters for it.

WiBotic wireless charging systems all have four primary hardware components—the transmitter antenna coil, the receiver antenna coil, the on-board charging unit, and the transmitter unit.

Using an AC source, the transmitting unit produces a high-frequency wireless signal, that travels to the transmitting antenna coil and generates electric and magnetic fields.

The transmitter unit has the capability to recognize an incoming drone equipped with a receiver antenna coil, which automatically activates itself to receive the right amount of energy.

Protecting Against Ground Faults

Faults are instances of something happening when it should not. Electrical faults are when electric current flows where it should not be flowing. Electric current flowing from the live wire to the ground in place of the customary neutral wire constitutes a ground fault.

There are two major problems that a ground fault may cause. One is excessive current may cause overheating and fire may break out. The other is a ground fault could be fatal for any person being a part of the ground circuit. That is why it is important to protect against ground faults occurring.

Earlier to the 1970s, people did not realize the necessity of grounding electrical systems. As a result, most industrial and commercial systems remained ungrounded. Although ungrounded systems do not result in significant damage, the numerous disadvantages that they present led to a change to grounded systems. Grounded systems also help in protection against lightning, and reduction of shock hazards.

In electrical supply and distribution systems, faults are mainly of two types—phase-to-phase faults, and ground faults—with ground faults being 98% of them. While fuses form the main methods of protection in case of phase-to-phase faults, protecting against ground faults requires the additional use of protective relays.

For instance, a toaster may have the hot wire shorted to its metal casing. Turning on the toaster causes all or a part of the current to pass through the toaster frame and then on through the green ground wire. If the current is high enough, the circuit breaker will trip. Adding a ground protection relay would have detected the current flow at a significantly lower level and opened the circuit much quicker than the circuit breaker.

Ground faults occur for different reasons. These could be due to inclement weather, causing a tree to fall over and rest on power lines during a storm. Insulation degraded by age can also cause ground faults—heat from a current flow can break down old insulation. Moisture from high humidity can break down insulation. Excessive overvoltage and puncture the insulation and cause ground faults.

Protecting against ground faults means isolating the circuit with the fault so that there is no power to that part of the circuit. However, to clear the fault, it is necessary to first establish the presence of a fault, and then determine the source of the fault. System designers use a ground fault protection relay for this purpose.

In normal operation, electric current flows from the phase or hot wire into the appliance and returns via the neutral or the cold wire. As the two currents are equal, their resultant electromagnetic fields cancel out. A current transformer placed across the phase and neutral wires will yield zero output while the two wires carry equal currents.

In case of a ground fault, part or all the current from the phase wire bypasses the neutral wire, since it now flows through the ground wire. As the two currents through the CT are now unequal, there is a resultant output from the CT, tripping the associated circuit breaker.

What are Motor Starters?

Starting up small motors is usually through a manual starter that can make or break the power supply line to the motor. The method is also known as DOL or direct online start. If the motor gets too hot due to an overload, a thermal protection circuit in the starter opens and disconnects the motor. DOL starters are the most common method of starting and stopping single-phase motors up to 5 HP, 230 VAC, and three-phase motors up to 15 HP, 600 VAC.

Magnetic starters can have controls such as float switches, pressure switches, timers, relays, limit switches, and push buttons, as they have a separate mechanism for closing and opening a set of contacts for the motor circuit. They also include a thermal overload protection device. The mechanism consists of a coil, which, when energized, closes contacts to complete the electrical circuit of the motor. Likewise, de-energizing the coil opens the contacts, switching off the motor.

However, one of the problems with DOL or magnetic starters is both allow the motor to start with a high current. Under normal conditions, motors must start with a current that is nearly 6 to 7 times the rated running current of the motor. This is necessary for the motor to overcome the initial torque due to friction. However, for some motors, the starting current can go up to 9-10 times the rated current.

Reversing any two phases of a three-phase induction motor results in the motor reversing its direction of rotation. Adding an extra set of contacts to a basic starter can turn it into a reversing starter. Appropriate electrical and mechanical interlocking mechanisms must also be present for safeguarding the motor operations.

A soft starter applies a low voltage to the motor, ensuring a low starting current and torque. The torque gradually increases as the soft starter begins to apply higher voltage.  Semiconductor switches such as thyristors, inside the starter, accomplish the gradual increase in the voltage that the starter applies to the motor.

A slow start is essential to prevent stress on the internal components of the motor, and to the machinery, the motor is driving, especially belts and gear drives. The soft starter also features soft stopping. This is essentially helpful for stopping conveyor belts and pumps, where a sudden stop may cause water hammering in the pipe system.

Multispeed induction motors have multiple windings that require special starters. For instance, two-speed motors with separate windings need starters with two built-in standard starters within a single enclosure with mechanical and electrical interlocks.

Consequent-pole two-speed motors need a three-pole starter unit or a five-pole starter unit. The design of the motor winding determines whether the three- or five-pole unit makes a slow-speed or fast connection.

Delta-type multi-speed motors require different power circuits for the currents circulating within the unconnected and inactive windings. Two-speed motors with separate open-delta windings require a pair of four-pole starter. For each speed, a different four-pole starter is necessary. Therefore, very complex starters are necessary for motors with open-delta windings capable of running at three or four speeds.

How Terminal Block Contacts Work

Quick-connect type terminal block contacts consist of a flat blade or a simple tab with a design that accepts a push-on connector holding the end of a wire. A force-fit metal sleeve pushed over the tab makes the contact. Such quick-connect type terminal blocks are meant for thin wires up to AWG 12.

Tubular contacts are a length of rectangular metal tubing, with screws threaded through the top of the tube at both ends. In tubular screw contacts, the flat bottom of the screws secures the inserted wires by providing pressure on them. Tubular clamp contacts use a pressure plate between the screws and the wire to apply pressure on the wires. The screws usually hold the pressure plates captive, which makes tubular clamp contacts useful for fine stranded wires.

Feed-through contacts have mounting surfaces with studs going through them. Feed-through contacts are useful for wire leads passing through a wall under a block directly or very close to the wall. Stud contacts or strap-screws secure the wires for connection.

For installations that must stay connected even during shock and vibration, dead-front connectors with two-part plug-ins are very useful. For multiple points of contact on posts, quality connectors typically use socket-mating springs. Wire protectors made of beryllium-copper protect both single and multi-stranded wire terminations. Flush-mount designs for boards are best for minimizing stress on solder joints when tightening screw terminals.

Flat metal strap with screws through each end make up strap-clamp contacts. The screw heads usually have a wire-clamping element under them for exerting pressure on the wires. These contacts require the insertion of bare wires within the pressure contact.

Strap-screw contacts are similar in construction to the strap-clamp contacts but without the wire-clamping elements. The user simply loops the wires over the screws or may attach a ring or spade lug on them. Tightening the screws on the loop, ring, or spade lug serves to secure and connect them.

Fuse blocks usually consist of a fuse in series with a circuit. Usually, there are contacts at each end, like that of standard blocks. It is possible to insert a cartridge-fuse pug into clips connected to each contact. Apart from circuit identification, this arrangement facilitates easy fuse changing.

Plane and rigid insulating members can mount multiple one-piece blocks for connecting one or more circuits. There may be open barriers facilitating easy contact accessibility. Other variants may offer contact protection through closed barriers or dad fronts. A single base may hold standard units of 2, 4, 6, 8, 10, or 12 circuits.

Terminal block contacts may also be of the short-circuit type, like the one-piece blocks. Short-circuit contacts require a screw short-circuiting two strips, allowing current flow into the desired circuit by direct connection or by shunting out other circuits.

Section blocks usually come with individual molded units containing contacts. It is possible to form any desired number of circuits by assembling them together with end barriers in between. Formation of preassembled lengths requires snapping off or adding sections in the desired number of groups of contact sections to form a sectional terminal block assembly.