Category Archives: Guides

New Battery Technology for UPS

Most people know of the Lithium-ion battery technology in use mainly due to their overwhelming presence in mobile sets. Those who use uninterruptible power supplies for backing up their systems are familiar with the lead-acid cells and the newer lithium-ion cells. Another alternative technology is also coming up mainly for mission-critical facilities such as for data centers. This is the Nickel-Zinc technology, and it has better trade-offs to offer.

But the Nickel-Zinc battery technology is not new. In fact, Thomas Edison had patented it about 120 years ago. In its current avatar, the Nickel-Zinc battery offers superior performance when used in UPS backup systems. They offer better power density, are more reliable, safe, and are highly sustainable.

For instance, higher power density translates into smaller weight and size. This is the major difference between a battery providing energy and a battery providing power. In a data center, the UPS must discharge fast for a short period for maintaining operational continuity. This is what happens during brief outages, or until the backup generators spin up to take over the load. This is the most basic power battery operation, where the battery must deliver a high rate of discharge, and it does so with a small footprint.

On the other hand, Lead-acid and Lithium-ion technologies offer energy batteries. Their design allows them to discharge energy at a lower rate for longer periods. Electric vehicles utilize this feature, and the automotive industry is spending top dollars for increasing the energy density of such EV batteries so that the user can get more mileage or range from their vehicles. This is not very useful for data center backup, as the battery must have a higher energy storage footprint for supporting short duration high power output requirements.

This is where the Nickel-Zinc battery technology comes in. With an energy density nearly twice that of a Lead-acid battery, Nickel-Zinc batteries take up only half the space. Not only is the footprint reduced by half, but the weight also reduces by half for the same power output. As compared to Lithium-ion batteries, Nickel-Zinc batteries not only excel in footprint reduction, but they charge at a faster rate while retaining thermal stability. This feature makes them so useful for mission-critical facility uptime.

Nickel-Zinc batteries have proven their reliability as well. They have clocked over tens of millions of operating hours for providing uninterrupted backup power in mission-critical applications. Another feature very useful for data center operations is the battery string operations of the Nickel-Zinc technology.

When a Lithium-ion or a Lead-acid battery fails, the battery acts as an open circuit, preventing other batteries in the string from transferring power. On the other hand, a weal or a failed Nickel-Zinc cell remains conductive, allowing the rest of the string to continue operations, with a lower voltage. In emergency situations, this feature of the Nickel-Zinc battery is extremely helpful, as the faulty battery replacement can proceed with no operational impact and at a low cost.

In parallel operation also, Nickel-Zinc batteries are more tolerant of string imbalances, thereby maintaining constant power output at significantly lower states of health and charge as compared to batteries of other technologies.

Power Transmission Through Lasers

Wireless power transfer has considerable advantages. The absence of transmission towers, overhead cables, and underground cables is the foremost among them, not to exclude the expenses saved in their installation, upkeep, and maintenance. However, one of the major hurdles to wireless power transmission is the range it can cover. But now, Ericsson and PowerLight Technologies have provided a new proof of concept project that uses a laser beam to transmit power optically to a portable 5G base station.

Wireless power transmission is not a new subject to many. People use wireless power for charging many devices like earbuds, watches, and phones. But the range in these chargers is short, as the user must place the device on the pad of the charger. This limits the usefulness of the wireless charging station for transmitting power. Although labs have been experimenting with larger setups that can charge devices placed anywhere within a room, reports of beaming electricity outdoors and for long distances have been rather scarce.

PowerLight has been experimenting with wireless power transfer for quite some time now, and they have partnered with Ericsson, a telecommunications company, for a proof of concept demonstration. Their system consists of two components, a laser transmitter, and a receiver. The distance between the transmitter and receiver can vary from a few hundred meters to a few thousand meters.

However, unlike a Tesla coil, the PowerLight device does not transmit electricity directly. Instead, at the transmitter end, electricity powers a powerful laser beam, sending it directly to the receiver. In turn, the receiver uses specialized photocell arrays to convert the incoming laser back into electricity for powering connected devices.

Such a powerful laser-blasting through the open air can be a dangerous thing. Therefore, PowerLight has added many safeguards. They surround the beam with wide cylinders of sensors that can detect anything approaching. The sensors can shut off the beam within a millisecond, if necessary. In fact, the safety system is so fast that a flock of birds is not affected when flying through the laser beam, but there is an interruption at the receiver.  To overcome such fleeting interruptions, and cover longer-term disruptions as well, the PowerLight system has a battery back-up at the receiver end.

PowerLight is using their system to power a 5G radio base station from Ericsson, that has no other power source connected to it. The base station received 480 watts from the transmitter placed at a distance of 300 m. However, according to the PowerLight team, the technology can send 1000 watts over a distance of over 1 km. They also claim there is room for future expansions.

Wirelessly powering these 5G units could make them more versatile, as they will then become portable, and capable of operating in temporary locations. This will also allow them to operate in disaster areas, where there has been a disruption of infrastructure.

According to PowerLight, their optical power beaming technology may be useful in several other applications also, such as for charging electric vehicles, in future space missions, and in adjusting the power grid operations on the fly.

Improving Computer Vision with Two AI Processors

Computer vision is becoming a necessity in IoT and automotive applications. Engineers are trying for the next level in computer vision with two AI processors. They hope that two AI processors will help to make computer vision not only more efficient but also more functional.

One of the fastest-growing applications of artificial intelligence, computer vision is jostling for attention between prestigious fields like robotics and autonomous vehicles. In comparison to other artificial intelligence applications, computer vision has to rely more on the underlying hardware, where the underlying imaging systems and processing units overshadow the software performance.

Therefore, engineers are focusing on cutting-edge technology and state-of-the-art developments for the best vision hardware. Two companies, Intuitive and Syntiant, are now making headlines by supporting this move.

Israeli company, Intuitive, recently announced that its NU4000 edge Artificial Intelligence processor will be used by Fukushin Electronics in their new electric cart, POLCAR. The processor will allow the cart to have an integrated obstacle detection unit.

Requiring top performance and power efficiency when operating a sophisticated object detection unit in a battery-powered vehicle like an electric cart made Fukushin use the NU4000. The edge AI processor from Intuitive is a multicore System on a Chip or SoC that can support several on-chip applications. These include computer vision, simultaneous localization and mapping or SLAM, and 3d depth-sensing.

The NU4000 achieves these feats by integrating three Vector Cores that together provide 500 COPS. There is also a dedicated CNN processor offering three CPUs, 2 TOPS, a dedicated SLAM engine, and a dedicated depth processing engine. Intuitive has built this chip with a 12nm process, and it can connect up to two displays and six cameras with an LPDDR4 interface.

With a small form factor and low power consumption, the NU4000 is a powerful processor providing several key features that could make the obstacle detection unit a special application for Fukushin’s POLCAR.

California-based Syntiant was in the news with their Neural Decision Processor, the new NDP200. Syntiant has designed this processor for applications using ultra-low-power, especially useful for deep learning. With a copyrighted Syntiant core as its core architecture, it has an embedded processor, the ARM Cortex-M0. With this combination, the NDP200 achieves operating speeds up to 100 MHz.

Meant for running deep neural networks like RNNs and CNNs, Syntiant has optimized the NDP200, especially for power efficiency. Deep neural networks are necessary for computer vision applications.

Syntiant claims NDP200 performs vision processing at high inference accuracies. It does this while keeping the power consumption below 1 mW. Judging its performance, the chip could reach an inference acceleration of more than 6.4 GOP per second, while supporting more than 7 million parameters. This makes the NDP200 suitable for edge computing of larger networks.

Syntiant expects its chip will be suitable for battery-powered vision applications, such as security cameras and doorbells. In fact, the combination of the chip’s capability to run deep neural networks and power efficiency can allow it to take the next evolutionary step towards creating a better processor for computer vision applications.

Low-Power Circuit Timing using SPXOs

A wide range of electronic devices relies on circuit timing as a critical function. These include microcontrollers, Bluetooth, Ethernet, Wi-Fi, USB, and other interfaces. In addition, circuit timing is essential for consumer electronics, wearables, the Internet of Things (IoT), industrial control and automation, test and measuring equipment, medical devices, computing devices and peripherals, and more. Although designing crystal-controlled oscillators seems an easy process for providing system timing, there are numerous design requirements and parameters that designers must consider when matching a quartz crystal to an oscillator chip.

Among the several considerations are the negative resistance of the oscillator, its drive level, resonant mode, and the motional impedance of the crystal. When the designer is making the circuit layout, they must consider the parasitic capacitance of the PC board. They must also consider the on-chip integrated capacitance, and include a guard band around the crystal. Finally, the design must not only be compact, with a minimum number of components, and reliable. While the circuit must be capable of operating with a wide range of input voltages, consuming minimal power, it must also have a small root-mean-square jitter.

An optimal solution to the above is to use simply packaged crystal oscillators or SPXOs. Manufacturers optimize SPXOs for low RMS jitter and minimal power consumption. These devices can operate with any supply voltage ranging from 1.6 VDC to 3.6 VDC. With these continuous-voltage oscillators, designers can implement solutions requiring minimal effort while integrating them into digital systems.

In small, battery-powered, wireless devices, power consumption is always a very important consideration. That is why designers prefer to base such devices on the system on a chip or SoC processor that consumes very low power to support battery lives of several years. Moreover, device cost depends on the battery size, as the battery is easily the most expensive component in the device—minimizing the battery size is, therefore, an important factor in small wireless devices. For battery life consideration, one of the important parameters is the standby current, apart from the self-discharge current of the battery. Minimizing the current drawn by the clock oscillator is important, as this is greater than the standby current.

Designing low-power oscillators can be challenging. Designers are tempted to save energy by allowing the circuit to enter a disabled state for minimizing the standby current while starting the oscillator when needed. However, this is not an easy task as starting crystal oscillators quickly is not a simple and reliable task. Reliable start-up conditions require careful design efforts when designers attempt it across all environmental and operating conditions.

Most low-power wireless SoCs favor the Pierce oscillator configuration. The circuit has crystal and tow load capacitors. It uses an inverting amplifier that has an internal feedback resistor. With the amplifier feeding back its output to its input, the right conditions cause a negative resistance to start the oscillations going.

Quartz crystal oscillators can have jitters caused by power supply noise, improper load, improper termination conditions, the presence of integer harmonics of the signal frequency, circuit configurations, and amplifier noise. The designer must use several methods to minimize jitter.

Hybrid Plug-in Connectors for Motor Control Systems

Motor control systems are increasingly becoming more compact while their use is growing with applications in Industry 4.0 and Industrial Internet of Things (IIoT). In fact, motor control systems are prevalent in varied industries like food and beverages, material handling, and robotics. However, as the size of the controller shrinks, designers are facing a new challenge—routing power and signal easily and cost-effectively—while ensuring operator safety and electromagnetic compatibility.

One can use advanced open source interfaces to connect both power and data signals with a single compact connector. Although this does simplify connectivity, the quality, design, and performance of the connector become critical to ensure signal integrity, EMC, and compliance with IP20 requirements.

Designers have moved to Hiperface DSL and SCS open Link, open-source interfaces, to allow the same connector to carry both power and data. This not only saves space but also lowers the cost and simplifies the design of high-performance motor controllers.

The communicating cable has two shielded wires for bi-directional communication based on RS-485, and other wires for encoder power, motor power, and motor brake controls. There are three elements—a three-phase power supply cable, a shielded motor brake cable, a shielded data pair for digital data transfer—enclosed within a shielded cable.

The Hiperface DSL offers a data transmission rate of 9.375 MBaud, over a cable distance of up to 100 meters between the motor controller and the motor. It is possible to transmit data on the cable in two ways—cyclically, given signal and noise conditions, or synchronously with the controller clock.

The motor feedback interface design of the SCS open Link system can supply bidirectional data between the motor and controller. This includes encoder data at rates up to 10 MBaud. It is possible to use two or four-wire implementation. This link is optimized for Industry 4.0, and especially for emerging IIoT solutions, including motor condition monitoring and predictive maintenance.

For SCS open Link and Hiperface DSL to operate reliably, the connection needs optimum shielding between the motor/encoder and its drive. The number of interfaces reduces with the use of plug-in connectors and connection terminals. It is also important to have unbroken shielded cables between the motor/encoder and the drive. However, as the drive connector is non-standard, designers must be careful when designing their own connectors for meeting performance requirements.

OMNIMATE Power Hybrid connectors are an alternative to the SCS open Link and Hiperface DSL. These are a three-in-one solution providing signal, power, and EMC features that implement the SCS open Link and Hiperface DSL protocols. Moreover, the hybrid connectors save space on the motor drive printed circuit board and in the controller cabinet.

The hybrid connectors are available in several configurations. These include six-, seven-, eight-, and nine-position connections. They include power and signal contacts with push-in wire connections. The pitch is 7.62 mm, conforming to the IEC 61800-5-1 and UL 1059 Class C 600 V standards. Several practical design features in the connectors provide high reliability. For instance, the adequate separation between encoder and power connections ensures minimum EMC.

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.

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.