Making a PiPlateBot with the Raspberry Pi

Turtle robots of the yesteryears had always fascinated Robert Doerr and he decided to create one with the popular single board computer, the raspberry Pi or RBPi. He hid all components of the robot inside the plate case, and decided to call his robot PiPlateBot.

Robert Doerr is the owner of Robot Workshop, and a dedicated robot builder. He used the Bud Pi Plate case, as this was strikingly similar to the turtle-style robots computer science students used earlier.

The Pi Plate has a circular design. Twisting off the top allows easy access to the space within that can house additional components. That led Robert try to fit an RBPi inside, along with the other parts required to build a moving robot. According to Robert, the PiPlateBot is the only robot that runs on an RBPi and uses an off the shelf RBPi case. Robert claims he is using as many RBPi-type products as possible for the construction.

To get everything to fit, Robert had to cut two rectangular holes in the Pl Plate enclosure base. Then he glued servos to the bottom and clipped the RBPi and RoboPi boards on the top. On the boards, he placed a BZO power bank to work as a battery. To enable communicating wirelessly with the RBPi, Robert uses a USB Wi-Fi adaptor. This allows him to SSH directly into the RBPi.

The RoboPi is an impressive motor controller, and the most powerful one for the RBPi. Using an eight-core 32-bit Parallax Propeller RISC micro-controller at 100 MHz, it allows offloading hard real time IO from the Linux OS running on the RBPi, thereby giving timing with greater precision to projects. The RoboPi will work with any RBPi model.

Each core on the RISC controller works at 25 MIPS, with each instruction taking only four clock cycles to complete. The RoboPi has three ten-pin IO module expansion connectors and they provide 24 servo-compatible headers. Some of these connectors use jumper selectable power from the internal 5 VDC or the external servo power supply for powering the sensors.

The user can connect servos to screw terminals that provide external power. There are eight headers for setting up an eight channel 0-5 V analog to digital converter. The user has a choice of using MCP3008 for 10-bit AD conversion or MCP3208 for 12-bit AD conversion.

Therefore, while the RBPi does the high-level thinking, the Parallax Propeller chip on the RoboPi board handles all the IO controlling and the real-time tasks. As the RoboPi controller has both C and Python libraries, Robert plans to write a Logo Interpreter to make the PiPlateBot use Logo to emulate the early turtle robots.

As the PiPlateBot has only two servos controlling its two wheels, the robot actually wobbles when operated. Robert had to use furniture gliders to prevent this. He attached them to the front and rear of the PiPlateBot. A sonar sensor fitted on the PiPlateBot allows it to sense its surroundings.

Building a robot is the fun way of learning to use the RBPi, and a great way to learn programming on the SBC.

What are Laminated Bus Bars?

Rather than use one solid bar of copper, the industry prefers laminated bus bars. These are fabricated components with layers of engineered copper bars separated by flat dielectric materials, bound together into a unified construction. Laminated bus bars offer several advantages—improved reliability and reduced system costs. They are available in various sizes and shapes, some as big as a fingertip while others more than twenty feet in length. Several industries use multilayered bus bar solutions routinely and they include telecommunications, computers, industrial, military, transportation, alternative energy, power electronics, and many more.

Laminated bus bars are good for reducing the system costs, improving system reliability, increasing capacitance, lowering inductance, and eliminating wiring errors. Additionally, the physical structure of the bus bars also acts as structural members of a complete power distribution subsystem. Multilayer bus bars function as a structural integration that other wiring methods cannot match.

The decreased assembly time and the internal material handling costs for laminated bus bars bring down the overall manufacturing costs. Assembly operating procedures can be difficult to follow and assemblers often resort to guesswork, leading to wiring errors. Using laminated bus bars eliminates this totally, as installers have to terminate various conductors at specified locations. Not only does this reduce the parts count, it also reduces ordering, inventory costs, and material handling.

Fabricators can make laminated bus bars fit specific needs and customize them for maximizing efficiency. The use of laminated bus bars, therefore, helps the organization build quality into processes. With reductions in wiring errors, the organization has fewer reworks, and they can lower their quality and service costs.

Laminated bus bars offer increased capacitance and lower inductance, resulting in lower characteristic impedance. The benefit to the industry is greater noise cancellation and effective noise suppression. Manufacturers can control the capacitance by using dielectrics of various thicknesses and different relative K factor.

Multilayered bus bars can replace cable harnesses—this eliminates mistakes in wirings. Moreover, failure rate of bus bars is extremely low, while wiring harnesses fail very often. That makes repairing and or replacing wire harnesses an expensive process, while using bus bars in the system is adding an effective insurance.

According to physics, a conductor carrying current develops an electromagnetic field around the conductor. As laminated bus bars have thin parallel conductors with thin dielectric material separating them, the effect of inductance on electrical circuits is a minimum. With opposing potentials laminated together, the magnetic flux cancellation reaches a maximum. Semiconductor applications routinely use laminated bus bars to reduce the proximity effect. GaN and or SiC high frequency circuits also use laminated bus bars to reduce high electromagnetic interference.

Using wide and thin conductors and laminating them together to form bus bars actually decreases the space requirement, thereby allowing a better airflow in systems and improving system thermal characteristics. Moreover, the flexibility of these bus bars provides the industry with a wide variety of interconnecting methods. Assemblers commonly use tabs, embossments, and bushings for installing laminated bus bars. Manufacturers also offer pressed-in fittings that can integrate into the design. This makes laminated bus bars compatible with almost any type of interface.

What is a PCB Via and How is it Made?

Vias are actually holes drilled into PCB layers and electroplated with a thin layer of copper to provide the necessary electrical connectivity. Three most common types of plated through via are in use—plated through holes, blind holes, and buried holes—with plated through holes running through all the layers of the PCB. These are the simplest type of holes to make and the cheapest. However, they take up a huge amount of PCB space, reducing the space available for routing.

Blind vias connect the outermost circuit on the PCB with other circuits on one or more adjacent inner layers. As they do not traverse the entire thickness of the PCB, they increase the space utilization by leaving more space for routing.

Buried vias connect two or more circuit layers in a multi-layered PCB, but do not show up on any of the outer layers. These are the most expensive type of vias and take more time to implement, as the fabricator has to drill the hole in the individual circuit layer when bonding it. However, designers can stack several buried vias in-line or in a staggered manner to make a blind via. Therefore, buried vias offer the maximum space utilization when routing a PCB. Fabricators of high-density interconnect (HDI) boards usually make use of buried vias, most often using lasers for drilling them.

Drilling a Via

At positions for the vias, the fabricator drills holes through the PCB using a metal drill of small diameter. He or she then cleans the hole, de-smears it, and de-burrs it to prepare it for plating. Rather than removing copper as is normally the case with the etching process, the fabricator then adds a thin layer of copper to the newly formed hole through a process of electroplating, thereby connecting the two layers. For a two-layer board, the fabricator then etches circuit patterns on both sides. Via usually have capture pads on both layers.

The process of drilling a via hole using a laser is somewhat different. In general, fabricators use two types of lasers—CO2 and UV—with the latter able to make very small diameter via holes. UV laser-drilled via holes are about 20-35 µm in diameter. As the laser beam is able to ablate through the thin copper layer, capture pads with a central opening are not necessary. Most fabricators program a two-step process for drilling a hole with a laser beam.

In the first step, a wider-focused laser heats the top copper layer, driving the metal rapidly through the melt phase into the vapor phase prior to gas-dynamic effects expelling it from the surface. The laser repeats this for all via positions on the PCB layer.

In the next step, the program focuses the beam tightly and controls the depth the laser can burn. For blind vias, It allows the laser to burn through the intervening dielectric and stop when it has reached the bottom copper layer, before moving on to the neighboring via position.

The same process of electroplating as above deposits a thin layer of copper along the walls of the holes left behind by the laser beam, thereby connecting the two layers. The rest of the process for etching the circuit pattern on the two sides remains the same.

How useful are PCB Vias?

Designers use a plated through via as a conduit for transferring signals and power from one layer to another in a multi-layer printed circuit board (PCB). For the PCB fabricator, the plated through via are a cost-effective process for producing PCBs. Therefore, vias are one of the key drivers of the PCB manufacturing industry.

Use of Vias

Apart from simply connecting two or more copper layers, vias are useful for creating very dense boards for special IC packages, especially the fine-pitch components such as BGAs. BGAs with pitch lower than 0.5 mm usually do not leave much space for routing traces between neighboring pads. Designers resort to via-in-pads for breaking out such closely spaced BGA pins.

To prevent solder wicking into the via hole while soldering and leaving the joint bereft of solder, the fabricator has to fill or plug the via. Filling a via is usually with a mixture of epoxy and a conductive material, mostly copper, but the fabricator may also use other metals such as silver, gold, aluminum, tin, or a combination of them. Filling has an additional advantage of increasing the thermal conductivity of the via, useful when multiple filled vias have to remove heat from one layer to another. However, the process of filling a via is expensive.

Plugging a via is a less expensive way, especially when an increase in thermal conductivity does not serve additional value. The fabricator fills the via with solder mask of low-viscosity or a resin type material similar to the laminate. As this plugging protects the copper in the via, no other surface finish is necessary. For both, filled and plugged vias, it is important to use material with CTE matching the board material.

Depending on the application, fabricators may simply tent a via, covering it with solder mask, without filling it. They may have to leave a small hole at the top to allow the via to breathe, as air trapped inside will try to escape during soldering.

Trouble with Vias

The most common defect with vias is plating voids. The electro-deposition process for plating the via wall with a layer of copper can result in voids, gaps, or holes in the plating. The imperfection in the via may limit the amount of current it can transfer, and in worst case, may not transfer at all, if the plating is non-continuous. Usually, an electrical test by the fabricator is necessary to establish all vias are properly functioning.

Another defect is the mismatch of CTE between the copper and the dielectric material. As temperatures rise, the dielectric material may expand faster than the copper tube can, thereby parting the tube and breaking its electrical continuity. Therefore, it is very important for the fabricator to select a dielectric material with a CTE as close as possible to copper.

Vias placed in the flexing area of a flex PCB can separate from the prepreg causing a pad lift and an electrical discontinuity. It is important designers take care to not place any vias in the area where they plan the PCB will flex.

HiFiBerry & Raspberry Pi Put New Life into Old Loudspeakers

If you have some old stereo speakers stored away in your basement, chances are they connect through the old way—with wires—to an amplifier, and that is the reason they were banished to the basement. With HiFiBerry Amp+ and a single board computer, such as the Raspberry Pi (RBPi), you can resurrect your vintage speakers. Using the latest in open source technology, you can now use the renovated loudspeakers wherever you want, since they now operate wirelessly.

HiFiBerry offers their Amp+ as an amplifier for the RBPi. As it is a Class-D power amplifier, it is highly efficient as a stereo module, and you only need to connect the loudspeakers. This high-quality amplifier is ideal for setting up multi-room audio installations.

The amplifier is stable enough to drive 4-Ohm loudspeakers and those with higher impedance as well, pumping out 25 W of output power. However, the best part is the RBPi can fully control the amplifier. As the amplifier includes on-board digital to analog converters, you do not need external sound cards or DACs to provide the 44.1 KHz and 48 KHz sample rates. The board connects directly to the RBPi without needing additional cables, and this provides a full digital sound path for optimal audio performance.

The HiFiBerry Amp+ comes as a pre-fabricated kit, so it needs no soldering. It is a daughter board for the RBPi, and when the RBPi plugs into it, you need to connect only a single external power supply of 12-18 V to supply both the amplifier and the SBC, as the RBPi draws power from the Amp+. You can use the Amp+ with all RBPi models that have the 40-pin GPIO connector. The board sits on four small plastic spacers that come with the kit.

The specialty of the Amp+ kit is it converts the digital signal into audio with far greater clarity than the RBPi can, and delivers that to the speaker as a 25 W audio amplifier. On the reverse side of the board, the female connector is easily visible, so it is easy to plug in the GPIO pins of the RBPi.

On one side of the board are a jack for powering the board, and six wire-terminals. If for some reason you cannot use the jack to power the board, use the two wire-terminals on the left. The rest of the four wire-terminals are for connecting to a pair of stereo loudspeakers, using two audio cables per speaker.

As the board takes in 12-18 V supply and delivers power to the RBPi as well, it is important to not power the RBPi from its usual 5 V power supply. This reduces the number of wires to the assembly. As the Amp+ board is very small, it does not protrude beyond the RBPi. It is important to mount the board on the four plastic spacers to avoid breaking the GPIO pins.

The SD card for the RBPi can be of the 8 GB type and people have reported better performance with Transcend cards. However, you can use 16 GB cards as well.

Are Ferrites Good for Interference Suppression?

Although ferrite beads and sleeves are a common sight on cables, the technique for reducing both outgoing and incoming RF interference is the least understood. To study ferrites, and to do some comparative frequency domain measurements, one needs actual ferrite samples, a specially designed test jig, a spectrum analyzer, and a tracking generator.

Any current flowing through a metal conductor will create a magnetic field around it. The inductance of the conductor transfers the energy between the current and the magnetic field. A straight wire has a self-inductance of about 20 nH per inch. Any magnetically permeable material placed around the conductor helps to increase the flux density for a given field strength, thereby increasing the inductance.

Ferrite is a magnetically permeable material, and the composition of the different oxides making it up control its permeability, which is frequency dependent. The composition is mainly ferric oxide, along with nickel and zinc oxides. Furthermore, the permeability is complex with both real and imaginary parts. Therefore, the line passing through the ferrite has both inductive and resistive components added to the impedance.

The ratio of these components varies with frequency. The resistive part dominates at higher frequencies, and the ferrite behaves as a frequency dependent resistor. Therefore, the assembly shows loss at high frequencies, with the RF energy dissipating in the bulk of the material. At the same time, there are few or no resonances with stray capacitances.

Cables are usually in the form of a conductor pair, carrying signal and return, or power and return. Multi-way cables may carry several such pairs. The equal and opposite return current in each circuit pair usually cancels the magnetic field from the current in the forward line. Therefore, any ferrite sleeve place around a whole cable will have zero effect on the differential mode currents in the cable. This is true as long as the sum of differential-mode currents in the cable is zero.

However, for currents in the cable in common mode, with conductors carrying current in the same direction, the picture is different. Usually, such cables produce ground-referred noise at the point of connection or have an imbalance of the impedance to ground, causing a part of the signal current returning to ground through paths other than through the cable.

For instance, a screened cable, improperly terminated, may carry common-mode currents. As their return paths are essentially uncontrolled, these currents have a great potential for interference, despite being of low levels. Sometimes, the incoming RF currents, although generated in common mode, convert to differential mode and so affect circuit operation. This happens due to differing impedances at the cable interface.

As common mode currents in a cable generate a magnetic field around it, placing a ferrite sleeve around the cable increases the local impedance of the cable and operates between the source and load impedances.

When interfacing cables, low source impedance implies the ferrite sleeve is most effective when adjacent to a capacitive filter to ground. Since the length and layout of a cable will usually vary, engineers take the average value of the cable impedance as 150 ohms.

How do Antistatic Bags Work?

Computer boards and sensitive electronic components need protection from electrostatic discharge, especially at the time of shipping, handling, and assembly. This requirement has led to the development of an entirely new class of antistatic packaging materials. Now, a multi-million dollar packaging industry exists, with major developments in polymers. These are special conductive polyethylene and other laminates covered with very thin metalized films. This packaging industry saves several hundred million dollars each year for the computer and electronic industry, dwarfing almost all other industrial and commercial antistatic abatement enterprises.

To demonstrate the working of an antistatic bag that store and ship assembled boards and electronic components, one needs an apparatus including a tonal electrostatic voltmeter or TESV, several antistatic bags big enough to cover the TESV mounted on a tripod, a plastic tube or rod, and a rubbing cloth. Wool or silk cloth will work well with a Teflon, Nylon, or PVC pipe.

To disallow any movement of the TESV when operating, mount the instrument on a tripod, turn it on, and zero the instrument. Now charge a plastic rod by rubbing it with the cloth, and bring it close to the sensing head of the TESV. The instrument will respond by indicating the presence of electrostatic charge.

Covering the TESV with one of the antistatic bags shows it now registers little or no charge when repeating the experiment. Even with the charged conducting object discharging directly to the bag, the TESV shows little or no charge indication. The only possible explanation is the conductive bag shields the TESV from the electrostatic field.

The bag shields the instrument even though it is not connected to ground. If it were necessary to ground the bag to make it work, the antistatic bag would have been more inconvenient and ineffective than they are now. Grounding is not necessary here as electric charge resides only on the outer surface and does not penetrate inside, or into any void enclosed by the conductive material. The ungrounded bag simply holds the charge harmlessly only on the outside.

This also solves the problem of removing a sensitive component from inside the bag. When a person handles the bag, the contact with the hand grounds the bag and drains the charge from its surface. However, if the person were wearing an insulated glove, the component would draw a strong electric spark when it is withdrawn from the bag, and may be damaged.

Antistatic and static shielding materials are commercially available for every size and shape necessary. Specifications usually refer to MIL standards or the rate of charge dissipation, along with abrasion resistance, thickness, and others. Some advertisers refer to their antistatic bags as Faraday cages, since it does not allow charge to penetrate inside the bag.

Another type of antistatic bag has no metal layer, but is actually a bag made of a conductive polyethylene film. The manufacturer claims the bag can dissipate 5 KV in 2 seconds. Although in practice it is the electric charge that dissipates, the voltage is far easier and more convenient to monitor, and is directly proportional to the charge for a fixed capacitance geometry.

Problems Mains Harmonics Cause

Single-phase power converters are specifically problematic since they generate significant levels of triplen harmonics, such as the 3rd, 9th, 15th, etc. As they do not undergo phase cancellation, they add up linearly in the neutral conductor to create a particular nuisance. Apart from this, they are also present in zero-phase transformer flux, and heat up cables and transformers. Although three-phase converters also generate harmonic emissions, the triplen currents produced by them are of much lower levels.

Other non-linear loads also contribute to harmonic currents in the mains supply. Such loads include motors and transformers, welding equipment and arc furnace rectifiers. Another source is the fluorescent lamp with magnetic ballast. However, rectifiers produce much higher frequencies as compared to that from fluorescent lamps.

The harmonic currents an equipment draws from the AC mains supply do not alter the power the equipment consumes when measured in Watts. However, the harmonic currents increase the VA rating of the equipment. Since Power Factor is the ratio of the Watts to the VA the equipment consumes, the equipment that produces significant emissions of harmonics also has a lower power factor.

A resistive load, such as an incandescent lamp, has a PF of 1.0 since it consumes the same amount of power in Watts, as it does in VA. Therefore, an incandescent lamp cannot emit any harmonic content. On the other hand, electronic equipment with rectifiers at the input and with no harmonic reduction techniques have power factors of around 0.6, implying they generate harmonic currents. Fluorescent lamps with magnetic ballast, running at 50/60 Hz, usually have PF of the order of 0.3, so they generate significant amounts of triplen harmonics.

The power factor of the load is significantly different from the power factor traditional electrical generation and distribution engineers use—the latter is the cosine of the angle between the sine-wave supply voltage and its load current. While the traditional PF assumes all loads are linear using sine wave voltages, engineers adjust this PF by adding capacitance or inductance to the power line, depending on whether the load is resistive, inductive, or capacitive.

However, the traditional method of PF correction for linear loads fails when trying to correct the PF of a rectifier-input electronic power converter. Mains power distribution networks are now driving significant numbers of electronic loads as these operate at higher efficiencies, and electronic loads are now replacing most linear loads.

The standard IEC 61000-4-7 [6] offers a survey of harmonics present in power supply systems. Typically, there are four major kinds of problems that harmonic currents cause when they are flowing in mains power supply networks:

  • Problems that harmonic currents themselves cause
  • Voltage distortion from harmonic currents
  • Problems that voltage distortions cause
  • Interference to telecommunication networks

In large installations with several single-phase electronic loads, such as in modern offices, the total neutral currents may reach as high as 1.7 times the highest phase current. This is the effect of harmonic currents, mainly the triplens, as these flow without being cancelled, in the neutral conductor. As many older buildings have half-sized or even smaller diameter neutrals, there can be a risk of fire hazard.

Raspberry Pi and Traffic Lights

Although we come across traffic lights almost every time we step out of our homes, we rarely stop to think about how they work. However, Gunnar Pelpman has done just that, and he has put the hugely popular single board computer, Raspberry Pi to good use. While most of the tutorials introduce turning on and off LEDs, he has prepared a somewhat more complex tutorial, one that teaches how to program traffic lights. Moreover, he has done this with the Raspberry Pi (RBPi) running the Windows 10 IoT Core.

Traffic Lights may look very complicated installations, but they are rather simple in operation. They mostly comprise a controller, the signal head, and the detection mechanism. The controller acts as the brains behind the installation and controls the information required to light up the lights through their various sequences. Depending on location and time of the day, traffic signals run under a variety of modes, of which two are the fixed time mode and the vehicle actuation mode.

Under the fixed time mode, the traffic signal will repeatedly display the three colors in fixed cycles, regardless of the traffic conditions. Although adequate in areas with heavy traffic congestion, this mode is very wasteful for a side road with light traffic—if for some cycles there are no waiting vehicles, the time could be more efficiently allocated to a busier approach.

The second most common mode of operation of the traffic signal is the vehicle actuation. As its name suggests, the traffic signal adjusts the cycle time according to the demands of vehicles on all approaches.

Sensors, installed in the carriageway or above the signal heads, register the demands of the traffic. After processing these demands, the controller allocates the cycle time accordingly. However, the controller has a preset minimum and maximum cycle time, and it cannot violate them.

The hardware for the project could not be simpler. Gunnar has used three LEDs—red, orange, and green—to represent the three in a traffic light. The LEDs have an appropriate resistor in series for current limiting, and three ports of the RBPi drive them on and off. The rest of the project is the software, for which Gunnar uses the UWP application.

According to Gunnar, there are two options for writing UWP applications—the first a blank UWP application and the second a background application for IoT—depending on your requirement. The blank UWP is good for trying things out as a start, as, at a later point of time, you can build a User Interface for your application.

After creating the project with the blank UWP application, Gunnar added a reference to Windows IoT Extensions for the UWP. Next, he opened the file MainPage.xaml and added his own code, which begins with a test for the wiring. He uses the init() function to initialize the GPIO pins and stop() to turn all LEDs off. Then the code turns on all LEDs for 10 seconds to signal everything is working fine.

According to Gunnar, the primitive code mimics the traffic lights. He uses a separate code for the cycling of the traffic lights, and another for blinking them on and off. He uses the play() function for running ten cycles of the traffic light.

USB Type C and USB 3.1 Gen 2 – What is the Difference?

With the need for increasing capabilities, USB technology has evolved and improved over several years. Recently, the USB Implementation Forum has released the specifications for the SuperSpeed+1 standard or USB 3.1 Gen 2 signal standard and the USB Type C connector. Data transfer rates have been increasing from USB 1.0, released in January 1996, with a full speed of 1.5 MB/s, to USB 2.0, released in April 2000, with full speed of 60 MB/s, and to USB 3.0, released in Nov 2008, with a full speed of 625 MB/s. The latest standard, USB 3.1 Gen 2 was released in Jul 2013, and has a full speed of 1.25 GB/s.

Confusion between USB Type C and USB 3.1 Gen 2

When discussing the relationship, people are often confused between the USB Type C and the USB 3.1 Gen 2 standard. The major point to note is the USB Type C standard defines the physical connector alone, whereas the USB 3.1 Gen 2 standard defines the electrical signal for communication.

Therefore, system designers have the freedom to select signals conforming to USB 3.1 Gen 2 to pass through USB Type C connectors and cables or through a connector that do not conform to the USB Type C specification. Designers can implement their own proprietary connector and still use the USB 3.1 Gen 2 signal standard in case they want to use their own hardware or to ensure their system remains isolated from other systems.

The reverse is also equally true and applicable. One can use the USB Type C connector to transmit and receive signals that do not conform to the USB signal standards. Although the implementation will benefit from the inexpensive and easily available USB Type C connectors and cables, the OEM must label it correctly, since the user will be at the risk of connecting the proprietary non-conforming system to a USB 3.1 Gen 2 standard system and damaging one or both the systems.

OEMs can also transmit legacy USB signaling configurations using the USB Type C connectors and cables. This is because the USB standard allows using pre-USB 3.1 Gen 2 on USB Type C connectors, as they have designed the standard to cause no damage to either system. However, the most optimum power and data transfer will occur only when both systems are negotiating a common power configuration and communication standard.

Why USB Type C

Compared to the older configurations, the use of the USB Type C connector offers several advantages. Apart from being a smaller package with more conductors, the USB Type C supports higher voltage and current ratings, while offering greater signal bandwidths.

Physically smaller, the USB Type C plugs and receptacles fit in a wide range of applications where space is restricted. Moreover, one can connect the plugs and receptacles any way—either right-side up or up-side down. This allows easier and faster insertions of plugs into their receptacles.

While USB Type A and B connectors can have a maximum of four or five conductors, there are 24 contacts within the USB Type C and it can carry 3 A at 5 V, or 15 W of power.