Author Archives: Andi

Room Automation and Raspberry Pi

Most people prefer to come back to a cozy room after a full day’s work. For many, this may not always be possible, unless someone turns on the AC at the right time. For those living alone, help is available in the form of a single board computer, the Raspberry Pi or the RBPi. In addition, the RBPi operates the blinds and you can control it from anywhere in the world – the RBPi is connected to the Internet.

For this project, you will need an RBPi with a suitable SD card, a Wi-Fi dongle, a stepper motor. You will also need a power source capable of driving the RBPi and the motor, a stepper motor driver board, an IR receiver, an IR LED and an NPN transistor.

Controlling the AC is a simple affair, with the RBPi simulating the infrared information the remote control normally uses. You need to use the LIRC library for the RBPi to record this IR information via the IR receiver. The infrared LED driven through the NPN transistor duplicates the signal sent by the remote control of the AC. Initially, you must let RBPi learn the IR codes by recording those using commands in the LIRC library. LIRC produces a configuration file that holds the IR codes for your AC. Playing back these codes through the IR LED allows you to control the AC just as its own remote does.

The RBPi and the motor driver board control a stepper motor for driving the blinds. The RBPi merely drives a GPIO pin to let the motor driver board know if it must operate the stepper. The driver board already has the necessary parameters stored within it for driving the motor. By default, the motor remains off so that it does not waste power when it is not needed. The software takes care of this by turning off the Enable pin on the stepper driver board. When you need to operate the blinds, a script on the RBPi turns the GPIO pin on and off.

To operate the unit from remote, you need to connect the RBPi to the Internet via a wireless network. Use the Wi-Fi dongle for this, configuring the RBPi to switch on the wireless connection immediately after booting. Web access to the stepper motor controller is through Nginx and PHP.

The entire setup works when the RBPi connects wirelessly to the network. You access a web interface and use it to send commands to the controller script running on the RBPi. Depending on the commands sent, you can access either the blind opener or the AC control. For opening the blinds, the RBPi sends on or off signals to the stepper motor controller board.

On the other hand, the RBPi sends the appropriate commands to the air conditioner via the IR link. Depending on the code transmitted over the IR link, the AC will switch either on or off. Additionally, with proper codes transmitted from the RBPi to your AC, you can even set the temperature of the room before returning at the end of the day.

Drive a 16-Channel Servo with the Raspberry Pi

To drive servomotors micro-controllers must have PWM outputs. These are output pins on which the micro-controller will generate pulse outputs with controlled or modulated variable widths. Most embedded micro-controller units have one or more of these outputs. The famous single board computer, the tiny credit card sized Raspberry Pi or RBPi also has one IO pin dedicated for PWM. This is the PWM channel available at the GPIO18 of the RBPi and with this, you can drive a single servo at best. However, if you want the RBPi to drive more than one servo, it will need additional circuitry.

A PWM driver IC such as the PCA9685 can drive 16 servos at a time, but requires commands and data through its I2C interface. Fortunately, the RBPi can also communicate using the I2C protocol, enabling it to control 16 servos via the PCA9685. Adafruit has a very convenient breakout board with the PCA9685 on it and that makes it very convenient to connect to the RBPi. Not only can you drive servos with the PWM outputs, you can use the PWMs for controlling LED lighting as well.

To let RBPi communicate with the I2C protocol, it will require a special OS available from Adafruit. This is the Occidentalis flavor and it has all the libraries required for invoking I2C. However, if you are using the stock Raspbian OS, you must install the python-smbus and the i2c-tools using the “sudo apt-get install” command. To learn more about using I2C, refer Adafruit’s rather informative tutorial.

The two packages will allow you to search for any I2C device connected to the RBPi. The easiest way you can connect the servo breakout board to your RBPi is with the help of the Adafruit Pi Cobbler. Here, VCC is the digital supply for the IC or 3.3V, and V+ is the supply for the servomotors (typically 5V).

The actual chip that drives the servos, the PCA9685, needs 3.3V, and connects to the VCC on the cobbler board. Servos usually require much higher currents to operate. Therefore, they are powered from a separate power supply, typically 5V, and are connected to the V+ on the Cobbler. Note that this 5V is different from the 5V supply for the RBPi. The PWM operation on the servos creates a huge amount of electrical noise, which can cause the 5V supply voltage to fluctuate significantly. RBPi may not be able to tolerate such voltage fluctuations, and this may cause it to crash and lock up.

If you are driving many servos, it will be a good idea to add a capacitor to the driver board. There is a spot already marked for such a capacitor. As a thumb rule, you need a capacitor with a value n x 100uF, where n is the number of servos you are driving. Capacitors are manufactured in standard ratings, and you may have to go for the next higher standard value that you have calculated.

Depending on whether you are using a standard or continuous rotation servo, your python code will vary. For the actual code with which you can control the various parameters of I2C and hence the servo, you may refer to this site.

Here Comes the Raspberry Pi 3

The world woke up to a 256MB Raspberry Pi, or RBPi, Model B on 29 February 2012, and found it fascinating enough to order over eight million pieces since that date. That has made the Raspberry Pi Foundation of UK grow from a few volunteers to over sixty full-time employees, and the RBPi 2 an all-time best-selling SBC or single board computer.

In celebration of their fourth birthday, the Raspberry Pi Foundation has released their new model of the RBPi, keeping the price same as that for the existing RBPi 2. The new RBPi 3 offers over 10 times the performance of the RBPi 1, and comes with an integrated Bluetooth and wireless LAN, while keeping complete compatibility with the RBPi 1 & 2.

RBPi 3 Model B, as the new RBPi is called, features the BCM2837 SoC, belonging to the same family of Broadcom processors as its predecessors. That means all the projects and tutorials you relied on for the precise details of the RBPi hardware so far, will continue to work for the RBPi 3 as well.

RBPi 3 comes with a new ARM Cortex-A53, quad-core processor, custom-hardened and running at 1.2GHz. Along with various architectural enhancements, including a 33% increase in the clock speed, the new SBC offers a 50-60% increase in performance, when operating in 32-bit mode, over its immediate predecessor, the RBPi 2. Compared to the original RBPi, the new RBPi 3 gives nearly a ten-fold improvement in performance.

Designing the RBPi 3 with the BCM2837 was not a simple task, as it also contains the BCM3438 wireless combo chip, while it retains the same form factor as that of the RBPi 2 Model B. However, the designers have done it, with only the position of the LEDs changing to the other side of the SD card socket to allow the antenna to be positioned. Running an extensive and expensive wireless conformance campaign has allowed the Raspberry Pi Foundation launch the RBPi 3 in almost all countries simultaneously.

As all the connectors are in the same place, with the same functionality, you can house the RBPi 3 in the same enclosure that you had been using for the RBPi 2. Although the board still runs from the same 5V, 2A adapter via the micro-USB connector, it is recommended to upgrade to a 5V, 2.5A adapter if you are connecting power-hungry USB devices to the RBPi 3.

You will need an updated operating system – a Raspbian or NOOBS image – to take advantage of the functions of the new board. Although the new image remains 32-bit for the time being, there is likely to be a shift towards a 64-bit image after a few months. There is also a plan for an RBPi 3 Model A, with the form factor of the RBPi Model A+.

Industrial customers who want to stick with the RBPi 1 or RBPi 2, including Models B and B+, can do so because these models will be continued for as long as there is a demand for them. Additionally, VideoCore IV 3D will continue to be the 3D graphics core for all RBPi models.

Is the Odroid SBC Better than Raspberry Pi 3?

The world of inexpensive SBCs or single board computers has been taken by a storm with the unveiling of the new Raspberry Pi board or the RBPi 3. The claim being it blows the competition away, and that no one can match its price. However, that may not be entirely true, as the Odroid C2 SBC seems to best the RBPi 3.

Hardkernel promotes its Odroid C2 as another cheap and speedy SBC with a 64-bit ARM-based quad core processor. A comparison of the specifications shows the C2 may be giving the RBPi 3 a run for its money. Compare for instance, the BCM2837 of the RBPi 3 with the Amlogic S905 SoC of the C2. Although both are quad-core ARM Cortex-A53, the C2’s processor runs at 2GHz to the 1.2GHz of the RBPi 3. At 2GB, the C2 has double the RAM of the RBPi 3, which has only 1GB. Moreover, the C2 comes with a Mali-450 GPU, able to deliver 4K video.

Although the C2 does not have the on-board wireless and Bluetooth features of the RBPi 3, it has a high-speed Gigabit Ethernet port directly wired into the SoC. The RBPi 3 also has Ethernet on-board, but as this is a 100-megabit port and is on a USB interface, its speed is likely to be limited.
The two boards share a very similar form factor and are nearly identical in their GPIO capabilities. In addition, for both the boards, you can choose the storage to be either the usual micro SD card or eMMC. However, it is worth stating that the C2 comes with a built-in ADC or analog to digital converter. When it comes to operating systems, the C2 can operate with Ubuntu 16.04, or Android lollipop.

The RBPi family, just like Apple products, has always faced competition. However, most look good only on paper, but their prices always let them down in the end, and we never hear of them after some time. The price of $40 for the C2, being very close to that of the RBPi 3, may just escape this fate. Of course, there is the matter of adding shipping and customs to the price, as the origin of C2 is Korea.

So, which of them is preferable – the C2, or the RBPi 3 – and why? The faster processor of the C2 and its faster wired networking would make it attractive to someone working on network-attached data processing applications. Although one can add a USB wireless network adapter for only a few dollars, the onboard Wi-Fi and Bluetooth of the RBPi 3 makes it so much more attractive. Therefore, the RBPi 3 would be coveted by anyone who is a home user or planning to use a computer on a platform that will remain unfettered by wires.

Although the C2 may be more impressive when compared to the RBPi 3, the latter will likely outsell the C2 many times over. This may not be because of the massive publicity advantage that the RBPi 3 is receiving from the Pi foundation, but more likely due to the wide ecosystem of hardware and software developers the RBPi family has at present.

New Combination of Materials for Efficient Solar Cells

An international team of scientists have come together to build solar cells with high efficiency using a new blend of materials. The materials used allow the cells to convert sunlight into electrical energy without the addition of dopants. The design, termed DASH, uses molybdenum oxide and lithium fluoride.

Doing away with doping

Most of the solar cells use silicon wafers in the crystalline form. The wafer, along with the layers of materials deposited on it are doped or injected with special impurity atoms that either introduce free electrons or create electron deficiencies called holes. The presence of these extra electrons or holes increases the electrical conductivity of the material. However, the impurities introduce certain complexities within the crystalline structure, which bring down the performance.

Since solar cells are all about increasing the performance of these devices, researchers have been looking at means to eliminate the doping process. The international team has made available a cell prototype with a simple architecture. The journal Nature Energy has published an article on the design of the solar cell. James Bullock, a faculty member of Australian National University and a team member is the principal author of the paper. He has been a visiting researcher at Lawrence Berkeley National Laboratory and UC Berkeley as a part of the project.

Bullock explains that the simple structure of the cell designed by them would cut down the production and operational costs considerably, thereby enhancing the efficiency. The silicon cell, free from doping impurities designed by the team is termed DASH, which is the acronym for dopant-free asymmetric heterocontact. The efficiency of this product is 19%, which exceeds that of other dopant-free cells. The efficiency of previous cells of this category did not exceed 14%.

Special properties of the contact materials

The researchers applied several layers of amorphous silicon over a wafer of crystalline silicon. This was overlaid with very thin films of molybdenum oxide on the sun exposed surface and lithium fluoride at the bottom one. These two external layers are only a few nanometers thick and act as contacts for the holes and electrons. Ali Javey, a team member and a professor of Electrical Engineering and Computer Science at UC, Berkeley, explains that both molybdenum oxide and lithium fluoride have been selected for making up the contacts because of their special properties. The materials form transparent layers at this thickness. Molybdenum oxide has several imperfections in its crystalline structure that allow it to act as an effective hole contact.

Likewise, the defects in the lithium fluoride structure allow it to be a useful electron contact. Stefaan de Wolf, another team member has described in the article how the molybdenum oxide and lithium fluoride layers work as effective contacts when used with a combination of amorphous and crystalline silicon. In addition, these materials have allowed the scientists to come up with remarkable variations in their properties with different thicknesses.

The scientists used the thermal evaporation technique at room temperatures to apply the coatings. Javey said that the researchers intend to use the material combination for other semiconductor applications like transistors to improve their performance.

Solar Deployment Component Selection

The market for renewable energy is in turmoil right now, mainly because of lower utility costs, a desire for energy independence, incentivized solar installations, and low-cost batteries. Homeowners are now trending towards storing energy from solar cells rather than selling it back to the grid. However, that requires selecting storage components wisely.

Although 2016 was the cutoff year for the current solar energy tax incentives, there has been a successful bid to the Congress to extend the incentives up to 2020. As a result, the solar industry finds itself rejuvenated and this is having a reflective effect on the battery-based energy storage systems as well.

This has created a massive surge for ESS or energy storage systems in general, with particular emphasis on RES or renewable energy storage systems. Designers of inverters and power conversion architectures now have enormous opportunities, especially those designing for home applications. For instance, Tesla has announced the Powerwall, a 10-kWh storage system suitable for homes, businesses, and utilities.

Designers and manufacturers are looking at advanced storage options such as ultra-capacitors and battery chemistry such as solid electrolytes, magnesium-ion, lithium sulfur, and next-generation flow and metal-air. The next-generation technologies for energy storage are expected to increase from near zero in 2015, to above $9 billion by 2030. Overall, the demand for batteries will increase from 66 GWh in 2014 to over 225 GWh in 2023
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Traditionally, people assumed that any excess power generated from solar panels and not used by the homeowner would be sold back to the utility. However, they are beginning to realize that saving the extra energy in batteries can help in the evenings, when the energy consumption is the highest and so are the utility rates. In the evenings, when there is no sun, the home can be less reliant on the grid, and be more self-sufficient if it relies on the backup batteries to supply electricity.

So far, people had to buy all parts separately and put them together for a solar system. This included the battery, inverter and metering. However, all this involved multiple voltage conversions leading to unnecessary losses and overall lower efficiency.

Now, all that is changing. You can opt for a fully integrated system. This includes the PV monitoring, the inverter, and the DC/DC conversion to charge the battery. Metering now is highly advanced, with wireless technologies such as ZigBee, providing either computerized or application-based monitoring of the entire system.

However, that does not mean it simplifies optimizing the PV conversion. One still needs MPPT or maximum power point tracking to make sure of capturing the varying PV energy and transferring it to the battery with the minimum of power losses, regardless of the strength of the sun. For instance, this involves using a capacitor for stabilizing the PV voltage and dropping it sufficiently, ensuring the charging voltage matches the battery chemistry.

Although efficiency, cost, and ease of use are all factors critical to the system level, safety is still the highest priority. The emphasis is on isolation including both digital isolators and opt couplers to meet the IEC 62109-1 standards.

What are Optically Isolated Relays?

Popularly, relays are known to be electromechanical devices. However, engineers today have access to solid-state relays that operate without any electromagnetic or moving parts. Where reliability and performance is paramount, engineers prefer to use solid-state relays to their electromagnetic versions. However, solid-state relays are more expensive.

While traditional relays have several mechanical failure modes associated with moving parts, solid-state relays offer several advantages in performance and design. These include low power consumption, low leakage current, stable on-resistance, high reliability, extremely long life, small size, fast switching speeds, high vibration and shock resistance, and no switching noise from contact bounce.

Another important feature of solid-state relays is they are optically isolated. That means the relays use an LED or light emitting diode on their input side, MOSFETs or metal oxide semiconductor field effect transistors on their output side, and an array of photo sensors isolating the two.

The design and packaging affect the relay’s performance crucially. Translucent resin molds the electronic and optical components – the LED, photo array, and the MOSFETs – allowing light to pass through, while applying a dielectric barrier between the input and the output.

That means you only need to drive a switchable voltage directly to the input pin of the solid-state relay through a resistor to limit the current through the LED and control the relay. The value of the resistor has to be selected carefully, so the LED can reach its full intensity without being overdriven.

Optically isolated relays are increasingly used in sophisticated test and measurement systems. However, these systems require solid state relays to have characteristics such as low capacitance, low on-resistance, physical isolation, and high linearity. As data acquisition devices become faster and more precise, the above characteristics play an increasingly important role.

Low capacitance results in improved switching times and better isolation characteristics when switching high-frequency load signals. You need low on-resistance for reducing power dissipation when switching high currents. This also improves switching speeds improving the precision of measurement. Temperature range of the relay is an important factor when considering on-resistance values, as rising temperatures drive up the on-resistance.

To enhance precision by minimizing noise, physical isolation between the input and the output of a relay plays an important part. Expect isolation voltages as high as 5 KV AC for optically isolated relays as these offer a truly physical separation between their input and the output. Solid-state relays also offer high linearity leading to accurate measurements.

Industrial applications also benefit from using optically isolated relays, although the requirements here are different. For instance, an industrial plant using several relays, the low power consumption of optically isolated relays offers substantial savings. Where an electromagnetic relay requires 50-100 mA to actuate, a typical optically isolated relay requires only 5 mA.

Latching-type models of solid state relays have built-in protective circuits that safeguard power supplies, motors, and other industrial devices susceptible to disturbances from the output side. Such disturbances come from voltage peaks or overcurrent conditions arising from short circuits or improper use. Their reliability and small form factor saves space, while speeding up development.

Do You Need A 2K Display on your Smartphone?

One of the biggest selling points of flagship smartphones is their display resolution. A high resolution allows for better rendering of images and text on the screen and enhances the overall viewing pleasure. While grainy displays have become a thing of the past, with even sub $100 smartphones touting qHD and HD displays, the question now is, how much is too much.

Phone manufacturers are constantly striving to equip their devices with the sharpest displays, outperforming rivals in terms of clarity and accuracy of color reproduction. While shopping for a new smartphone, you might have come across terms like retina, HD, 2K and 4K displays. However, post a certain figure, it is doubtful if there is any discernible improvement in the clarity.

When launching the iPhone 4, Apple had claimed that a resolution of 960×640 pixels on a 3.5″ screen (translating to 326 pixels per inch) was as much as a normal human eye could discern when viewing from a distance of 9″. Going by that statement, a screen resolution north of 326 ppi would not cause any tangible improvement in clarity, while increasing production costs. Though iPhones have bigger screens now, their ppi remains constant at 326, whereas some other manufacturers have been pushing increasingly higher resolution screens on their latest releases. Most smartphones launched in the past year by tech giants like Samsung, LG and newcomer Oppo have panels with pixel densities of and above 415. The first smartphone to feature a 2K display was the Xplay 3S, launched by Vivo with a 6″ screen that sported 491 ppi. Soon after, Oppo launched the Find 7 smartphone, also with a 2K display of 2560×1440 or an astronomical 538 ppi. These figures are way ahead of retina displays, but in case of smartphone displays, after a certain point, more might not always be merrier.

Of course, the screen size has a huge role in determining how many pixels need to be packed in per square inch for delivering the perfect viewing experience. Moreover, a lot depends on the distance at which the screen is kept from the eyes, as closer viewing distances mean that more pixels can be resolved by the human eye. However, in no way is the average smartphone user going to be able to appreciate the difference between say, a 350- and a 500-ppi display. Stuffing more pixels per inch into an LCD panel is only more taxing on the battery. Therefore, an ultra-high resolution 2K display needs to be powered by a bigger battery as well, along with a superfast CPU to provide juice for all those extra pixels.

A 2K display, or the absence of it, should not be the only factor to consider when looking for a new smartphone. While it does make for a great viewing experience, it is more than likely a slightly less ppi count will not cause any noticeable decrease in clarity. It is a good feature to have on a smartphone to boast about, but it comes at the cost of battery life and processing speed.

The ExaGear Desktop for the Raspberry Pi

Normally, the Raspberry Pi or RBPi does not allow running Intel x86 applications. This is because the RBPi is ARM-based. That means it has a different architecture from the Intel-based PCs we are used to using. This is as if a letter addressed to a Russian town landing up in Denmark – the address is all wrong, so it is tough to deliver.
Virtual machines are available that create a local environment for running applications where the basic architecture differs. For the x86 platform, the most popular virtual machine software are VMware and VirtualBox. With virtual machines, you may be running Linux as your main operating system, but you can also run a full-fledged Windows operating system simultaneously and vice versa. The main operating system is termed the Host, while the OS running under the virtual machine is termed the Guest.
Eltech has produced such a virtual machine for RBPi that have ARM platforms as their base. This is the ExaGear Desktop and it allows you to run Intel x86 applications directly on your RBPi through a virtual x86 Linux container on ARM. For example, on the ExaGear Desktop, if you install Wine, the open source compatibility layer software application will allow you to run even Windows applications on your RBPi.
You can run the ExaGear Desktop on most ARM-based Mini PCs operating with Linux such as the RBPi, Banana Pi, Wandboard, Jetson TK1, Utilite, CuBox, CubieBoard, ODROID including the ARM-based Chromebook. Unlike Linux, ExaGear Desktop is not free and you can download it only after paying for its license key. However, before buying, it is prudent to check up if your Mini PC has the proper hardware and software base to allow ExaGear Desktop to run on it.
If you are using the RBPi ver1, you will need the ARMv6 instruction set with VFP32. For other RBPi versions and ARM devices, you will require the ARMv7 instruction set with VFP32. If you are planning to use x86 applications that require MMX/SSE, you will also need NEON as support. On the software side, you must be using the Linux operating system variants such as Raspbian, Debian 7, Ubuntu 14.04 or Ubuntu 12.04. Check with the Eltechs Tech Forum if you still harbor doubts about system requirements.
Eltech has published some test results to demonstrate the speed with which the ExaGear Desktop works. For benchmarking, they have used SysBench, which was built for ARM and Intel x86 platforms. Using the same ARM machine for both tests, they have compared the results of ARM-based tests against x86 tests running under the ExaGear Desktop. The tests cover parameters such as File IO read/write, CPU cycles, Memory usage, Threads speed and Mutex. Results show ExaGear to be superior to QEMU in almost all parameters.
Using their setup, Eltech has also compared the performance of ExaGear against the performance of QEMU, the user mode emulator. For benchmarking, they used GeoBenchmark and found that ExaGear Desktop was nearly five times as fast as QEMU was.
Eltech has also compared the ExaGear Desktop performance against QEMU using the nbench benchmark. Here too, ExaGear Desktop was able to show far superior performance compared to the performance of QEMU when both were run on the same platform.

Stackable Pi-Plates for the Raspberry Pi

If you are faced with a paucity of projects for your Raspberry Pi or RBPi, the tiny, credit card sized single board computer, you should get the circuit boards from Pi-Plates and connect your RBPi to the outside world. Pi-Plates offer a family of stackable, add-on boards that provide your SBC with a robust set of features at a minimal cost.

Pi-Plates design their circuit boards to be economical with the GPIO pins they use from the RBPi header. For example, when using the DAQCplate board, it uses only two dedicated GPIO pins. However, you can stack eight of these Pi-Plates to get 64 digital inputs, 56 open-collector outputs, 64 analog inputs and 16 analog outputs. Whether you are an experimenter, a hobbyist or a professional, Pi-Plates have designed these boards to be useful for all. Additionally, these are mechanically and electrically compatible with all revisions of the RBPi. That includes versions A, B, A+, B+ and the new version 2.

At present, Pi-Plates offer four products. The flagship product is the DAQCplate board that has ADCs or Analog to Digital Converters, DACs or Digital to Analog Converters and expanded digital IO. MOTORplate is a new product for controlling motors and you can use it to drive two stepper motors or four DC motors, while its onboard software can handle all drive logic including acceleration profiles. If you want to add custom hardware on your Pi-Plate stack, you can use the PROTOplate board.

When stacking Pi-Plates, you will need a secure structure and this is provided by the BASEplate mounting system. All hardware necessary for mounting to the BASEplate is already available with each Pi-Plate board. Pi-Plate also offers two great kits.

The DAQC kit comprises two BASEplates and one DAQCplate boards for the price of a single unit. This makes a great beginning for those starting with the DAQCplate for the first time.

For those starting with a MOTORCplate, the MOTOR Kit may be very useful. This kit comprises one MOTORplate and two BASEplate boards for the price of a single unit.

For example, the DAQCplate is a data acquisition and control board. Its digital output section has a connector that provides seven open-collector outputs and a pair of 5VDC outputs that you can use for driving loads. You can protect these with a flyback diode connected to the terminals.

You can use these outputs to drive incandescent automotive light bulbs, ultrasonic rangefinders, resistive heating elements, unipolar stepper motors, buzzers, solenoids, relays, DC motors or LED strings. Green LEDs connected to each digital output light up to indicate a high on the output. To light up these LEDs, you do not require connecting anything to these outputs. At the same time, these LEDs will not affect anything that you connect to these outputs.

Darlington pair transistors drive the seven open-collector digital outputs. They can sink a maximum of 350mA and handle a maximum load voltage of 12VDC. With a load voltage of 200mA, the on voltage is typically 1.1V. When using inductive loads such as solenoids or relays, you must connect the high side power supply to the flyback protection terminal.