Crowbar transient voltage suppression Devices-Spark gap-GDT-Thyristor-TSPD

Crowbar transient voltage suppression Devices

Spark gaps, gas discharge tubes (GDTs), thyristors and thyristor surge protective devices (TSPDs) are TVS devices that are capable of attenuating very large surge currents.

When these devices are switched “ON”, the protected circuit is connected to ground through a very low impedance switch.  

Crowbars are difficult to turn “OFF” and often require an additional commutation circuit, especially in a DC system. 

Spark gaps are constructed from two carbon block electrodes that are connected to the signal line and ground. The electrodes typically are separated by an air gap of 3 to 4 mils. The surge voltage causes an arc to form that shunts the transient voltage to ground. 

Spark gap

GDT devices are similar to spark gaps; however, they are constructed with a glass or

ceramic tube that contains an inert gas which ionizes and conducts during a transient event.

If a voltage across the device reaches the breakdown or sparkover voltage, the gas ionizes and the device “fires”. At this point, the GDT provides low impedance and remains in the “ON” state until the voltage falls below the holdover voltage.

GDT

Thyristors are constructed with four layers of P− and N−type semiconductor material. A thyristor surge protection device can be created by combing a SCR and a Zener diode, where the Zener is used to control the gate terminal’s turn−on

voltage. 

Thyristor

TSPD devices are another popular thyristor option for surge protection. TSPDs are a two terminal bidirectional device that has a junction capable of handling very high surge currents.

Comparison Table

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TVS Selection Guidelines-Embedded board design

TVS Selection Guidelines

1. Select a device with a working voltage that is greater than the maximum bus voltage.

2. Select a device with a clamping voltage less than the maximum specified surge voltage for the protected circuit.

TVS IC

3. A bidirectional TVS device may be required for differential amplifier circuits with a common mode offset voltage requirement. The common voltage specification is required when there is a significant difference in the voltage potential between the ground reference of the transmitting and receiving nodes.

4. Choose a TVS device that is capable of dissipating the energy of the surge pulse.

5. The power rating of most TVS devices decreases with temperature and a derating of the TVS’s energy specification maybe necessary.

6. The capacitance of the TVS device should be minimized for high speed circuits.

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Decoupling Caps Placement in Embedded Hardware Boards

Board Level Decoupling

Decoupling the Power Distribution Network of the micro controller IC is critical to the PCB design process, because careful selection of the decoupling capacitors and placement has a big influence on the high speed performance of the board, and can reduce the emissions.

The on-board decoupling capacitors have an effective range of 1MHz – 200MHz. The range above 200MHz can be covered by using power plane capacitance. The effectiveness of the decoupling capacitors depends on the optimum placement and connection type.  

• Place capacitors as close as possible to the µC.  
• Keep the interconnection inductance of capacitors to the µC as low as possible.  

• Use low effective series resistance and inductance (ESR and ESL) capacitors. − Since parasitic inductance is the limiting factor of the capacitor response to high frequency demand of current from the device, the ESL of the capacitor and the connection inductance should be selected so that the optimum value for the design is reached.  

• Connect capacitors with vias close to the side of the pads. − Use side placement of the vias to reduce the current loop.

Connection of decaps

• Dual vias can be used to reduce the parasitic inductance.  
• Solder lands, traces and vias should be optimized for capacitor placement.
• Do not use long traces to connect capacitors to GND or to VDD. − Always keep the return path of the high frequency current (lowest inductance path) small.
• Select the smallest package available for the capacitors. − Select capacitors of type: ceramic multilayer X7R or X5R.  
• To reduce the radiation / coupling from the oscillator circuit, a separated ground island on the GND layer should be made. This ground island can be connected at one point to the GND layer.

              − This helps to keep noise generated by the oscillator circuit locally on this separated island.

              − The ground connections of the load capacitors and VSSOSC should also be                connected to this island.

              − Traces for the load capacitors and Xtal should be as short as possible.

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Design Rule Checking (DRC)

Design Rule Checking (DRC)

Design Rule Checking (DRC) allows you to automatically check your PCB design for connectivity, clearance, and other manufacturing errors.

With the large and complex PCBs being designed today, it is impractical to manually check a PCB design. This is where the DRC comes into its own, it is an absolutely essential step in professional PCB design.

Examples of what you can check with a DRC are:  

• Circuit connectivity. It checks that every track on your board matches the connectivity of your schematic.
• Electrical clearance. You can check the clearance between tracks, pads, and components.  
• Manufacturing tolerances like min/max hole sizes, track widths, via widths, annulus sizes, and short circuits.

A complete DRC is usually performed after you have finished your PCB. Some packages however have the ability to do “real time” (or “online”) DRC checking as you create your board. For instance, it wont let you connect a track to a pad it shouldn’t go to, or violate a clearance between track and pad. If you have realtime DRC capability, use it, it’s an invaluable tool.

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USB Programing of STM32 Controllers -Flashing/Reprogrming

USB debugging in STM32L/F Microcontrollers

In this post ,it is explained about how a STM32L controller can be programmed via USB . 

NOTE: Binary/hex file is converted to .DFU format initially. this file is loaded via usb using DFUSE software.

Requirements:

•  PC
• STM32L controller with usb connection
• DFUSE SOFTWARE   

Generate a DFU file from a binary

The DFU tool requires a .dfu file in order to work. Here is how it is generated:

1. Start the Dfu file manager application

2.Choose the first option (generate a DFU file)

3.On the following GUI, select “Multi BIN…”

4.Select the “…” to browse for the source file

5.Select the .bin file and select “save”. (the file will not be modified)

6. On the following GUI, change the Address to 0x08000000, i.e. the STM32F411’s start address of the first sector of the internal flash, and add the file via “Add to list >>”, so that the file appears in the centre list and choose “OK”.

7. Finally, change the PID and version if required and select “Generate…” to generate the .dfu file.

8.Choose the destination folder and file name

9.Success

* Note: if you can’t find the file, look in the following folder:

C:\Users\(user name)\AppData\Local\VirtualStore\Windows\SysWOW64

Configure the the Board to load the STM32 DFU boot-loader

System Boot code will not execute automatically , BOOT0 pin has to be pulled High and Power ON Sequence / Reset Sequence has to be done for the execution.

1.Run the “DfuSe demonstration” application (Start -> All Programs ->

  STMicroelectronics -> DfuSe -> DfuSe Demonstration).

2.Connect the Board via USB and verify that it is listed and selected as DFU device.

3. Select & Select  “Choose” in the “Upgrade or Verify Action” subsection to select the .dfu source file.

5. Select “Upgrade” to program the board.

6. Success!

So yea , you had flashed your device successfully.

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Terminations methods in a transmission line

Terminations methods in a transmission line

There are different types of termination techniques:

1. Near End (source) Termination  
2. Far End Termination Near End (Source) termination
   

Near End (source) Termination  

This is normally used by the single ended lines where the output driver has lower impedance than the transmission line. In this case the series termination is added to the output of the driver to match the line impedance.

Near-End (Source) Termination for Single Ended Lines  

• Place the resistor very close to the source driver.  
• Use source termination in cases of point-to-point connection.  
• Do not use daisy-chain topology.  
• All loads must be at the end of the line.

Far End termination

The most common type of Far End termination for HSSI is Parallel or AC Termination.

Parallel and AC Termination for Single Ended Lines  

• Parallel termination resistance should be matched to the characteristic impedance of the line.  
• Parallel termination causes power consumption due to the DC path at the end of the line for high signal level. The thermal treatment should be done by selection of the parallel termination resistor.  
• The power consumption can be avoided with AC termination, where a capacitor is inserted in series to the termination resistor.  
• The Capacitor value in AC termination should be in the range of 100-200pF
• This termination technique increases the rising and falling times at load due to the capacitive load. Timing considerations should be made by selection of the value of C.  
• Place the components close to the receiver pins so that no long stubs are required.

Termination of Differential lines

Special attention should be given to the termination of the differential lines. The differential lines require more than 50 Ohm line impedance and 100 Ohm differential impedance between the lines. So the termination must be matched to the 100 Ohm

Terminations for Differential Lines  

Place termination after the connection of the trace to the pin of receiver so that no stubs are created before the receiver. This avoids reflections generated by the impedance discontinuity.  Do not use layer change or a via for the placement of the termination.

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TRANSIENT VOLTAGE SUPPRESSOR-VARISTOR EXPLAINED

TRANSIENT VOLTAGE SUPPRESSOR- VARISTOR'S IN PRACTICAL CIRCUITS

A transient is a change in the steady-state condition of voltage, current, or both. if its for short duration then it is refereed as spikes or transient voltages. if the time duration is longer then it is called surge voltages.

In order to suppress this transient voltage changes some components are used in the electrical/electronic  industry . some of them are .Varistor,TVS diodes ,GDT,Spark gaps etc.

Here in this post , the Varistor is explained.

VARISTOR

Varistor's are voltage dependent, non-linear devices that behave electrically similar to back-to-back Zener diodes.When exposed to high voltage transients, the varistor impedance changes many orders of magnitude—from a near open-circuit to a highly conductive level and thereby clamping the transient voltage to a safe level.

SCHEMATIC SYMBOL

Varistor is connected in parallel with the circuit or device which is to protected from transient voltages. when the voltages raises above its breakdown voltage , the resistance of the varistor will reduces and there by clamping the voltage to a safer level by shunts down the current. The power hence generated will be dissipated by heat.Thus the potentially destructive energy of the incoming transient pulse is absorbed by the varistor, thereby protecting vulnerable circuit components.

Compared with the other clamping and crowbar technologies that are used for voltage

suppression, varistor technology is still one of the most cost-effective ways to protect against high energy surges on these 12VDC–96VDC lines.

Varistor's can be connected in parallel if the power requirement is high and it can be connected in series if there is higher voltage handling capability required. 

VARISTOR IN CIRCUIT BOARD

For selecting the MOV , the rating should be selected in such way that the tolerance is more than 20 percent of the required voltage level .

ie :- I/P voltage * 1.2

The disadvantage of varistor's is , it can't handle transient currents and 

will be destroyed in too many surges.

Ratings of MOV:

●Energy measured in Joules

●Breakdown/Clamping Voltage

●Capacitance Response time

Unlike GDT it wont get short circuited in tripped conditions, but instead it reduces its impedance. MOVs are very fast, reacting in the nanosecond range. Imagine GDT using in the INPUT of power supply ! it causes short circuit in the Input during transients which will lead to more severe damages.damages has higher load capacitance which will causes problems in high frequency circuits 

On power lines, a Metal Oxide Varistor is usually the best type of suppression device. TVS Diodes and Gas Discharge Tubes are also used occasionally.

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END OF LIFE /OBSOLETE INFORMATION OF ELECTRONIC COMPONENTS

Obtain the End-Of-Life for electronic components

EOL information is very important for a production industry. obtaining the EOL information from the manufacture is really a pain for a designer and most of the manufactures wont reveal the expected EOL dates to its customers . one way is to contact the distributors other than manufactures. but there is no guarantee that you will obtain the information .

There are few professional services which integrate notifications from manufacturers and can manage your BOM'S

Most of big companies will subscribe to these services and will have dedicated component management departments.

SILICON EXPERT

The best easiest method to find the end-of-life dates for electronic components and connector is through the SILICON EXPERT a web based tool. Silicon expert offers a 14 days trial with almost its full functions in part search.The EOL date of component can be obtained providing the IC part number in the silicon expert part search options.



Silicon Expert predicts the EOL dates with an average accuracy of 80%. Silicon expert uses different criteria to obtain the EOL dates like customer base, availability , period , PCN Notices etc.SILICON EXPERT has two product services PART SEARCH and BOM Manager .BOM manager is like a full option to the part search , in which you can directly import the BOM and list the EOL information, Alternatives,data sheets ,suppliers ,unit costs etc.

LINK TO SiliconExpert

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64-BIT SINGLE BOARD COMPUTER @ $15

A single-board computer (SBC) is a complete computer built on a single circuit board with microprocessor(s), memory, input/output (I/O) and other features required for a functional computer. SBC were made as demonstration or development systems, for educational systems, or for use as embedded computer controllers. Many types of home computer and portable computer integrated all their functions onto a single printed circuit board.

The Pine A64 is an index card sized 64-bit single board super computer. It can perform like your desktop or portable PC with browsing the Internet, playing games, watching video, and execute programs like spreadsheets and word-processing.it can also play ultra high definition 4Kx2K video.CPU is quad-core ARM A-53 64-bit processor and runs at 1.2GHz. The CPU’s MIPS benchmarks around 11,040 which makes it capabilities roughly equivalent to the Sony PS3’s level of performance or a netbook running AMD E-240 CPU at 1.5GHz.

The Pine A64 GPU is dual-core MALI-400 MP2 and runs at 500MHz, capable of 1.1 Gpixel/s throughput. Graphics capabilities are slightly higher than the original Xbox’s level of performance. The GPU provides OpenGL ES 2.0, hardware-accelerated OpenVG, 4Kx2Kp30 H.265 decode, and 1080p60 H.264 high-profile encode and decode.

All the Pine A64 has 46 dedicated GPIO pins, three UART, two i2c bus, two SPI bus, i2s audio, SPDIF out, IR receiver, Speaker out, 3v3, 5v, and ground. In the “PLUS” model, there are additional three ports: CSI-Camera, Touch Control, and DSI-LCD Panel.

KICKSTARTER LINK :- PINE A64

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CONTROL THE DEVICES USING VOICE RECOGNITION- MSP430 ,GOOGLE API

CONTROL THE DEVICES CONNECTED TO MSP430 USING VOICE RECOGNITION

In this post , speech recognition from google API is used for controlling the devices connected to the micro controller. voice is converted to a low size format and sent over to google servers .The corresponding text will be returned from google. this text is again sent back to controller for control purposes.

Materials Required :

• Smartphone with internet .
• Relay(for controlling AC / high voltage devices)
• Bluetooth module.
• MSP430 launchpad controller.

1. Please read the Interfacing of Bluetooth-Module with MSP430-Launchpad before starting this project.
2. please read how to Interface relay with MSP430 to control devices 

NOTE : Since pin 2 and 3 are used for Bluetooth interfacing , please connect the transistor base to the pins other than 2 and 3 . In this Post the pin 4 is used for connecting the device as per the article how to Interface relay with MSP430 to control devices 


Combine and connect the circuit from the below links (USE PIN 4 INSTEAD OF 2 to connect relay)
 Interfacing of Bluetooth-Module with MSP430-Launchpad 
 how to Interface relay with MSP430 to control devices (Ex:Light)

Download the Android  APP 

link : DOWNLOAD EMBEDDEDHW APP

Android App from EmbeddedHW.com

• Click on the Home Button

Home screen of EmbeddedHw Android App

INTERNET IS REQUIRED FOR VOICE CONTROL

•  Turn on your Internet in the smartphone
•  Turn On the Bluetooth of the smartphone & Pair the device (password:1234)
•  Click on the connect button and select our device.
•  click on the voice control to speak

The speech will be converted to text using google API .This converted Text will sent to our controller using the bluetooth module.

EXAMPLE :-

you can turn on the LIGHT by saying "LIGHT ON". the controller will receive the text "LIGHT ON" from the smartphone.this text can be used to turn on the light . 

An example program is given below

byte ehw = 0; // incoming serial byte

void setup()

{

  // start serial port at 9600 bps:

  Serial.begin(9600);
 pinMode(4, OUTPUT); 

}

void loop()

{

  // if we get a valid byte, read analog ins:

while (!Serial.available() > 0)

    ehw = Serial.read();

   Serial.println(ehw);

if(ehw="LIGHT ON"){

  digitalWrite(4, HIGH); }

else if(ehw="LIGHT OFF"){

  digitalWrite(4, LOW); }

else 

Serial.println("Incorrect message");

delay(10);

  }

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