PC817 High Density Mounting Type Photocoupler

An optical isolator is known as a device which enables transmission of an electric signal by making use of the signals induced by light. The theory behind this is that coupling needs to be done between the insulation of input and output of a circuit board or a single wire which makes use of these principles. The basic purpose of any kind of optical isolator or a photo coupler is to make sure that any high changing voltages do not damage the components. This is done via carefully designed and manufactured photo couplers which are sold by a couple of different electronics manufacturers out there. Most known manufacturer of photo couplers is Sharp. If you’re interested in upgrading your circuitry with a device like this, you will need to do some proper researching first. Since this is a component which is intended to protect your devices, it’s important to know exact specifications of the photo coupler you’re looking for. Fortunately, this is no problem since there are plenty of datasheets specific to PC817 photo couplers which you can get for free online and get all the information you need. For starters, you can visit HQEW.net ’s official website where you might find some decent information on how can you order their products, but it’s more important for you to test your circuits first to know what numbers need to be matched and to what extent. Tolerances are very important here and this research will help you save cost on future purchases.

Recharge a 9V NiMh battery with a Solar Panel / Constant Current Generator LM317LZ

 
If you enjoyed the previous post solar-powered Arduino board, you should keep reading this one as well to improve your solar power generator. In fact, with that setup the 9V battery would decay too soon: A NiMh (Nichel – metal hydroxide) battery must be recharged with a constant current generator, a solar panel alone is not.

In order to do so, we can assemble a quite simple circuit using the following components:

    LM317M or LM317LZ
    A 200Ohm trimmer
    10Ohm resistance
    A LED to check if the current is actually flowing

The core of this circuit is the integrated three-terminal adjustable linear voltage regulator LM317. The ‘adj’ pin is a control terminal that is used to adjust the output current. So, the trick is to use a variable resistor (in our case, a trimmer with a small resistance put in front of it) to set the current at a definite value.

With an input DC voltage of max 24V, and the resistances shown in the diagram, one can obtain an output current of:

I_out = 1.2/(10 + R_trim) [A]

This current must be less than 1/10 of the battery output, e.g. for a 750mAh battery the output current must be less than 75mA. As usual, it is customary to insert a capacitor (100uF should be ok) in parallel at the input node to smooth out fast-varying voltages.

The CA3046 was pure simplicity

When you learn about making things like amplifiers in EE class, you learn about how important it is to have matched pairs of transistors. Symmetry tends to be just as important in electronic circuits as it is in plant life: pairs of tubes supply and remove fluids from a plant leaf much the same way electrons flow through paired transistors in an amplifier. Optimal behaviour occurs when these sides respond in a balanced, symmetrical manner (in the most common cases.)

The more closely you can match the behaviour of these 2 transistors, the more symmetrical the circuit becomes. So, someone got the bright idea — what if we put more than one transistor on the same piece of silicon? Thus, the integrated circuit was born: not with the goal of putting computers on chips (or anything digital, for that matter), but with the idea of making the performance of a circuit uniform.

The earliest ICs only had simple transistors on them. The CA3046 was pure simplicity: 5 matched NPN type BJT transistors on the same chip. You could continue to build circuits the way you were used to — with resistors and capacitors on the circuit board or prototype board — and simply replace the transistors in there with matched transistors, formed from the same piece of silicon. Presto, your circuit sounded a lot better. If you went high volume, you could have your circuit burned into its own integrated circuit; many opamps (the building block of modern analog circuit design) were designed this way. Or you could create a printed circuit board, and go that way — the sort you might have seen in just about every consumer electronics product in the 1970s and 1980s.

The CA3046 (and its strange partner, the CA3096: 3 NPN, 2PNP in a single chip) helped us ring in an age of harmony. Matched pair transistors were essential to building harmonic circuits that were pleasing to the ear. The original Moog “transistor ladder” design required hand matching of transistors; were the CA3046 available then, Moogs probably would have been a lot cheaper (had they not already become a “fad”)  .

Later I had a few missed starts trying to make circuits: a failed design for a video game emulator cartridge that was already halfway into production nearly bankrupted me, and I lost heart. I put away my skills for many, many years, always thinking that i could fall back on it if I really needed to. Now I see it’s a skill I’ve neglected for far too long, and one that can enrich my life if I only take the time to apply it artfully. 

Best DC power supply 3Amp LM317T

There is the high quality power supply to provide high current 3A. And still adjust voltage in steps from 3V, 6V, 9V, 12V. adjust voltage is continuous 1.25V to 20V. Using LM317T and 2N3055 are main parts so easy to made and cheap.

Friends would known the power supply as well. Because you must use in various circuit experiment. It originally had a small supply current, when found projects that uses lot of current. Such as an audio amplifier circuit so provide current is not enough.
This project can help you. Because of provide high current 3A. And still adjust voltage in steps from 3V, 6V, 9V, 12V. adjust voltage is continuous. And you do not have to worry. This creates a simple and economical. If interested, please read on.

How it works
In the circuit below can be seen that, when opening switch S1 is current through the transformer. To convert from 220V AC to 18V, then through diode bridge rectifier BD1. But is a DC supply that still not smooth. Then, a filter capacitor C1 serves electricity, out of BD1 to be more smooth with the LED1 to show that power is supplied to already.
When the filter current is smooth on one order. The current will through the regulator circuit that the main components are IC1(LM317T) and Q1(2N3055).
-IC1 is the regulator IC number : LM317T.
-Q1 is power transistor NPN type number : 2N3055.

Before the DC volt through IC1 would have C2 served filter noise off. When we adjust the variable resistor VR1 or rotary switches S3 twist choose it. Will cause changes the voltage at the ADJ pin and OUT pin of IC1. Which will be resulting the voltage drop across the base pin and the emitter pin of transistor Q1 changes. Makes the voltage on the connector is changed accordingly. And before the voltage is applied to current C3 filter to smooth again.
Detail see in circuit image.

12V Low side and High side PWM Motor/Light Controller IRFZ48N

 

 

Here these two schematics are variations on addition PWM circuit that I designed. The diagrams are for 12V operation alone and there are aerial ancillary (common ground) and low ancillary (common +12V) versions. The low ancillary adaptation of the ambit uses an N Channel FET, the aerial ancillary adaptation of the circuit uses a P Channel FET. N Channel accessories tend to handle added accepted than P Channel devices, they are additionally beneath expensive. The aerial ancillary adaptation of the ambit is advantageous back one ancillary of the bulk has to be grounded.

This Circuit can about-face a adequately aerial bulk of current, an IRFZ34N MOSFET can handle over 35 Amps if affiliated to a able calefaction sink. Higher ability FETs, such as the IRFZ48N or IRF1010Z can be commissioned if alike beyond currents are required. It is additionally accessible to affix assorted FETs in alongside for alike added accepted capacity. Always use thermally conductive grease amid the FET and the calefaction sink, and bethink that the calefaction bore is electrically live.

Inductive endless (motors) may crave appropriate affliction back they can accomplish ample voltage spikes that can accident the MOSFET. Replacing the 1N4002 with a fast accretion diode may advice blot the about-face voltage bang back active an anterior bulk such as a motor. If you use these circuits for abstracts with electric vehicles, be abiding to install a ambit breaker in alternation with the battery, the ambit breaker should be accessible to ability by the driver. This is abnormally important due to the actuality that back MOSFETs fail, they generally abbreviate out, abrogation the motor on at abounding speed.

Note that the pwm ascendancy has an adverse aftereffect on these two circuits, the low ancillary adaptation is on with a aerial pin 7 achievement voltage and the aerial ancillary adaptation is on with a low output.

The inductor on the aboideau ancillary of the ability MOSFET transistor can be a ferrite bean or a few turns of wire captivated about a 10 ohm, 1/4W resistor. The purpose of this allotment is to anticipate RF oscillations from occurring in the MOSFET circuitry.

Remote Control by using RF remote control Encoder and Decoder PT2272

RF Modules are used wireless transfer data and low cost application . This makes them suitable for remote control applications, as in where you need to control some machines or robots without getting in touch with them (may be due to various reasons like safety, etc). Now depending upon the type of application, the RF module is chosen. For short range wireless control applications, an RF Transmitter-Receiver Module of frequency 315 MHz is the most suitable type. This RF modules are works with PT2262(encoder) and PT2272(decoder) as remote control.


Specification:

Frequency: 315Mhz
Modulation: ASK
Transmitter input voltage: 3-12V
Transmitter(RF-TX-315) and Receiver(RF-RX-315)

Range in open space(Standard Conditions) : 100 Meters

PT2262

Is a remote control encoder paired with PT2272 utilizing CMOS Technology. It encodes data and address pins into a serial coded waveform suitable for or IR modulation. PT2262 has a maximum of 12 bits of tri-state address pins providing to 531,441 (or 312) address codes; thereby, drastically reducing any code collision and unauthorized code scanning possibilities.

 

PT2272

Remote Control Decoder PT2272 is a remote control decoder paired with PT2262 utilizing CMOS Technology. It has 12 bits of tri-state address pins providing a maximum of 531,441 (or 312) address codes; thereby, drastically reducing any code collision and unauthorized code scanning possibilities. This IC has Latch or Momentary output type.

VENDOR chip data sources offer PDF | IPSec and NAT compatibility analysis and solutions

Network security protocol IPSec (IP Security) and TLP181 datasheet and Network Address Translation NAT (Network Address Translation) has been widely used, but if the words run together, will encounter many problems. From the perspective of IP, NAT to the IPs were revised lower, to the IP protocol, it is a departure; and TLP181 price and from the application point of view, network managers have to deal with the problem of network addresses, NAT allows the user to take a variety of ways to their own network and TLP181 suppliers and the host of the external public network hiding is a good tool, now, whether large or small and medium enterprises are in use. And NAT, like, IPSec: is also a good tool, he can safely allow users to connect through the Internet to a remote terminal. However, the IPSec protocol architecture itself and the lack of support for IPSec, NAT devices, when the IPSec and NAT will be running with a lot of problems. To solve the problem of coexistence between the two, it is necessary for IPSec and NAT have a certain understanding.

NO-NC SSR Plastic Box ICL7107CPL

This was a Fire Retardant Plastic Box which was made for the SSR I/O Stackable Modules. DC Control for an AC Load. Usually it is to control another Big Three phase contactor; Pneumatic or Steam Valve, Solenoids-Motors. When Mounted at the end of the PCB it offers over 2kV Isolation from the Digital Circuits. The Output 230V signals NO-NC, can control Light Loads like the Coil of a Big 230V Relay also called contactor.

NO NC SSR Box

20N60      ICL7107CPL       SSM2164        2SC2625

It could be Mounted on a PCB by soldering or a Plugin Base. It is better to have Crimped connections or Terminals. A very good quality spring Loaded Socket may also work but it has to be rated for many operations. Things like Nickle Alloy Plated, Beryllium Copper were the Materials Jargon. A contact resistance in the Terminals, a mismatch of alloys, electrochemical reactions, Corrosive Fumes, Brine or High Humidity can build a Loose connection into a Dangerous Sparking Contact.

Not only the Functionality of the SSR will be affected in a Sparking Contact, but a Risk of a Fire Developing. When Inflammable Materials or Volatile Liquids are Present Nearby, the risk is even greater. Read More – Solid State Relays SSR

Accelerometer, Arduino and Processing - MMA7260Q

Accelerometers can measure acceleration and tilt (angle). They are used in many devices nowadays such as Mobile phones (iPhone), Gaming consoles and gadgets (Nintendo Wii), Navigation (GPS navigators, Airplanes), and etc. In physical computing accelerometers are used to measure device’s position relative to the ground.  A simple Accelerometers can measure acceleration along one axis. Here, a simple program is presented that interfaces a 3-axis MMA7260Q accelerometer from Sparkfun to an Arduino board.

Use a MMA7260Q “triple Axis Accelerometer Breakout board” from Sparkfun. Connect the board as shown below to an Arduino board:

Be careful while making connections to your Arduino, not to misconnect the Negative and Positive supply.

Download the code for Processing and Arduino in a zip package . Unzip and upload the code provided for the Arduino to your Arduino board. Then run the code provided for Processing. Press ‘X’, ‘Y’, ‘Z’ key on your keyboard to see the real time graph for the corresponding axis on your screen.

The Arduino code sends three consecutive bytes by serial baudrate of 9600. On the computer side the processing program gets the data and translates the bytes (each byte for one axis[X,Y,Z]) into a graph representation.

Diagram Block IC TDA7377

The TDA7377 is a new technology class AB car radio amplifier able to work either in DUAL BRIDGE or QUAD SINGLE ENDED configuration.



The exclusive fully complementary structure of the output stage and the internally fixed gain guarantees the highest possible power performances with extremely reduced component count. The on-board clip detector simplifies gain compression operation. The fault diagnostics makes it possible to detect mistakes during car radio set assembly and wiring in the car.

The stand-by can be easily activated by means of a CMOS level applied to pin 7 through a RC filter. Under stand-by condition the device is turned off completely (supply current = 1µA typ.; output attenuation= 80dB min.). Every ON/OFF operation is virtually pop free. Furthemore, at turn-on the device stays in muting condition for a time determined by the value assigned to the SVR capacitor.

While in muting the device outputs becomes insensitive to any kinds of signal that may be present at the input terminals. In other words every transient coming from previous stages produces no unplesantacoustic effect to the speakers.

Voltage Comparator Circuit with MOSFET - CA3140

I would like to present the voltage comparator circuit ,you can bring this circuit to apply with your project that concern in voltage checking or comparison.
This circuit provides an indication if has the input voltage differs from the two defined limits, V1 and V2 voltage source. We can adjustable limit and made to trigger from the adjustable “window”.

As to the amplifiers to the CA3140 MOSFET is used in circuit. They are used to benefit, as they have very little influence and can counteract the tension for change near 0 volts.

If a second operational amplifier is used as LF351 and CA741, will require a zero transverse force control.

This is only a predetermined 10k contact between pins 1 and 5, the wiper connected to the negative supply voltage and the pin of the fourth operational amplifier With this circuit, both operational amplifier, the LED when the input voltage out of range, 1N4148 diodes both “Y” to the exit door. The input voltage to be monitored is supplied through a 10K series resistor to the inputs of the two amplifiers operational amplifiers. If the input voltage exceeds the threshold value V1 and CA3140, the output voltage swing almost completely and turn off the LED. Similarly, if the input voltage is lower than the limit defined by V 2, then this is the operational amplifier moves to the Vcc and light the LED.

When PWM is turned on - IRFP450

During the ON time of the cycle, the MOSFET turns on and starts conducting. Since inductor poses no resistance to DC current, large current flows through the MOSFET. This large current then becomes constant at some point during the ON time of the cycle. Due to the property of inductor, the energy is stored in its magnetic field around it.

During the OFF time of the cycle, MOSFET turns off and no conduction can take place. Due to the property of inductor it blocks any change in current. Because of this, the energy stored in its magnetic field is released. This creates high current. But since the MOSFET is turned off, the large current flows through the diode and charges the capacitor.

When the whole process is done fast enough, we are able to achieve a large voltage at the output.

In this experiment, I have used an old inductor from switch mode power supply that I found in the computer’s monitor. So I don’t know the value, but it is definitely greater than 200uH. IRFP450 MOSFET (HEXFET as they call it) can carry 14 amperes of current, and has a very very low drain to source resistance. The reason for using such a large MOSFET is, it does’t heat up. If you use a MOSFET with large drain to source resistance, you are going to get a lot of heat, this increases the possibility of destroying the transistor (I already destroyed like 4 expensive MOSFETs)

MOSFETs are very sensitive to heat and over voltage, so please take care that you do no exceed the specifications. My advice would be to obtain MOSFETs from old power supplies. You can also get a good number of high voltage fast response diodes from those old circuits.

I suggest you to build this circuit and try out different values of inductor and PWM. Here is a small arduino code used for generating PWM with On time of 50 uS and OFF time of 15 uS.

When this PWM configuration is used with my circuit it can yeild upto 394 V. I did not go beyond that, because the capacitors I have used are limited to 400V and so is the diode. So it is better to be safe below the range.

A CL Version 2N7000

The CL version shows the basic ideas but the LTspiceIV version runs much faster and it is far easiler to see the detail of the waveforms concerned.

There are some minor differences between the LTspiceIV and CL versions to do with the availability of models: namely the CL version uses the 2N7000 MOSFET which has a somewhat different SOA compared to the 2N7002 used in LTspice.
 

Two Wire Arduino Knight Rider PCF8574

This tutorial shows how to interface eight LEDs to an Arduino using only two Arduino pins. This is made possible by using a PCF8574 I/O expander IC. A “Knight Rider” display is shown on the LEDs.

The suggested sequence of building the circuit is:

    Insert the PCF8574 IC
    Make power and ground connections to the IC
    Connect pin 1, 2 and 3 of the IC (U1) to ground
    Insert capacitor C1 (100n) and wire it between power (5V) and ground (GND)
    Insert the eight LEDs with anodes (longer pin) on the left
    Connect resistors R1 to R8 between the LED anodes and the top breadboard rail (5V)
    Wire the cathode of each LED to the correct pins on the IC
    Connect R9 and R10
    Connect the two wires from Arduino pins A4 and A5 to the IC
    Connect the Arduino 5V to the top breadboard rail and GND to the bottom breadboard rail

You may have noticed that the breadboard circuit swaps the position of the LEDs and resistors from the circuit diagram – e.g. R1 and D1 swap positions. This will make no difference to how the circuit operates. It has only been done to simplify the breadboard circuit.

Is the bc337 and 2n4401 similar enough to use each other?

For many applications, yes. 
The BC337 comes in different gain grades, but the 2N4401 is about in the middle of the middle grade. The 4401 is a bit faster, but has a bit lower voltage and lower max current rating. But if you operate it with under 40 volts collector to emitter and with a collector current no higher than 100 mA, they should both work well in most circuits. 
Note that you have to reverse the flat side orientation to get the leads to have the same definitions.

60kHz PIC Function Generator - LF353

  This project is based on the Function Generator described on Mondo Technology web site. I just did very slight changes and fixed some obvious typos in schematic. The code is rewritten for the Microchip MPLAB IDE syntax.

    Device features

        Frequency range: 11Hz – 60KHz
        Digital frequency adjustment with 3 different steps
        Signal forms: sine, triangle, square, pulses, burst, sweep, noise
        Output range: ±15V for sine and triangle, 0-5V for others
        Sync output for pulses

    The device is powered from 12VAC which provides a sufficiently high (over 18V) DC voltage needed for a normal operation of 78L15 and 79L15. The 12V power supplies are replaced with 15V ones. This is done in order to LF353 Op-amp could output the full range of signals to a 1K load. By using a ±12V supply this resistor must be at least 3K.
 

Types of Serial EEPROM Chips - 93C46

There are several types of Serial EEPROMs, but most of them fall into either a 2-wire or 3-wire interface category. Usually, the 3-wire devices require an addition wire (beyond the 3 for data transfer) for each chip to be used. The 2-wire interface, called I2C or IIC or "I squared C" uses only two wires, regardless of how many chips are attached. I2C is a trademard of Philips. The three wire interfaces include SPI and Microwire, which is a trademark ofNational Semiconductor.

As the pressure on engineers to make products smaller has grown, semiconductor manufacturers have introduced several new interfaces, usually aimed at lower a product's size and cost... and undoubtedly many more will appear in the future.
As a practical matter, the code offered below only works with the Microwire 3 Wire interface, and is specifically intended to work with the 93C46, which is a standard part available from a variety of distributors.

What is an FM transmitter?

An Fm transmitter is a circuit/device to transmit audio signals to an fm radio receiver through air (wirelessly). The input (audio)to an fm transmitter can be fed using a microphone or the output of your music player to be transmitted, and the signal which you transmit can be received using an FM radio, the advantages of FM TRANSMITTERS ARE many:

1.You may transmit audio to another room/floor of your house without using any wires!

2.You may transmit your own voice if you used an electret microphone in the circuit

3.You don’t need to build a receiver to receive the ransmitting audio as any standard fm radio can be used to receive your voice/audio and many..!

building the circuit
this circuit can transmit audio to a distance of around 50 meters if you used 2n3904 transistor and boost the supply voltage to 6V, and 1Km(1 kilometer) if used S8050 transistor with 9V supply!

BS170 - is used for the QRP rig PA

The 2N7000 PA was described in my blog message sometime ago. The BS170 by Fairchild can be also used for QRP rig PA. It is N-Channel Enhancement Mode FET. The Maximum Power Dissipation Pd is 830mW, therefore it can be suitable for QRP rig PA. The transmitter section of ADC-40 is the dual BS170 and it generates about 4watts with 13.8V power supply. The small heatsink is required to use BS170s for PA because it will be hot and drops the power. The PFR-3A is the triple BS170 for PA and generates 5 Watts with 12V power supply.

An integrated circuit MAX232

The MAX232 is an integrated circuit, first created by Maxim Integrated Products, that converts signals from an RS-232 serial port to signals suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver and typically converts the RX, TX, CTS and RTS signals.

The drivers provide RS-232 voltage level outputs (approx. ± 7.5 V) from a single + 5 V supply via on-chip charge pumps and external capacitors. This makes it useful for implementing RS-232 in devices that otherwise do not need any voltages outside the 0 V to + 5 V range, as power supply design does not need to be made more complicated just for driving the RS-232 in this case.

The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to standard 5 V TTL levels. These receivers have a typical threshold of 1.3 V, and a typical hysteresis of 0.5 V.

The later MAX232A is backwards compatible with the original MAX232 but may operate at higher baud rates and can use smaller external capacitors – 0.1 μF in place of the 1.0 μF capacitors used with the original device.

The newer MAX3232 is also backwards compatible, but operates at a broader voltage range, from 3 to 5.5 V. 

Pin to pin compatible: ICL232, ST232, ADM232, HIN232.

Metal sensor detector circuit schematic TDA2822

The metal detector circuit is shown here that the limits represent the sake of simplicity for a metal detector, but the design works remarkably well. It only uses 40,106 Hex Schmitt inverter IC, a capacitor and a search coil – and of course batteries. An advantage of IC1b Pin 4 is to be connected to a medium-wave radio antenna, or it should be wrapped around the radio. It can also be used as a hand-held metal detectors. As you can see what metal a good selection of beat-frequency operation (BFO), up to 90 mm for a bottle-top. In fact, for the ultimate in simplicity, the capacitor C1 is omitted. In this way, the author reaches is astonishing, 150mm range for the bottle top. But with the frequency then to more than 4 MHz, the instability is a major problem. TDA2822

 

As shown in the circuit, oscillates at 230kHz. You can also experiment with the frequency by changing the value of C1. Faraday shield can be added to reduce ground-effect and capacitive coupling, and this is connected to 0V.
Since the inductance is resistance to rapid change in voltage, the charging of fees C1 delayed a bit like the logical level IC1a 2-pole change. This requires a rapid oscillations, which is repealed by an AM radio. Any change in the inductance in the search coil (by the presence of metal) to a change in the oscillator frequency. Although 230kHz is out of reach for the medium-wave band, an AM radio will significantly increase this frequency harmonics.
Metal detector calibration
This makes the search coil L1 is much room for error and is not far from conclusive. The author uses seventy turns 30 s.w.g. (0,315 mm) copper wire on a former 120mm diameter.
The metal detector, set up by the AM radio to pick up a whistle. Not all of these harmonic functions well, and are best suited to. The presence of metal will significantly change the sound of the whistle.

* Metal Detector FAQ *
This is not an industry or security metal detector and is not even near loma or ERIEZ metal detection system. It’s just a notebook, but not hand-metal detector.

LED Bike Light System 2N3906

This LED Bike Light System can be made to be just a headlight or both a headlight/taillight bike light.

The circuit use simple electronic components such as LM555,PNP Transistor (2N3906),NPN Transistor (2N2222) plus some resistors and capacitors.

 My NiteRider light was off getting fixed at the factory and I needed something for my daily commute. I have used it in a 50 minute pouring rain commute on the way in to work and it worked like a champ.

Blinking LED using AVR ATmega16

         Blinking a LED using 555 timer ic is simple, you can do the similar job using AVR atmega16. This is a simple program, perhaps simplest, and an introduction to ATmega16. To make a led blink you have to set (logic 1) and reset (logic 0) a pin of the controller continuously.
         there's a code for blinking a LED connected to any pin of portA of the controller.


#include<avr/io.h>
#include<util/delay.h>
int main(void)
{
DDRA=0xFF;            // set portA as out put
while(1)                     // run forever
{
PORTA=0xFF;          //All the pins of portA is set
_delay_ms(1000);      //wait  for 1sec
PORTA=0x00;          //all the pins of portA is reset
_delay_ms(1000);      // wait for 1 sec
}
return(0);
}


        DDR is data direct resister, DDR determines whether a particular pin of a port will work as an input or as an output, writing logic 1 to DDR makes the pin behave as output pin, writing logic 1 to DDR makes the pin behave as input pin. As we I wrote DDRA=0xFF, it will make all pins of portA work as output pin. Suppose you need only PA2 ( pin3 of portA ) as output pin, you need to write 1 to Bit 0 of  data direction resister for portA (DDRA). You can write like this

                                                              DDRA=0x01;
                                                                   or
                                                             DDRA|=(1<<PA2);
                                                                   or
                                                             DDRA|=_BV(2);  

6 Vintage Nixie tubes MC34063

I recently purchased a set of 6 Vintage Nixie tubes from ebay. The gentleman was very kind to offer me a good deal. I was looking for at least 4 numeric tubes but he only had two. I ended up buying 2 x IN-4, 2 x IN-15A and 2 x IN-15B. Nixie tubes are pretty cool, these were used long before the invention of Led’s or LCD’s. Here is what Wikipedia has to say about them.

To test drive these I used the MC34063 DC-DC converter as it is cheap to use and that is all I had to hand. What we need is at least 170 volts to drive one of these. AN920-D Page 28 has a step up converter schematic which suites this application. The circuit redrawn looks like:

There are many circuits on the internet but most have not mentioned the series 47k resistor, this is very important as it limits the current drawn. Without this the tube will appear brighter but can burn out very soon. The transformer details can be found in the application note mentioned above.

A female D connector was sacrificed on a bench wise for the sake of obtaining the pins that would perfectly fit the electrodes of the Nixie tubes. I don’t think soldering directly to these tubes is a good idea. Connectors can be purchased from ebay but they are expensive.

Headphone Amplifier - NE5532

NE5532 is a low-distortion, low-noise Hi-Fi OP-Amp.
NE5532 is able to drive low-impedance Loads to a full
Voltage swing while maintaining low distortion.
NE5532 output is short-circuit proof.

This Circuit was implemented with a single 5532 Chip forming a pair of inverting Amplifiers, having an AC Gain of about 3.5 and capable of delivering up to 3.6V Peak-to-peak into a 32Ω Load (corresponding to 50mW RMS) at less than 0.025% total harmonic distortion (THD).

Possible To Achieve 1kw With UC3842 ?

Is that possible to achieve 1kw with UC3842 ?

The answer is "Yes",  you could get 1KW out of this circuit with the following conditions met:
1) The switching FET needs to be a pretty big device (like an IRFP460) with very good heatsinking
2) The switching transformer needs to be pretty serious (like an ETD49), well designed, and close to the PCB
3) You need to add an R-C filter that includes a steering diode (see other flyback SMPS's for an idea how to implement)
4) The 300V supply needs to be quite robust (are you going to use PFC?)
5) Make sure the switching frequency is not too high to have copper losses impact the power level (like maybe 25 to 50KHz)

The small transformer you have a question-mark over looks to be a feedback and Vsupply source. During normal operation, the power FET's switching is coupled through the 22nF/250VAC cap and the transformer generates two voltages - one to supply Vcc, pin 7, of the 3842 IC and the other voltage as feedback to pin 2. It looks like the current sense is set to about 4.5A (1V/0.22ohm Source resistor), so with 300V in, you're at about 1.3KW - on target with your goal.

This looks like a great project to experiment with!

Make a DIY LM317 Power Supply

     HI. Being able to poke voltages into your projects will help you debug. You can buy an adjustable power supply for $50 or so, or build your own from a kit (another one) Just look for any power supply kit that has a LM317 in it.

    You can also build it for $10 using a 9V battery as input and test clips for outputs. This won’t be able to provide a lot of power (cause its just a 9V) but it can go pretty far for testing and debugging.

NE555 based inductivty meter

Hi!
This blog is about new inductivity meter based on a NE555.

For my experiments with switch mode converters, I needed a simple way to compare inductivities of coils.
Since I don't have a multimeter which can do inductivity measurement (but I have a really great multimeter, more infos perhaps in the next blog), I decided to build one.

And this is the schematic of it:

A NE555 works in its most simple rectangle osciallation configuration.
In this mode, the duty-cycle should be around 50%, but this depends on the load on pin 3.
Over the amplifying transistor Q1 the AC is given on an LC circuit.

It oscillates a freqency given by the equation:

This oscillating waves are amplified by Q2 and frequency is converted into a voltage by the RC-network of C3 and the ampmeter.
Due to the capacity of both C3 and C2 being constant, the current through the ampmeter is defined by the inductivity.

LM386 based stereo audio amplifier with digital volume control

Due to its simplicity (requires minimum external components) and high availability, LM386 is very popular among hobbyists for use in low-voltage audio amplification applications. Most of the time a potentiometer is used at the input side of LM386 to provide a volume control in the output speaker. The potentiometer does not control the gain of the amplifier itself, but it creates a voltage divider network at the input, which in fact controls the fraction of the audio signal that is fed to the amplifier. This project is about a stereo audio amplifier using two LM386 ICs with digital volume control for both left and right speakers. So, how would you control the volume digitally?

You are right, by replacing the traditional electro-mechanical form of potentiometers with digital potentiometer chips. This project uses MAXIM’s DS1868 dual digital potentiometer chip and a PIC microcontroller to control the volume of a stereo output from two LM386 ICs.

Digital voltmeter using ICL7107

The circuit given here is of a very useful and accurate digital voltmeter with LED display using the ICL7107 from Intersil. The ICL7107 is a high performance, low power, 3.5 digit analog to digital converter. The IC includes internal circuitry for seven segment decoders, display drivers, reference voltage source and a clock. The power dissipation is less than 10mW and the display stability is very high.

 The working of this electronic circuit is very simple. The voltage to be measured is converted into a digital equivalent by the ADC inside the IC and then this digital equivalent is decoded to the seven segment format and then displayed. The ADC used in ICL7107 is dual slope type ADC. The process taking place inside our ADC can be stated as follows. For a fixed period of time the voltage to be measured is integrated to obtain a ramp at the output of the integrator. Then a known reference voltage of opposite polarity is applied to the input of the integrator and allowed to ramp until the output of integrator becomes zero. The time taken for the negative slope to reach zero is measured in terms of the IC’s clock cycle and it will be proportional to the voltage under measurement. In simple words, the input voltage is compared to an internal reference voltage and the result is converted in a digital format.

Why does the LM1117 data sheet specifically specify tantalum capacitors?

I'm planning on using an LM1117 to regulate 5v to 3.3v. Looking at (any of the several) data sheets for the LM1117, they recommend 10uF Tantalum capacitors between input and ground and between output and ground. I understand the need for the capacitors, but it's not clear to me why these should specifically be Tantalum. I have a bunch of electrolytic 10uF capacitors sitting around here, whereas if it does for some reason need to be Tantalum, I'll have to order those.

Why are they so specific about using tantalum capacitors?

The LM1117 datasheet provides clear guidance on the essential and desirable characteristics of the input and output capacitors. Any capacitor which meets these specifications is suitable. Tantalum is an OK choice but is not the best choice. There are various factors and cost is one. Tantalum offers OK cost per capability at capacitances from about 10 uF up. The output capacitor is "safe" against spikes in most cases. The input capacitor is at risk from "bad behavior" from other parts of the system. Spikes above rated value will produce a (literally) flaming melt down. (Smoke, flame, noise, bad smell and explosion all optional -
I have seen one tantalum cap do all of these in turn :-))

Medical ECG Monitors using the AD620 Instrumentation Amplifier

One of features of the AD620 instrumentation amplifier is low current noise, this benefit allows its use in theMedical ECG Monitor Circuit DiagramElectrocardiography (ECG) monitors. A medical ECG Monitor Circuit is shown in the following picture, please click to enlarge the picture.
The picture tells the use of AD620 in ECG monitors where high source resistances of 1 MOhm or higher are not uncommon. It can improve the dynamic range for better performance when low bias current and low current noise coupled with the low voltage noise of the AD620.

Capacitor C1 maintains the stability of right leg drive loop. An isolation addition to this circuit may protect the patient from possible danger.

DS18B20 – ground connectors complete

I am getting closer to getting 20 probes ready to test.DS18B20 ground connectors.  Everything is just about in place to make a run at it.  And what would happen….

The truth : I have only run about 10 to 12 feet so far. I have read that others have run 75 to 100 feet with no problems. But as always on the internet fact and fiction run close together on these type questions. I have not done it, so I do not know for sure. All the connections I do and have done are all bus type. I really do not yet understand star topology to the fullest. It used to drive me crazy when computer networks were configured this way.

ADC input protection BAT54S

Hi guys , do you know how do you protect your PIC adc inputs against reverse polarity ? Ì'm feeding battery volrtage to my PIC16F877A and would like to protect it against operator error.

The best protection scheme is a series resistor and a pair of schottky diodes (such as BAT54S) one to each power rail. The resistor should be sized to not burn out the diodes and no affect the sample accuracy of the A/D. The Microchip data sheets give info on the accuracy issue.

The schottky keeps the voltage drop below the processors internal protection diode forward drops and therfore prevents latchup and destruction.

We have used this approach for many years with complete success. Typically we use a 10K, 1206 resistor although sometimes go smaller depending on how we are using the A/D, which comes down to the sample rate. The same circuit is also effective on digital inputs that are exposed to the external world.