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 This requires a rapid oscillations, which is repealed by an AM radio.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.

Power Pulse Generator THE LM150/LM250/LM350

Power Pulse Generator THE LM150/LM250/LM350 is an adjustable voltage regulator capable of delivering from 1.2 to 33 volts at a maximum current of 3 amperes. Normally this chip is used in both fixed and adjustable power supplies, voltage regulators and voltage references. Since I'm always looking for a new way to obtain high-current pulses for flashing lamps and driving motors, motors, I have recently been experimenting with ways to switch the output of the LM350T on and off. Since the output voltage of this chip is fully adjustable, a circuit which switches its output on and off provides a variable- amplitude power pulse generator. Before looking at an LM350T power pulse generator, let's first examine the operating characteristics of this versatile chip. Figure 2-42 shows the pin diagrams for both the TO-220 packaged LM350T and the TO-3 versions of the LM150/LM250//LM350. The chip requires a minimum of external components. 

Specifications - FR107

FR107

High current capability High surge current capability High reliability Low reverse current Low forward voltage drop Fast switching for high efficiency

* Case : DO-41 Molded plastic * Epoxy : UL94V-O rate flame retardant * Lead : Axial lead solderable per MIL-STD-202, Method 208 guaranteed * Polarity : Color band denotes cathode end * Mounting position : Any * Weight : 0.34 gram

Rating 25 °C ambient temperature unless otherwise specified. Single phase, half wave, 60 Hz, resistive or inductive load. For capacitive load, derate current by 20%.

Maximum Recurrent Peak Reverse Voltage Maximum RMS Voltage Maximum DC Blocking Voltage Maximum Average Forward Current 0.375"(9.5mm) Lead Length 55 °C Peak Forward Surge Current, 8.3ms Single half sine wave Superimposed on rated load (JEDEC Method) Maximum Peak Forward Voltage = 1.0 Amp. Maximum DC Reverse Current at Rated DC Blocking Voltage 100 °C

Maximum Reverse Recovery Time ( Note 1 ) Typical Junction Capacitance ( Note 2 ) Junction Temperature Range Storage Temperature Range

1 ) Reverse Recovery Test Conditions 1.0 A, Irr 2 ) Measured at 1.0 MHz and applied reverse voltage of 4.0 VDC
FIG.1 - REVERSE RECOVERY TIME CHARACTERISTIC AND TEST CIRCUIT DIAGRAM

NOTES : 1. Rise Time 7 ns max., Input Impedance = 1 megaohm, 22 pF. 2. Rise time 10 ns max., Source Impedance = 50 ohms. 3. All Resistors = Non-inductive Types.
FIG.3 - MAXIMUM NON-REPETITIVE PEAK FORWARD SURGE CURRENT PEAK FORWARD SURGE CURRENT, AMPERES
AMBIENT TEMPERATURE, ( °C) FIG.4 - TYPICAL FORWARD CHARACTERISTICS REVERSE CURRENT, MICROAMPERES

More information, or you can see this:
http://www.hqew.net

Popular Transistors MMBT3904

This is the MMBT3904 NPN SMT Transistor Design Kit. It includes the very popular SMT version of the 2N3904, General Purpose NPN Transistor: MMBT3904. This was one of the most popular transistors used in all kinds of circuits for years and years. It was designed for general purpose amplifiers with a 500 milliamp Collector current requirement. This kit also includes a few pieces of the MMBT3906 (PNP) which is the complement to the MMBT3904 (NPN) and a SMT Voltage Regulator, LM317M in the SMT package. 


This kit also includes a tremendous amount of different SMT components that you would use to develop numerous circuits. Included are different values of SMT Transistors, SMT Resistors, SMT Aluminum, Ceramic & Tantalum Capacitors, SMT Inductors, SMT Signal (Single & Dual) & Zener Diodes, SMT Trimpots, SMT LEDs, Pushbutton Switches, an Electret Microphone, and a miniature Speaker. It also includes some electronic hardware that are used in most projects for I/O.