Schematic Rise

Showing posts with label circuit. Show all posts

Showing posts with label circuit. Show all posts

Monday, November 17, 2014

Simple 100W inverter circuit

Here is the circuit diagram of a simple 100 watt inverter using IC CD4047 and MOSFET IRF540. The circuit is simple low cost and can be even assembled on a veroboard.

CD 4047 is a low power CMOS astable/monostable multivibrator IC. Here it is wired as an astable multivibrator producing two pulse trains of 0.01s which are 180 degree out of phase at the pins 10 and 11 of the IC. Pin 10 is connected to the gate of Q1 and pin 11 is connected to the gate of Q2. Resistors R3 and R4 prevents the loading of the IC by the respective MOSFETs. When pin 10 is high Q1 conducts and current flows through the upper half of the transformer primary which accounts for the positive half of the output AC voltage. When pin 11 is high Q2 conducts and current flows through the lower half of the transformer primary in opposite direction and it accounts for the negative half of the output AC voltage.

Circuit diagram.

Notes.

B1 can be a 12V/ 6Ah lead acid battery.

Q1 and Q2 must be fitted to a proper heat sink.

T1 can be a 9-0-9 V primary, 230V secondary, 150VA transformer .

Do not expect much from this circuit. The is very simple one suitable for low grade applications.

Insect Repeller Circuit Diagram

In this section we talk about a type of insect repellent insect repellent is a circuit that repel insects from your home or garden effectively. This circuit uses the frequency of bullying of insects to the insect goes.

For this insect repellent skesta be installed inside or outside the home can / the speakers. This series of in-circuit PLL oscillator circuit adl / phase looked loop by using a CMOS 4047 at a rate 22 khz.gunakan external power supply for best results.

IC 4047 Description

The CD4047B is capable of operating in either a monostable or astable. It requires an external capacitor (between pins 1 and 3) and an external resistor (between pins 2 and 3) to determine the output pulse width in the monostable mode and the output frequency in astable mode

Absolute Maximum Ratings IC IC 4047

DC Supply Voltage (VDD)...........-0.5V to +18VDC
Input Voltage (VIN)...............-0.5V to VDD +0.5VDC
Storage Temperature Range (TS)....-65°C to +150°C
Power Dissipation (PD)
Dual-In-Line...................... 700 mW
Small Outline..................... 500 mW
Lead Temperature (TL)
(Soldering, 10 seconds)........... 260°C.

Saturday, November 15, 2014

60 WATT AMPLIFIER CIRCUIT

STK4038 is an integrated AF power amplifier that can deliver 60 watts of output power into a 4 ohm load. The internal fixed current circuitry reduces switch ON/OFF clicks. The IC supports the addition of external circuits for thermal shutdown, pop noise reduction, output short circuit protection etc. This circuit is based on datasheet and it includes a Zobel network ( called filter section ) which improves the high frequency stability of the amplifier.

The 60 watt amplifier shown below is designed based on the datasheet and performs very well. Capacitor C1 is the input DC decoupling capacitor which blocks any DC level present in the audio input and C12 is the input by-pass capacitor. R1 is the input resistor.C10 and C8 are the ripple filter capacitors for the positive and negative power supply rails. R9 and R7 are the current limiting resistors for the internal driver stage while C11 and C3 are their corresponding filter capacitors. Resistor R6 feeds back a portion of the output signal to the inverting input (pin2). Gain of the amplifier depends on the value of R6. C9 and R2 forms a Zobel network which improves the high frequency stability of the amplifier.

Circuit Diagram

Points to Remember

A good quality PCB improves the performance of the circuit.
Maximum supply voltage for STK4038 is +/- 57V DC.
K1 is a 4 ohm / 75 watt loud speaker.
While using 4 ohm speaker as the load, the power supply must not exceed +/- 32V DC.

Thursday, November 13, 2014

Latest Step Up Booster Powers Eight White LEDs Diagram Circuit

Tiny white LEDs are capable of delivering ample white light without the fragility problems and costs associated with ﬂuorescent backlights. They do pose a problem however in that their forward voltage can be as high as 4 V, precluding them being from powered directly from a single Li-Ion cell. Applications requiring more white LEDs or higher efficiency can use an LT1615 boost converter to drive a series connected array of LEDs. The high efficiency circuit (about 80%) shown here can provide a constant-current drive for up to eight LEDs. Driving eight white LEDs in series requires at least 29 V at the output and this is possible thanks to the internal 36-V, 350-mA switch in the LT1615.

The constant-current design of the circuit guarantees a steady current through all LEDs, regardless of the forward voltage differences between them. Although this circuit was designed to operate from a single Li-Ion battery (2.5V to 4.5V), the LT1615 is also capable of operating from inputs as low as 1 V with relevant output power reductions. The Motorola MBR0520 surface mount Schottky diode (0.5 A 20 V) is a good choice for D1 if the output voltage does not exceed 20 V. In this application however, it is better to use a diode that can withstand higher voltages like the MBR0540 (0.5 A, 40 V). Schottky diodes, with their low forward voltage drop and fast switching speed, are the best match.

Many different manufacturers make equivalent parts, but make sure that the component is rated to handle at least 0.35 A. Inductor L1, a 4.7-µH choke, is available from Murata, Sumida, Coilcraft, etc. In order to maintain the constant off-time (0.4 ms) control scheme of the LT1615, the on-chip power switch is turned off only after the 350-mA (or 100-mA for the LT1615-1) current limit is reached. There is a 100-ns delay between the time when the current limit is reached and when the switch actually turns off. During this delay, the inductor current exceeds the current limit by a small amount. This current overshoot can be beneﬁcial as it helps increase the amount of available output current for smaller inductor values.

This will be the peak current passed by the inductor (and the diode) during normal operation. Although it is internally current-limited to 350 mA, the power switch of the LT1615 can handle larger currents without problems, but the overall efficiency will suffer. Best results will be o btained when IPEAK is kept well below 700 mA for the LT1615.The LT1615 uses a constant off-time control scheme to provide high efficiencies over a wide range of output current. The LT1615 also contains circuitry to provide protection during start-up and under short-circuit conditions.

When the FB pin voltage is at less than approximately 600 mV, the switch off-time is increased to 1.5 ms and the current limit is reduced to around 250 mA (i.e., 70% of its normal value). This reduces the average inductor current and helps minimize the power dissipation in the LT1615 power switch and in the external inductor L1 and diode D1. The output current is determined by Vref/R1, in this case, 1.23V/68 = 18 mA). Further information on the LT1615 may be found in the device datasheets which may be downloaded from www.linear-tech.com/pdf/16151fa.pdf

Author: D. Prabakaran
Copyright: Elektor Electronics

Photovoltaic Transimpedance Amplifier Circuit Diagram

Photovoltaic

The following schematic shows the Photovoltaic Transimpedance Amplifier Circuit Diagram. This design combines two Intersil X9258T digitally controlled potentiometers with an AD822 low noise dual op amp to create a flexible, digitally calibrated, wide dynamic range transimpedance amplifier topology that can be used with virtually any photovoltaic detector technology. The amplifier output is given by:

Vo = Is(1MΩ) ((1+P1)/(256-P1))

Where P1 is the 8-bit (0 to 255) digital value written to DCP1. For more detail information on Photovoltaic Transimpedance Amplifier Circuit Diagram, download the following file.

LED Sound level display circuit by using IC LM3915

This circuit is about audio sound level LED display, indicator, monitor or you can say it “Audio VU (Volume Unite) Meter”.
This is a simple audio sound level LED display circuit diagram. The circuit is completely based on a single ic LM3915 from National Semiconductor. The LM3915 is a monolithic integrated circuit. It displays the audio sound level in terms of 10 LEDs and providing a logarithmic 3 dB/step analog display.

Audio sound level display circuit diagram

Fig: Circuit diagram of sound level display using ic LM3915

The audio sound level LED display circuit can operate from a single supply 3V to 25V. But I suggest to use 9-12V. LED brightness can be controlled with a single pot( variable resistor) as shown 10K ohm in the circuit. Connect the audio input signal in Pin-5 of LM3915 from output of a audio device like output of audio amplifier or any other source.

The Pin-9 of LM3915 is to select dot or bar mode display. To make the circuit moving dot display instead of a bar graph display disconnect the Pin-9 from +V.

Wednesday, November 12, 2014

Model Railway Short Circuit Beeper

Short circuits in the tracks, points or wiring are almost inevitable when building or operating a model railway. Although transformers for model systems must be protected against short circuits by built-in bimetallic switches, the response time of such switches is so long that is not possible to immediately localise a short that occurs while the trains are running, for example. Furthermore, bimetallic protection switches do not always work properly when the voltage applied to the track circuit is relatively low.

Circuit diagram :

Model Railway Short-Circuit Beeper Circuit Diagram

The rapid-acting acoustic short-circuit detector described here eliminates these problems. However, it requires its own power source, which is implemented here in the form of a GoldCap storage capacitor with a capacity of 0.1 to 1 F. A commonly available reed switch (filled with an inert gas) is used for the current sensor, but in this case it is actuated by a solenoid instead of a permanent magnet. An adequate coil is provided by several turns of 0.8–1 mm enamelled copper wire wound around a drill bit or yarn spool and then slipped over the glass tube of the reed switch. This technique generates only a negligible voltage drop. The actuation sensitivity of the switch (expressed in ampèreturns or A-t)) deter-mines the number of turns required for the coil. For instance, if you select a type rated at 20–40 A-t and assume a maxi-mum allowable operating current of 6 A, seven turns (40 ÷ 6 = 6.67) will be sufficient. As a rule, the optimum number of windings must be determined empirically, due to a lack of specification data.

As you can see from the circuit diagram, the short-circuit detector is equally suitable for AC and DC railways. With Märklin transformers (HO and I), the track and lighting circuits can be sensed together, since both circuits are powered from a single secondary winding.

Coil L1 is located in the common ground lead (‘O’ terminal), so the piezoelectric buzzer will sound if a short circuit is present in either of the two circuits. The (positive) trigger voltage is taken from the lighting circuit (L) via D1 and series resistor R1. Even though the current flowing through winding L1 is an AC or pulsating DC current, which causes the contact reeds to vibrate in synchronisation with the mains frequency, the buzzer will be activated because a brief positive pulse is all that is required to trigger thyristor Th1. The thyristor takes its anode voltage from the GoldCap storage capacitor (C2), which is charged via C2 and R2. The alarm can be manually switched off using switch S1, since although the thyris-tor will return to the blocking state after C2 has been discharged if a short circuit is present the lighting circuit, this will not happen if there is a short circuit in the track circuit. C1 eliminates any noise pulses that may be generated.

As a continuous tone does not attract as much attention as an intermittent beep, an intermittent piezoelectric generator is preferable. As almost no current flows during the intervals between beeps and the hold current through the thyristor must be kept above 3 mA, a resistor with a value of 1.5–1.8 kΩ is connected in parallel with the buzzer. This may also be necessary with certain types of continuous-tone buzzers if the operating current is less than 3 mA. The Zener diode must limit the operating voltage to 5.1 V, since the rated volt-age of the GoldCap capacitor is 5.5 V.

PWM Discrete Generator Circuit and explanation

PWM waveforms are commonly used to control the speed of DC motors. The mark/space ratio of the digital wave-form can be defined either by using an adjustable analogue voltage level (in the case of a NE555 based PWM generator) or digitally using binary values. Digitally derived PWM waveforms are most often produced by the timer/counter modules in microcontrollers but if you do not want to include a microcontroller in your circuit it’s also quite simple to generate the signals using discrete logic components.Circuit diagram:

Discrete PWM Generator Circuit Diagram

An extension of the circuit shown can produce two PWM wave-forms from an 8-bit digital input word. Each signal has 15 values. The 8-bit word can be produced for example from an expansion board fitted in a PC or from an 8-bit port of a processor which does not have built-in PWM capability or from a laptop’s printer port. The mark/space ratio is only programmable up to 15/16 rather than 16/16; a binary input of 0000 produces a continuous low on both outputs turning both motors off.

Similar circuits often employ a dedicated ‘enable’ input to turn the motors off but it is not necessary in this design. The diagram shows the circuitry required to produce just one waveform. For the full two channel circuit it is necessary to use an additional 74HC193. The clock signal produced by the HCF4060 generator can be used to drive both channels and the free flip flop in the 74HC74 package can be used for the second channel (the corresponding pin numbers are shown in brackets). Altogether the entire two channel circuit can be built using just four ICs.

Friday, November 7, 2014

50 W Power Amplifier Circuit using STK084

50W

This is the circuit diagram of 50W power amplifier circuit which built based on single power amplifier chip of STK084. Its an well-known old IC for audio frequency (AF) amplifier.

This circuit requires dual polarity / split power supply with maximum supply of ± 50. The recommended supply is ± 35 / 2-3A DC current. You may use this split power supply circuit for the amplifier. Use 28V center tap transformer to get about ± 36V output.

Technical Details:

Power output: 50W
RL : 8 Ohm
TDH : 0.2 %
Rin : 52K
Gain : 26.4 dB
Noise : 0.3 mV

Take a note that heatsink is required to be mounted on the power IC since it will going to hot when operated and deliver high power output (high audio volume level).

Wednesday, November 5, 2014

Triangular Wave Generator Circuit

Triangular Wave Generator Circuit

This is a circuit for a constant amplitude triangular-wave generator. A variable frequency triangular wave whose amplitude is independent of frequency is provided by this circuit. This circuit is based on LM101.

Triangular Wave Generator Circuit

As a reset circuit, the generator embodies an integrator as a ramp generator and a threshold detector with hysteresis. There is no further explanation is needed because the integrator has been described in a previous section. It’s a latch circuit with a large dead zone, on that case, the threshold amplifier detector is similar to a Schmidt Trigger. By using positive feedback around an operational amplifier, we can implement this function. The positive feedback network provides a voltage at the non-inverting input which is determined by the attenuation of the feedback loop and the saturation voltage amplifier when the amplifier output is in either the positive or negative saturated state. The voltage at the input of the amplifier must be caused to change polarity by an amount in excess of the amplifier input offset voltage to cause the amplifier to change states. When this is done, until the voltage at its input again reverse, the amplifier saturates in the opposite direction and remains in that state. By examining the operation with the output of the threshold detector in the positive state, the complete circuit operation may be understood. To cause a current I+ to flow, we have to apply the detector positive saturation voltage to the integrator summing junction through the combination R3 and R4.

Then, a negative-going ramp with a rate of I+/C1 volts per second until its output equals the negative trip point of the threshold detector is generated by the integrator. After that, at the integrator summing point , the threshold detector changes to the negative output state and supplies a negative current, I-. A positive-going ramp with a rate of I-/C1 volts per second is generated by the integrator until its output equals the positive trip point of the threshold detector where the detector again changes output state and the cycle repeats. R3, R4, C1, and the positive and negative saturation voltages of the amplifier A1 determine the triangular-wave frequency. Amplitude is determined by the threshold detector saturation voltages and the ratio of R5 to the combination of R1 and R2. If the detector has equal positive and negative saturation voltages, positive and negative ramp rates are equal and positive and negative peaks are equal. If the inverting input of the threshold detector, A1, is offset with respect to ground, the output waveform may be offset with respect to ground. If the detector is clamped with matched Zener diodes as shown in following figure, the generator may be made independent of temperature and supply voltage. If power supply impedance causes oscillation during its transition time, the detector may be compensated and the integrator should be compensated for unity-gain. For maximum symmetry, the current into the integrator should be large with respect to Ibias and offset voltage should be small with respect to Voutpeak.

Tuesday, November 4, 2014

Metal Detector Circuit Schematic using Beat Frequency Oscillator BFO

The simplest method of detecting metal is by beat frequency oscillator. The circuit basically consists of two balanced oscillator. One acts as the detector element, the other provides the reference signal. This oscillator frequency reference is set to fix value, whilst the detector oscillator varies depending on the metal presence. The reference oscillator can be constructed using various circuit topology: inductor-capacitor (LC), resistor-capacitor (RC), or even a crystal (quartz) oscillator. While the reference oscillator can be implemented using various circuit topology, the detector oscillator always use inductor-capacitor topology, because the mechanism will be using the magnetic induction property of the detected object, and the inductor component of the detector oscillator will be the detecting probe.

With the absence of a metal near the detector probe (the inductor component of the detector oscillator), the detector oscillator is tuned to have same frequency as the reference oscillator. The output of the detector oscillator and the reference oscillator output is mixed using hetero-dyne mixer circuit, producing a beat frequency output of zero Hz, or a very low frequency if both oscillator is slightly unbalanced. In the presence of a metal near the detector probe, the detector oscillator will shift it’s frequency, and the mixer output will produce a tone with frequency equal to the difference of the reference and the detector frequency.
The figure below shows one of the simple metal detector circuit.You can see the reference circuit is a simple RC circuit, and its frequency is determined by R1-P2-C1. The detector oscillator is an LC oscillator with the frequency is determined by the L1-C2-C3 values.

The NAND gates use CMOS 4011 chip, a low power component that is suitable for this battery-operated circuit. You can see that this chip is supplied by a 5V voltage coming from an LM7805L regulator. You might wonder what the purpose of this regulation is, since the power supply come from a 9V battery and the CMOS gates can handle the voltage of 3-15 Volt. The main purpose of the regulator is to keep a constant voltage source for the reference oscillator frequency stability, since the frequency is affected by the power supply voltage variation as the battery voltage drops in the long time of usage.

Here the complete parts list:

Parts list:

U1: CD4011
U2: LM389
U3: 78L05
R1: 2.2k 5%
P2: 4.7k lin.
R3: 330k 5%
R4: 270k 5%
R5: 1k 5%
C1: 390pF (NPO)
C2,C3,C4: 10nF
C5: 10uF 16v electrolytic
C6,C8: 220 uF 16v electrolytic
C7: 100uf 16v electrolytic
C9: 100nF ceramic
P1: 4.7k log
L1: 22cm in diameter with 14 turns AWG 26
K1: SPDT toggle switch
J1= Headphone jack 1/4 or 1/8 inch
Other parts: 9v battery connector, speaker or headphones

To tune the circuit, plug a headphone at the output, and remove any metal around the inductor L1. Set the volume control P1 around at center. Set the reference oscillator tuner P2 at the maximum or minimum position, you should hear no sound since the frequency should be in ultrasonic range. Turn slowly P2 until you hear a very high audio frequency, continue turning the pot until the frequency is decreasing and stop turning when the note is just disappeared (the frequency is decreased down below 20 Hz). After this, you can test the circuit by placing a metal near the inductor L1 and now the output will give an audible frequency as the detection alert.

Saturday, November 1, 2014

Automatic detectors water tank pump circuit

This is a circuit detectors on the water pump. This circuit works automatically when the water is discharged to storage tanks or redundant. If the storage tank water runs out then the circuit will work running the pump, and an excess of water this circuit will automatically stop the pump working. Below the detection circuit:

Automatic

Automatic detectors water tank pump schematic diagram

R1 10K ohms resistor
R2 10K ohms resistor
R3 10K ohms resistor
R4 1K ohms resistor
R5 10K ohms resistor
R6 1K ohms resistor
C1 100nF cap
Led1 5mm green led
Led2 5mm red led
D1 4V7 zener diode
Piezo Piezo HPE-120
VR1 78L05 regulator
IC1 12F683 SOIC microcontroller from Microchip
S1 Push button
Others:
Box
9V battery
PCB
Metal strips
Hex program for the microcontroller

Friday, October 31, 2014

Outdoor Lighting Controller Circuit Diagram

When you step out of your brightly-lit house into the darkness, it takes a while for your vision to adjust. A solution to this problem is this outdoor light with automatic switch-off. As a bonus, it will also make it a little bit easier to find the keyhole when returning late at night. Often no mains neutral connection is avail-able at the point where the switch-off timer is to be installed, which makes many circuit arrangements impractical. However, the circuit here is designed to work in this situation. The design eschews bulky components such as transformers and the whole unit can be built into a flush-mounted fitting. The circuit also features low quiescent current consumption.

Outdoor Lighting Controller Circuit Diagram :

Outdoor

Outdoor

The circuit is star ted by closing switch (or pushbutton) S1. The lamp then immediately receives power via the bridge rectifier. The drop across diodes D5 to D10 is 4.2 V, which provides the power supply for the delay circuit itself, built around the CD4060 binary counter.

When the switch is opened the lighting sup-ply current continues to flow through Tri1. The NPN optocoupler in the triac drive circuit detects when the triac is active, with antiparallel LED D1 keeping the drive sym-metrical. The NPN phototransistor inside the coupler creates a reset pulse via T1, driving pin 12 of the counter. This means that the full time period will run even if the circuit is retriggered. The CD4060 counts at the AC grid frequency. Pin 3 goes high after 213clocks, which corresponds to about 2.5 minutes. If this is not long enough, a further CD4060 counter can be cascaded. T2 then turns on and shorts the internal LED of opto-triac IC2; this causes Tri1 to be deprived of its trigger current and the light goes out. The circuit remains without power until next triggered.

The circuit is only suitable for use with resistive loads. With the components shown (in particular in the bridge rectifier and D5 to D10) the maximum total power of the connected bulb(s) is 200 watts. As is well known, the filament of the bulb is most likely to fail at the moment power is applied. There is little risk to Tri1 at this point as it is bridged by the switch. The most likely consequence of overload is that one of diodes D1 to D6 will fail. In the prototype no fuse was used, as it would not in any case have been easy to change. However, that is not necessarily recommended practice!

Circuits at AC line potential should only be constructed by suitably experienced persons and all relevant safety precautions and applicable regulations must be observed during construction and installation.

Author : Harald Schad - Copyright : Elektor

Thursday, October 30, 2014

What is The Parallel Resonance Circuit

The Parallel Resonance Circuit, In numerous ways a parallel resonance circuit is precisely the identical as the series resonance circuit we looked at in the preceding tutorial. Both are 3-element systems that comprise two reactive constituents making them a second-order circuit, both are influenced by variations in the supply frequency and both have a frequency point where their two reactive constituents cancel each other out influencing the characteristics of the circuit. Both circuits have a resonant frequency issue.

The difference this time however, is that a parallel resonance circuit is influenced by the currents flowing through each parallel branch within the parallel LC tank circuit. A tank circuitis a parallel combination of L and C that is used in filter networks to either select or reject AC frequencies. Consider the parallel RLC circuit below.

Parallel RLC Circuit

parallel rlc circuit

Let us define what we already know about parallel RLC circuits.

A parallel circuit containing a resistance, R, an inductance, L and a capacitance, C will produce a parallel resonance(also called anti-resonance) circuit when the resultant current through the parallel combination is in phase with the supply voltage. At resonance there will be a large circulating current between the inductor and the capacitor due to the energy of the oscillations.

A parallel resonant circuit stores the circuit energy in the magnetic field of the inductor and the electric field of the capacitor. This energy is constantly being transferred back and forth between the inductor and the capacitor which results in zero current and energy being drawn from the supply. This is because the corresponding instantaneous values of I_L and I_C will always be equal and opposite and therefore the current drawn from the supply is the vector addition of these two currents and the current flowing in I_R.

In the solution of AC parallel resonance circuits we know that the supply voltage is common for all branches, so this can be taken as our reference vector. Each parallel branch must be treated separately as with series circuits so that the total supply current taken by the parallel circuit is the vector addition of the individual branch currents. Then there are two methods available to us in the analysis of parallel resonance circuits. We can calculate the current in each branch and then add together or calculate the admittance of each branch to find the total current.

We know from the previous series resonance tutorial that resonance takes place when V_L = -V_C and this situation occurs when the two reactances are equal, X_L = X_C. The admittance of a parallel circuit is given as:

Resonance occurs when X_L = X_C and the imaginary parts of Y become zero. Then:

Notice that at resonance the parallel circuit produces the same equation as for the series resonance circuit. Therefore, it makes no difference if the inductor or capacitor are connected in parallel or series. Also at resonance the parallel LC tank circuit acts like an open circuit with the circuit current being determined by the resistor, R only. So the total impedance of a parallel resonance circuit at resonance becomes just the value of the resistance in the circuit and Z = R as shown.

At resonance, the impedance of the parallel circuit is at its maximum value and equal to the resistance of the circuit and we can change the circuits frequency response by changing the value of this resistance. Changing the value of R affects the amount of current that flows through the circuit at resonance, if both L and C remain constant. Then the impedance of the circuit at resonance Z = R_MAX is called the "dynamic impedance" of the circuit.

Impedance in a Parallel Resonance Circuit

impedance in a parallel resonance circuit

Note that if the parallel circuits impedance is at its maximum at resonance then consequently, the circuits admittance must be at its minimum and one of the characteristics of a parallel resonance circuit is that admittance is very low limiting the circuits current. Unlike the series resonance circuit, the resistor in a parallel resonance circuit has a damping effect on the circuits bandwidth making the circuit less selective.

Also, since the circuit current is constant for any value of impedance, Z, the voltage across a parallel resonance circuit will have the same shape as the total impedance and for a parallel circuit the voltage waveform is generally taken from across the capacitor.

We now know that at the resonant frequency, ƒ_r the admittance of the circuit is at its minimum and is equal to the conductance, G given by 1/R because in a parallel resonance circuit the imaginary part of admittance, i.e. the susceptance, B is zero because B_L = B_Cas shown.

Susceptance at Resonance

susceptance at resonance

From above, the inductive susceptance, B_L is inversely proportional to the frequency as represented by the hyperbolic curve. The capacitive susceptance, B_C is directly proportional to the frequency and is therefore represented by a straight line. The final curve shows the plot of total susceptance of the parallel resonance circuit versus the frequency and is the difference between the two susceptances.

Then we can see that at the resonant frequency point were it crosses the horizontal axis the total circuit susceptance is zero. Below the resonant frequency point, the inductive susceptance dominates the circuit producing a "lagging" power factor, whereas above the resonant frequency point the capacitive susceptance dominates producing a "leading" power factor. So at resonant frequency, the circuits current must be "in-phase" with the applied voltage as there effectively there is only the resistance in the circuit so the power factor becomes one or unity, ( θ = 0^o ).

Current in a Parallel Resonance Circuit

As the total susceptance is zero at the resonant frequency, the admittance is at its minimum and is equal to the conductance, G. Therefore at resonance the current flowing through the circuit must also be at its minimum as the inductive and capacitive branch currents are equal ( I_L = I_C ) and are 180^o out of phase.

We remember that the total current flowing in a parallel RLC circuit is equal to the vector sum of the individual branch currents and for a given frequency is calculated as:

At resonance, currents I_L and I_L are equal and cancelling giving a net reactive current equal to zero. Then at resonance the above equation becomes.

Since the current flowing through a parallel resonance circuit is the product of voltage divided by impedance, at resonance the impedance, Z is at its maximum value, ( =R ). Therefore, the circuit current at this frequency will be at its minimum value of V/R and the graph of current against frequency for a parallel resonance circuit is given as.

Parallel Circuit Current at Resonance

The frequency response curve of a parallel resonance circuit shows that the magnitude of the current is a function of frequency and plotting this onto a graph shows us that the response starts at its maximum value, reaches its minimum value at the resonance frequency when I_MIN = I_Rand then increases again to maximum as ƒ becomes infinite. The result of this is that the magnitude of the current flowing through the inductor, L and the capacitor, C tank circuit can become many times larger than the supply current, even at resonance but as they are equal and at opposition ( 180^o out-of-phase ) they effectively cancel each other out.

As a parallel resonance circuit only functions on resonant frequency, this type of circuit is also known as an Rejector Circuit because at resonance, the impedance of the circuit is at its maximum thereby suppressing or rejecting the current whose frequency is equal to its resonant frequency. The effect of resonance in a parallel circuit is also called "current resonance".

The calculations and graphs used above for defining a parallel resonance circuit are similar to those we used for a series circuit. However, the characteristics and graphs drawn for a parallel circuit are exactly opposite to that of series circuits with the parallel circuits maximum and minimum impedance, current and magnification being reversed. Which is why a parallel resonance circuit is also called an Anti-resonance circuit.

Bandwidth & Selectivity of a Parallel Resonance Circuit

The bandwidth of a parallel resonance circuit is defined in exactly the same way as for the series resonance circuit. The upper and lower cut-off frequencies given as: ƒ_upper and ƒ_lower respectively denote the half-power frequencies where the power dissipated in the circuit is half of the full power dissipated at the resonant frequency 0.5( I² R ) which gives us the same -3dB points at a current value that is equal to 70.7% of its maximum resonant value, ( 0.707 x I )² R.

As with the series circuit, if the resonant frequency remains constant, an increase in the quality factor, Q will cause a decrease in the bandwidth and likewise, a decrease in the quality factor will cause an increase in the bandwidth as defined by: BW = ƒ_r /Q or BW = ƒ₂ - ƒ₂. Also changing the ratio between the inductor, L and the capacitor, C, or the value of the resistance, R the bandwidth and therefore the frequency response of the circuit will be changed for a fixed resonant frequency. This technique is used extensively in tuning circuits for radio and television transmitters and receivers.

The selectivity or Q-factor for a parallel resonance circuit is generally defined as the ratio of the circulating branch currents to the supply current and is given as:

Note that the Q-factor of a parallel resonance circuit is the inverse of the expression for the Q-factor of the series circuit. Also in series resonance circuits the Q-factor gives the voltage magnification of the circuit, whereas in a parallel circuit it gives the current magnification.

Bandwidth of a Parallel Resonance Circuit

Example No1

A parallel resonance network consisting of a resistor of 60Ω, a capacitor of 120uF and an inductor of 200mH is connected across a sinusoidal supply voltage which has a constant output of 100 volts at all frequencies. Calculate, the resonant frequency, the quality factor and the bandwidth of the circuit, the circuit current at resonance and current magnification.

Example

Resonant Frequency, ƒ_r

Resonant

Inductive Reactance at Resonance, X_L

Quality factor, Q

Bandwidth, BW

The upper and lower -3dB frequency points, ƒ_H and ƒ_L

Cut-off

Circuit Current at Resonance, I_T

At resonance the dynamic impedance of the circuit is equal to R

Current Magnification, I_mag

Note that the current at resonance (the resistive current) is only 1.67 amps, while the current flowing around the LC tank circuit is larger at 2.45 amps. We can check this value by calculating the current flowing through the inductor (or capacitor) at resonance.

Parallel Resonance Tutorial Summary

We have seen that Parallel Resonance circuits are similar to series resonance circuits. Resonance occurs in a parallel RLC circuit when the total circuit current is "in-phase" with the supply voltage as the two reactive components cancel each other out. At resonance the admittance of the circuit is at its minimum and is equal to the conductance of the circuit. Also at resonance the current drawn from the supply is also at its minimum and is determined by the value of the parallel resistance.

The equation used to calculate the resonant frequency point is the same for the previous series circuit. However, while the use of either pure or impure components in the series RLC circuit does not affect the calculation of the resonance frequency, but in a parallel RLC circuit it does.

In this tutorial about parallel resonance, we have assumed that the components are purely inductive and purely capacitive with negligible resistance. However in reality the coil will contain some resistance. Then the equation for calculating the parallel resonant frequency of a circuit is therefore modified to account for the additional resistance.

Resonant Frequency using Impure Components

Parallel

Project Mini RS232 Data Switch Circuit Diagram

This is the Project of Mini RS232 Data Switch Circuit Diagram. Only simple materials and a little bit of skill are needed to build an RS232 switch. All that you need are two 9-way sub-D plugs with solder pins, a small piece of sheet aluminium, two sets of screw retainer posts, a 4-pole double-throw switch, a strain relief sleeve and a suitable plastic connector shell for a 25-way sub-D connector, with both in-line and right-angle cable entries (such as Conrad Electronics #711322). What is important is that the side cable entry together with its associated strain relief leaves enough room for the switch. If necessary, you may have to cut away a few square millimetres of the sidewall or a few ribs of the plastic shell.

Project image :

Mini

Mini RS232 Data Switch Image

The switch is operated via the in-line cable opening, as can be seen from the photo. A suitable switch with an overall length of 29 mm can be found in the Conrad catalogue under order number 708232. The only modification that must be made to the connector shell is to drill two holes for the retaining screws for the switch (M2.6 screws) at a spacing of 24 mm.

Mini RS232 Data Switch Circuit diagram :

Mini

Mini RS232 Data Switch Circuit Diagram

Connect the two sub-D connectors together using the piece of aluminium and the screw retainer posts. Then solder the cable to the connectors and the switch as indicated. The two connectors are wired somewhat differently. While the upper sub-D plug is connected 1:1 with the input cable (with the switch in the appropriate position), the DCD, DTR, DSR and RI pins of the lower connector are left open. This is because RTS and CTS are fully sufficient for handshaking, as long as DTR and DSR are connected to each other. The only leads that are switched are RXD, RTS, TSD and CTS. The ground potential is fed from the cable to both connectors. After everything has been properly soldered together, you can fit everything into the cable shell as shown.

On Demand WC Fan Using 555 Circuit Diagram

In most WCs with an extractor the fan is connected to the lighting circuit and is switched on and off either in sympathy with the light or with a short delay. Since toilets are sometimes used for washing the hands or just for a quick look in the mirror, it is not always necessary to change the air in the smallest room in the house. The following circuit automatically determines whether there really is any need to run the fan and reacts appropriately. No odour sensor is needed: we just employ a small contact that detects when and for how long the toilet seat lid is lifted.

On-Demand WC Fan circuit Using 555

On-Demand

If the seat lid is left up for at least some presettable minimum time t1, the fan is set running for another presettable time t2. In the example shown the contact is made using a small magnet on the lid and a reed switch mounted on the cistern. The rest is straightforward: IC2, the familiar 555, forms a timer whose period can be adjusted up to approximately 10 to 12 minutes using P2. This determines the fan running time. There are three CMOS NAND gates (type 4093) between the reed switch and the timer input which generate the required trigger signal. When the lid is in the ‘up’ position the reed switch is closed.

Capacitor C1 charges through P1 until it reaches the point where the output of IC1a switches from logic 1 to logic 0. The output of IC1b then goes to logic 1. The edge of the 0-1 transition, passed through the RC network formed by C2 and R2, results in the output of IC1c going to logic 0 for a second. This is taken to the trigger input on pin 2 of timer IC2, which in turn switches on the relay which causes the fan to run for the period of time determined by P2. The circuit is powered from a small transformer with a secondary winding delivering between approximately 8 V and 10 V. Do not forget to include a suitable fuse on the primary side.

The circuit around IC1b and IC1c ensures that the fan does not run continuously if the toilet seat lid is left up for an extended period. The time constant of P1 and C1 is set so that the fan does not run as a result of lavatorial transactions of a more minor nature, where the lid is opened and then closed shortly afterwards, before C1 has a chance to charge sufficiently to trigger the circuit.

Wednesday, October 29, 2014

Fog Lamp Sensor Circuit Diagram

Here are simple Fog Lamp Sensor Circuit Diagram. For several years now, a rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under foggy conditions.

Circuit diagram :

Fog Lamp Sensor Circuit Diagram

When this fog lamp is switched on, the fog lamp of the pulling vehicle must be switched off to avoid irritating reflections. For this purpose, a mechanical switch is now built into the 13-way female connector in order to switch off the fog lamp of the pulling vehicle and switch on the fog lamp of the trailer or caravan. For anyone who uses a 7-way connector, this switching can also be implemented electronically with the aid of the circuit illustrated here.

Here a type P521 optocoupler detects whether the fog lamp of the caravan or trailer is connected. If the fog lamp is switched on in the car, a current flows through the caravan fog lamp via diodes D1 and D2. This causes the LED in the optocoupler to light up, with the result that the phototransistor conducts and energises the relay via transistor T1. The relay switches off the fog lamp of the car.

For anyone who’s not all thumbs, this small circuit can easily be built on a small piece of perforated circuit board and then fitted somewhere close to the rear lamp fitting of the pulling vehicle.

Author :Harrie Dogge - Copyright : Elektor

Triangle Square Wave Oscillator Circuit Diagram

By making Rt variable it is possible to alter the operating frequency over a 100 to 1 range. Versatile triangle/squarenvave oscillator has a possible frequency range of 0 Hz to 100 kHz.

Simple Triangle Square Wave Oscillator Circuit Diagram

Simple

Tuesday, October 28, 2014

Two Colour LED Light Bar Circuit

This circuit is a circuit run on alternating two insignia.It uses the 2-color LED with a built-participating in 3-pin single.This preference look for away the glow of every LED until the base.It turns alternating to one more color.In in the least way to the moon on the moon essential end, afterward the LED end of the first LED.Circuit consists of, nand gate ic.Two 10 Counter circuits IC, and IC JK flip washout.

company of the circuit is not speaking into 3 sets.It is a solid of gesture generators, a set of parade and control.Set the signal generator is IC1a,and IC1b quantity 4011 is a signal generator.The R2, R3, C2 determine the frequency generated.The hint is fed to a set of impressions is the figure 4011 IC2 and IC3.The 10 counter circuits to output to the LED, and Is the same, but the effort should ensue performed individual by the side of region. Therefore, the show from pin 11 of IC 2 and tested pro D2 and D3,To pin 3 of IC4.The integrated circuit IC 4 is a JK flip slump is connected to a T flip flop.The signal input pin 3 and pin 1 is the output hint at.Which sends a signal to the Reset IC either obstruct working.IC4 on the anniversary, it want output the originally moment in time, happening contrast to pin1.IC3 progress to handiwork, IC2 stopped.

IC2 is controlled by signals from pin 1 of IC4, to IC1c.earlier to control IC2.The IC3 is connected to pins 1 through D1 to the control again.

Monday, October 27, 2014

TDA2030 bridge 35 watt power amplifier Diagram Circuit

A very simple 35 watt power amplifier electronic project can be designed using the TDA2030 power audio IC. The TDA2030A is a monolithic IC in Pentawatt package intended for use as low frequency class AB amplifier.
The TDA2030A provides high output current and has very low harmonic and cross-over distortion. TDA2030 ICs connected in bridge mode.
This circuit require few external electronics parts and supports a 8 ohms load . This 35 watt power amplifier require a very good filtered DC power supply , that will provide an output voltage of +/- 16 volts .

Using this circuit you can design a very simple and efficiency subwoofer amplifier with a maximum output power of 35 watt power .
The device incorporates a short circuit protection system comprising an arrangement for automatically limiting the dissipated power so as to keep the working point of the output transistors within their safe operating area. Also a conventional thermal shut-down system is also included .
However a heatsink must be used for the TDA2030 bridge circuit but for any reason, if the junction temperature increases up to 150oC, the thermal shut-down simply reduces the power dissipation and the current consumption.

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