PWM Motor Controller

PWM Motor Controller With Forward And Reverse is circuit controllers for DC motors controlled by PWM technique . The series PWM Motor Controller With Forward And Reverse It can control the DC motor rotation direction. Speed ​​control by PWM technique through MOSFETs Q1 IRF150. Then to play with the directional control relay which is controlled by Q10 using control signals in the form of logic 0 and 1. The series PWM Motor Controller With Forward And Reverse It requires 12 VDC supply voltage.

Circuit PWM Motor Controller With Forward And Reverse the above can be used to control large DC motor with maximum current consumption 10A.

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METAL DETECTOR CIRCUIT

Metal detector is very common devices for checking the person in shopping malls, hotels, cinema halls to ensure that person is not carrying any explosive metals or illegal things like guns, bombs etc. metal detectors can be created easily and the circuit is not that complex.

Block Diagram

The LC circuit is nothing but inductor and capacitor which is connecter in parallel. The LC circuit will trigger the proximity sensor if it detects any metal near to it. Proximity sensor will give glow the led, and also make the buzz with the help of the buzzer.

Main Components in Metal Detector Circuit

LC CIRCUIT : LC Circuit is a resonating circuit which will resonate when exact same frequency material comes near. The LC circuit consist of inductor and capacitor connected in parallel , when the capacitor is fully charged the charge of the capacitor will be given to the inductor, here inductor will have improve its magnetic field. After some time the capacitor will have no charge and current from the inductor will be given to the capacitor in a reverse polarity and capacitor will get charge and now the inductor magnetic field and current will become nil. Again charged capacitor will give current to the inductor to improve its magnetic field. Note inductor is a magnetic field storage device and capacitor is electric field storage device.

PROXIMTY SENSOR : The proximity sensor can detect the objects with out any physical interference. The proximity sensor will work same as infrared sensor, proximity also release a signal, it will not give output unless and until there is no change in the reflected back signal, If there is a change in signal it will detect and give the output accordingly. There are different proximity sensors for example to detect plastic material we can use capacitive type proximity and for metals we should use inductive type.

Circuit Diagram

Circuit Working

• When the LC circuit that is L1 and C1 has got any resonating frequency from any metal which is near to it, electric field will be created which will lead to induces current in the coil and changes in the signal flow through the coil.
• Variable resistor is used to change the proximity sensor value equal to the LC circuit, it is better to check the value when there is coil not near to the metal. When the metal is detected the LC circuit will have changed signal. The changed signal is given to the proximity detector (TDA 0161), which will detect the change in the signal and react accordingly. The output of the proximity sensor will be of 1mA when there is no metal detected and it will be around 10mA when coil is near to the metal
• When the output pin is high the resistor R3 will provide positive voltage to transistor Q1. Q1 will be turned on and led will glow and buzzer will give the buzz. Resistor r2 is used to limit the current flow.

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Digital to Analog Converter using Binary Weighted Resistors R 2R

The R-2R ladder DAC which is a binary-weighted DAC that uses a repeating cascaded structure of resistor values R and 2R. This improves the precision due to the relative ease of producing equal valued-matched resistors (or current sources). However, wide converters perform slowly due to increasingly large RC-constants for each added R-2R link. The D/A converter using binary-weighted resistors is shown in the figure below. In the circuit, the op-amp is connected in the inverting mode. The op-amp can also be connected in the non-inverting mode. The circuit diagram represents a 4-digit converter. Thus, the number of binary inputs is four.

Circuit Diagram

Fig. 1

We know that, a 4-bit converter will have 2⁴ = 16 combinations of output. Thus, a corresponding 16 outputs of analog will also be present for the binary inputs.

Four switches from b0 to b3 are available to simulate the binary inputs: in practice, a 4-bit binary counter such as a 7493 can also be used.

Working

The circuit is basically working as a current to voltage converter.

1. b0 is closed
It will be connected directly  to the +5V.
Thus, voltage across R = 5V
Current through R = 5V/10kohm = 0.5mA
Current through feedback resistor, Rf = 0.5mA (Since, Input bias current, IB is negligible)
Thus, output voltage = -(1kohm)*(0.5mA) = -0.5V

2. b1 is closed, b0 is open
R/2 will be connected to the positive supply of the +5V.
Current through R will become twice the value of current (1mA) to flow through Rf.
Thus, output voltage also doubles.

3. b0 and b1 are closed
Current through Rf = 1.5mA
Output voltage = -(1kohm)*(1.5mA) = -1.5V

Thus, according to the position (ON/OFF) of the switches (bo-b3), the corresponding “binary-weighted” currents will be obtained in the input resistor. The current through Rf will be the sum of these currents. This overall current is then converted to its proportional output voltage. Naturally, the output will be maximum if the switches (b0-b3) are closed,

V0 = -Rf *([b0/R][b1/(R/2)][b2/(R/4)][b3/(R/8)]) 

Where each of the inputs b3, b2, b1, and b0 may either be HIGH (+5V) or LOW (0V).

The graph with the analog outputs versus possible combinations of inputs is shown below.

Fig. 2

The output is a negative going staircase waveform with 15 steps of -).5V each. In practice, due to the variations in the logic HIGH voltage levels, all the steps will not have the same size. The value of the feedback resistor Rf changes the size of the steps. Thus, a desired size for a step can be obtained by connecting the appropriate feedback resistor. The only condition to look out for is that the maximum output voltage should not exceed the saturation levels of the op-amp. Metal-film resistors are more preferred for obtaining accurate outputs.

Disadvantages

If the number of inputs (>4) or combinations (>16) is more, the binary-weighted resistors may not be readily available. This is why; R and 2R method is more preferred as it requires only two sets of precision resistance values.

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LM390 Simple 2 Way intercom Circuit

This is a very simple two way intercom circuit based on a LM390 audio amplifier circuit . the intercom circuit is a stand-alone electronic communications system intended for limited or private dialogue. For this circuit you can use a 8 ohms speaker, one for each station and require a 6 volts dc power supply. Gain control can be done by capacitively coupling a resistor (or FET) from pin 6 to ground.

LM390 Simple 2-Way intercom Circuit

LM390 Pin out

The LM390 Power Audio Amplifier is optimized for 6V, 7.5V, 9V operation into low impedance loads. The gain is internally set at 20 to keep the external part count low, but the addition of an external resistor and capacitor between pins 2 and 6 wil increase the gain to any value up to 200. The inputs are ground referenced while the output is automatically biased to one half the supply voltage.

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Transistor Schmitt Trigger Oscillator

The Schmitt Trigger oscillator below employs 3 transistors, 6 resistors and a capacitor to generate a square waveform. Pulse waveforms can be generated with an additional diode and resistor (R6). Q1 and Q2 are connected with a common emitter resistor (R1) so that the conduction of one transistor causes the other to turn off. Q3 is controlled by Q2 and provides the squarewave output from the collector.

In operation, the timing capacitor charges and discharges through the feedback resistor (Rf) toward the output voltage. When the capacitor voltage rises above the base voltage at Q2, Q1 begins to conduct, causing Q2 and Q3 to turn off, and the output voltage to fall to 0. This in turn produces a lower voltage at the base of Q2 and causes the capacitor to begin discharging toward 0. When the capacitor voltages falls below the base voltage at Q2, Q1 will turn off causing Q2 and Q3 to turn on and the output to rise to near the supply voltage and the capacitor to begin charging and repeating the cycle. The switching levels are established by R2,R4 and R5. When the output is high, the voltage at the base of Q2 is determined by R4 in parallel with R5 and the combination in series with R2. When the output is low, the base voltage is set by R4 in parallel with R2 and the combination in series with R5. This assumes R3 is a small value compared to R2. The switching levels will be about 1/3 and 2/3 of the supply voltage if the three resistors are equal (R2,R4,R5).

There are many different combinations of resistor values that can be used. R3 should low enough to pull the output signal down as far as needed when the circuit is connected to a load. So if the load draws 1mA and the low voltage needed is 0.5 volts, R3 would be 0.5/.001 = 500 ohms (510 standard). When the output is high, Q3 will supply current to the load and also current through R3. If 10 mA is needed for the load and the supply voltage is 12, the transistor current will be 24 mA for R3 plus 10 mA to the load = 34 mA total. Assuming a minimum transistor gain of 20, the collector current for Q2 and base current for Q3 will be 34/20 = 1.7 mA. If the switching levels are 1/3 and 2/3 of the supply (12 volts) then the high level emitter voltage for Q1 and Q2 will be about 7 volts, so the emitter resistor (R1) will be 7/0.0017 = 3.9K standard. A lower value (1 or 2K) would also work and provide a little more base drive to Q3 than needed. The remaining resistors R2, R4, R5 can be about 10 times the value of R1, or something around 39K.

The combination of the capacitor and the feedback resistor (Rf) determines the frequency. If the switching levels are 1/3 and 2/3 of the supply, the half cycle time interval will be about 0.693*Rf*C which is similar to the 555 timer formula. The unit I assembled uses a 56K and 0.1 uF cap for a positive time interval of about 3.5 mS. An additional 22K resistor and diode were used in parallel with the 56K to reduce the negative time interval to about 1 mS.

In the diagram, T1 represents the time at which the capacitor voltage has fallen to the lower trigger potential (4 volts at the base of Q2) and caused Q1 to switch off and Q2 and Q3 to switch on. T2 represents the next event when the capacitor voltage has risen to 8 volts causing Q2 an Q3 to turn off and Q1 to conduct. T3 represents the same condition as T1 where the cycle begins to repeat. Now, if you look close on a scope, you will notice the duty cycle is not exactly 50% This is due to the small base current of Q1 which is supplied by the capacitor. As the capacitor charges, the E/B of Q1 is reverse biased and the base does not draw any current from the capacitor so the charge time is slightly longer than the discharge. This problem can be compensated for with an additional diode and resistor as shown (R6) with the diode turned around the other way. 

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Simple 2 1 Surround Speaker System Circuit Diagram

 "Simple 2.1 Surround Speaker System " . Here I have used  three TDA 2030 IC for making signal amplification . Here you need a sub filter extra ( Sub filter circuit diagram link showing below ) . This project  mostly used in computer  . Part list and applications are showing below.

Part List

Component No:	Value	Usage
All C1	100MF	Grounding
All C2	100nF	Grounding
All C3	100nF	Grounding
All C4	100MF	Grounding
All C5	100MF	Feedback
All C6	100MF	Audio Coupling
All C7	220nF	Noise Grounding
All R1	1K
All R2	10K ( Not 1K )
All R3	22K
All R4	22K (Not 1K )
All RV1	100K	Volume Controlling
All D1 To D2	IN4007	Potential Breaking
U1 To U6	TDA2030	Amplification

Applications* 2.1 Surround Amplifier

* 2.1 Home Theater

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Wireless Microphone simple

 

  Wireless Microphone simple Parts list:

* T1,T2,T3: 2N2222 transistor
* R1: 10k 5%
* R2: 33k lin.
* R3: 12k 5%
* R4: 5.6k 5%
* R5: 2.2k 5%
* R6,R8: 47k 5%
* R7: 470 ohms 5%
* R9: 180 ohms 5%
* C1,C2: 47nF
* C3: 1nF
* C4: 33pF
* C5: 5.6pF
* C6: 8.2pF
* C7: 10nf
* L1: 3mm in diameter with 5 turns 0.61 mm copper wire
* K1: SPDT toggle switch
* Other parts: 2 AA battery holder, Electret microphone, antenna wire

Wireless FM microphone is simple to body and it has a advantageous transmitting ambit (over 300 meters in the accessible air). Despite its baby basic calculation and a 3V operating voltage it will calmly access over three floors of an accommodation building. It may be acquainted anywhere in the FM bandage (87-108MHz) and its transmissions can be best up on any accepted FM receiver.

The braid (L1) should be about 3mm in bore with 5 turns 0.61 mm chestnut wire. You can alter the Tx abundance by artlessly adjusting the agreement of the coils. The antenna should be a bisected or division amicableness continued (for 100 MHz 150 cm or 75 cm).

Circuit description:The audio addition date (T1) is a accepted accepted emitter amplifier. The 47nF capacitor isolates the microphone from the abject voltage of the transistor and alone allows AC signals to pass.

The LC catchbasin ambit is complete with T2, the acknowledgment capacitor C5 and the alongside LC ambit L1, C4. The coupling capacitor(C6) directs the arresting to the RF amplifier (T3).

Circuit calibration: Place the transmitter about 10 anxiety from a FM radio. Set the radio to about about 89 – 90 MHz. Spread the ambagious of the L1 braid afar to tune to the adapted frequency.

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