Showing posts with label for. Show all posts
Showing posts with label for. Show all posts

Friday, October 4, 2013

Watch Dog For Telephones

Most of the telephone security devices available in market are simple but quite expensive. These devices provide blinking or beeping type line-tap/misuse indications. Quite often they do not offer guaranteed protection against unauthorized operation. A very simple and unique circuit of a telephone watch-dog to safeguard subscriber telephone lines against any fraud is described here. This little circuit keeps continuous watch over the telephone lines and sounds an alarm in case of any misuse. In addition it transmits a loud tone through the telephone lines to prevent further misuse. When switch S1 is turned on, the normal (on-hook) telephone line voltage at the output of bridge-rectifier diodes D1 to D4 is approximately 48 volts, which being well above the break-down voltage of zener diode D5, the diode conducts.

Watch-Dog For Telephones  Circuit DiagramAs a result transistor T2 gets forward biased. This effectively grounds the base of transistor T1 which is thus cut off and the remaining circuit does not get any power supply. In this state, only a small (negligible) current is taken by the circuit, which will not affect the telephone line condition. However, when handset of any telephone connected to the telephone lines is lifted (off-hook), line voltage suddenly drops to about 10 volts. As a result, transistor T2 is switched off and transistor T1 gets forward biased via resistor R1. Now, the astable multivibrator built around timer IC1 starts oscillating and the speaker starts sounding.

Output of the astable multivibrator is also connected to the base of transistor T1 through capacitor C5. As a result, only a loud (and irritating) tone is heard in the ear-piece of the unauthorized telephone instrument. This circuit can be constructed on a veroboard using easily available low-cost components and it can be connected to any telephone line without the fear of malfunctioning. No extra power supply is required as it draws power from the telephone line for operation.

Note:
  • Please disconnect the gadget when you are yourself using the telephone as it cannot distinguish between authorized and unauthorized operation.
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Friday, July 12, 2013

LED Driver for Automotive Applications using AT9933

Using the AT9933 variable frequency PWM controller IC, can be designed a very simple and high efficiency LED lamp driver using a low-noise boost-buck topology.The AT9933 uses patent pending hysteretic current-mode control to regulate both the input and the output currents.

This enables superior input surge immunity without the necessity for complex loop compensation. Input current control enables current limiting during startup, input under-voltage and output overload conditions. The AT9933 provides a low-frequency PWM dimming input that can accept an external control signal with a duty cycle of 0 - 100% and a high dimming ratio.


LED Driver for Automotive Applications using AT9933

This LED driver electronic project , require an input voltage range between 9 and 16 volts and will provide an 28 volt output at a maximum output current of 350 mA .The switching frequency of this electronic project is 350kHz . Values for components are : L1 = 82μH,L2 = 150μH,C1 = 0.22μF , RCS2 = 1.65Ω 1/4W, RREF2 = 10kΩ 1/8W, RS2A = 100Ω 1/8W,RS2B = 5.23kΩ 1/8W, RCS1 = 0.228Ω 1W, RREF1 = 10kΩ 1/8W,RS1 = 4.42kΩ 1/8W .
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Thursday, July 11, 2013

Infrared Remote Control for Operates on 115 Volts AC

This circuit will allow you to turn on any piece of equipment that operates on 115 volts ac. The receiver circuit is based on the Radio Shack infrared receiver module (MOD), part number 276-137. It is also available from some of the other sources listed on my Links page. The MOD accepts a 40khz IR signal that is modulated at 4 khz.

Circuit Diagram

When a signal is received the MOD will go low. The sensitivity of the MOD is set by different values for R1 and C1. The values for R1 may need to be as high as 10,000 ohms and for C1 40uf. This will prevent the unit from turning on under normal lighting conditions. You will need to experiment with the values that work best for you. The output of the 4013 chip a flip flop toggles on and off with the reception of a IR pulse. The output of the 4013 turns on the MOC optical coupler which in turn switches on the triac and supplies power to the AC load.
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Saturday, July 6, 2013

Step Up Converter For 20 LEDs

The circuit described here is a step-up converter to drive 20 LEDs, designed to be used as a home-made ceiling night light for a child’s bedroom. This kind of night light generally consists of a chain of Christmas tree lights with 20 bulbs each consuming 1 W, for a total power of 20 W. Here, in the interests of saving power and extending operating life, we update the idea with this simple circuit using LEDs. 

Power can be obtained from an unregulated 12 V mains adaptor, as long as it can deliver at least about 330 mA.  The circuit uses a low-cost current-mode controller type UCC3800N, reconfigured into voltage mode to create a step-up converter with simple compensation. By changing the external components the circuit can easily be modified for other applications. To use a current-mode controller as a voltage-mode controller it is necessary to couple a sawtooth ramp (rising from 0 V to 0.9 V) to the CS (current sense) pin, since this pin is also an input to the internal PWM comparator.

Circuit diagram :
Step-up Converter For 20 LEDs -Circuit-Diagram
Step-up Converter For 20 LEDs Circuit Diagram

The required ramp is present on the RC pin of the IC and is reduced to the correct voltage range by the voltage divider formed by R3 and R2. The RC network formed by R4 and C6 is dimensioned to set the switching frequency at approximately 525 kHz. The comparator compares the ramp with the divided-down version of the output voltage produced by the potential divider formed by R6 and R7. Trimmer P1 allows the output voltage to be adjusted. This enables the current through the LEDs to be set to a suitable value for the devices used. The UCC3800N starts up with an input voltage of 7.2 V and switches off again if the input voltage falls below 6.9 V. The circuit is designed so that output voltages of between 20 V and 60 V can be set using P1.

This should be adequate for most cases, since the minimum and maximum specified forward voltages for white LEDs are generally between 3 V and 4.5 V. For the two parallel chains of ten LEDs in series shown here a voltage of between 30 V and 45 V will be required. The power components D1, T1 and L1 are considerably over specified here, since the circuit was originally designed for a different application that required higher power. To adjust the circuit, the potentiometer should first be set to maximum resistance and a multimeter set to a 200 mA DC current range should be inserted in series with the output to the LEDs. Power can now be applied and P1 gradually turned until a constant current of 40mA flows. The step-up converter is now adjusted correctly and ready for use.


www.ecircuitslab.com
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Friday, July 5, 2013

Pump Controller For Solar Hot Water System

This circuit optimises the operation of a solar hot water system. When the water in the solar collector is hotter than the storage tank, the pump runs. The circuit comprises two LM335Z temperature sensors, a comparator and Mosfet. Sensor 1 connects to the solar collector panel while Sensor 2 connects to the hot water panel. Each sensor includes a trimpot to allow adjustment of the output level. In practice, VR1 and VR2 are adjusted so that both Sensor 1 and Sensor 2 have the same output voltage when they are at the same temperature. The Sensor outputs are monitored using comparator IC1.

When Sensor 1 produces a higher voltage than Sensor 2, which means that sensor 1 is at a higher temperature, pin 1 of IC1 goes high and drives the gate of Mosfet Q1. This in turn drives the pump motor. IC1 includes hysteresis so that the output does not oscillate when both sensors are producing a similar voltage. Hysteresis comprises the 1MO feedback resistor between output pin 1 and non-inverting input pin 3 and the input 1kO resistor. This provides a nominal 12mV hysteresis so that voltage at Sensor 1 or Sensor 2 must differ by 12mV for changes in the comparator output to occur.

Circuit diagram:
pump-controller-for-solar-hot water system
Pump Controller For Solar Hot Water System

Since the outputs of Sensor 1 and Sensor 2 change by about 10mV/°C, we could say that there is a degree of hysteresis in the comparator. Note that IC1 is a dual comparator with the second unit unused. Its inputs are tied to ground and pin 2 of IC1 respectively. This sets the pin 7 output high. Since the output is an open collector, it will be at a high impedance. Mosfet Q1 is rated at 60A and 60V and is suitable for driving inductive loads due to its avalanche suppression capability. This clamps any inductively induced voltages exceeding the voltage rating of the Mosfet.

The sensors are adjusted initially with both measuring the same temperature. This can be done at room temperature; adjust the trimpots so that the voltage between ground and the positive terminal reads the same for both sensors. If you wish, the sensors can be set to 10mV/°C change with the output referred to the Kelvin scale which is 273K at 0°C. So at 25°C, the sensor output should be set to (273 + 25 = 298) x 10mV or 2.98V.

Note:
The sensors will produce incorrect outputs if their leads are exposed to moisture and they should be protected with some neutral cure silicone sealant. The sensors can be mounted by clamping them directly to the outside surface of the solar collector and on an uninsulated section of the storage tank. The thermostat housing is usually a good position on the storage tank.
 
 
 
 
 
Source by : Streampowers
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Tuesday, May 14, 2013

AUTO fast battery charger for cars

This circuit is a fast and auto car charger circuit.By using this one you can charge your lead acid battery easily.After charging the battery this circuit will cut off the power to your battery. so this is very useful circuit for you.# use IC 7805 as power supply for this circuit
# LM311 control test volt battery.
# Use PCB To build your circuit.
# Be careful when you deal with 230v
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Monday, May 13, 2013

Brightness controller for low power lamps

This is a circuit which can control the brightness.This circuit base on NE555 IC.This circuit can be used to control the speed of DC motors.


Notes.

* The switch S1 can be SPST ON/OFF switch.
* The lamp L1 can be a 6V / 200 mA lamp.
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Monday, April 1, 2013

Radio Control for toy car

Radio Control for toy car
Play toy cars controlled by radio signals is an interesting game. The much-loved toy cars children, plus a simple circuit would be ideal for toy cars. This series of families use traditional digital CMOS IC which requires a very small electric current, so it does not impose on the performance of the original toy cars.
In this system, radio signals emitted not continuously but only generated when the controller sends a command left / right or forward / backward, and even then only a radio frequency of an intermittent, so it is sending pulses of radio wave frequency.
Number of pulses sent represents a command is sent, the command GO is represented by 8 pulses, represented by 16 pulses LEFT, RIGHT DOWN 32 pulses and 64 pulses. Command sent to a combination of two orders once gus, which is a combination of command forward / backward and right / left, for example, could be sent forward command and left once gus, in this case the number of pulses sent is 24, which is the sum of the forward command command as much as 8 pulses and left as many as 16 pulses.
Once a command is sent, the system stops sending commands in a certain time lag, the lag time it takes the receiver circuit will have sufficient time to execute properly. Frequency pulses were visible on the right side of Figure 1.

How it works The transmitter
Radio signals generated by the oscillator circuit formed by transistors Q1 9016, the working frequency of the oscillator is determined by the crystal Y1 is worth 27.145 MHz. A very critical part of this oscillator circuit is T1, L1 and L2, which specifically dealt with separately at the end of this article.
Work of the oscillator is controlled by a NOR gate U2D 14001, while the output gate (pin 3) is worth 1 , the oscillator will work and transmit radio frequency 27.145 MHz, and at the output U2D value 0 the oscillator will stop working.
U2D NOR gate receives the clock signal from the NOR gates U2B. NOR gate CMOS type with the help of resistors R4 and R5 and capacitor C8 to form a low frequency oscillator circuit to control the clock shaper of existing digital circuits. Working from the clock generator is controlled via the input leg 6, the circuit will generate the input clock that is berlevel 0 .
NOR gate U2A and U2C form a latch circuit (RS Flip Flop), due to the influence of resistor R2 and capacitor C11 which is fed to pin 9 on U2C, when the circuit gets power supply output U2C must be 1 and U2A output (pin 3) to 0 . This situation resulted EUIS clock generator generating a clock U2B work and release the reset state of the enumerator 14 024 IC (U1), so that the U1 start chopping and 27.145 MHz oscillator circuit to send pulses of the clock generator frequency during work.
At the start chopping, all the output IC 14 024 enumerators in kedaan 0 , after chopping the 8 pulse output Q4 (pin 6) will be 1, after chopping 16 Q5 pulse output (pin 5) to 1 , after chopping 32 Q6 output pulse (pin 4) to 1 , after 64 counts pulses output Q7 (pin 3) to 1.
Outputs are used to control the voltage above 9 feet U2C through diode D1 and D2, as long as it remains one of the output value 0 then the plant U2B clock still works, it will continue until dankatode D2 D1 cathode to 1 so that the foot 9 U2C a 1 as well. This situation will lead to 3 feet U2A output to 1 , which stops the clock generator and reset U2B enumerator 14 024 danberhenti is sending pulses of frequency 27 145 MHz.
To generate the lag time for the receiver circuits have enough time to perform the command, used a series of 9014 Q2, the resistor R7 and capacitor C10. The magnitude of the delay time is determined by the value of R7 and C10. The switch to send the command forward / backward and to send the command left / right are two separate switches. Each switch has three positions, the center position means that the scalar does not send commands.
How It Works Recipients
Figure 2 is a recipient of a series of paired images dimobil toy, serves to receive signals from the transmitter to control the motor cars, so cars can move forward / backward and left / right. Transistor Q1 with the help of resistors; capacitors and T1 form as a series of 27.145 MHz radio signal receiver. T1 in series with a T1 is exactly the same used in the transmitter circuit, how to make it are discussed below.
Transistor Q2 perlangkapannya formed following a series of pulses to change the radio frequency received from the transmitter into the box pulses that can be accepted as a digital signal by the CMOS IC. Digital signal will be received as the clock had to be chopped by enumerator 14 024 IC (U2). Output of 14 024 would correspond to the number of pulses sent by the transmitter, forward command and left (which is used as an example in the discussion of the transmitter) is the pulse number of 24, the enumeration of these pulses resulted in 14 024 to be output Q4 = 1 , Q5 = 1, Q6 = 0 and Q7 = 0.
The received digital signal other than U2 used as counter clock IC 14 024 discussed above, is also used to move the 3 pieces of the time delay circuit to generate pulses which controls the sequence of work.
The first control pulse will appear after submission frequency pulse stopped because the lag time between sending the code, this pulse count function to record the results of 14 024 to 14 042 U3 (D Flip Flop), so that the final condition of 14 024 will be retained to control the motor. After the results were recorded for 14 024 14 042, 14 042 counter is reset by the second pulse, so that after the lag time counter counts up starting from 14 042 to 0 again.
Circuit formed by transistors Q3, Q4, Q7, Q8, Q9 and Q10 H Bridge is named as a series, this series is very powerful to drive the DC motor. With this circuit the DC motor can be rotated to the right-to-left or stop motion. The main requirement is the use of this circuit Q7 and the base voltage of Q10 base voltage must be opposed, for example, the base Q7 = 1 and the base of Q10 = 0 motor rotates to the left, the base of Q7 = 0 and the base of Q10 = 1 motor will turning to the right, the base Q7 = 0 and Q10 base = 0 motor stop motion, but should not be happening base Q7 = 1 and the base Q10 = 1.
Similarly, Q5, Q6, Q11, Q12, Q13 and Q14 form an H Bridge. H Bridge to the left in Figure 2 is used to control a motor that regulates the movement of cars left / right, while the H Bridge to the right is used to control a motor that regulates the movement forward / backward cars.
The relationship between outpur enumerator 14 042 and input D Flip Flop 14 024 is arranged such that the signal is fed to each of the H Bridge can not be all 1 simultaneously.


Manufacture of transformer TX and RX
Transformer T1 in the series transmitter and receiver, is the same stuff, and have made ​​themselves. Transformer was built using a plastic transformer Koker (spare part radio) that has a step that appears 5 lines that can be filled with coils of wire, as shown in the photograph. Wearing this Koker facilitate wire transformer windings. Otherwise it could be similar Koker, just the usual wear. Koker is a small transformer and feritnya also small (3 mm) as that used to be used for the assembly of CB 27 MHz radio.
Can wear a wire to wire the transformer in the unloading of Koker, carefully open coil of wire that already exist in the Koker because the wire is quite smooth and quite easy to break.
Step 1: rolls of wire which is numbered 5 feet to 4 feet in the direction of h (CW) for 3 rolls right on level 1 (pathway level above the bottom line)
Step 2: Roll the wire from 1 foot to 2 feet in a clockwise direction as much as 4 rolls right on level 2.
Step 3: Continue the roll (from step 2) in a clockwise direction as much as three quarter roll to 3 feet on three levels. (Can be determined exactly a quarter of the roll, because it has a track kokernya split into 4).
Manufacture of coil L1
Roll of copper wire diameter from 0.3 to 0.5 mm by 10 quarter rolls on Koker diameter of about 4 mm (which will be released) is also in a clockwise direction.
Manufacture of coil L2
Roll of copper wire 0.1 mm diameter by 50 rolls in plastic Koker without ferrite diameter of about 3.5 - 4 mm (look for the plastic material from scrap) is also in a clockwise direction. Long section on liputi rolls along the 5 mm.
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Saturday, March 30, 2013

Test Beeper For Your Stereo

The test beeper generates a sinusoidal signal with a frequency of 1,000 Hz, a common test  frequency for audio amplifiers.  It consists of a classical Wien- Bridge oscillator (also known as  a Wien-Robinson oscillator). The network that determines the  frequency consists here of a series connection of a resistor and  capacitor (R1/C1) and a parallel connection (R2/C2), where  the values of the resistors and  capacitors  are  equal  to  each  other. This network behaves, at  the oscillator frequency (1 kHz  in this case), as two pure resistors. The opamp (IC1) ensures  that the attenuation of the net- work  (3  times)  is  compensated  for.  In  principle  a  gain  of  3 times should have been sufficient to sustain the oscillation,  but  that  is  in  theory.  Because  of tolerances in the values, the  amplification needs to be (automatically) adjusted.

Circuit diagram:
Test Beeper For Your Stereo circuit-Diagram
Test Beeper For Your Stereo circuit Diagram

Instead of an intelligent amplitude  controller  we  chose  for  a  somewhat simpler solution. With  P1, R3 and R4 you can adjust  the gain to the point that oscillation takes place. The range of P1 (±10%) is large enough the cover the tolerance range. To sustain  the oscillation, a gain of slightly  more than 3 times is required,  which  would,  however,  cause  the amplifier to clip (the ‘round-trip’ signal becomes increasingly  larger, after all). To prevent this  from happening, a resistor in se-ries with two anti-parallel diodes  (D1 and D2) are connected in  parallel  with  the  feedback  (P1  and R3). If the voltage increases to the point that the threshold  voltage of the diodes is exceed-ed, then these will slowly start to  conduct.

The consequence of this  is that the total resistance of the  feedback  is  reduced  and  with  that  also  the  amplitude  of  the  signal. So D1 and D2 provide a  stabilising function. The distortion of this simple oscillator, after adjustment of P1 and  an output voltage of 100 mV (P2  to  maximum)  is  around  0,1%.  You can adjust the amplitude of  the output signal with P2 as required for the application. The  circuit is powered from a 9-V battery. Because of the low current  consumption  of  only  2 mA  the  circuit will provide many hours  of service.
 
 
http://streampowers.blogspot.com/2012/05/test-beeper-for-your-stereo.html 
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