Showing posts with label line. Show all posts
Showing posts with label line. Show all posts

Wednesday, 29 March 2017

Telephone line Based Audio Muting and Light On Circuit


Telephone line Based Audio Muting and Light-On Circuit. Very often when enjoying music or watching TV at high audio level, we may not be able to hear a telephone ring and thus miss an important incoming phone call. To overcome this situation, the circuit presented here can be used. The circuit would automatically light a bulb on arrival of a telephone ring and simultaneously mute the music system/TV audio for the duration the telephone handset is off-hook. Lighting of the bulb would not only indicate an incoming call but also help in locating the telephone during darkness.
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Circuit diagram :
Telephone line Based Audio Muting and Light-On Circuit Diagram Telephone line Based Audio Muting and Light-On Circuit Diagram 
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On arrival of a ring, or when the handset is off-hook, the inbuilt transistor of IC1 (opto-coupler) conducts and capacitor C1 gets charged and, in turn, transistor T1 gets forward biased. As a result, transistor T1 conducts, causing energisation of relays RL1, RL2, and RL3. Diode D1 connected in antiparallel to inbuilt diode of IC1, in shunt with resistor R1, provides an easy path for AC current and helps in limiting the voltage across inbuilt diode to a safe value during the ringing. (The RMS value of ring voltage lies between 70 and 90 volts RMS.) Capacitor C1 maintains necessary voltage for continuously forward biasing  transistor T1 so that the relays are not energised during the negative half cycles and off-period of ring signal. Once the handset is picked up, the relays will still remain energised because of low impedance DC path available (via cradle switch and handset) for the in-built diode of IC1. 

After completion of call when handset is placed back on its cradle, the low-impedance path through handset is no more available and thus relays RL1 through RL3 are deactivated. As shown in the figure, the energised relay RL1 switches on the light, while energisation of relay RL2 causes the path of TV speaker lead to be opened. (For dual-speaker TV, replace relay RL2 with a DPDT relay of 6V, 200 ohm.) Similarly, energisation of DPDT relay RL3 opens the leads going to the speakers and thus mutes both audio speakers. Use ‘NC’ contacts of relay RL3 in series with speakers of music system and ‘NC’ contacts of RL2 in series with TV speaker. Use  ‘NO’ con-tact of relay RL1 in series with a bulb to get the visual indication. 


Author : Dhurjati Sinha - Copyright : EFYmag

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Thursday, 2 March 2017

Automatic Night Light Feeds Directly From the AC Line


There are many approaches to the problem of activating a light when it becomes dark, and a recent Design Idea covers this topic (Reference 1). Some approaches require a dc power supply and an electromechanical relay, but a better approach involves feeding the device directly from the ac line, minimizing the number of components 

(Figure 1).


Figure 1. The photoresistor activates the TRIAC and the load when darkness falls.

The heart of the device is a light-sensitive cadmium-sulphide resistor, PR, with a resistance of approximately 200 kΩ in the dark and decreasing to a few kilohms in the light. PR and capacitor C1 form an ac-voltage divider. In daylight, the voltage across PR is too low to generate the required gate-trigger current to turn on bidirectional ac switch Q1, thus keeping the load – usually a lamp – off. When it becomes dark, PR’s resistance rises, resulting in an increase in the TRIAC’s gate current that triggers the TRIAC and lights the lamp.

The circuit uses inexpensive, off-the-shelf components, including the VT90N1 photoresistor; a 0.1-μF, 275V capacitor; and an L2004F61 TRIAC with a load current of 4A rms, a peak blocking voltage of 200V, and a gate-trigger current of 5 mA. The exact specifications of these components are not critical; you could use others instead.

Editor’s note:
Attributes worth mentioning include the fact that the capacitor introduces a phase shift, which places the peak of the gate voltage close to the zero crossing of the load’s sine wave for optimum turn-on timing. Another benefit is thermal hysteresis, which occurs due to the reduction of the required triggering voltage and current as the TRIAC warms up after the initial turn-on. 

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Friday, 9 December 2016

Creating a Line Follower Robot with AVR


The article "Creating a Line Follower Robot with AVR [Censorship]" is a continuation of Line Follower Robot article with a new AVR ATMega8535 samapai phase Line Follower Robot block diagram. In the article "Creating a Line Follower Robot with AVR Part 1 [Sensor]" This is a review of the sensor used on Line Follower Robot, and the components used. Sensors, can be analogous to the 'eye' of a robot that serves to 'read' the black line of the track robot or vice versa. So that the robot is able to know when he will turn right, when he turned left and when he stopped. Sensors used are usually photo reflector, LDR (Light Dependent Resistor), Photo Diodes and Photo Transistor - mounted on the front two or more below the line follower robot.There also are using the camera as a sensor (or image sensor) to a higher-resolution readout line, making more accurate robot motion.
Line Follower Robot Sensor circuit with AVR ATMega

Robot Sensor circuit with AVR ATMega
Robot Sensor circuit with AVR ATMega  Circuit

The working principle of the sensor is simple, when the transmitter (infrared) emitting light onto a white field, the light will be reflected back to the receiver by the white areas and vice versa. This gives the change in the voltage level at the receiver output, but it usually changes the voltage can not be accepted as a TTL logic level. To be able to read by the microcontroller, the sensor voltage should be adjusted to TTL voltage level that is 0-1 volts for logic 0 and 3-5 volts for logic 1. This can be done by installing the operational amplifier is used as a comparator as shown in the picture above.
Op Amp is used as a comparator LM324 IC, because IC is able to work at VCC 5 volt range and there are 4 in 1 Op Amp IC corresponding to the number of sensors are used. The sensitivity of this sensor can be set through R9 which controls the comparator reference point.
Maximizing Sensor Line Follower Robot

Line follower robot sensors can be made with a combination between LED and photo diode. Line follower robot sensor configuration is good to be able to read the track with a hard and fast. To make the robot sensor is firm and fast can not merely rely on the ability of photo diodes and LED configurations only. As an alternative to maximize the performance of line follower robot sensors can be added to the voltage comparator with Op-Amp. Sensor circuit line follower robot equipped with a voltage comparator that is ready to be connected to a microcontroller or PIC can use the following series of robot sensor.
Line Follower Robot Sensor circuit with voltage comparator

voltage comparator
Voltage comparator Circuit


Function of the voltage comparator circuit line follower robot sensor above is:

  1. Reinforce the logic level sensor output
  2. Amplifies the sensor output signal
  3. Control and determine the reference point sensor
  4. Reinforce the logic level sensor output is intended to avoid the floating logic conditions, with the goal of getting the process of transition logic (high) to a logic low (low) or vice versa in a fast sensors. So as to enhance the response to the sensor readings track work.

Sensor output voltage levels should be read as well by the TTL logic processor. If the robot sensors rely on photo diodes and LED configurations, then during the reading process is fast track, then the resulting signal has a logic low loevel differences and can not be read as a TTL logic. Therefore, robot sensor voltage levels are still weak need to be corroborated by a voltage comparator, so the TTL logic level differences firm with a strong signal.

The purpose of controlling and determining the sensor reference point is, we can determine the position of the robot sensor readings can be considered as a logic high or logic low.  Choosing process reference value line follower robot sensor readings can be done by adjusting VR1 10kOhm the series "Line Follower Robot Sensor Voltage Comparator With" above.


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Thursday, 24 November 2016

Off Hook Telephone Line Indicator


The circuit is designed to connect in parallel with the telephone line, to monitor and detect if any telephone in the same line is busy, with the indication of the LED and which is self-powered so that it does not provide any load on a telephone line.

Light Emitting Diode (LED) – a semiconductor diode that is commonly a source of light when electric current pass through it Metal Oxide Semiconductor Field Effect Transistor (MOSFET) – a device utilized for switching and amplification of signals BS108 – a 250 mA and 200 Volts small signal MOSFET designed for high voltage, high speed switching applications such as relay drivers, CMOS logic, line drivers, TTL or microprocessor to high voltage interface and high voltage display drivers Diode Bridge – also known as bridge rectifier which has four diodes arranged in a bridge configuration where the output voltage has the same polarity with either polarity of the input voltage 1N4007 – a general purpose plastic rectifier with reverse voltage from 50 Volts to 1000 Volts and forward current of 1.0 Ampere

When none of the telephone lines is in use or on-hook, the voltage across the line is around 48V. In this state, the gate of transistor Q2 is shorted to its source during the conduction of Q1. This causes the LED to be disabled while Q2 is turned OFF. When one telephone extension along the telephone line changes to off-hook or in use condition, a voltage drop from 5V to 15V is detected. This will in turn cause Q1 to turn OFF because of the very low voltage across the gate of Q1 which is equal to 6% of the line voltage. Transistor Q2 then will be biased at around half of the line voltage.

Off-Hook Telephone Line Indicator Circuit Diagram


Off-Hook Telephone Line Indicator

 The sudden line drop of voltage triggers Q2 to light up the LED that will give a sign that the line is in use. Using the same line, the circuit is unseen with other telephone devices. A current-limiting resistor is used to maintain the low current of LED1 while the local telephone line parameters dictate the variation of other component’s values. The power of the circuit is provided by the telephone line. Other voltage protection may be used with some reliable design in addition to the current-limiting resistor. This is important to avoid any grounding effects from conducting surfaces within the circuit.

To ensure that transistor Q1 is fully biased while the line is free or not in use where LED1 is OFF, a 500K ohm MOSFET trimmer is used for the desired adjustment. A MOSFET is a three-terminal semiconductor component with a conducting channel in its output and a built-in capacitor at its input. To increase the values of any of the two resistors connected to the gate of Q2, a 200V MOSFET can be used in the place of Q2 if BS108 is not available. However, plain transistors like the bipolar junction can be used but with lower values to allow greater currents to pass through the line that is not in use. The bridge rectifier comprising of four 1N4007 diodes are performing the conversion of AC input into DC output.

MOSFET can function in two ways. The first is known as depletion mode wherein the channel shows its maximum conductance in the absence of a voltage on the gate. The second way that the MOSFET can function is known as enhancement mode wherein the device is not conducting even in the absence of a voltage on the gate because no channel is produced. A channel is being created with the application of a voltage to the gate. To generate better conductivity, greater voltage to the gate is required.

MOSFET drivers are applied in electronic motor control for different types of motors. Also, they are specifically used with long duty cycles, high operating frequency above 200 KHZ, lower output power, and wide load variations. The largest application of MOSFETs are the switched mode power supplies and in battery charging applications. In transducer drivers for high power devices such as light bulbs and motors, large current output with a small input is provided by MOSFETs. Since they are more non-linear than BJTs while producing less distortion, they can be utilized with Hi-Fi amplifiers. In constructing integrated circuits, MOSFETs are very useful since they can be made very compact. Although MOSFETs can get damaged by static electricity at higher voltages, they still provide several advantages as compared to other transistors which include faster switching time than BJT, lower losses than BJT, very small switching current, and least effects of temperature.

This telephone line indicator does not only tell when a telephone line is in use if a plurality of telephones are all setup to the same telephone line, but also prevents interruptions during personal calls. Additionally, it can also help to prevent costly and unwanted disruption of modem calls and fax, it alerts a person when a call is done and the phone is free to use, and the LED light indicates the line is in use.

To avoid any injury, it is a prerequisite to take extra precautionary measures when connecting any circuit to the telephone lines, which can produce life-threatening voltages during normal operation. During a lightning storm, it is better to keep distance from telephone lines.. Legal aspects are imposed in different countries for connecting things to telephone lines. The circuit should be better built with a plug-in cord for easy removal in case of fault occurrences. Otherwise, it would be best to consult a licensed telephone operator.

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Sunday, 20 November 2016

White line Flower Circuit Diagram


This circuit will be used for a toy automotive to follow a white line. The motor is either a 3v sort with gearing to steer the automotive or a rotary actuator or a servo motor.When equal lightweight is detected by the photo resistors the voltage on the base of the primary transistor are mid rail and the circuit is adjusted via the 2k2 pot that the motor doesn't receive any voltage. When one in all the LDR's receives a lot of (or less) lightweight, the motor is activated. and also the same thing happens when the other LDR receives less or more light.


White line Flower Circuit Diagram

White line Flower Circuit Diagram


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Wednesday, 14 September 2016

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