The figure shows the block diagram of the complete communication system, which can be divided into three main sections; namely a master unit, remote unit and signal transmission via free space optics. The remote unit is used to control the master unit. The operation hierarchy is as follows:
1) For Remote Module.
The DTMF keypad will provide control signal to the DTMF encoder.
The DTMF encoder generates the tone frequency signal.
The IR transmitter converts the above into a light signal.
two) Free Space Optics
IR signal generated by IR transmitter to master unit through free space
The IR receiver reads the light signal and converts it into the tone frequency signal.
DTMF to BCD decoder converts the above signal into BCD
The demultiplexer provides control signal for the required switching.
Project block diagram
Block Diagram Overview:
DTMF Keyboard Input:
The. The unit provides the input for DTMF dual sine wave generation.
B. By pressing a button, the 2 sine wave frequencies are fetched from the DTMF encoder.
DTMF Encoder:
The. The 2 sine wave signals are combined and a dual tone signal unique to the specific key is generated and made available for later use.
B. The IC used in this is the DTMF Generator IC named UM912141B.
Optical Transmitter:
The. In optical transmitter, IR transmission is used.
B. The IR signal is generated by the IR transmitter in the form of tone.
w. Then the signal is converted into light form and then transmitted.
FSO (Free Space Optics):
The. The FSO is the signal transmission medium.
B. FSO is line-of-sight technology that uses LASER and provides optical bandwidth connection, which can send and receive voice, video and data information in invisible light beam.
w. FSO technology requires light that can be focused using LEDs or LASER
Optical receiver (IR photo diode):
The. The optical receiver receives light from space optics.
B. Then the light is converted into the tone frequency signal.
DTMF decoder for BCD and DEMUX:
The. DTMF or tone dialing is commonly used
B. DTMF is a tone composed of 2 sine waves of a certain frequency.
w. DTMF standards specify 50 ms tone and 50 ms space duration.
d. HT9170B is a complete DTMF receiver that integrates ICs.
Device Control Relays:
The. To control the device, the SUGAR CUBE relay is used.
B. It consumes relatively less power compared to other relays.
w. It is compact in size and easily available for various current relays.
Sensors:
The. It detects appropriate changes and activates the corresponding sugar cube relay (from sensors) and performs switching.
Why this project?
Why this project?
Cost Effectiveness:
It is necessary to install a large number of wires for all applications requiring control and measurement purposes. This method will provide a cost-effective means of achieving all of this with a single thread. Transmitting different frequency signals through a single wire and then using them for different applications provides single-wire control.
Lossless System:
Transmitting the control signal through optical fiber in the form of infrared signal will provide a lossless system. Since the loss in the optical fiber is negligible, signal weakening due to losses does not occur. Furthermore, the transmitted signal is not affected by stray signals because the fiber does not allow them to enter inside.
Central Control:
This project will provide a means of establishing a control center, which will monitor all industry applications. Sitting in the control room, a person can check and control all the major operations of an industry.
Remote Operation:
Regardless of the distance of the devices from the control room, it can be controlled without any problems.
Transmitting Unit:
The Fig below shows the transmitter module keyboard. The various signals corresponding to key presses are generated through this pad.
Keyboard
The Figo is the transmitter unit that contains the dialer IC UM912141B. This unit transmits the tone generated by the keyboard.
Transmitting Unit
Circuit Diagram Explanation
Circuit Explanation:
The figure is shown in the transmitter module circuit diagram tab. Its main parts are DTMF dialer, IC UM91214B and optical transmitter.
The circuit employs the DTMF technique to control ten applications. However, it can be modified for multiple applications. A 9 volt B battery is used for the remote control circuit. However, the DTMF dialer IC requires only 3 Volts for its operation, which is achieved with the help of the zener diode voltage regulator.
The controller has 7 relays. They are organized into 4 rows (R1-R4) and 3 columns (C1 to C3) using 7 lines terminating at the corresponding inputs of the DTMF encoder UM91214B.IC generates distinct dual tone signals corresponding to the driven relay. optical fiber.
UM91214B DTMF Tone Generator:
DTMF encoder IC UM91214B is commonly used as dialer IC in telephones. Its function is to generate the DTMF tones corresponding to the energized relay. Its internal block diagram is shown in the figure.
For its time, the UM91214B requires a 3.58 MHz quartz crystal that is connected between pins 3 and 4 of the IC dial to form part of an internal oscillator circuit. The oscillator output is converted to appropriate DTMF signals through frequency division and mixing via logic control. Pins 15 to 18 are row pins and pins 12 to 14 are column pins.
IC UM91214B also incorporates a 20-digit dialed number. memory. This IC feature is not used in the current remote control system. The memory unit and read and write pointer logic are controlled by the control logic. DTMF tones are obtained at pin 7 of the IC. The IC also has some control inputs that are not used in its current application.
OPTICAL TRANSMITTER AND RECEIVER:
Introduction:
This unit generates light signals, which have a wavelength slightly longer than the wavelength of visible light. These signals are called infrared beams.
In the infrared-based remote control system, the transmitter's infrared LED is used in the transmitter, the optical fiber is used as signal transmission, and the receiver uses a corresponding infrared photodiode or phototransistor to receive the transmitted infrared signals. The transmitted signal is invisible to the naked human eye, but an infrared photodiode detects the signal.
The light that we can see as the wavelength of 4×10 (-7) m to 7 x 10 (-7) m just above and below this visible light spectrum, two invisible lights are situated, the UV light and the IR light .
RECEIVING UNIT:
The figure below shows the receiving unit.
Receiver unit
Receiver Circuit Explanation:
The receiver module decodes the received DTMF signals with the help of DTMF decoder IC HT9170B which provides binary oo/p according to the key pressed in the remote area. It also provides STD signals that indicate receipt of a valid DTMF code.
Whenever a certain key is pressed on the Remote Control, the signal transmitted via free space is received by the DTMF Decoder and generates the corresponding binary code on its o/p line A, B, C, D (on pin no. 11, 12, 13 , 14). The o/p delayed steering trigger (STD) also goes high, which goes low when the key is released.
The binary o/p of the DTMF decoder is connected as input to the 4 to 16 line IC TC4514BP decoder. One of the 16 o/p latches corresponding to the input data goes high when the latch enable (LEN) is held permanently high, when the control input EN is connected to the STD signal, which goes high while a key on the keyboard and all o lines /p of this IC remain low. However, when the user releases the keypad switch on the remote unit, transmission of the DTMF signal stops and the STD o/p signal goes down to the already locked data o/p. The o/p line of this IC corresponding to the release key on the keyboard goes high. Thus, a transition from low to high occurs on one of the o/p lines of the decoder corresponding to the key pressed and released on the Remote Unit.
The positive pulse triggers the corresponding D-Flip flop, which is wired in a toggle mode to control the desired device. Thus, a specific device can be turned on by momentarily pressing the corresponding key. It can later be turned off by momentarily pressing the same key again.
The Set and Reset keys on the keyboard function as master switches to turn all devices on and off, respectively. When these keys are pressed (one at a time), they generate signals that are decoded by the IC HT9170B as B and C (HEX) respectively. The corresponding o/p lines of IC TC4514BP are connected to the configuration and reset terminal respectively of all the alternate flip-flops to turn on/off all the devices simultaneously.
Explanation of the Continuation Circuit
DTMF to BCD decoder unit (IC HT9170B):
Description:
HT9170B is a complete DTMF receiver that integrates band-split filter and digital decoder function. The filter section uses switched capacitor techniques for high and low group filters; The decoder uses digital counting techniques to detect and detect all 16 DTMF tone pairs in a 4-bit word. The external component count is minimized by providing on-chip a differential input amplifier, clock oscillator, and latch 3 state bus interface (9) .
Characteristics:
The. Complete DTMF receiver
B. Low energy consumption.
w. Internal gain setting amplifier.
d. Adjustable storage time.
It is. Head office quality
f. Shutdown mode
g. Inhibit mode
Functional Description:
The HT9170B monolithic DTMF receiver offers small size, low power consumption and high performance. Its architecture consists of a band-split filter section, which separates the high and low tones of the group followed by a digital counting section that checks the frequency and duration of the received tones before passing the corresponding code to the o/p bus. .
Filter Section:
Separation of the low group and high group tones is achieved by applying the DTMF signal to the input of the two 6th order switched capacitor bandpass filters , whose bandwidth corresponds to the low and high group frequencies. The filter section also incorporates notches at 350 and 440 Hz for exceptional tone dial rejection. Each o/p filter is followed by a single-order switched capacitor filter section that smooths the signals before limiting, which is performed by high-gain comparators, which are provided with hysteresis to prevent detection of unwanted low-level signals. . The o/p of the comparators provide full logical oscillations at the frequencies of the input DTMF signals.
Decoder Section:
Following the filter section is a decoder that employs digital counting techniques to determine the incoming tone frequencies and verify that they match standard DTMF frequencies. A complex averaging algorithm protects against tone simulation by extraneous signals such as voice, while providing tolerance for small deviations and frequency variations. This averaging algorithm was developed to ensure an ideal combination of chatter immunity and tolerance to the presence of interfering frequencies (3 third tones) and noise. Whether the detector recognizes the presence of 2 valid tones (this is called a “signal condition” in some industry specifications), the “early steering” o/p will go into an active state. Any subsequent loss of signal will cause the ESt to enter an inactive state.
Steering circuit:
Basic Driving Circuit.
Before recording a decoded tone pair, the receiver checks whether there is a valid signal during (referred to as character rearrangement condition). This check is performed by an external RC time constant driven by ESt. A logic high in ESt causes V c (see figure above) to increase as the capacitor discharges. As long as the signal condition is maintained (ESt remains high) during the validation period (tGTP), V c Reaches the threshold (VTSt) of the steering logic to register the tone pair, locking its corresponding 4-bit code into latch o/p. At this point, the GT o/p is activated and drives V c to V dd . GT remains high as long as Est remains high. Finally, after a short delay to allow the o/p latch to stabilize, the o/p direction delay (StD) flag goes high, signaling that an incoming tone pair has been registered. The contents of the o/p latch are made available on the 4-bit o/p bus by increasing the 3-state control input (TOE) to logic high. The steering circuit works in reverse to validate the intrepid pause between signals. Thus, in addition to rejecting signals that are too short to be considered valid. The receiver will tolerate signal interruptions (dips) that are too short to be considered a valid pause. This facility, along with the ability to externally select driving time constants, allows the designer to tailor performance to meet a wide variety of system requirements.
Forms:
The. Paging systems
B. Repeater/mobile radio systems
w. Credit card systems
d. Remote Control
It is. Personal computers
f. Answering machine
4-line to 16-line decoder unit (TC4514BP):
General description
The TC4514BP and TC4515BP are 4-16 line latched input decoders implemented with complementary MOS (CMOS) circuits constructed with n and p channel enhancement mode transistor. These circuits are mainly used in decoding applications where low power dissipation and/or high noise immunity is required. The IC TC4514BP (active high o/p option) presents a logical “1” at the selected o/p, while the TC4514BP presents a logical “0” at the selected o/p. The input latches are RS-type flip-flops, which store the last input data presented before the stroboscopic transition from “1” to “0”. This input data is decoded and the corresponding oo/p is activated. One o/p inhibit line is allowed.
Lock (HEF4013BP):
Description:
The HEF4013BP is a double D flip-flop that has independent set direct (SD), clear direct (CD), clock inputs (CP) and outputs (O,O). Data is accepted when Cp is low and transferred to o/p on the positive edge of the clock. The asynchronous active high clear direct (CD) and set direct (SD) are independent and replace the D and CP inputs. Outputs are buffered for better system performance. The action of the Schmitt trigger on the clock input makes the circuit highly tolerant to slower clock rise and fall times.
Yearning:
The. CP clock input (L to H edge driven).
B. Direct SD asynchronous pool input (active high).
w. CD asynchronous clear direct input (active high).
d. True o/p.
It is. Complement o/p.
Application information:
The. Counter/Divisor
B. Records
{ w. Toggle flip-flop
Sugar Cube Relay:
This relay is known as sugar cube relay because its shape is the same as the sugar cube. It is a low-cost relay for electrical appliances.
It consumes relatively less power compared to other relays. It is compact in size and easily available for various current ratings.
It has 5 terminals, 2 for normally closed operations, 2 for normally open operations and 1 common terminal. This sugar cube relay will act as a switch in the circuit in both normally closed and normally open mode. The common terminal will decide whether there will be normally closed or normally open operation.
APPLICATION :
Introduction:
Output 16 line S1 stuck goes high. This output line is connected to the latch, which is a double D-Flip Flop. This way the relay will work. As a result, the engine power circuit will be completed and the engine will start.
When the same key is pressed again, the same output line will receive a low logic level due to the latch. Due to this, the motor supply circuit will be incomplete and the motor will stop.
Changing connection concept
Reverse operation (change of connection concept):
Single-phase induction motor forward/reverse operation
In the figure above, relay 1 is closed; relays 2 and 3 are in normally open mode.
When key 2 is pressed, the control signal generated as shown below in the block diagram will activate relays 1 and 2. As a result, the motor will operate in reverse direction. When the same key is pressed again, the motor will return to operating in the forward direction. Here relay 3 is provided for on/off operation of the motor.
As shown in the above figure Fig, when the control relay is energized by the received signal, the normally open contacts will be closed and the motor will start.
Block diagram for reverse operation
The keyboard output is connected to 2 input lines R1 and C1 of DTMF dialer IC UM91214B. Depending on the BCD code received at the output pins, the corresponding relays will operate and the BCD code will be passed to the DTMF dialer IC. At the output of the DTMF IC dialer, an IR led is provided which converts the frequency signals into corresponding light signals of wavelength above 0.7 µm. this light signal is then transmitted through free space. The receiver uses an IR photodiode or corresponding phototransistor to receive the transmitted IR signals
HT9170 is used to convert the received DTMF signal into BCD code. Separation of the low group and high group is achieved by applying DTMF to the input of two sixth-order switching capacitor bandpass filters, whose bandwidth corresponds to the low and high group frequencies. The binary output of the DTMF decoder is connected as input to the 4-16 CD4514 line decoders.
Block diagram Forward/reverse operation
Speed control (voltage variation concept):
Speed Control Circuit
Block diagram for speed control
When the speed control key is pressed, the engine speed decreases. And when the same key is pressed again the original speed is restored.
When control signal 1 is supplied, relay A, which is a normally open relay, is activated. This results in the engine starting. Relay B is a normally closed relay and relay C is a normally open relay. With control signal 2, relays B and C will be activated and the motor will run in reverse operation.
Relay D is in normally open mode. With control signal 3, relay B will be open and relay D will be closed, resulting in a decrease in speed. Therefore, speed control can be provided.
Light Control:
When the LIGHT key is pressed, a lamp lights up and pressing it again turns it off. This application in a broad sense can be used to provide central light control in industries.
A siren operation that beeps on key press indicating an interruption, a danger signal, etc. can be provided. .
PCB LAYOUT
The PCB layout of the transmitter and receiver is shown in the figures below.
Transmitter Part:
Keyboard:
Keyboard PCB Layout
This Layout is the DTMF keyboard layout that we use for generating the dual tone multifrequency signals. It contains 12 keys and they are organized in the form of a matrix consisting of 4 rows and 3 columns. For military purposes, a 4th column is also used to maintain privacy.
Transmitter Part:
Transmitting Unit
This PCB contains the main heart of the system and is the IC UM912141B. This IC is used for generating dual tone signals from the combination of 2 frequencies; one from the lower band and one from the upper band. The output obtained is later sent for transmission through the fiber optic cable after converting it into light signals.
Receiver part:
Receiver unit
Project application videos
Project application videos
Fire sensor
Transmitter and Receiver
Vibration sensor
Project source code
Circuit diagrams
| TX_CKT |  |
