5 channel radio remote control

TX-2B / RX / 2B  5 channel radio remote control.

This article is about a simple 5 channel radio remote control circuit based on ICs TX-2B and RX-2B from Silan Semiconductors. TX-2B / RX-2B is a remote encoder decoder pair that can be used for remote control applications. TX-2B / RX-2B has five channels, wide operating voltage range (from 1.5V to 5V), low stand by current (around 10uA), low operating current (2mA), auto power off function and requires few external components. The TX-2B / RX-2B was originally designed for remote toy car applications, but they can be used for any kind of remote switching application.

Circuit diagrams and description.

Remote encoder / transmitter circuit.

The TX-2B forms the main part of the circuit. Push button switches S1 to S5 are used for activating (ON/OFF) the corresponding O/P channels in the receiver / decoder circuit. These push button switches are interfaced to the built-in latch circuitry of the TX-2B. Resistor R7 sets the frequency of the TX-2B’s internal oscillator. Resistor R1 and Zener diode D1 forms a simple Zener regulator circuit for providing the IC with 3V from the 9V main supply. C2 is the filter capacitor while C1 is a noise by-pass capacitor. D2 is the power on indicator LED while R6 limits the current through the same LED. S1 is the ON/OFF switch. The encoded control signal will be available at pin 8 of the IC. The encoded signal available at pin 8 is without carrier frequency. This signal is fed to the next stage of the circuit which is a radio transmitter. Crystal X1 sets the oscillator frequency of the transmitter section. R2 is the biasing resistor for Q1 while R3 limits the collector current of Q1. The encoded signal is coupled to the collector of Q1 through C3 for modulation. Transistor Q2 and associated components provide further amplification to the modulated signal.

Remote receiver / decoder circuit.

The remote receiver circuit is built around the IC RX-2B. The first part of the circuit is a radio receiver built around transistor Q1. The received signal is demodulated and fed to pin 14 of the IC. Pin 14 is the input of the built in inverter inside the IC. R2 sets the frequency of the IC’s internal oscillator. O/P 1 to O/5 are the output pins that are activated corresponding to the push buttons S1 to S5. Zener diode D1 and resistor R12 forms an elementary Zener regulator for supplying the RX-2B with 3V from the 9V main supply. C12 is the filter capacitor while R11 is the current limiter for the radio receiver section. Diode D2 protects the circuit from accidental polarity reversals. C15 is another filter capacitor and C14 is a noise by-pass capacitor.

Notes.

§  This circuit can be assembled on a vero board or a PCB.

§  Use 9V DC for powering the transmitter / receiver circuits.

§  Battery is the better option for powering the transmitter / receiver circuit.

§  If you are using a DC power supply circuit, it must be well regulated and free from any sort of noise.

§  Both ICs must be mounted on holders.

Interfacing relay to the RX-2B output.

The method for interfacing a relay to the output of RX-2B is shown below. When push button switch S1 of the transmitter circuit is pressed, pin O/P1 (pin 7 of the RX-2B) goes high. This makes the transistor 2N2222 to conduct and the relay is activated. The same technique can be applied to other output pins of the RX-2B. The relay used here is a 200 ohm type and at 9V supply voltage the load current will be 45mA which is fine for 2N2222 whose maximum possible collector current is 900mA. When using relays of other ratings this point has to be remembered and do not use a relay that consumes a current more than the maximum possible collector current of the driver transistor.

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Water Level Sensor Schematics

This simple water level sensor circuit monitors the presence of water in a certain location or container. The circuit sends an acoustic alarm when it senses a drop of water leak. It is very simple to build and it is made of a single IC and some passive components. Check out the water level indicator circuit too.

The IC LM1801 is a low power comparator that can deliver high output current if needed. When water hits the sensor, the reference voltage is overshot and the IC drives the ceramic transducer to beep. It is also possible to connect several sensors to the water level monitor circuit. The sensor can be easibly made out of a small piece of PCB that is etched with the proper pattern. The decoupling capacitor C3 is a 100uF/16V electrolytic capacitor.

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USB Player Circuit Diagram

USB series player is an electronic device or electronic circuit that functions as an MP3 player that is stored on a storage device such as USB flash.

In this USB circuit using an IC as a modifier of digital voice data into analog so that it can be applied to a headphone, or again through the power amlplifier strengthened so that it can be heard through the speakers. IC used in this circuit using IC PCM2902 as a modifier of a digital data into analog data storage.

Below is a schematic diagram of a USB player

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USB Lamp Circuit

Description.

Here is a simple USB powered lamp that can be used to light your desktop during power failures. The circuit operates from the 5 Volt available from the USB port.The 5V from the USB port is passed through current limiting resistor R2 and transistor Q1. The base of transistor Q1 is grounded via R1 which provides a constant bias voltage for Q1 together with D2.The diode D1 prevents the reverse flow of current from battery.C1 is used as a noise filter.Two white LED’s are used here for the lamp, you can also use a 2 V torch bulb instead of LED’s. LED D3  indicates connection with USB port.

USB Lamp Circuit Diagram with Parts List.

Notes.

§  USB port is only able to provide up to 100 mA current.So don’t overload the circuit with more no of LED’s.

§  Before wiring the circuit confirm the positive and ground leads of USB by a multimeter.

§  Switch S1 can be used to turn on the lamp.

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USB sound card

Description.
Designing and building a USB sound card is no longer a head ache because we have got the PCM 2702 integrated circuit from Texas Instruments. The PCM2702 is an integrated 16 bit digital to analog converter that has two digital to analog output channels. The integrated interface controller of PCM2702 is compliant to the USB 1.0 standards. The IC can handle sampling rates of 48 KHz, 44.1 KHz and 32 KHz. The IC also has a number of useful features like on-chip clock generator, digital attenuator, play back flag, suspend flag, zero flag, mute function etc. The most interesting thing is that this circuit is plug & play and doesn’t need any driver software for Windows XP and Windows Vista operating systems.

The circuit gets control data and audio data from the USB through the D+ and D- pins of the PCM2702 all the data transferring is carried out at full speed. The decoded audio signals will be available at the VOUTL and VOUTR pins of the IC. The 12MHz crystal is connected between the XT0 and XT1 pins of the IC. The VBUS (USB bus power) pin and DGND (digital ground) pins of the IC are connected to the +5V and ground pins of the USB respectively. The circuit requires +5V DC and +3.3V DC for operation and both of these voltages can be derived from the USB port using LDO (low drop out) voltage regulators (not shown in circuit).

Circuit diagram.

§  requires further amplification for driving low impedance head phones or loud speakers.

§  The PCM2702 is available only in SSOP28 package and requires special care while assembling.

§  Before attempting this circuit please go through the datasheet of PCM2702 and get a clear idea about the device.

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TV Transmitter Audio and video (IC-LM1889)

This small circuit transmitter processes the signs of audio of a table or microphone, and the signs of video of a camera, or still the audio signs and video of a DVD, Video-cassette or even it sweats her video plate has an exit of composed video, you can transmit direct of your computer. Playing them in a channel free from the strip of VHF.

These signs can be irradiated with a common antenna and captured in an it distances of until about 500 meters that it is the most appropriate for urban areas, reminding that and necessary to be a lot of caution and careful for not interfering in frequencies of other issuing, as well as to emergency services. Depending on the local conditions (existence or not of obstacles). Fed with tensions from 12 to 15 Volts, the circuit has excellent I carry out so much in the emission of monochrome signs, as in colors. An important point of this project ‘the easiness with that he can be set up and adjusted, since only two coils are used. Ideal to be used with surveillance cameras turning the without thread.

As it Works the TV video and audio transmitter with lm1889n

The heart of this circuit transmitter ‘is the integrated circuit LM1889N of National Semiconductor, that consists of a Modulator of Video for TV in an involucres of 18 pins DIL.

This integrated circuit ‘used in videocassettes and videogames, exactly to process the image information and sound, so that they can be played in a channel free from the strip of VHF.

As it is component that ‘used in commercial equipments, besides the reliability, we have a certain obtaining easiness. The readers, with luck, until they can find this available component in an old videogame that it is out of use, and you take advantage of it to set up your station communitarian. count all the necessary stages to the processing of the video signals and audio of a transmitter of signs of TV.

The coil L1 together with the capacitor in parallel, it generates the sign of 4,5 MHz that, modulated with the sound, it should be separate from the bearer of video of this frequency. Like this, the adjustment that should do in this coil it simply consists in you take it to 4,5 MHz, in way we obtain it sound.

The audio modulation ‘done by a varicap in a very simple way, so that the intensity of the audio sign obtained in most of the exits of the sound table it should provide a good reproduction.

The video sign, that obtained ‘of the video exit of any camera, videocassette, DVD, applied in the pin 13 of the circuit integrated after going by an amplification stage with two transistors.

This sign will modulate in width the video bearer whose frequency certain ‘for L2 and the capacitor in parallel.

We should adjust the frequency of this oscillator for the channel free from the strip of VHF, usually a channel baixo(2 to 6) in that the broadcasting station will operate.

The exit of RF, obtained in the pin 11 mischievous ‘to an amplifying stage with a transistor and of this for the antenna expresses or a telescopic antenna, in case the transmission is of short reach. Observe that in the modulation of audio of this circuit, the sign generates two subportator being below a 4,5 MHz above the frequency of the channel and other 4,5 MHz.

As one of them not eliminated ‘, she can cause interferences in the adjacent channel. That means that you should choose a free channel in your place, but that doesn’t have adjacent channels operating.

The power supply of the circuit can be made with tensions of 12 (7812) or 15(7815) Volts of a source with at least 1A and excellent filter. A deficient filter in this type of so much circuit can provoke snores in the sound, as undulations in the image.

Suggestion of power supply for circuit using the ic 7812

Schematic for assembly of the tv transmitter with lm1889n

Assembly of the circuit of the TV transmitter

The healthy resistors of 1/8W or larger. The power source so much can be the one of 12V/1A, as it can be made a modification to operate with 15V, being enough for that to change the transformer and the integrated circuit. The circuit plate printed for the assembly ‘shown below in the illustration. The coils, as always, are the elements more critics of the project. L1 ‘formed by 40 you exhale of thread enameled fine (30 to 34) in a form of 5 diameter mm and 18 height mm, with nucleus of adjustable ferrite. The form for this coil can be obtained in old radios and televisions. The coil L2 that determines the frequency of the channel can have from 2 to 6 you exhale of thread 18 to 22, in used similar form her for L1. For 2 or 3 you exhale we will have the operation in the high channels of VHF, between the 7 and the 13, and for 4 to 6 you breathe the operation it will be among the channels 2 and 6. For the entrance of audio and video important ‘to use armored threads and appropriate connectors. For the antenna to use a connector for cable of 75 Ohms. The transmission section should not be in the same box that the source. The transmitter should be shielded for larger operation stability and to avoid the reception of noises that affect the transmission. The trim pot P1 has for purpose to adjust to component DC of the video sign, important to obtain the maximum revenue in the transmission.

Adjust alignment of the video, audio, the coils, antenna and frequency of the operation

To test and to adjust the transmitter, call in your entrance the exits of audio and video of a videocassette with any ribbon of good quality. Use appropriate cables. Tie the transmitter and, in that she intend to do the operation. The antenna of the transmitter can be a piece of some centimeters of covered common thread. Adjust the coil initially L1 so that the sign of maxim image intensity is captured. Adjustment the way trimpot to obtain the best image. Then, adjust slowly the coil L2 until obtaining the sound sign. Obtaining the sound sign, retouch the tuning of way L1 to obtain the maxim transmission. If it has difficulties in obtaining the tuning in the wanted channel, alter the value of C7 or I number it of you exhale of L1. If it has difficulties in tuning in the sound, alter C6 or then the number of you exhale of L2.

Proven the operation, make the connection of the definitive antenna (it expresses or it interns) and re-do the way fittings to obtain the best transmission quality. After that, it is only to operate the station.

LIST OF MATERIAL

Power supply

• CI1 – 7812 or 7815
• D1 D4 1n4004 or equivalent
• C1 C4 – 10NF
• C5 – 2200µF TO 4700µF / 50 V
• C6 – 100NF
• C7 – 100µF 35V
• C8 – 100NF
• L1 – Shock of RF 100µH / 1 THE
• T1 – Transformer, primary in agreement with the net (110/220) and secondary from 18 to 24V / 1A
• Several – printed circuit board, threads, box, etc.

Semiconductors:

• Cl1 – LM1889- Integrated Circuit – Modulator of Video
• Q1, Q2, Q4 – BC547 or equivalent
• Q3 – BD135 or equivalent, example 2n2218 (different Pinage)
• D1 – BB809 VARICAP or equivalent

Resistors 1/8W, 5%:

• R1, R15 – 82 Ohms-
• R2 – 120 K Ohms
• R3 – 27K Ohms
• R4 – 1,2 K Ohms
• R5, R13, R14 – 270
• R6 – 470 Ohms
• R7 – 56k Ohms
• R8 – 68k Ohms
• R9 – 220 K Ohms
• R10 – 2,7 K Ohms
• R11, R17 – 1 K Ohms
• R12, R16. R19 – 10 K Ohms
• R18 – 47 Ohms x 1W
• R20 – 22 K Ohms
• P1 – 10 K Ohms trimpot

Capacitors:

• C1 – 4,7µF/1 6V – ELECTROLYTIC
• C2, C3 – 10µF/1 6V – ELECTROLYTIC
• C4, C8 – 1 nF – ceramic
• C5 – 120 pF – ceramic
• C6 – 47 pF – ceramic
• C7 – 56 pF or 47 pF – ceramic

Several:

• L1, L2 – Coils – L1 – 0.3µH and L2 – 7 to 13µH.
• XRF – it Collides of 100 µH – to see text.
• Several -printed board circuit , entrance Jacques and output of signs, box for assembly, power source, forms for the coils, enameled threads, etc.

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TV transmitter circuit (IC-MC374).

A very simple and high quality TV transmitter circuit based on IC MC374 is shown in this article.MC1374 is an integrated TV modulator circuit that can be used in various TV transmitter applications. The MC1374 includes all necessary circuitries required for a TV modulator such as sound carrier oscillator, FM audio modulator, dual input RF modulator etc. The IC packed with a lot of great features like wide dynamic range, single supply operation, low distortion, variable gain radio frequency modulator section, minimum intermodulation distortion, + or – Sync etc. The IC requires few external components and can be operated from a supply voltage range from 5 to 12V DC.The circuit diagram of the TV transmitter using MC1374 is shown below.

Circuit description.

Video section.

The video signal input to the circuit can be either negative or positive. The RF output will be approximately zero when the voltages at pin 1 and 11 are equal and the RF output increases linearly as the difference in voltage increases. Resistors R1,R2 and R3 determines the Q factor of the circuit are here their values are so chosen that the Q factor is around 15 which is the desired value for this IC. Resistor R8 connected between pins 12 and 13 sets the modulator gain. The RF output is available from pin 9 which is actually a source which drives a load connected from positive supply line to pin 9. The frequency of the RF oscillator is controlled by the tank circuit comprising of components L1 and C2 connected in association with pins 7 and 6. With the present values of L1 and C2 the RF oscillator frequency is around 105MHz. Components L3, L4, C11, C12 and C13 forms a double pi low pass filter which filters away second harmonics from the radio frequency output. These second harmonics usually occur at very high frequencies due to small imbalances in the device. Resistors R9 and R11 forms the bias circuit for the video input pin. Switch S1 can be used for selecting channel 3 or channel 4 operations.

Audio section.

Frequency modulation is used for transmitting the audio signals. Inductor L2 connected between pin 2 & 3 and the capacitor C3 from pin 3 to ground forms the necessary tank circuit for the FM sections oscillator. Resistor R12 and R13 forms a biasing network for the audio input pin (pin14). C6 is the decoupling capacitor for the audio input while C10 is the decoupling capacitor for the video input. The modulate FM signal available at pin 3 of the IC is coupled pin 1 of the IC through resistor R6 and capacitor C4 and then this signal is modulated onto the AM carrier. Capacitor C9 filters off noise if any from the power supply. R4 and R5 form a biasing network for the pin 1 of the IC. C14 a noise bypass capacitor for the oscillator B+ pin (pin14) of the IC. This pin can be used for shutting down the sound system during the alignment of the AM section.

Notes.

§  Assemble the circuit on a good quality PCB.

§  Use a holder for mounting the IC.

§  Circuit can be powered from anything between 5 to 12V DC.

§  Using a battery for powering the circuit will reduce noise and improve the performance.

§  If a DC power supply is used, then it must be well regulated.

§  For L1 make 4 turns of #22 enamelled copper wire on a 0.25 inch plastic former.

§  For L2 make 40 turns of #36 enamelled copper wire on a 0.18 inch plastic former.

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TV transmitter circuit

Description.
The TV transmitter circuit given here uses UK standard 1 FM modulation for sound and PAL for video modulation. The audio signal to be modulated is pre-amplified using the transistor Q1 and associated components. The transistor Q2 has two jobs: production of carrier frequency and modulation. The pre-amplified audio signal is fed to the base of transistor Q2 for modulation. Capacitor C5 and inductor L1 forms the tank circuit which is responsible for producing the carrier frequency. The video signal is fed to the emitter of transistor Q2 via POT R7 for modulation. The modulated composite signal (audio+video) is transmitted by the antenna A1. This TV transmitter circuit can be operated from 12V DC. Either a 12V DC power supply or a battery can be used for the purpose, using a battery will surely reduce noise and improve the performance. If you are going with a DC power supply, then it must be well regulated and free of  noise.

Circuit diagram with Parts list

Notes.

§  Assemble the circuit on a good quality PCB.

§  Inductor L1 can be made by making 4 turns of 24SWG enameled copper wire on a 6mm dia: plastic former.

§  T1 can be a radio frequency transformer with built in capacitor. (Can be found on old transistor radio boards).

§  Antenna A1 can be a 1M long copper wire. (Experiment with the length to get optimum performance).

§  This transmitter is working in VHF band somewhat between 50 – 210MHz.

§  This transmitter is compatible only with PAL B and PAL G systems.

§  Slight adjustments are required on the value of C8 for getting optimum performance.

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VHF Video Transmitter 60-200 MHz

Here's a simple video transmitter for VHF TV channel will accept baseband video input, hence it can be driven by most CCD cameras and VCR video outputs. It ouputs roughly 80mW and when used with a 40cm telescopic antenna over 100 metres range is possible.

The transistor of the video transmitter can be a BC108, BC546, BC337 or a 2N2222. L1 is wound on a 10 mm air former. Use 6 turns 24 SWG for frequency 60-80 MHz, 4 turns for 150-180 MHz, and 2 turns for 180-200 MHz

You can use this with a monochrome or color video signal. To transmit sound just build the wide band FM transmitter and tune it to the audio channel.

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Fined It…

• Where is the middle rod?

• How many planks? Count top and bottom.

• Is it open to the inside or outside?

• Are the pillars round or square?

• How many planks? 3 or 4?

• Is this a frame?

• Strange construction!

• The beam in the middle disappears from left to right

• 2 or 3 posts ?

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