Circuit Diagram

The input changing circuit using operational amplifier

Published:2012/11/18 21:07:00 Author:Ecco | Keyword: input changing , operational amplifier

Figure a shows a voltage follower, the input signal source resistance RE > 20MΩ, voltage amplification coefficient Vu = 1. In figure b, it uses the first connected field effect source follower circuit to further increase the RE. The RE value is related to FET parameters, and it can be high to 1GΩ. The bypass connected FET can be used to increase the put.   (View)

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Basic radio transmission circuit with surface acoustic wave resonator SAW

Published:2012/11/15 21:03:00 Author:Ecco | Keyword: Basic radio transmission , surface acoustic wave, resonator , SAW

Figure (a) shows a basic circuit of the transistor UHF radio transmitter with surface acoustic wave resonator (SAW), and the SAW is used as a positive feedback element connected between the transistor VT base and LC network in parallel. Figure (b) shows another basic transistor UHF radio transmitter circuit with the surface acoustic wave resonator, in this circuit, SAW is connected between the transistor's base and emitter; the phase relationship between them is 180 degree.   (View)

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The fishponds hot days hypoxia automatic oxygen control circuit

Published:2012/11/16 2:14:00 Author:Ecco | Keyword: fishponds, hot days, hypoxia , automatic oxygen, control

In the hot days, fishponds water temperature also will increase, there is a sharp decline about the oxygen content in water. It is extremely detrimental to the growth of hypoxia on fish, and the added oxygen control circuit will automatically start when the water temperature is higher ( 28 ℃), the water plus oxygen machine is driven by the motor for agitation. The control circuit is composed of thermostat voltage comparing circuit, multivibrator circuit, thyristor motor control circuit, audio sounding circuit and AC buck rectifier circuit and other components, and it is shown in figure.   (View)

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DC compound motor commutation circuit

Published:2012/11/16 2:29:00 Author:Ecco | Keyword: DC, compound motor , commutation

Excitation windings of such a motor is also formed by a parallel winding Ll and series winding, and it is shown in ( a ). In order to change the steering of the motor by changing excitation current, the direction of the current of L1 and L2 must be simultaneously changed, but such a change method is relatively trouble. The commonly used method is to change the direction of the armature winding current.   (View)

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Line lamp transformer checking current transformer circuit

Published:2012/11/16 2:43:00 Author:Ecco | Keyword: Line lamp , transformer , checking , current transformer

10% error qualification of the current transformer has a direct impact on power system relay protection. If it is failed, it will cause current protection to refuse to move and the expansion of the accident, it must be calibrated periodically. The method to check current transformer by line lamp transformer is shown as the figure. Operation method: closing the knife-switch QS, slowly adjusting regulator TA will make line lamp transformer T's voltage gradually increase, then ammeter PA1 , PA2 reading will slowly increase.   (View)

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A multifunctional pump control circuit

Published:2012/11/16 2:52:00 Author:Ecco | Keyword: multifunctional pump control

Many high-power devices need circulating cooling water for cooling. When it has many cooling equipment units, you can install a shared water pump using multifunctional control method, then each operating point can start pump separately, and they can separately stop pump, when any one is using water, it also can prevent other point from turning off the pumps.   (View)

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Gate Alarm

Published:2012/11/15 21:18:00 Author:muriel | Keyword: Gate Alarm

A cheap and simple gate alarm made from a single CMOS Integrated Circuit.Circuit NotesFigure 1 represents a cheap and simple Gate Alarm, that is intended to run off a small universal AC-DC power supply. IC1a is a fast oscillator, and IC1b a slow oscillator, which are combined through IC1c to emit a high pip-pip-pip warning sound when a gate (or window, etc.) is opened. The circuit is intended not so much to sound like a siren or warning device, but rather to give the impression: You have been noticed. R1 and D1 may be omitted, and the value of R2 perhaps reduced, to make the Gate Alarm sound more like a warning device. VR1 adjusts the frequency of the sound emitted. IC1d is a timer which causes the Gate Alarm to emit some 20 to 30 further pips after the gate has been closed again, before it falls silent, as if to say: I'm more clever than a simple on-off device. Piezo disk S1 may be replaced with a LED if desired, the LED being wired in series with a 1K resistor. Figure 2 shows how an ordinary reed switch may be converted to close (a normally closed switch) when the gate is opened. A continuity tester makes the work easy. Note that many reed switches are delicate, and therefore wires which are soldered to the reed switch should not be flexed at all near the switch. Other types of switches, such as microswitches, may also be used.   (View)

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Wireless Microphone FM Transmitter

Published:2012/11/15 21:16:00 Author:muriel | Keyword: Wireless, Microphone , FM , Transmitter

This Wireless Microphone FM Transmitter has been a very popular project with beginners and experienced constructors alike. It has been used inside guitars and as the basis of a remote control system. I do however, receive many requests for a higher powered circuit and better microphone sensitivity. Now I can introduce the new FM Wireless Microphone, which also has a better frequency stability, over 1Km range (under ideal conditions) and is good on microphone sensitivity. This has been achieved by adding an RF amplifier buffer (with 10dB gain) and an AF preamplifier to boost the modulation a little. Construction is quite simple. L1 is 3.25 turns in spiral form and is an integral part of the PCB foil pattern. The two BC547 transistors can be replaced with (almost) any small-signal NPN transistor, such as the 2N2222. The final stage is a BC557 PNP general purpose device. If you use different devices then you should select the 1M0 resistor for 5-volts DC at the collector of the the first transistor. Select the 47K resistor for 3 - 4 volts on the collector of the third transistor. Here is the V5 component overlay drawing. Note that there is a modification: There used to be a 1n0 5mm cap for supply decoupling, but after a cange of component supplier (manufacturer?) there developed some form of RF instability when the gain of the PA transistor was a little above normal. Replacing the 1n0 to an electrolytic capacitor of 22uf cured this problem totally. Any radial (the leads both come out of the same end) type electrolytic capacitor from 0.47uf upwards cures the problem. The finished unit draws about 30mA which should vary as you touch the tuned circuit, a good test that the unit is oscillating. You should remove the 4K7 resistor if you use a dynamic microphone. The PCB is 50mm x 25mm, a little larger than the first version but there are three stages instead of just the one. The first prototype is shown above, beside the battery powering it. The output power is about +10dBm which is about 10dB more than the first FM Wireless Microphone. This would theoretically give it 3.12 times the range (1.6Km) but I have only tested it using a handheld receiver with the TX laying on the bench indoors. But I got a comfortable 700 meters (and a few funny looks from our neighbours). Above you can see the addition of a gimmick capacitor added across the 12p tuning capacitor to lower the frequency of the transmitter. Make the capacitor by twisting two lengths of single core insulated hook-up wire, about 2cm long. This will reduce the frequency to the bottom end of the band. Cut short the capacitor to increase the frequency to the desired final frequency. If you cut it a few KHz too high then just twist the gimmick a little tighter. The PCB foil pattern and layout will be placed in the download section of my homepages. Have fun and please be aware that the higher power of this project may render it ILLEGAL in your own country. I can accept no responsibility and it is up to you to check that you may legally use it. I will accept NO complaints from any country/state correctional facility.   (View)

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Wideband RF Field Strength Meter

Published:2012/11/15 21:15:00 Author:muriel | Keyword: Wideband, RF , Field , Strength Meter

Field strength meter is extremely useful when working with RF devices. It can be used to quickly diagnose whether a transmitter circuit is working, and can be used to detect RF signals in the environment. The simplest field strength meter could be built with a tuned LC circuit and a germanium diode, just like the way of a building a crystal radio except replacing the ear piece with a high sensitivity current meter. While this approach fits the needs of most simple applications, it has a pretty narrow frequency range (~100 MHz) and requires tuning the LC circuit to the correct frequency before measurements can be made and the design can become complicated if wider frequency range tuning is desired.   (View)

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Wide Band RF Amplifier for 10MHz - 500MHz Input

Published:2012/11/15 21:14:00 Author:muriel | Keyword: Wide Band, RF Amplifier, 10MHz - 500MHz Input

This is a wide band amplifier cicuit which is suitable for the frequencies between 10MHz and 500MHz. Wide band amplifiers are used in communication receivers, RF measuring equipment and tons of other devices. The circuit described here uses a state of the art transistor to get maximum performance at high frequencies. It can be used as a low noise pre-amplifier due to his low noise characteristics.   (View)

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Video/Audio Wireless Transmitter

Published:2012/11/15 21:13:00 Author:muriel | Keyword: Video/Audio , Wireless , Transmitter

Television signals operates as two separate transmissions. One for the video and the other for sound. And just like our project, two different devices are going to be built.   (View)

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VHF/UHF TV Modulator2

Published:2012/11/15 21:12:00 Author:muriel | Keyword: VHF/UHF , TV, Modulator

Simple oscillator that generates a frequency in the VHF or UHF region. The oscillator is modulated with the video signal and the modulated carrier wave thus generated is fed into the TV set's aerial input via a cable. Then all that remains to do is tune the TV to the correct frequency.   (View)

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VHF/UHF TV Modulator

Published:2012/11/15 21:10:00 Author:muriel | Keyword: VHF/UHF , TV , Modulator

Simple oscillator that generates a frequency in the VHF or UHF region. The oscillator is modulated with the video signal and the modulated carrier wave thus generated is fed into the TV set's aerial input via a cable. Then all that remains to do is tune the TV to the correct frequency.   (View)

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VHF/UHF Prescaler

Published:2012/11/15 21:10:00 Author:muriel | Keyword: VHF/UHF, Prescaler

The recommended Prescaler is ridiculously simple. It consists of just one IC, a TV tuner prescaler, the Philips SAB6456A, which can divide by 64 or by 256. This chip is widely available both new and in the surplus market at much lower prices than conventional divide by 10 prescalers.   (View)

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VHF Video Transmitter 60-200 MHz

Published:2012/11/15 21:09:00 Author:muriel | Keyword: 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 meters 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.   (View)

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VHF FM Transmitter MAX2606

Published:2012/11/15 21:08:00 Author:muriel | Keyword: VHF, FM, Transmitter, MAX2606

If you want to be independent of the local radio stations for testing VHF receivers, you need a frequency-modulated oscillator that covers the range of 89.5 to 108 MHz � but building such an oscillator using discrete components is not that easy. Maxim now has available a series of five integrated oscillator building blocks in the MAX260x series which cover the frequency range between 45 and 650 MHz. The only other thing you need is a suitable external coil, dimensioned for the midrange frequency. The MAX2606 covers the VHF band, although the frequency can only be varied by approximately �3 MHz around the midrange frequency set by the coil L. The inductance values shown in the table can serve as starting points for further experimenting. The SMD coils of the Stettner 5503 series are suitable for such oscillators. In Germany, they are available from B黵klin (www.buerklin.de), with values between 12 nH and 1200 nH. You can thus directly put together any desired value using two suitable coils. If you want to wind your own coils, try using 8 to 14 turns of 0.5-mm diameter silver-plated copper wire on a 5-mm mandrel. You can make fine adjustments to the inductance of the coil by slightly spreading or compressing the coil. The circuit draws power from a 9-V battery. The BC238C stabilises the voltage to approximately 4 V. Although the MAX2606 can work with a supply voltage between +2.7 V and +5.5 V, a stabilised voltage improves the frequency stability of the free-running oscillator. The supply voltage connection Vcc (pin 5) and the TUNE voltage (pin 3) must be decoupled by 1-nF capacitors located as close as possible to the IC pins. The tuning voltage TUNE on pin 3 may lie between +0.4 V and +2.4 V. A symmetric output is provided by the OUT+ and OUT� pins. In the simplest case, the output can be used in a single-ended configuration. Pull-up resistors are connected to each of the outputs for this purpose. You can use a capacitor to tap off the radio signal from either one of these resistors. Several milliwatts of power are available. At the audio input, a signal amplitude of 10 to 20 mV is enough to generate the standard VHF frequency deviation of �40 kHz.   (View)

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VHF Audio Video Transmitter2

Published:2012/11/15 21:01:00 Author:muriel | Keyword: VHF, Audio, Video, Transmitter

  (View)

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VHF Audio Video Transmitter

Published:2012/11/15 21:01:00 Author:muriel | Keyword: VHF, Audio, Video, Transmitter

  (View)

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VERONICA 1W - 5W FM Transmitter

Published:2012/11/15 21:00:00 Author:muriel | Keyword: VERONICA , 1W - 5W , FM , Transmitter

The Veronica is an easy to build and tune transmitter for the FM band. It's known for it's stability and clean signal, does not use any IC's or similar specialized parts, and it has a built-in tuning aid that makes it possible to tune it with no extra equipment. It's available in two versions, 1 and 5 watts.   (View)

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USB RDS Coder Board using ATmega32

Published:2012/11/15 20:59:00 Author:muriel | Keyword: USB , RDS, Coder Board , ATmega32

This board is a RDS coder using an ATMEL AVR ATmega32. This board can be controled by a RS232 link, USB interface or SPI. TA data is displayed wiyth a LED and can be controled by : - Hardware input - RS232 - USB - SPI (not yet implemented)   (View)

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