Wiring & diagram Info: the

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Thursday, November 13, 2014

VHF UHF TV Modulator

The electronic circuit is a TV modulator that is really no more than a transmitter. It is a very small transmitter, admittedly, but none the less that is what it is. What does a modulator actually do? In general -and this design is no exception to the rule - it is a simple oscillator that generates a frequency somewhere 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 sets aerial input via a cable. Then all that remains to do is tune the TV to the correct frequency.

Circuit Schematic
The crystal oscillator is based on a very fast HF transistor, Tl (BFR91), which performs the amplitude modulation. Apart from this there is little to be said about the oscillator except, perhaps, that it is essential to use the correct values for the components surrounding Tl. This is, of course, simply common sense in this sort of HF circuit.

The harmonics generator is formed by two Schottky diodes, Dl and D2. These diodes must switch very quickly in time with the 27 MHz signal so they provide strong harmonics up into the gigahertz range. The modulation depth can be set with Pl, while the oscillators d.c. value can be varied by means of P2. The combination of these two presets enables either positive or negative amplitude modulation to be selected.

This is essential as the harmonics produced vary in this respect. We will discuss the calibration of Pl and P2 later in this article. The power for the circuit can be provided by either an unstabilized 8...30 V or a stabilized 5 V. The latter could be taken from a computers power supply and in this case ICI is not needed.

The printed circuit board for the modulator is only single-sided. The largecopper surface acts as a ground plain.

Parts list
Resistors:
R1, R2 = 4k7
R3, R4 = 56ohm
P1 = 100 ohm preset
P2 = 500 ohm preset
Capacitors:
C1 = 4mf7/16 V
C2= 10p
C3 = 220p
C4 = 47p
C5 = 47n, ceramic
C6 = 100n*
C7 = 330n*
Inductors:
L1, L2 = 3.5 turns of 0.2 mm (SWG 35 or 36) CuL on a ferrite bead of about 3.5 x 3.5 mm
L3 = 1 microH
L4 = 1 turn of 0.8. . .1 mm (SWG 19...21) CuL, air wound with a diameter of 8 mm
Semiconductors:
D1, D2 = 1N6263 (Ambit/Cirkit)
D3 = lN4148
T1 = BFR91 (Ambit/Cirkit)
IC1 = 7805*
Miscellaneous:
X1 = crystal, 27 MHzd(3rd overtone) or other 3rd overtone crystal between 25 and 30 MHz

*= not needed if the circuit is powered from a stabilised 5 V supply

Monday, October 13, 2014

Infrared Light Photo Detector Circuit This is a basic infrared light photo detector circuit In this circuit the light falling on the phototransistor

Infrared Light Photo-Detector Circuit

This is a basic infrared light photo detector circuit. In this circuit the light falling on the phototransistor will be from an Infrared Light Emitting Diode (IrLED) but otherwise it is the same as the phototransistor circuit shown above.

When the light falling on the phototransistor (Q1) is blocked, its conductance will decrease and the voltage across Q1 will rise. When the voltage rises above 1/2 of the supply voltage the output of the comparator will turn ON and the LED will be lit.

Source: Infrared Light Photo-Detector

Tuesday, September 16, 2014

Mixed connection acoustics bi amplifier and the output fader

In the operation is still a lot of these "dinosaurs" of the mid 90s. A characteristic feature of built-in amplifiers such devices - they are designed for load 2 ohms and have a good supply of power. This is due to the fact that in the middle position fader front and surround speakers are connected in parallel. However, to use them in conjunction with acoustic component is impossible. The reason is simple - the introduction of the fader increases the output impedance of the amplifier, which leads to a change in crossover. Therefore, the only option enhancers such devices with modern acoustics - dual channel configuration, with the fader excluded from work.

In this version, you can add a subwoofer to include it in a "mixed-mono". Since the relationship between the levels regulate front speaker and subwoofer impossible, depending on the sensitivity applied to select one of the heads of connectivity options.

Option A is used in the case where the sensitivity of the front speakers 3-5 dB higher than that of the subwoofer. In this embodiment, they are connected to the amplifiers are not bridged, and the usual way, and the power supplied to them is not more than 7 w / 4 ohms. To obtain sufficient volume of the front acoustic desirable to use high-sensitivity head about 91-93 dB. Pay attention to their phasing - one of the "poluusiliteley" inverting the second - non-inverting. HPF cut formed by the capacitors C1 and C2 can be chosen arbitrarily, but the presence of capacitors is crucial - they do not miss out on the dynamics of the DC component from the output amplifiers. Front head shown conventionally broadband, but they may be coaxial or component.

Option B is used in nearly all heads of sensitivity. The presence of capacitors C1, C2 for the normal functioning is not necessarily because it is used in a bridge connection. In the absence of capacitors in the passband head subwoofer filter work in parallel. This reduces the load impedance to 2 ohms, but the amplifier is designed. Subwoofer in both cases the second-order filter (C3L1R1).

Tuesday, September 9, 2014

Make a series letters from the LED

Make a series letters from the LED , Things to consider before making the sign of the LED array,
1) Use LED nodes.
2) Paint the top of the PCB with a dark color (black).
3) Note the LED specifications. In this experiment use a 5mm diameter LED nodes
that emit red, specification voltage of 3 volts.

The assembly of LED:
1) One letter composed at most 5 columns and 7 rows.
2) One column mostly composed by 6 LEDs are arranged series.
3) Then the fifth column are connected in parallel.

4) Each column given the constraints, Rx, which amount depends on the number of LEDs in one column and depends also on the type of LED (in this experiment that used LED 5mm in diameter, clear with red light beam).

5) In a column consisting of 6 LEDs, Rx = 330 ohm, 5 LEDs, Rx = 560 Ohms, 4 LEDs, Rx = 680 Ohms

Remember, this provision applies to 5 mm LED red light beam nodes.

6) Every letter was given FCS9013 transistor amplifier.

Here is one letter LED scheme.

Medium picture below is the lay out of the 2-letter nameplate. To make the sign 8 letter, copied from a second stay this letter.

Example of LED on the letters A and B:

Value Rx in the first and the fifth column (letter A) of 560 ohms, because it consists of 5 LEDs are arranged series. Rx in the second column, third, and fourth, amounting to 680 ohms because it consists of two LEDs.

Rx first column letter B, 330 ohms. Rx second column, third, fourth, and fifth at 680 ohms.

Auto Sound Systems are more than meets the Eye

The auto sound systems of today are much more involved and complicated than the simple car stereo and speakers of years long past. Todays sound systems have all kinds of bells and whistles that many us could have only imagined during our younger years. In fact, it is quite possible that many of us did imagine these and those imaginings are how they came to be. One thing you need to do before you even begin to put the auto sound system of your dreams together is learn what kinds of components exist, how they work together, and which ones you really think you need as part of your auto sound system and which components you honestly feel you can live without.

Life is about compromise and most of us will readily admit that we are quite unlikely to ever use all the bells, whistles, and upgrades that are made available to us within our lifetimes. I dont know about you, but my cell phone has features Ive never even gotten around to learning how to use. I know I can use them and I have a subscription to do so, but have never managed to actually get around to watching the news, I find that if I am on my phone the news would be an interruption and if I am in the mood to watch the news, Ill generally find a television and watch on a larger Lcd.

Our auto sound systems are a lot like this. If you dont do an extensive amount of travel with little ones in your car, it is unlikely that you will need a sound system that allows wireless speakers for the back seat. However if you are putting a good sound system in your family car, this may be a good idea, as we dont always enjoy the same music as our children. I dont know about you, but I can only handle "The Wheels on the Bus" so many times in one car trip. For that reason alone I think the individual headphones are a wonderful idea.

One thing that I have found I cant live without in my auto sound system is an MP3 player. Im literally addicted to audio books and have found that I can subscribe to an online service that allows me to download entire books to my computer and either burn them to a CD or put them on a memory stick to play on my next road trip. It makes the trip seem to go so much more quickly when I have something to occupy my mind rather than switching radio stations on a regular basis in search of a song I enjoy that hasnt been overplayed.

Some people cant live without at least a 6-disc CD changer as part of their auto sound system and others find that XML is the only way to go. Whatever your choice, the thing to remember is that it is your choice. Only you can choose the auto sound system that works best with your tastes and requirements. Only you can decide whether or not you enjoy the sound your sound system provides, and only you can decide which bells and whistles are important and essential and which ones you can live without. It is your money that will pay for the upgrades you desire and your tastes they should please.

Take the time to study not only the music, but also the sound and the components that are available for the sound system you choose. Also pay close attention to what is included in the price you think you are paying. More often than not each component is sold as either an add on or an upgrade so be careful that you arent getting less than you think you are or paying more than you think you will be paying for the auto sound system you choose.

Wednesday, August 27, 2014

Google might have revealed the new Nexus 6

Well, Google I / O 2014 is very close and some clues about new devices or software may be popping up any day now. Moreover, it is possible that Google has revealed the Nexus 6 through his Twitter account to promote the role of voice OK Google. Of course, this could just be a representation of a device or simply the next Nexus phone.

In the published photo, Google shows a cell with a very thin bezel and a design that does not currently see in the market. At the bottom of the image is the cheese section of a supermarket and not much pointing to the name of the next version of Android, as there are many desserts in the image. Could it be that Google knocked on the next version of Android with a name of cheese? I really doubt it and may be just the background image that focused only on promoting functionality.

The Android phone image would appear to be a little larger than 5 inches in May Nexus website and given the size it occupies in hand. Apparently might be 5.2 or 5.5 inches.

It is difficult to confirm or notice something else about this picture, but it is certain that Google will be confirmed or not this device at its developer conference Google I / O to be held in late June.