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transformer help!!

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cs200939

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hey guys i am stuck with some transformer problem here.Actually i dont really have much knowledge about transformers except that they step up or step down voltages.I've been busy with this simple laser communicator project (i hope everyone knows about it).In that there is mentioned a transformer with this information "one 1000 ohm coil and the other 8 ohm coil".Can any body help explain this to me?.And above all whats the use of transformer here anyway?.I've included the transmitter part of the laser communicator as a help.thanks
 

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The impedance ratio of a transformer is the square of the turns ratio (see this for more info).

But without knowing more about what the circuit does, I can't offer much help as to what the transformer is for. Where does the plug from the 8 ohm side of the transformer go?
 
well its a laser communicator.You transmit sound in the form of light through a laser pointer.The laser is attached to an audio device ,as shown in the transmitter circuit, and the reciver is simply a solarcell connected to an audio amplifier .Now the music is played on the audio device the changing voltage changes the laser light falling the solercell which in turn genrates chaninging electricity that flows through the audio amplifier and hence we hear the same music we're playing on the audio device.heres the link to this project **broken link removed**
 
That looks like an audio output transformer used in reverse. The 8 ohm secondary somewhat matches the output impedance of the audio amplifier driving it. The transformer increases the voltage by a 100/8 ratio. This audio voltage is supposed to add or subtract from the voltage of the battery and then is supposed to vary the brightness of the laser diode.
The transformer will need a power rating such that the 1000 ohm primary winding is capable of handling the current requirement of the laser diode.
If the laser diode has a built in voltage regulator it might negate the effect of the modulation because the regulator will eat some or all of the modulation voltage as it maintains a constant voltage for the laser diode..

Here is a circuit I found by poking around the net:

**broken link removed**

It is not nearly as simple as the one you presented.
 
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A good transformer is a power coupling device. When the the primary winding is shorted the secondary is nearly shorted with only a small amount of leakage inductance value and winding resistance.

With a low impedance driving source when your audio amp has zero volts (volume turned down), the secondary will be a low impedance near zero resistance short with little voltage drop across secondary windings.

You need to know what the voltage modulation you want on top of the 4.5 vdc bias level current and the voltage swing of the amplifier output. My guess is you don't want more then a couple volts of modulation on the secondary. Your amp will put out a peak to peak voltage near the voltage supply for the amplifer. You probably want a three or four times step down from primary to secondary. A small 120vac to 25 vac or 120vac to 40vac transformer should do. 120vac primary winding fed from amp.
 
yeah i think that would be just fine..tahnks guys.that was really helpful.you people rock:).But ive some questions related to another project please do reply to that thread too thanks
 
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