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Ramji

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  1. Hi all, Im trying to implement a discrete phase locked loop circuit(PLL). I know the basic functioning of the PLL and its different parts and i have used it as an IC. But I want to implement a discrete PLL circuit using separate components for Phase Detector, Loop filter, VCO etc. Plz help me. I found a file on this in the net which is actually a kind of e-book which contains some design info on discrete PLL's. I have attched it. If anyone has got a schematic or design ideas regarding this plzz help me out... Ramji
  2. Because of lack of time i havent been able to design a FM circuit for this.. Instead i have stuck to the AM circuit which i have sent earlier in the file "irfm.pdf" The circuit workd perfectly for me once i modified the transmitter. I replaced the amplifying stage into a 2-stage common emitter with the same transistors shown in the diagram. I just biased them with different resistors. The receiver is the same. I was able to hear the melody clearly but the range is very limited. Its about 2feet. I want to improve my range to about 10-12feet. Any suggestions on how to do it?? Also I have set 5mA as the DC bias current for the current through the transistor BD140 and the IR led's. I heard that increasing this current will improve range. If so how much can i increase the LED bias current to?? Can i use lenses? What type of lenses and any suggestions on type of arrangement? Can i use more than 2 IR Led's?? Will it improve my range?? Any other suggestions are welcome..... plzz help me out....
  3. ok... I'l hv to read about VCOs n PLL's n then construct the circuit myself. But assumin that i produce a FM audio signal. How do i transmit and receive using IR? Do i use the same LED n photo transistor mechanism?(Isnt that AM then?) Or do u suggest a different mode of transmission??
  4. And one more thing. The schematics for FM transmitters of radios are easily available. Can i use those schematics to produce a FM audio signal and then try to transmit using infrared? Again its the transmission part that i dont kno much. How do i transmit such an FM signal thro possibly IR LED's? Will this kind of coupling of an FM transmitter with IR transmitter work? And ofcourse the receiving end also needs to be dealt with... Any ideas or tips??
  5. Yes the music IC does bias the transistor i think. And it'l cause distortion. How about giving a bias DC current to the transistor to prevent it? Will it minimise distortion? How much of a current do u reckon wud be enuf? And the red LED simply acts as an indicator. So it can be removed and replaced by a resistance. And ofcourse the interference is something i hv not yet been able to address. I have still not been able to find a FM schematic.
  6. Ya even i hvnt got the FM circuit. But i found that a similar AM IR transmitter has figured in the Jan 2007 edition of EFY magazine. I hv sent the schematic along. It transmits a musical signal thro IR and i suspect it uses AM too. Just hv a look n see if this is a workin design. I kno its similar to the one i sent(maybe a different receiver section) but its given that the circuit has been tested by the magazine(there's a seal which says that). So plz post ur views on it... ir_fm.pdf
  7. Hi audioguru, Thanks for the info. And i get most of wat u meant. I dint know bout AM or FM in IR transmission. Anyway i think i'l drop this circuit and go for a FM design. So can u help me Find a schematic for FM transmission using IR. And also i hv some clarifications regardin some of the points u mentioned.. 1. How did u identify the circuit to be AM? are there any distinctive features for AM n FM? 2. I agree that the transistor T1 has no bias current. That means most of the signal im sending (i.e. negative part of the signal to be precise) will be lost. Am i right in that?? 3. What is the difference between stereo and mono? Has it got somthing to do with digital and analog audio signals??
  8. Hi all, I hv gotta schematic to build a IR headphone set. It simply amplifies the audio output signal from a TV or Computer and transmits through IR Led's. This IR signal is received and given to the head phones wher the original sound can be reproduced. Im plannin to do this as a proj n have some doubts... 1. Firstly will this circuit work? I know it involves simple amplification of the audio signal but i have never dealt with data transmission using IR rays. So is this design good enough to make it work? 2. There is a potentiometer/variable resistor in the transmitter. What is the purpose of it? Is it related to volume control? 3. What do i need to do to increase the range of this design(assumin it works!). And should i tak any precautions for ensurin the correct reception of the transmitted signal(like avoidin interference, ambient lightin etc)
  9. hey the idea is pretty cool... It wud even help me regardin a telephone proj that i hv plannd on.. Can any1 get me the internal circuitry of the telephone...
  10. Hi indulis, Actualy i hv come acros fet's, mosfets etc.. i mean i knw their functionin structure, characteristics etc. But im nt able to figure wts the advantage of a NPN over an PNP transistor. The only benefit i find is that in NPN the base current adds to the output collector current whereas in PNP the base current reduces the output collector current. Also can u plz tel me som examples of applications in which NPN or PNP wud be more suited....
  11. In my short exp of electronics fr the last one year i hv come across mostly only NPN transistors. Is there any particular advantage of an NPN transistor which makes it more favored in circuit design than PNP transistors??
  12. Hi ante, What exactly do u mean by "compound"? I understand that the transistor must be mounted on the heat sink through an insulator(should it necessarily be an insulator??) having high thermal conductivity. And what r the benefits u get from using mica or "compound"?
  13. Thanks fr ur responses. I understand the general outline of a heat-sink and how it works. Now i am keen to see the real device. I'l just browse through some sites and get back to u guys if i have any more doubts.
  14. Yes i get what u mean in theory but i want to know its application in electronics. To be frank i dont know how a heat sink wil actualy look. Is it somthing external that u connect to a transistor or does it come built-in to the transistor? Can u help me with some diagrams or pictures? I myself am searching in the net too. And thanks very much fr ur rply.....
  15. Hi all, Im a starter in Electronics as well as starter in this forum. I have learnt somthings about heat sinks and how they limit the heating up of transistors. But im not able to grasp it fully. Can anyone provide me with any explanation or notes on heat sinks preferably with some diagrams and equations? And do they work only for transistors or for other devices as wel?
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