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  1. Hero999

    FM Transmitter help!

    Read up on transistors and amplifier configurations. I'll have a go at explaining it but you won't understand if you're new to electronics. Q1 is configured as a common emitter amplifier with shunt feedback provided by R1 which also biases it at around half the supply voltage. This amplifies...
  2. Hero999

    Help about op-amp...

    What do you want to use these crappy op-amps for? You do know they're no good for audio. If it's just DC voltage amplification they'll be fine as long as you're aware that the inputs and outputs need to be 3V above the negative supply and 3V below the positive supply in order for them to work...
  3. Hero999

    How to distinguish between FM and AM transmitter circuits

    Yes, the frequency will go down as the battery discharges. You need to use a voltage regulator to stop the frequency being dependant on the battery voltage.
  4. Hero999

    Please help me with High Low voltage cutoff with time delay

    Your circuit is poorly drawn and contains an obvious error. Compare it to my circuit connection by connection and you'll see what I mean. Here's my revised version of the circuit. The one I posted previously will work but it didn't show the power connections to the comparator IC and I got the...
  5. Hero999

    How to distinguish between FM and AM transmitter circuits

    Think about it. Re-read my previous post paying close attention to what I said about the FM transmitter.
  6. Hero999

    How to distinguish between FM and AM transmitter circuits

    That's because cheap FM transmitters built with a single transistor and no varactor diode produce both AM and FM. AM is produced because the transistor's gain alters as the base current is varied and FM because the capacitance between the PN junctions also alters as the voltage varies. The...
  7. Hero999

    Help about op-amp...

    Look onb the datasheet, which can be found using a search engine.
  8. Hero999

    RF coupling transformers

    Kevin, Here are the articles I'm talking about. It doesn't matter whether it's RF or audio. http://en.wikipedia.org/wiki/Impedance_matching http://en.wikipedia.org/wiki/Balun Pay attention to the formula. If you can't figure out whether an impedance matching transformer changes the voltage or...
  9. Hero999

    Balancing dual secondary rails

    There's no way to do it without using switching regulators. The circuit you've posted has several issues: The filter capacitors are undersized by at lease two orders of a magnitude. No fuses are required on the output because the voltage regulator ICs will limit the current. Only one bridge...
  10. Hero999

    RF coupling transformers

    You obviously didn't bother to search Wikipedia as I suggested. Next time I'll ignore you when you ask a question.
  11. Hero999

    Making switching NPN with PNP

    Here's a link to a page with some possible solutions. http://www.winpicprog.co.uk/pic_tutorial_extras.htm
  12. Hero999

    HiJack Public Speakers

    It's also illegal, even if it's possible.
  13. Hero999

    Question lng po mga Master Sir/Ma'am

    How about asking English so we can help you?
  14. Hero999

    Sata toUSB Converter

    I've had a job for the last month which has being going quite well. Mixos has made me a supermoderator so help remove the spam but I'm not online as much nowadays as I'm busy working/socialising.
  15. Hero999

    RF coupling transformers

    If you look at the impedance matching transformer article on Wikipedia, you should be able to figure it out for yourself.
  16. Hero999

    1958 Hifi play MP3 - Can it be done ????.

    He only has to connect the MP3 player to the amplifier input. Interfacing with the buttons is the hard part.
  17. Hero999

    LDR offset + span adjustment

    C1 is connected backwards and isn't required. To invert the operation, simply exchange LDR and P1. R1 should also be removed.
  18. Hero999

    Motion Activated Dice

    I've never made it before. You can buy components in India from Futurlec.
  19. Hero999

    Balancing dual secondary rails

    Why do you need to balance the load on the secondaries? Unless it's a polyphase transformer, the load on the primary will be the same, regardless of whether the secondaries are balanced or not.
  20. Hero999

    Sata toUSB Converter

    It's more economical to buy it than to make it yourself. I'm being helpful by saying this is not a feasible project. If someone here did go to the trouble of designing such a project for you, you wouldn't learn much because the best way to learn is to design yourself. Copying someone else's...
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