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Posts posted by trigger

  1. 2.4GHz ISM band is a bit difficult for me esp. to build transmitter, because it involves a lot of matching problem.
    Although you can build using simple LC+transistor circuit but if you don't have a spectrum analyzer or signal generator, it will not an easy job.

    For me, I will start with 433.92MHz where it is simple and need lesser equipments esp. you can build a transmitter using saw resonator and a transistor based receiver.

  2. Would like to know if there are any good websites about AM/FM tuning methods......?

    Although I have worked on this stuff for quite a few years, I still keep on trial-and-error methods for fine tuning.....

    And what are the sensitivities standard for AM/FM radio?? (I have several info but different factories have differenct standard........)

    Anyway, Thanks first ;D

  3. It depends how complex your PCB is and the components you are choosing (through hole or SMT).....

    For my experience, try to put connected components closed together and try to route tracks through gaps of components (except IC pins)....

    But don't expect the auto-route function can give you much help, it always give you trouble

  4. Hi Trigger,
    Of course your triac will eliminate the spark, because it eliminates the relay contacts. And the diac-triacs must be optically-isolated, so that the entire circuit isn't "live". Four diac-triacs will need to be connected in an H bridge, to reverse the motor.
    But I think that a triac will create a problem where both the forward and reverse triacs will be conducting at the same time.
    The logic signal disconnects its drive to the forward diac-triac, to turn it off, then activates a logic signal to the reverse diac-triac, to turn it on. But since the load is inductive, the current lags the voltage by 90 degrees, therefore the reversing diac-triac will turn-on before the inductor's current has reduced low enough to turn-off the forward triac. Don't forget that a triac is a "latch" that doesn't turn-off exactly when you want it to.

    Thanks audioguru, that takes my a lesson to learn :)
    Actually, I know the problem as the circuits will gives me a blinking while the DC level is about the threshold level..... so finally I come up with a schemitt trigger circuit to have a voltage comparison, and give either a logic 1 or 0 to the diac. But for controlling the motor may be a big different from that of a light bulb..... so let see who will have a better solution... ;D
  5. That reminds me my old time in primary school............

    I disassembled batteries and take out the graphite, connected two with supply and dipped into a cup of salt water......

    I used test tube to fill with hydrogen and oxygen come out from the graphite....

    My game is lite a match to make a pop sound.........

    But the remains of water is dirty....... :P

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