I need Help Verifying somone's Schematic Design

Discussion in 'The Projects Forum' started by StToonz, Dec 1, 2012.

  1. StToonz

    Thread Starter New Member

    Nov 30, 2012
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    0
    Hey guys,

    I am brand new to this forum and still very new in electronics. im am trying to pull together a project for school and im asking you guys to just look at this voice switch (based from the MC2830) and tell me if you see anything shockingly wrong with this circuit. First, i dont understand what exactly the mic out is used for in this circuit or what it does. Second, from what ive learned about transistors the load can be taken off of the collector but ive never seen the load/output as the collector itself. is this even possible? can somebody help me straighten this out?

    any help is deeply appreciated.
    thanks,
    Conrad

    Schematic are in attatchments:

    The original schematic is the black and white version

    I didnt like how it was drawn so i tried re-drawing it (handwritten version)
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    The usual approach is get the data sheet about the chip, where you can find detailed information on the function and voltage level on each pin. It is worth going through it and try to make sense of it first.

    In many cases, the designer would provide a typical usage diagram showing how the chip can be wired up to perform its function. Not surprisingly, your hand drawn circuit is what is shown in the data sheet. See image below.

    This chip is a support chip which help to provide support for other chip, like starting up the motor of a voice recorder(in those days where MP3 is unheard of and voice is recorded on cassette tape). That's why the VOX output is the collector of a transistor to ground, which allows one to control a small motor to run/stop. The MIC output of course goes to the usual audio circuit for it to be recorded on tape via the magnetic head.

    When You speak, VOX turn ON cassette tape motor and your voice is recorded on tape.

    [​IMG]
     
    Last edited: Dec 1, 2012
  3. StToonz

    Thread Starter New Member

    Nov 30, 2012
    14
    0
    thanks that helps. my idea is to use a relay and a separate recording system

    Another Question i have is the original schematic didn't specify the transistor or the diode in the schematic. would i be able to use "just any" part (say an NPN 2n309 and GP 1n4001 diode)?
     
  4. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    If you plan to use a 5V relay, then you should look for a NPN transistor with 200mA collector current rating or more. BC337 or other part number is good.

    For the diode, a common 1N4148 will do. Don't forget you will also need to place a diode across the relay coil to surpress the back emf while switching, again the 1N4148 will do.
     
  5. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,866
    988
    OP,

    You do know there is free software such as Free PCB, Diptrace, ExpressSch etc. There is no need to hand draw anything. Though you did do a pretty good job of it. A lot better than most hand drawn schematics posted here.
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Did you know that the MC2830 IC is obsolete and has not been made for many years?
    Did you find one to use in your project or is your project only on paper?
    I had a difficult search for its datasheet but I found one on a German (!) site.

    The "mic" is an electret microphone (look at its details in Google). It is identified as an electret type by the resistor R3 that powers it. A dynamic mic (coil and magnet like a tiny speaker) is not powered. A piezo mic also is not powered.

    This circuit is unique that it is not triggered by continuous background noise like simpler circuits. It is triggered by speech (and other sounds that are similar to speech).
    It also has ALC (automatic level control).
     
  7. StToonz

    Thread Starter New Member

    Nov 30, 2012
    14
    0
    Well i did not realize that this was an out-of-date part. That kind of sucks.

    Does anyone happen to know where i can find a fairly simple vox switch schematic? the ultimate goal is to record a voice when someone walk up to this "robot" and the play it back when another action is performed.

    Another way i was thinking about doing this is to use some Cds photocells to activate the circuit when someone walks in front of the sensor. i have this schematic (schematic 1) but am still new to all of this. and i was wondering if i can modify the circuit to this (Schematic 2) so that i can use a relay as the output and not an LED.
     
  8. StToonz

    Thread Starter New Member

    Nov 30, 2012
    14
    0
    Also would anybody happen to know of a replacement part for the MC2830?
     
  9. bmb_10

    New Member

    Jul 28, 2012
    2
    0
  10. StToonz

    Thread Starter New Member

    Nov 30, 2012
    14
    0
  11. Audioguru

    New Member

    Dec 20, 2007
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    SKOOL?!
    Ask your teacher how to design the circuit.
     
  12. bmb_10

    New Member

    Jul 28, 2012
    2
    0
    You don't have to buy a kit, (did you see the pdf document?) that's only a example of a google search.

    Regards!
     
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