Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Need help on a circuit

  1. Aug 13, 2011 #1
    Hi!
    I was working on a circuit today.I soldiered all the capacitors, resistors, transistors,... just as the paper-guide said except the Microphone;Because it was said in there that if you want to use this kit as an earphone, simply solder the MIC to the board,else use a "shield wire(?)" to attach the MIC to it's slots...I assumed that shield wire is simply the ones that have some golden torn wires as their kernel...I used a 3.5 mm standard headphone
    But after plugging the batteries, some irrelevant noise(not the environment sound) and sometimes continuous beep is heard (However, when I blow to the MIC some relevant noise can be heard)
    WHERE IS THE PROBLEM?
    My suspects[!]:
    -the "shied wire"?
    -mis-soldering the shield wire to the MIC?
    -mis-soldering the battery wires?
    -I misplaced a 4.7 capacitor in a 0.47 capacitor,then I desoldered it with lots of troubles[!]. Perhaps the capacitor failed?

    This is a picture of my cuisine[!]:
    http://i52.tinypic.com/339n0qg.jpg
    I will be glad if you help...
    Thanks
     
    Last edited: Aug 14, 2011
  2. jcsd
  3. Aug 13, 2011 #2

    berkeman

    User Avatar

    Staff: Mentor

    Welcome to the PF.

    It almost looks like a transmitter and receiver together? I see the microphone in the picture, but also see what looks like an earpiece jack. Is this meant to be a wireless microphone, or a wireless receiver? Or can it do both somehow?
     
  4. Aug 13, 2011 #3
    a 3.5 mm headphone would be plugged into the down left device in the picture
    I think it is just a sensitive amplifier.
     
  5. Aug 13, 2011 #4

    berkeman

    User Avatar

    Staff: Mentor

    Ah, I see. It is an audio amplifier from the microphone to the earphone jack.

    Can you post a copy of the schematic? That would be helpful in debugging the circuit operation.

    Also, what measurement equipment do you have? Do you have a digital multi-meter (DMM)? How about an oscilloscope?
     
  6. Aug 13, 2011 #5
    Here:http://www.freeimagehosting.net/t/ea24f.jpg
    Sorry about photo's poor quality
    Well,I don't have any measurement tools yet!(Say, I am a first year electrical engineering student and I don't even have a multimeter!!!)
    Going to buy a good DMM tomorrow... (It is 2:15 A.M now in here!)
     
  7. Aug 13, 2011 #6

    berkeman

    User Avatar

    Staff: Mentor

    Do you have the schematic? That is the paper diagram of the parts, and how they are connected together. The photo that you posted just now is the "layout" of the circuit, not the "schematic".
     
  8. Aug 13, 2011 #7
    you mean kind of these things:[PLAIN]http://www.dekits.com/images/images_big/shematic8.jpg [Broken]
    No,I don't.
    BTW,the picture in this post is something like my circuit
     
    Last edited by a moderator: May 5, 2017
  9. Aug 13, 2011 #8

    berkeman

    User Avatar

    Staff: Mentor

    The schematic example link at dekits.com is not working.

    It will be very difficult to help you debug the problem without the schematic for the kit. Can you get it from dekits.com somehow?
     
    Last edited by a moderator: May 5, 2017
  10. Aug 13, 2011 #9
    I've been using the Extech meters, less expensive than a Fluke and seem to be competetive in quality.

    Scopes are expensive, no way around that. I picked up a 20MHz one online that wasn't terribly expensive. It seems to do the job for me.
     
  11. Aug 13, 2011 #10
    It isn't my circuit's schematic.But I think it is similar to it in practice:
    http://www.freeimagehosting.net/e7b2d
     
  12. Aug 13, 2011 #11
    Also:
    Never assume anything when building circuits. *wink*
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Need help on a circuit
Loading...