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InterCom / Door Phone

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Non89, Nov 11, 2010.

  1. Non89

    Non89 Member

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    any specified colour cable should using for AF , and which is for ground?
     
    Last edited: Nov 25, 2010
  2. Boncuk

    Boncuk New Member

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    I guess the device connected doesn't care for the color of the insulation.

    Normallly red is used for +UB (+12V), black is used for circuit ground and any other color is used for the AF signal. The shield is wire mesh around the entire bundle of cables.

    Once again, use 4 wire shielded cable between master and slave.

    Boncuk
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Do you really think that the colour of a wire affects the sound?
    One wire is the signal wire that is surrounded by a shield. But the cable you showed has no shield.
     
  4. dave

    Dave New Member

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  5. Boncuk

    Boncuk New Member

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    I guess pink wires make the best sound. :)
     
  6. Non89

    Non89 Member

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    then what kind of cable should i using , could you show me please :)
     
    Last edited: Nov 25, 2010
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    You showed a cable with RCA connectors. They are usually shielded. If they are used for speakers then they are not shielded.
    Simply cut off an RCA plug and look at the cable. If it is shielded then you will see a signal wire that is surrounded by the shield.
     

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  8. Non89

    Non89 Member

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    maybe i need more description about the DTDP swith in this circuit ...
     
  9. audioguru

    audioguru Well-Known Member Most Helpful Member

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    A DPDT switch is Double Pole Double Throw. It has two (double) separate switches called Poles. Its toggle contact goes in two (double)Throws (directions). It has 6 contacts, 3 for each switch.

    When the DPDT is in one direction then the mic signal is shorted by one of its switches and the other switch turns on the "silent" LED. when the switch is in the other direction then the mic is allowed to work by one of its switches and the other switch turns on the "speak" LED.

    When I use a switch to short a low-power signal then I use a switch that has gold contacts. Gold doesn't corrode like high current silver switch contacts. It costs the same.
     
    Last edited: Nov 29, 2010
  10. Non89

    Non89 Member

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    R7 is 22k until ? k .... ??
     
  11. Non89

    Non89 Member

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    Mean this circuit is also Pull To Talk ?
     
  12. Boncuk

    Boncuk New Member

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    Hi,

    R7 is a potentiometer ranging from 0Ω to 22KΩ.

    It's purpose is to adjust speaker volume for the master unit. The slave unit has a fixed volume setting through the voltage divider consisting of R10 (4.7KΩ) and R11 (10KΩ).

    If that volume setting is too low increase the value of R11 to 12 .. 15KΩ. If it's too high increase the value of R10 to to 6.8 .. 8.2KΩ leaving R11 unchanged.

    S1 (A and B) is the "privacy" switch. It should be a latching switch and needs to be operated if somebody rings the door bell and you want to talk to the person. Part A of the switch prevents AF to go through the amplifier and part B switches LEDs for visual control of the switch setting "SILENT/SPEAK".

    Without that switch all communication from inside the house will be heard at the door.

    If you don't need the switch omit it completely as well as R9 and and D1/D2. Make a wire jump from switch terminals 1 to 3.

    Boncuk
     
  13. Non89

    Non89 Member

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    S1A & S1B all connected within 1 DTDP switch (On-Off-On) ? so how i connect it , is this left side 3 pin for S1A , and right side 3 pin for S1B???

    this is the 4-wire shielded cable you mean ??

    and the npc transister is bc 547 =.=? my eyes cant see it clearly .....
     

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  14. Boncuk

    Boncuk New Member

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    Hi,

    the cable is not shielded! It's twisted pair cable used for telephones. Check the attached image of a four wire shielded cable. You don't need a cable with a drain wire (blank copper wire within the insulation), but you need either copper mesh or any metal foil for shielding.

    The switch doesn't have double pin names. There are two electrically isolated switches in the enclosure being activated simultaneously.

    A DPDT-switch is a double pole double throw switch.

    Pin numbers in my schematic are 1 through 6. Switch part A has pins 1 through 3 and part B has 4 through 6.

    Pin assignments for functions are pin1 (4), pin 2 (5) and pin 3 (6).

    Take a good look at the PCB design. The switch functions are clearly visible.

    Yes, the transistor is a BC547.

    Boncuk
     

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  15. Non89

    Non89 Member

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    something like this ??? and the ic used is audio amp right ?
     

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    Last edited: Nov 30, 2010
  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    No.
    Each R7 is adjusted for a null of your voice in your speaker to prevent acoustical feedback. Then the circuit will operate in full duplex without using press-to-talk switching. Both people can talk to each other at the same time without switching.

    The two P1 pots are volume controls and maybe should be hidden trimpots so they are not turned down to zero.
     
  17. Non89

    Non89 Member

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    here are the circuits you 1st and 2nd time you sent for me , i want to ask why got 2 more extra connection , that mean i need shielded 6-wire cable ....?
     

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  18. Non89

    Non89 Member

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    two p1 pots?? not only have 1 p1 pots at master circuit there ?
     
  19. Dragon Tamer

    Dragon Tamer Member

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    You can do what I did and make a really simple intercom using an LM386, 2 mics, 2 speakers, and a relay. It was really simple to make, and I used it with my door lock. It is cheap and simple, but the sound quality is rather low but that is to be expected.
     
  20. Non89

    Non89 Member

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    because i need to pass up this circuit , if i choose simple intercom , my lecturer sure asking me add more circuit , etc output to door bell or any else ....
     
    Last edited: Nov 30, 2010
  21. Dragon Tamer

    Dragon Tamer Member

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    You can build the whole lock to go with it. Do you want the circuit?
     

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