Intercom design

Go To Last Post
9 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Dear avrfreaks,

I am going to make an intercom design. It's my first time of doing something like this. The final system will always consist of only 2 terminals connected with a wire. There is a need of using as less as possible number of cables for the 2 terminals interconnection. The power supply has to be from 8 up to 30Vdc. Also, there is no need for the products to be compatible with any similar comercial product.

Is there any opinion or eperienced freak to help me make the begining ? Is there a need of a microcontroller that could make the system more robust (in noise) or even that could limit the number of cables or to reduce the final price ?

Any links, topics, ideas are wellcome.

Thank you in advance.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Sounds like the telephone system! Dtmf for the control signaling and current loop for the audio.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I found this very simple circuit in the internet.

http://www.redcircuits.com/Page78.htm

Any opinions are wellcome.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

How far? Of late, I find myself thinking, "Forget the wires!" as RF modules are like one or two dollars on ebay.

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut. 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You could certainly do a digital intercom. Read the mic using the a/d 10 bit 8KHz, (gives 4K speech freq resp) maybe use gain of 10, send it out on an rs485 or rs422 in 128 or 256 byte clumps, straight pcm, hi byte lo byte with an 0xaa0x55 in the front to look for, receive the bytes and stuff em in a 10 bit pwm. If you use earbuds you might not need an amp. Or plug the audio out into the line in on the pc.

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Do it need to be duplex?
If you use 150 ohm speakers they can be used as mic. as well, but then you need a button at one end to change direction.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

icarus1 wrote:
I found this very simple circuit in the internet.

http://www.redcircuits.com/Page78.htm

Any opinions are wellcome.

That's pretty slick!

Greg

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Mine is a lot simpler.

       +---------> 250 Kbps 422 to other node
       |<--UART
     +---+    R
MIC--|   |-/\/\/\-+-|>----PHONES
     +---+  PWM   | AMP
    20MHz AVR    ---
                 --- C
                  |
                  V

Imagecraft compiler user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

YOU can eliminate the pushbutton for direction control with a simple VOX circuit on one end controlling a relay that would replace the switch.

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user