First Post/ DTMF question

Discussion in 'The Projects Forum' started by tm585, Mar 8, 2007.

  1. tm585

    Thread Starter New Member

    Mar 8, 2007
    6
    0
    I am new here . Found this forum while searching around the web looking for am answer to a problem I have. I built a dtmf decoder using a 8870 and then sending the signal from there into a 74154 demultiplexer. My problem is that the pin ( of the 74154) corresponding to the number I send into the 8870 stays low until I put in the next number then it goes back high again. I would like to have it so that it only stays low as long as it is actually recieving the tone then have them all go back high as soon as I stop sending the tone. I am not sure of how to post a schematic here but it is built right according to the reccomendations on the data sheets of the two chips. It works pretty well, but I would just like to make the 4 pins ( from the 8870)somehow ground out after the tone isnt being recieved anymore . I hope I explained it well enough and I hope that someone here can help me get rid of my headache. Thanks a bunch..
     
  2. tm585

    Thread Starter New Member

    Mar 8, 2007
    6
    0
    Sorry, Forgot to mention what Im using it for . I want to use it for controlling a robot.Thanks,
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Use pin 16 (early steering o/p) of the 8870. Invert with a switching transistor (or spare inverter gate if you have one available) and feed to pin 18 or 19 (gating) of the 74154.
     
  4. tm585

    Thread Starter New Member

    Mar 8, 2007
    6
    0
    Thank you so much for the help. Ill give it a try.
     
  5. tm585

    Thread Starter New Member

    Mar 8, 2007
    6
    0
    Works like a champ. Thank you very much.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Glad to hear it!

    So... what does your robot do?
     
  7. tm585

    Thread Starter New Member

    Mar 8, 2007
    6
    0
    Well right now it just moves forward and back right and left and has a camera on it that is going to pan/tilt(using servos). My next experiment will be with the dtmf decoder going into a BS2 OEM I just made and an accelerometer I bought at BGmicro for 8$. I am hoping to make it balance on 2 wheels. Right now I have a piece that sticks out like a tail that balances it as it moves ,turns etc. I would like to get rid of that piece if I am able to get it to all work fast enough to balance itself.
     
Loading...