interconnection of CM8870C with HT12E

Discussion in 'The Projects Forum' started by architjain_17, Mar 4, 2010.

  1. architjain_17

    Thread Starter New Member

    Feb 20, 2010
    i am trying to make a dtmf operated robot.i have made the the whole robot part but am getting problem in making the rf transmitter part.please tell me how to interconnect the encoader ic HT12E and dtmf decoder ic CM8870C ic.rply fast please...
  2. BMorse

    AAC Fanatic!

    Sep 26, 2009
    If you look at the datasheets for these devices, it gives you circuit samples to use....



    Q1 to Q4 of the CM8870C IC should replace the buttons connected to the HT12E's AD8 to AD11 respectively, and just keep TE of the HT12E tied to ground and remove the button for it in the circuit (this is a feature used in low power remotes, so the device doesn't use any power unless that button is pressed along with 1 of the data buttons.).....

    B. Morse
  3. architjain_17

    Thread Starter New Member

    Feb 20, 2010
    thanks sir
    sorry...i didn't intensionaly put the question again.....
    it happened by mistake....i'll avoid it hereafter....
  4. architjain_17

    Thread Starter New Member

    Feb 20, 2010
    sir,i just connected the 8870 ic as u said to understand its working...

    i made the connections as u said.i placed LEDs in q1,q2,q3,q4,std pins.
    but problem is that all the 4 Q LEDs are glowing without even giving the input via mobile.the std LED blinks when the power is turned on and then it doesn't glow at all even when the input's given.

    i accepted the dtmf input through the headphone wire by burning it and taking the 2 metal wires out, earthening one(arbiterily) and connecting the second to the the 8870 ic at 0.1microF capacitor.could there be a problem with this??
  5. SgtWookie


    Jul 17, 2007
    Did you connect a 3.58MHz crystal to it?

    Usually, crystals need a 20pF cap to ground on either side of them.