First Post/ DTMF question

Thread Starter

tm585

Joined Mar 8, 2007
6
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..
 

thingmaker3

Joined May 16, 2005
5,084
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.
 

Thread Starter

tm585

Joined Mar 8, 2007
6
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.
 
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