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Remote switching using DTMF

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stickpin

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Right suppose i have a main transmitter (rig) remotely linked with STl to get the audio to it Either band 1, 3, or x band)

I need to remotely switch the rig on and off. This is what i have though of doing.
Using a DTMF receiver chip to trigger an electronic latch which will then hold the relay to switch my rig. (i.e. one pulse from the DTMF receiver rig goes on. Another pulse from DTMF receiver rig goes off toggling the latch and therefor the relay). Ok thats fine and will most probably work but...

What are the chances of whilte noise or audio/speech/music accidently triggering the remote latch circuit? example i could use 697 Hz and 1209 Hz sent down the audio link to toggle the relay/switch rig on/off. obviously having some DTMF generator sent down the audio link.

Would this be an acceptable way of doing it?


Hope someone can help with this one or maybe suggest an alternative.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
stickpin said:
Right suppose i have a main transmitter (rig) remotely linked with STl to get the audio to it Either band 1, 3, or x band)

I need to remotely switch the rig on and off. This is what i have though of doing.
Using a DTMF receiver chip to trigger an electronic latch which will then hold the relay to switch my rig. (i.e. one pulse from the DTMF receiver rig goes on. Another pulse from DTMF receiver rig goes off toggling the latch and therefor the relay). Ok thats fine and will most probably work but...

What are the chances of whilte noise or audio/speech/music accidently triggering the remote latch circuit? example i could use 697 Hz and 1209 Hz sent down the audio link to toggle the relay/switch rig on/off. obviously having some DTMF generator sent down the audio link.

Would this be an acceptable way of doing it?


Hope someone can help with this one or maybe suggest an alternative.
DTMF is a 40 year old technique, 'modern' (20-25 years old?) methods would be to use a digital coded system - which is far faster, more reliable, capable of far more, and cheaper as well.

PIC's are the way to go!.
 

stickpin

New Member
Yeh agreed maybe i'll try that but with using DTMF a mobile phone could just be used down the mic. Easy! and the receiver would cost £2 max with the relay. I'd like to try this first since i have all the stuff. I dont have a pic programmer at home either.
What do you think about it being accidently triggered though? what are the chances of white noise or audio doing that?

thanks
 

Nigel Goodwin

Super Moderator
Most Helpful Member
stickpin said:
Yeh agreed maybe i'll try that but with using DTMF a mobile phone could just be used down the mic. Easy! and the receiver would cost £2 max with the relay. I'd like to try this first since i have all the stuff. I dont have a pic programmer at home either.
What do you think about it being accidently triggered though? what are the chances of white noise or audio doing that?
Depends on how long a reliable tone the decoder needs?.
 

audioguru

Well-Known Member
Most Helpful Member
30 years ago, DTMF receiver ICs had a spec in the datasheet called, "talkoff" where speech would cause random decoded DTMF outputs. It occurs a few times per minute. It would probably occur more often with loud white noise.
 

stickpin

New Member
well i built/tested it today and works well over a wire so it should work over a link (thats for another day).
I played some music through it and it didnt trigger it so hopefully this should work.
 
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