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Discussion Starter · #1 ·
I have a question I hope...REALLY HOPE there is an answer to regarding the use of touch tones for control.

I guess I should elaborate a little.
Everyone is familiar with Touchtones in thier phone, right? There is an inexpensive IC Chip that can decode up to 16 piared tones an average land based touchtone phone can produce..(Actually, phones only use 12, but 16 are available for decoding), and this got me thinking about using this for talking skull control. Imagine recording a tone, uploading it to your MP3 player on the left channel, audio on the right. The Chip would decode the tone, and send a latched signal to a relay turning on a DC motor in the jaw. The tone stops, but since the signal is latched, it will stay on. The work around is record another tone the relay isn't hooked onto and play that, turning off the relay. Ok, so we have potentially 12-16 relays we can control using the left channel of ONE mp3 player...pretty neat, huh? I thought so, until I played out the design in my mind and realized only one signal can be sent at a time....bummer for multiple skulls singing a group song where more than one skull needs to open thier jaw at the same time...


Question: Is there a way to, 1. Unlatch the signal. 2. have multiple signals decoded at the same time?


Does this make sense? I really think a controller like this would be awesome, CHEAP, and easy, but it needs to work simultaneously to be practical. Anyone?
 

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Discussion Starter · #5 ·
Yup...imagine. Get an old touch tone phone. Hook up the IC decoder circuit. Record in REAL TIME the switches as the audio plays. Use Audicity to mix the signals, then upload them to the left channel of your mp3 player, the right channel with audio. Now you would have one mp3 player and one simple circuit controlling all those relays. It would really work that way but only one relay at a time so far as I can tell. Maybe not for skulls, but a wiper motor goes on controlling your hangman with audio, then a fog machine goes while a strobe turns on...I mean, even if it doesn't work with multiple skulls, it's still a pretty neat control device.
 

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And for different people who have different set-ups and equipment, there's no other cross-platform decoding necessary. You just change CDs. Everyone could share their controller recordings because they're an audio track on the CD. Somebody trades Grim Grinning Ghosts for a barbershop quartet of I Ain't Got Nobody with someone accross the country in a minute online.

You are on to something big methinks.
 

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Looking up DTMF on wikipedia, it seems that a DTMF decoder should be able to decode a signal as short as 45 ms long. So if you have latches external to the decoder, you should be able to control several motors more or less simultaneously with one channel as long as the time accuracy doesn't need to be much better than 1 sec.

Also, it might be useful to consider using multiple LM567 tone decoders instead of the DTMF chip, since this thing doesn't need to be limited to the capabilities of POTS.
 

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Hmm...a bit pricey, especially since DM is proposing an external latch board as well.

If I were doing it, I would skip the DTMF decoder and latches altogether, unless there are cheaper kits/parts available. Instead I'd use a bunch of LM567/NE567/SE567 tone decoders. Each decoder would be activated by one tone, with the selected frequencies far enough apart that standard tolerance caps/resistors could be used. Each output (motor) would be controlled by one decoder, with the presence of the tone activating the motor. The decoders cost around $2.00 from Digikey (subject to their minimum order), and I'd just put them on one of the little 1.75"x1.75" perfboards (276-148 or 276-159) from Radio Shack.
 

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Discussion Starter · #12 ·
Hmm...a bit pricey, especially since DM is proposing an external latch board as well.

If I were doing it, I would skip the DTMF decoder and latches altogether, unless there are cheaper kits/parts available. Instead I'd use a bunch of LM567/NE567/SE567 tone decoders. Each decoder would be activated by one tone, with the selected frequencies far enough apart that standard tolerance caps/resistors could be used. Each output (motor) would be controlled by one decoder, with the presence of the tone activating the motor. The decoders cost around $2.00 from Digikey (subject to their minimum order), and I'd just put them on one of the little 1.75"x1.75" perfboards (276-148 or 276-159) from Radio Shack.
Sounds good...Which frequencies would you select? Seems that the phone company has done the research for us given the sinusoidal wave frequncies that won't interfer with each other has already been determined...
DTMF keypad frequencies (with sound clips)1209 Hz1336 Hz1477 Hz1633 Hz697 Hz123A770 Hz456B852 Hz789C941 Hz*0#D
 

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How many control channels do you want for each mp3 left-channel?

In any case, the scheme that I mentioned only really needs to have the frequencies differing by more than 10% to take into account component tolerances (the DTMF frequencies were selected, I'm sure, with the limitations of the phone system in mind, and perhaps based on prior network capabilities). So, perhaps 600 hz, 700 hz, 820 Hz, 950 Hz, 1110 Hz, 1300 Hz, 1500 Hz and so forth up to perhaps 5100 Hz. That is, if that there is a need for that many channels (16). The other thing that needs to be investigated is how does an mp3 encoder/decoder pair treat these signals. Part of the mp3 compression scheme is remove signals that the human ear can't really perceive, such as a low-volume tone right next in frequency to a high-volume tone.

Incidently, what are you thinking of for turning the mp3 player on and off, or would it be running continuously in some sort of loop?
 

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Discussion Starter · #15 ·
I think it wouldn't matter what is used to turn it on or off..If I were to automate that I would hack the play button and have something like VSA turn it on or off, but in this application a loop would be ok seeing as how an mp3 player can be set to repeat. Also, I agree the frequencies may have been chosen for DTMF because of network limitations, but also I read somewhere they were chosen so as not to interfere with each other.

I think 16 control channels would be enough to encode.
 

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Discussion Starter · #17 ·
Hmmm....I just thought of something. If there are 4 bits in each byte, then you CAN have 4 skulls open thier mouths at once..the key "D"= 1111...4 on states. Think of each byte as a combination where the number 1 = an open jaw. Programming it would be difficult manually though. Maybe I can find a tone generator software for free, then you can program the tones as you need the jaws to open in sync with audio. I'm gonna play around with this. True, this limits the prop to 4 skulls, but that's still pretty cool using 1 mp3 player, and one off the shelf decoder kit...I did find one for about 25 bucks. The only added cost would be relays and a perf board.
 

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Discussion Starter · #19 ·
Ok, I found a cool generator. It's free, and you can program pauses into it. I don't know how many numbers it's limied to, but you can always copy the tones to Audacity for an unlimited length. I wrote the digits in Notepad and used the clipboard feature to paste it in. To record the tones, you may need to use windows sound recorder. I haven't figured out how to sync with audio yet.
 
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