How to use DTMF tones to drive solenoids?

I suggest that you not use DTMF tones. The delay time inherent in the decoding process will be noticeable if the timing needs to be synchronized with other instruments in a performance, or if it controlled manually.

-Robert Scott Ypsilanti, Michigan

First, do you really have to use that scheme (I mean use a MP3 player and all that ...) ? Anyway, I'll first explain how to control solenoid from a digital signal then maybe a simpler scheme than DTMF tone for song storage.

So, you have a digital signal, either 3.3v or 5v representing a logic 1 (that is solenoid active). How to convert that will depend on your solenoid spec. You said AC or DC, the circuit might change depending on what it is. Then you also need the current flowing thru that solenoid.

Since you say, it's for music, it may be best to avoir mechanical relays, they produce a "clicking" sound. So the best solution for you might be a simple NMOS if it's DC, or a PhotoMOS (SolidState relay) if it's AC or you want optical isolation. That depends on the cur.rent requirements. In the simplest case :

Since the solenoid will produce high reverse peak voltage when turned on/off, you should add a diode to flow the current back to the supply (I'm too lazy to add it on the ascii schematics, just a diode across the NMOS Drain/Source, cathode on the solenoid side). Actually some NMOS might have that diode integrated, don't know but might be good enough.

Now, instead of you whole MP3 player stuff, using a simple uC with integrated EEPROM, you might store a big quantity of "music", with a decreased (IMHO) complexity. A low end pic or atmel AVR with integrated oscillator and enough IO. If you take one with UART, you could connect it to your PC to directly upload the songs to the internal eeprom or flash.

Sylvain

Be careful. Most NMOS do have a diode integrated (cathode connected to drain, anode to source), but that diode cannot provide an alternate path for the solenoid current when the NMOS is turned off. Therefore, that diode does not avoid or even reduce voltage buildup across drain and source, when the NMOS is opened. The diode to protect against this must be in parallel with the load (cathode to positive node of the load, anode to negative node).

Why do you want to use DTMF tones ?

It seems to me like you could use MIDI to do what you want and it would be vastly more versatile.

Graham

Offhand, I'd have thought MIDI would be the interface of choice, being a standard in the music world and all...

What's a castagnette?

Thanks, Rich

Dutch, French (and??) spelling for castanets. The word is related to "chestnut". I've got a wind chime-y kind of thing made from dried chestnut shells. Wish I could remember where I got it. Mexico, maybe.

Best regards, Spehro Pefhany

You mean those things that go clickety-clack when they're doing the flamingo [sic] dance? And he wants SIXTEEN of them?

Eek! Rich

a noisy spanish thing (apart from the goddamn mopeds)

martin

I think it's "flamenco" akshurely.

"Some tiny, emaciated Dago in tights, and a bint with a big arse and her hair Brylcreemed (sp?) down"