Halloween season is rolling around again, and my wife is goading me on to top last year’s project - a simple hack of a WalMart Singing Santa. Since it lacked auxilliary audio, and I was short of time, I gave it a monster head but left it singing christmas songs. (It was the wife’s idea to put the original santa head in a cooking pot in front of the monster. Several neighborhood children are still in therapy )
Anyway, for this year, I’d like to put together a moving “animatronic” head using servos and my ever-useful Bot Board. Most of it will be dead simple, but I need some help with one issue:
Anyone have a simple idea for making a “mouth” open and close proportionally to volume of sound - I.E. I would like to be able to talk through the head and have the mouth open and close more or less with my voice. I could simply use a manual joystick, but it’d be much cooler to do it in an automated fashion.
I found a product that would hook directly to a servo, but it’s $100, which is waaaaay more than I want to spend. (Also way beyond the spousal acceptance threshold)
I’d just use a solenoid connected to a button. When you talk you tap the button with your finger to have the solenoid make the jaw move. I’d put a web cam in the head so you could look at the kids, use the joy stick to pan/tilt the the head, and an intercom to talk to the kids.
Mike, with the help of Pete and others made that circuit for his Basic Stamp.
The circuit itself measures the intensity (loudness) of two microphones and converts that analog value into a digital signal.
You’ll only need to use one of those two, of course, and you won’t need the ADC (Analog to Digital Converter) if your micro has a free one.
All the rest can get done in software.
Figure out the max and min values (with a multimeter or with debug printf statements).
My meter measured a range of about 1.75V to 4.05V.
After you have the range of loudness and know the range of pulses that your mouth servo can travel, it’s just an easy matter of basic algebra to get whatcha want.
Make sure you put in thresholds in the servo pulses so that you don’t accidently go over.
I’m not sure yet the exact method I’ll use to get audio to the prop, but I figure I’ll clearly need a speaker there.
Could I split the feed to the speaker and connect that as though it were the microphone in the circuit above? Would I need to attentuate it since it would be at “speaker” level?
::scratches head::
I’m probably the worst person to ask that.
I’ll take a guess (a.k.a. I’ll start lying):
In general, a speaker will have an amplifier sending signals to it to make the pretty noises at a level we can actually detect.
The problem here is that amplifiers need to output an alternating current (AC) to get those buggers to whack out the sound we want to hear.
A speaker is really just a paper cone attached to a solenoid.
The amplifier continually reverses the direction of the current going into the solenoid, effectively making the output “shaft” (paper cone) vibrate back and forth quickly, producing sound.
So… long story short, I don’t think there’s any easy way to tie it into this circuit.
Although, there might be a simpler answer.
You could just build this circuit and place the microphone near your speaker.
Me doesn’t think that this will produce any nasty feedback, since the two will be totally independant systems.
Feedback generally arises when the input of an item is coupled to it’s output (i.e. hold an acoustic microphone near it’s speaker).
In this case, though, we’re just driving the input of one circuit with the output of a seperate one.
I suppose you could even call it acoustic coupling.
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