Saltwater-proof synth to arouse snails

[opg]

Once again, my wife's research and my hobbies magically collide. She has been working on her PhD in Ecology and Evolution studying the effects of heat on snails with varying shell colors (light-colored shells do better in the heat than darker ones, for example). However, working with snails is very difficult, especially if you are trying to determine whether they've actually died or not after being roasted out in the midday sun. Typically, a quick prod with a probe will create an involuntary response from the sweet, sweet innards of the snail, but my wife's assistant found a more interesting way to detect snail movement:

If the snail is subjected to a low tone against one's throat, the snail will begin to stretch out of its shell. Sexy, I know. My wife thought it would be a great idea to have a simple tone generator to do this. As I am already tinkering with simple VCOs myself, this would be very easy to build.

There are a few areas I haven't figured out yet.

1. There will of course be a pot for a frequency sweep, but I was wondering if there was a convenient way to determine what the frequency (in Hz) was. Apparently, there is a "sweet spot," according to her assistant. I'll certainly do a frequency analysis of her assistant's voice, so I will have a peak frequency to start with. But if they are going to sweep through the frequencies, how will they know exactly what frequency they are at?

2. My wife said the device must be saltwater-proof. Any ideas on what casing I should use, as well as the type of and sealing for pots, switches and knobs?

3. I would be able to give her different waveforms to choose from, but obviously, the human voice seems to be working quite well. What waveforms should I make available? They want to keep the design very simple: just frequency and volume knobs, power switch, and a switch for waveform selection (if really necessary).

This is so awesome! And it's not needed until the summer.

[Coriolis]

Hah! Sounds like fun!
Guess the biggest challenge will be making the thing saltwater proof.
I mean, it's got to have a speaker of sorts which has to withstand saltwater. Maybe cut a hole in your waterproof enclosure of choice, cover that hole with plastic membrane of some kind and somehow attach a speaker to that membrane, so it moves with the speakercone.

Or, google "hydrophone" and see how they make those...?

Keep us posted - I'd love to build a hydrophone or underwater speaker for that matter!

C

[para]

you could get a waterproof speaker from ebay and build the VCO inside of it, but i'm not sure about waterproof pots?

http://cgi.ebay.com/New-Pair-Pyramid-3-5-2-Way-Waterproof-Studio-Speaker_W0QQitemZ290070070975QQihZ019QQcategoryZ14995QQrdZ1QQcmdZViewItem

or use something like this, replace the existing board, but use its pots?

http://cgi.ebay.com/Soapie-AM-FM-Shower-radio-with-waterproof-speaker_W0QQitemZ200066617514QQihZ010QQcategoryZ103427QQrdZ1QQcmdZViewItem

[opg]

Good call with the showerproof stuff. I hadn't thought of that. I have one, like most people, but it never gets used. I can open it up and see what is different from your typical radio.

As for the pots, all I could think of was drilling the casing holes, then adding a tight gasket (or membrane, like you said) and adding a rubber knob, kind of like a Mackie mixer knob, but rubberier.

Mind you, this doesn't have to go IN the water. The idea so far is just to place a snail on top of the case and have it not only "hear" the sound but more importantly FEEL it. So, there doesn't really need to be an external speaker or jack. Of course, she would like to be able to take it out in the field if it turns out to be really handy, so that's why it is important to be rugged and waterproof.

Now I am reminded of this thing, after you mentioned the shower radio:

[para]

if you find the frequency range then you could just make a cd filled with it then put it in a waterproof player, is that what the dewalt is?. i guess that would be the easiest way





_

[Coriolis]

Ah, but then it wouldn't be synth diy...

C

[deknow]

...somewhere in the diy section is a thread about these membrane pots (they make "sliders" and "knobs"). these could be used to make waterproof pots.

http://www.electro-music.com/forum/viewtopic.php?highlight=ribbon+controller&t=10272

if you mount one of these under a waterproof membrane, you can use something mechanical outside the membrane that will push down on one spot.

deknow

[Yorky]

why not just record the assistant's voice when the snail comes out, then loop it, pop into an eprom, then play back via DAC, small amp/speaker etc

[opg]

[para]

[opg]

Hmmm....fancy. Perhaps I could get funding for this, as it is part of her research?

[13"]

What if you took some really small and powerful magnets like in the geomag toys, and put on top of the knob of the pots (off center), and some kind of magnetic switch for on and off, then you could manouvre the whole thingamajing from outside with some small magnets, without having any holes in the casing at all? (maybe not even a hole for the speaker since vibration seemed to be what you´re after)
Of course the casing must be unmagnetic in this case so to say..
/Martin

[opg]

Alright, so the components for the "snail detector" are coming in on Thursday! I decided to go with this case from Hammond:



It's watertight. When I'm putting in the pots, I'm going to see if I can get some sort of rubber grommet/gasket thing (like the rubber you can see on the case) to put around the hole. I bought a rocker switch for the power switch that will seal nicely, along with a led light that has a snap-in casing.

The only two questions I have are:

1. Is there anything in particular I should keep in mind when mounting the speaker on the underside of the case?

2. What do I name this thing?

[EdisonRex]

[etherline]

What about S-CarHorn?

[opg]

S-CarHorn....had to think about that one before I finally got it.

I could always go with what everybody names things these days: iSnail

[etherline]

[13"]

Brilliant!
Thank you very much for sharing this project.
Keep posting, I can´t wait to read further reports on build and field performance!
/Martin

[opg]

I got the parts today, and I need to finish by June 1st. I may need some advice on schematics, as I am going to base this on the WSG design (Schmitt trigger) but it obviously is much more minimal. Basically, I just need one of the I/Os on the Schmitt Trigger for a simple pulse wave, the same WSG lowpass filter, and the obvious frequency and volume pots. I'm going to have to figure out the 8 ohm speaker deal as everything I've worked on always involves a 1/4" output jack.

Keep in mind, this is supposed to be a replacement for the human voice's frequency spectrum and vibrations, so I wasn't sure whether I needed two oscillators (pulse and triangle) to get a more complex waveform.

I've seen the old schematics on a simple pulse generator using a 555 timer with an 8 ohm speaker, but I really like the Schmitt Trigger (I ordered six just to have around ).

Any advice on simplifying the WSG schematics for this?