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for the window, you could use something like one of these. http://www.lasersafetyindustries.com/Acrylic_Laser_Safety_Windows_s/553.htm
Just match it to the laser wavelength.

Thanks for the info Rylan. I should have some time coming up to try some further experimentation. I'm getting 50-100pF. I think to be able to use reasonable levels of resistance I will need some...

Would just take a charge resistor of high resistance, to charge the "capacitor", and a low value resistor to discharge.

The large resistance needs to be chosen to charge your capacitor slow enough...

Good point, I didn't think of the resistance in the "leads" running to the "capacitor". The salt water will act as a resistor in the lead, and will be part of the resistance. As you say though it...

I tested this with just a multimeter as a proof of concept. I just dangled one probe in the water, and touched the other to the foil. Seems to work, and level of salinity has no effect whatsoever. I...

The saltwater is the conductor, not the dielectric. The dielectric is the container wall. It will vary from build to build, but remain constant on a single container.

That's a good question. One that I think more relates to the parts used, and the resolution of said parts, than the method itself. I can test this maybe in the next day or two, just with some foil...

I think a capacitive sense would work best. Resistance is relative to salt concentration, and would require re-calibration every time. I could easily rig up a test with an arduino. you just need to...

I'll take his spot in line. ;-) I don't mind getting 2. I got in after the main campaign, and got in on the first backerkit sign up.

This would be cool. http://www.thingiverse.com/thing:191925
Snowflake Icosahedron Ornament

It's supposed to be printed in pieces and hooked together, but I'd love to see you print it...

I'd love to see something with some size, maybe 15cm+ tall. With some intricate details, just to see the big picture so to speak. Maybe also some kind of bottle, with a screw on lid, to see...

Other that the possibility of it becoming a galvanic cell if you use dissimilar metals both contacting the water, which would be minimal, and could be eliminated by using similar metals between the...

I think you may be going about it the wrong way. The water itself should act as one electrode. I think a fairly usable capacitor could be made using a strip of copper foil, as one capacitor plate,...

I'm far more interested in a cheap 3D printer than a cheap 3D scanner. I think a lot of people are probably the same way. The scanner would just be a bonus feature. You can make 3D models or use...

It shouldn't be any harder than the drip system. Just run the water a bit before you start the system, and tap the lines a bit to get the bubbles moving.

I guess it would just have to be tested to find out. If not, you could use a stepper motor pump. That should give some good precision. It's going to add more money to the cost of the printer, and yes...

Thinking about this, it actually makes sense as an external add on. It would have an output for the pump motor, and an output to the sound card to simulate drips. One adjustment knob to change drip...

You can use PWM from the attiny to control the speed. The H-bridge is what reverses the direction. It's just an input line on the H-bridge to reverse the polarity, and thus, direction of the motor.

What if you used a pump like this. http://www.ebay.com/itm/6v-dc-Dosing-Pump-Peristaltic-Dosing-Head-Motor-Aquarium-Lab-Analytical-Water-/201087635665?pt=LH_DefaultDomain_0&hash=item2ed1c1d0d1
You...