Some projects are inspired by a legitimate need, some are the result of moments when you say "wouldn't it be cool if...", and some lie in between.  This idea began closer to the second option but as it's progressed, I've realized that perhaps it could be a useful item in the right context.

I started by thinking how cool it would be if there existed a coaster that lit up, changing colors as your drink level decreased.  From a purely "what the heck" standpoint, it was a super neat idea that had to be pursued.  As I began designing and building and talking to different folks about the idea, I realized that it actually could be great to have, for example, in restaurants, bars, night clubs, and the like as a great way for waiters to keep an eye on drink levels and keep the customers satisfied.  If I ever own a nightclub, I'll definitely make these a standard issue.

Step 1: Supplies

The critical piece for this project is the force-sensitive resistor, or FSR.  As you can see in the photo, the FSR consists of interlocking (but not touching) wires connected to the two leads.  Since the wires aren't touching in its undisturbed state, it's essentially an open circuit - the FSR theoretically has infinite resistance.  As pressure is applied, the FSR deforms gradually, causing these wires to get closer and touch, lowering the resistance dramatically.  I definitely recommend checking out the documentation on the product's page at Jameco - super cool and informative.

I got all the electronics from Jameco, the acrylic from TAP plastics, and other misc. things (like batteries and wire) from RadioShack.  

  • (1x) 13 x 24 x 1/8" clear acrylic
  • (2x) green LEDs
  • (2x) yellow LEDs
  • (2x) red LEDs
  • (1x) comparator IC
  • (1x) NAND gate IC
  • (1x) force-sensitive resistor (Jameco)
  • (1x) solderable breadboard
  • (2x) 1k resistors
  • (3x) 680k resistors
  • (1x) 56k resistor
  • (1x) 6.8k resistor
  • (1x) 9V battery
  • (1x) 9v battery wire connector
  • (2x) rubber bands
  • various lengths of red, black, white wire
  • soldering iron + solder
  • wire cutters
  • wire strippers
  • small needle-nose pliers
  • laser cutter (if you want to make the same base - there are most definitely alternatives if you don't have access to a laser cutter - get creative!)
<p>this is similar to the 'barman' a kick starter project. However, it is still a very neat idea :)</p>
<p>You honestly might want to patent this and sell the product to nightclubs or restaurants. The parts are cheap enough that mass production would work extremely well, and for busy sports bars, an empty drink could be spotted a mile away. Capitalize on your great idea!</p>
<p>If you put a low-pass filter in the circuit, it could help reduce or eliminate the flickering you're getting near the threshold.</p>
Can I patent this?
This is great!

About This Instructable



Bio: Always looking for things to improve, repair, improvise, or modify. Studied mechanical engineering and physics at Stanford with a focus on robotics and international development ... More »
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