Soda Can platform

I have an instrumented soda can storage platform. The computer can sense if a can is present, and if present, how cold it is.

Soda can sensor platform, release 1.0

I put the can of soda on a hinged platform made out of some aluminum flashing. Aluminum flashing is very heavy aluminum foil. It is easy to bend with your hands. The weight of a can of soda operated a keyboard switch. I drilled a hole through the platform for a thermistor. The thermistor stuck up into the cavity in the bottom of a can of soda. This made adequate thermal contact. It takes about a minute for the thermistor to adjust to the can temperature.

I'm still surprised it worked the first time. The aluminum flexed with each can, and started to bind, so this was not a long term solution.

Soda can sensor platform, release 2.0

The new platform is made out of 4 CD-ROMs (obsolete software). I pretreated the CD-ROMs for good visual effect in the microwave oven, see CD-ROM cooking tips.

I used one CD-ROM to make a custom fit soda can holder. I placed an empty soda can upside down on a cookie sheet in the gas oven at 350 degrees. I put a CD-ROM on the can and waited until it bent to fit the can. (Did I mention that I own several fire extinguishers?)

I let the oven cool. After the formed CD-ROM had hardened, I glued it to a flat CD-ROM to make the top of the platform. I drilled some holes to mount a thermistor. Once again, the thermistor sticks up into the cavity in the bottom of the soda can.

I drilled some holes in the third CD-ROM to hold a "roller lever switch", Radio Shack part number 275-017. I also drilled some holes to make a strain relief for the cable to the computer hookup. I used four conductor silver satin phone cord. I soldered the two inner wires (red and green) to the thermistor on the top platform. I soldered the outer two wires (yellow and black) to the switch. I put a 27Kohm resistor across the switch. I glued the fourth CD-ROM to the bottom of the third CD-ROM to protect the solder joints.

I built a hinge with some 12 gauge wire and some brass tubing. The hinge is about as tall as the switch. I glued the hinge to the bottom platform on the opposite side from the switch.

I put an RJ-11 connector on the cable. I can unplug the platform from the refrigerator for maintenance, or if I just want to replace it with something else.

           |                            |
           |         Soda Can           |
      |    |                            |    |
      \    \    ____________________    /    /  <- CD-ROM #1
       \    \  /                    \  /    /      (Heat formed)
        \    \/  ## <- thermistor    \/    /
         \_______||_______________________/
  _______________||_____________________________________  <- CD-ROM #2
       O         ||                              o
       H                               #==========
       H                             +-#------------+
       H                             | roller       |
       H <-Hinge                     | lever switch |
       H                             +--------------+
  _____________________________________|__|_______|_____ <- CD-ROM #3
        Wiring layer                   |  |       |
  ______________________________________________________ <- CD-ROM #4

The new platform seems very durable. I don't have to be carefull when I insert the soda can.

Paul Haas, paulh@hamjudo.com

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