Instructables

Orb Flashes Temperature in Morse Code

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What do you do when you see something and immediately imagines a different use?  For me, I often will buy "A" to re-purpose into "B" ... and often with interesting results.  While walking through the pool section in WalMart to buy cat food, I was distracted by a small softball sized plastic float.  Upon examining the $2.50 item, I saw that it was actually a multicolored LED flashing ball for pool play.  The outside of the orb was plastic not unlike the feel of a ping pong ball.

Disassembling the Orb I found a small circuit board with some surface mount components: resistors and the LEDs and some little microcircuit all coated in black epoxy.  The prize was the plastic dome and the two lithium batteries that I needed for another project.  I set about rambling through my parts bin and soon had found a three-colored LED (red-green-blue) and a PICAXE microprocessor.  A few minutes on the computer and I had a rough program that would take the voltage from a voltage divider made of a 10K resistor and a 10K NTC thermistor and convert this to a range of three bands:
  • BAND 1 ... 50F - 59F
  • BAND 2 ... 60F - 69F
  • BAND 3 ... 70F - 79F
My thinking was that for inside use, it rarely gets below 50F and rarely above 79F, but these bands can be changed by the end-user by simply reprogramming.  In fact, a PICAXE such as the 14M2 could be used as it has more pins and control even more colors of LEDs.  Everything needed to build your own Morse Code Temperature Orb is in the attachments.  If you have never used the PICAXE line of microcontrollers, please seek out a few of the Instructuables that are introductory in nature before venturing out as this is not a hand-holding, step-by-step Instructable.

The photos show two separate units I built: one in a pedestal base (plumber tail plastic pipe for sink) and one on a $1 dollar store glass mirror using copper tape for the wiring from the bottom to the top for the LEDs.  The orb is secured with 5 minute epoxy and the battery pack is secured with hot-melt glue.  All electric components are point-to-point and the covered with Goop and allowed to dry for a full 24 hours to ensure there is no solvents still escaping that may damage furniture.

For the 5 volts required, you can probably get fair results by using three (3) AA batteries in series.  If you wish to use 4-cells, you may need 1 or 2 silicon diodes to drop the 6 volts closer to 5 volts.  The exact selection of 1 or 2 will depend upon the chemistry of the batteries you select, so test with your digital volt meter on a breadboard before committing everything to the final circuit.

PICAXE chips, 10K NTC thermistor, and other components are available from a variety of resellers or from http://www.phanderson.com/picaxe
Free software to program the PICAXE chip is available from http://www.picaxe.com/Software/

Oh, and in case you do not know Morse Code (numbers are so easy), head over to
http://en.wikipedia.org/wiki/Morse_code
and while you are there, consider making a small donation to keep their site viable.


- Ray


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