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
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
and while you are there, consider making a small donation to keep their site viable.