Public Lab Research note

Thermal Torch with Adjustable Temperature Scale

by dr_dbw | March 29, 2012 00:22 29 Mar 00:22 | #1553 | #1553

This is an extension I have developed of the basic thermal torch / thermal photography project -

What it does is measures the temperature (degrees Celsius) of an object using the infrared thermometer, map that temperature onto a sinebow colour wheel (300 degrees to -30 degree), then change the output to the RGB LED as appropriate. The maximum and minimum temperatures for the colour scale is adjustable using switches between two values that are set in the code. This means that the temperature scale can be set for four different temperature scales without having to recode / upload to the Arduino Uno board.

The circuit based on the one shown at - I have added three switches to this circuit and written some slightly different code. All temperatures in this code are in degrees Celsius.

This colour scale for the temperatures is based on the sinebow colour wheel, which is discussed here

The code requires you to specify the two minimum and two maximum temperatures for the temperature scale to work between. The selected temperature scale then maps the measured temperature onto the colour wheel from 300o to -30o, which equates to purple to pink.

Over the LED I place a Cree LED 45o collimator lens, which helps to disperse the distinct red, green and blue colours that you otherwise get. The 5mm RGB LED fits into the base of the lens, but has to be glued into place.

This is an extension / variation of the code I initially posted which will work on the basic torch circuit.



Going to have to wait a day or so before can do more, as I managed to short out the IR sensor while transferring things over to a small circuit board.


And I have now found the diagram software you are using to make the nice circuit diagrams, so will shortly be able to do a bit better than the simple hack job of did of Jeff's original circuit.

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This is really fantastic! Could you post some pictures of what the board and dials look like?

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Will do.

I have actually further modified it and the code to have two modes, the adjustable temperature scales as noted above, or dynamic temperature scales. The latter automatically changes the upper and lower limits on the temperature scale based on the maximum and minimum temperatures encountered since it was turned on. That way, you can get it to use the full colour scale in every situation. Of course, it does mean that the colour - temperature match up is always different, but that isn't an issue for the manner in which I use it.

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