Three LED lamp calibration light

I purchased the following multi-coloured LED strip light from ebay – Ed at the last RAG meeting asked whether coloured LEDs could be used as a calibration light for spectrometry – it seemed like a good idea! This one comes with a neat little remote control to allow it to be placed some distance away (ideal for focusing a telescope on it and then turning on and off and changing colours).

Andy

I made a calibration light out of the strip light above and a piece of Perspex made to diffuse light (off ebay designed for light boxes). I could then take spectra using my CCDSPEC spectrometer:

The first three spectra show that red, green, and blue are all very pure colours from the relevant LEDs in the strip:

Spectrum of LED strip light – green LED (below):

Spectrum of LED strip light – red LED (below):

Spectrum of LED strip light – blue LED (below):

Producing multiple lines on a single spectrum:

The above graphs demonstrate that the LEDs individually produce pure colours. However, for calibration purposes, it is useful to be able to have multiple lines on a single spectrum. This is where this particular colour-changing LED strip is useful – the strip uses three different coloured LEDs as above but allows you to select various combinations of LEDs to produce variety of “colours” – each of this is a mixture of LEDs switched on together in varying amounts.

The following are three examples of combinations – there are a total of 16 colours available (16 combinations):

Spectra from the three examples of colour combinations:

X-projections from spectra from the three examples of colour combinations:

White colour on the LED strip:

Probably the most useful combination is when all three LEDs are turned on together “white” – donated by a convenient “W” button. The spectrum from this produces three convenient peaks for calibration (below):

 

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