Gas station without pumps

2015 December 18

Examine pictures carefully

Filed under: Uncategorized — gasstationwithoutpumps @ 07:41
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I was considering buying a cheap color sensor board from Elecrow, because it claimed “This module is based on the color sensor TCS3414CS with digital output I2C.”  That chip is a pretty nice one with a good spectral response.

But I took a closer look at the image on the web page:

Elecrow's image of their color sensor board

Elecrow’s image of their color sensor board

Zooming in on the color sensor itself. Note that this is a leadless chip carrier package, not a ball-grid array package.

Zooming in on the color sensor itself. Note that this is a leadless chip carrier package, not a ball-grid array package.

The package that the chip is in is clearly the FN “dual flat no-lead” package and not the CS “6-lead chipscale” package, which is smaller and has no contacts on the sides. Normally, a change of packaging like that makes little difference (other than to manufacturing cost), but the TCS3414CS and TCS3414FN chips have different spectral responses:

The CS package has an infrared-blocking filter that is missing in the FN package, making the FN chip much less useful as a color sensor. (click image to embiggen)

The CS package has an infrared-blocking filter that is missing in the FN package, making the FN chip much less useful as a color sensor. (click image to embiggen) Spectra from the TAOS data sheet provided by Elecrow.

Since infrared light can throw the readings from the TCS3414FN chip way off, I can’t see any point to get a color sensor using the FN package (one would have to add external optical filters, which eliminates any price advantage the FN chip may have).  I’m a little surprised at Elecrow claiming to have a TCS3414CS chip, when their picture clearly shows the less useful TCS3414FN chip.  It makes me suspicious of other claims Elecrow makes.

Note: I’ve had Elecrow make boards I designed and assemble them, and they did fine work—but anything that they designed I’ll want to look at twice to make sure they’re not claiming more than they’re delivering.

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