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Light-To-Frequency or Light-To-Voltage — Parallax Forums

Light-To-Frequency or Light-To-Voltage

sunblocksunblock Posts: 55
edited 2013-01-09 13:44 in Propeller 1
I have been working with the TSL253R Light-To-Voltage unit, feedig the outpu into a MCP3204 ASC.
My question is, would the Light-To-Frequency version (TSL237) be better/more useful?
And I mean better/useful in terms of possibly direct connection to the Propeller without the need for the ADC?
Does anyone have a simple schematic using the 237 version?

Comments

  • JonnyMacJonnyMac Posts: 9,108
    edited 2013-01-09 11:42
    "Better" is subjective. That said, with the frequency output version you could eliminate the ADC. If you use 3.3v to power the device you can connect the output directly to the Propeller. If you're new, or want to be especially safe, put a 3.3K resistor between the output and the Propeller. This will also let you operate the device at 5v (in case that provides some benefit).
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2013-01-09 13:44
    The TSL253R saturates at about 24 uW/cm2. The TSL237S is useful out to about 100 uW/cm2. So, in terms of upper-end dynamic range, it is the better choice. L-to-F comes with a price, though, in that it may require a longer sample time to get the same precision that you'd get with an ADC. OTOH, unlike an ADC, the precision can be as great as you want it to be, depending upon the time interval over which you count pulses.

    -Phil
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