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Load Resistors for HomeWork Board — Parallax Forums

Load Resistors for HomeWork Board

MikerocontrollerMikerocontroller Posts: 310
edited 2008-06-30 05:59 in BASIC Stamp
·· I'm reading the Parallax text for the IR·LED and Detector pair (pt#'s 350-00014·& 350-00017) and it
shows the LED connected to a 220-ohm resistor and the detector's output directly connected to a
Stamp pin.·· I understand the HomeWork Board I am using has built-in 220-ohm resistors.· Does this
schematic apply to the HomeWork Board or should I omit the LED current limiting resistor?

································ THANK-YOU

Comments

  • bryan mcdonaldbryan mcdonald Posts: 27
    edited 2008-06-30 05:43
    i'd keep the current limiting resistors
  • Mike GreenMike Green Posts: 23,101
    edited 2008-06-30 05:59
    The HomeWork board does have 220 Ohm resistors built in. The LED would draw about 18 mA which is ok, but is a lot of current for a 9V battery if that's what you're using. It wouldn't hurt to add another 220 Ohm resistor for the LED. That would reduce the LED current to around 9 mA which should be fine for the experiments. If you wanted maximum range, you might use the higher current.
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