In SX Microcontrollers, SX/B Compiler and SX-Key Tool, PJ Allen wrote:

[quote="Three of Them"]
...are 7 LED's. They are colored and timed in accordence with a traffic light. They draw about 20ma each. The resistor across them is 470 ohms.
  Whoa! Whoa!  Resistor across them?  No, no, no.
  The resistor should be in series with the LED (output pin, resistor, LED, ground.)  If you have 20mA through/from an output, it's because the only thing limiting current is the LED and the output's limit (which isn't infinite.)
  The SX has nominal 5V outputs, so with a 470 ohm resistor the nominal current through each LED should be around 6mA.[/quote]

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