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Topic: Tx/Rx leds (Read 665 times) previous topic - next topic

Jose Francisco

Hello.

I'm designing my custom-duino with rs485 communication. I have  two leds directly connected to pin0 an pin1with 1k resistors to see serial activity.
My question is... do I need transistors to drive leds like shown in this schematic?

www.linksprite.com/upload/file/1294500698.pdf

Thank you very much.

CrossRoads

No. With 1K, there is only ~3mA load on the driving pin.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

I would suspect the LEDs would be very dim without the transistor drivers.
http://www.spcomputing.com

CrossRoads

Depends on the LED. 15mcd will not be bright, while a 10,000mcd LED will be very bright, even at just 3mA.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

hoff70

This may be helpful:

http://arduino.cc/forum/index.php/topic,114357.msg860483.html#msg860483

Jose Francisco

Thank you very much

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