Netduino output pin and external LED
#1
Posted 16 October 2010 - 12:39 PM
Paolo Patierno
Microsoft MVP on Windows Embedded & IoT
Azure Advisor
Twitter : @ppatierno
Linkedin : paolopatierno
Blog : DevExperience
Blog : Embedded101
?
#2
Posted 16 October 2010 - 01:27 PM
Digital pins 2, 3 and 7 can handle up to 16 mA, so you can calculate the resistor to limit current to ~15 mA: (3.3 - 2.1)/0.015 = 80 Ω. The LED will be very dim at 8 mA (if you have the datasheet, check Luminous Intensity vs. Forward Current char). You can use [general purpose NPN] transistor to switch the LED from any Netduino pin.I have a red LED 10 x 5 mm with the following specs : 2.1V - 20mA.
#3
Posted 16 October 2010 - 01:30 PM
Digital pins 2, 3 and 7 can handle up to 16 mA, so you can calculate the resistor to limit current to ~15 mA: (3.3 - 2.1)/0.015 = 80 Ω. The LED will be very dim at 8 mA (if you have the datasheet, check Luminous Intensity vs. Forward Current char). You can use [general purpose NPN] transistor to switch the LED from any Netduino pin.
Thank you very much...can you give me some information how I can use NPN transistor to switch the LED ?
Best regards,
Paolo
Paolo Patierno
Microsoft MVP on Windows Embedded & IoT
Azure Advisor
Twitter : @ppatierno
Linkedin : paolopatierno
Blog : DevExperience
Blog : Embedded101
?
#4
Posted 16 October 2010 - 01:46 PM
For example, look at the following article. You can wire the LED to Netduino exactly the same way, using the onboard 5V supply. If you wire the LED to 3.3V supply, use (3.3-2.1)/0.02 = 60 Ω resistor.Thank you very much...can you give me some information how I can use NPN transistor to switch the LED ?
#6
Posted 18 October 2010 - 12:11 PM
For example, look at the following article. You can wire the LED to Netduino exactly the same way, using the onboard 5V supply. If you wire the LED to 3.3V supply, use (3.3-2.1)/0.02 = 60 Ω resistor.
Thank you very much
Paolo.
Paolo Patierno
Microsoft MVP on Windows Embedded & IoT
Azure Advisor
Twitter : @ppatierno
Linkedin : paolopatierno
Blog : DevExperience
Blog : Embedded101
?
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