Basic Electronics Help Needed !!

[CTScott]

Here you go:


Traffic Light.jpg

[Ferret_san]

Originally Posted by CTScott

Here you go:

You're a good man. Thank you sir !

[jambo101]

Get your nephew some extra brownie points for creativity and run it off solar power.

[GeneW]

Originally Posted by CTScott

Here you go:


Attachment 24520

I think 390 ohms is a bit light, no pun intended, with an LED and a 9 volt source. I've seen about two to three volt drops on average with an LED, which gives you from 15mA to 18mA current with a nine volt battery and 390 ohm resistor. That's a wee bit high for an LED. You can do it but they get hot and won't last long. Also drains the battery faster.

Keeping that current around ten mA would run the LEDs cooler... I'd recommend a 560ohm resistor, which would give you a more gentle 11mA to 12.5mA range, assuming a 3 to 2 volt drop across the LED.

I used to use 470ohm resistors with 5 volt sources and LEDs... I like to keep things on the low to middlin end to preserve function and reduce heat on working parts.


Gene

PS

If someone can scan in the LED's spec sheet we can do a better job of calculating a good current limiting resistor for this project.