EEVblog® Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: ShadyK on June 14, 2014, 07:33:44 pm
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Hey guys.
I know that every one here is extremelly intelligent and knows what they are talking about ;)
Right this is my plan
I have a Dell inspiron 1545 In black,
I plan to modded the case accordingly trying so much not to effect the orignal airflow in the case, But i plan to have 2 plexi glass windows either side of the track pad,
Now for the fun stuff, I plan to run 15-20 1.8mm 3.3v LEDs in various areas of the casing, using the main power bus on the board of 5v. some of these also on the lid after a picture has been cut out and diffused, The leds are going in parallel with a 110Resistor on each LED, i think this is right as i worked it out using OHMs Law R=V/I, R110=3.3v/0.03Ampres. I hope that this is right, Does any one have any thing to add?
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The voltage over the resistor would be around 5-3.3=1.7V, so for 0.03A that gives 1.7/0.03 = 56.6 Ohm.
That said, 30 mA is probably the absolute maximum rating so you want to design for 20 mA ... which gives 1.7/0.02 = 85 Ohm (use 86.6 Ohm).
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The voltage drop on the resistor is 5v-3.3v (that number actually varies depending on the color of the led) = 1.7v.
Your number of 110ohm is in the ballpark. No reason to be super-precise here.
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Thank you guys for the super qucik replys. I do apologise if i come across as a bit of a beginner ( because i am ), so if i use a 80ohms resistor (only becasue i have a few at home), would this be ok? iu will post some pictures up of the gear i have and that when i finish work