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Basic LED Circuit

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thanks - that helps me - everyone is so helpful - its just so much to digest... and I was hoping tomorrow to wire this up...
 
i dont need nearly that much resistance with 20+ LEDs do I? the calc seems to say less than 10 Ohms....

Each LED needs its own resistor as in the schematic I posted on the previous page.

A typical blue or white LED will have a forward voltage of 3.5V.
 
Hey all - i need to combine white and red LEDs on the same circuit - I use 4 AA batteries and 150 Ohm resistor on the white - but my calc is showing 400 on the red? is that right? please advise...
 
Four AA alkaline battery cells in series make 6V to 6.4V only when they are brand new and fresh.
Four AA Ni-Cad or ni-MH cells in series make about 4.8V to 5.2V when fully charged.

A white LED has a forward voltage of 3.2V to 3.6V so with a 150 ohm resistor and a 6V battery its current is from 16mA to 18.7mA.

A red LED has a forward voltage of 1.7V to 2.2V so with a 6V battery and a 400 ohm resistor its current is from only 9.5mA to 10.8mA.
The red LED needs a current-limiting resistor value of 238 ohms (use 220 ohms or 240 ohms) for a current of about 17mA.

Your calculation with a 6V battery and a 400 ohm resistor produces 15mA if the LED is a dead short.
 
audioguru - Thanks! 150 and 220/240 it is... so the lights should be about the same intensity and draw i take it then?

Thank you so much!
 
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