If circuits a and b have the same current but b led has a vf of 9v will this be damaging to the led even though the current is limited ?


How do i limit the current at 9 v supply dc to .1amp if i only have .250watt resistors what layout can i use to dissipate the power and limit the current without buying a 1 watt resistor?

 

Hello,

Just take a look at Bill's thread:

LEDs, 555s, Flashers, and Light Chasers

Bertus

 

Ohm's law is enough to let you determine the resistance. Use the form R = E/I, where you substitute in your voltage and the desired current. Power dissipation in the resistors comes from I^2*R.