100 ohm Resistor vs. 86 ohm resistor

[MMG]

Okay, so I am really new to electronics. I am trying to make an array of led's. I used this website http://led.linear1.org/led.wiz and the inputs to the forms were, 5v Source voltage, 1.8v diode forward voltage, 20 mA diode forward current and 4 led's in the array. My question is can I use 100 ohm 1/4w resistors instead of 86 ohm 1/4w resistors? I checked radioshack and that is the closest i can get to 86 ohm resistors.

 

[davenn]

hi
welcome to the forums

yup that will be ok the LED may be just a little fainter, you may not even notice it. 86 Ohms isnt a standard value.

failing that you could always series a 68 Ohm and a 15 Ohm and get 83 Ohms

cheers
Dave

 

[MMG]

Thank you very much for the help!

 

[(*steve*)]

or 82 ohms

(which is a standard E12 value)

 

[KJ6EAD]

I reran your calculation. The optimal nonstandard value is 70Ω. The next higher standard value is given by the calculator.

Solution 0: 2 x 2 array uses 4 LEDs exactly
+----|>|----|>|---/\/\/----+ R = 82 ohms
+----|>|----|>|---/\/\/----+ R = 82 ohms

The wizard says: In solution 0:
each 82 ohm resistor dissipates 32.8 mW
the wizard thinks ¼W resistors are fine for your application
together, all resistors dissipate 65.6 mW
together, the diodes dissipate 144 mW
total power dissipated by the array is 209.6 mW
the array draws current of 40 mA from the source.

http://www.logwell.com/tech/components/resistor_values.html

 

[davenn]

or 82 ohms

(which is a standard E12 value)

DOH thats what ya get when I try to answer technical Q's too early in the morning before my first cup of coffee

Thanks Steve

 

[Resqueline]

The exact resistor value here depends very much on the diode voltage drop. In my experience 2V is more usual for red LED's, in which case 50 ohms (or more) is ok.