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### Author Topic: Led Array Dimmer  (Read 3864 times)

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#### rais6

• Guest
##### Led Array Dimmer
« on: September 23, 2012, 17:41:58 PM »
I want to make led array 8x12 = 96 leds which can be dimmed or brightened, i'm using 6 AA battery, so 9 V in total.
How is the configuration? I'm using 5 mm led which has Vf 3,1 V and maximum 20 mA

#### kam

• Hero Member
• Posts: 1849
##### Re: Led Array Dimmer
« Reply #1 on: September 25, 2012, 22:43:02 PM »
6 batteries in series means 6x1.5=9 volts. Each LED needs at least 3 volts of forward voltage, so 3 leds in series will have low brightness. So you go for 3 leds per series. Each series needs 3.1x2 = 6.2 volts, so the resistor must drop 9-6.2=2.8V @ 20mA, R = 2.8/0.02 = 140 Ohms

So, you need 48 series of 2 leds each and one resistor of 140 Ohms (or 120 Ohms).... All of them connected in parallel.