Help with making a board

[Jacksl]

Hi guys, not sure if i've put this in the right place.

im new to the circuit board scene. i want to make a LED circuit board that is capable to connecting 30 LEDS to it. my only problem is knowing how many batteries it will need and what type, and what resistor(s) i need.

if someone can help me out, id be greatful,

regards

jack

[tanzeel]

30 LEDs on 12V DC

[tanzeel]

To start out on your first LED circuit, you will have one resisitor, three LEDs in series. 'In series' means that they're daisy chained and a 12V battery.

This is how we calculate this circuit:
=================================
By Ohm's LAW = (V=IR)
=================================

( Source Voltage - LED Voltage Drop )
----------------------------------------------- = OHMs
Amps

Source Voltage = 12 volts
Voltage Drop = 9.3 volts (3.1 typical for a blue or white LED)
Desired Current = 20 milliamps (again, a typical value)
So the resistor we need is:

(12 - 9.3)
------------- = 135 ohms
(20/1000)
==================================

if we want 30 LEDs in an array?

The alternative is to split up all 30 LEDs into 10 chains.

positioned in (the opposite of series) parallel. The wire comes off the anode(+), gets split into 10 wires which each go through a resistor, three LEDs, and then meet back up before collecting on the cathode(-). Your power adaptor will be putting out (20mA * 10) because of the 10 chains of LEDs, but voltage running through the whole thing will still only be 12.