Oznium.com Store
Oznium Forum
The value of this forum is in the interaction with your fellow LED lighting enthusiasts.
Register today! - It is FREE and quick

LED wiring Question

Author
Message
Zaixon

Joined: Jan 27 2008
Posts: 74
Location: Ft. Lauderdale, FL


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 5:07 pm

Ok i want to wire multiple led's but not have to use a bunch of resistors. If I wire them in parallel can I just use one resistor for all or do they each need their own?

and if I go with wiring them in series do i not need a resistor at all? if thats the case how many must i wire together to get the correct resistance from 12v

color: blue
Kevin_S

Joined: Jul 20 2003
Posts: 2810
Location: WV


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 5:28 pm

Zaixon

Joined: Jan 27 2008
Posts: 74
Location: Ft. Lauderdale, FL


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 5:30 pm

ya i looked at that but can i wire multiple leds in parallel with one resistor? and in series i wont need one at all even if i just have 2 led's in series?
Phil
Owner, Oznium.com

Joined: Feb 11 2003
Posts: 7721


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 5:35 pm

Correct me if I'm wrong (some people on the forums have better electrical skills), but here's how I see it:

If you wire then in parallel you can use one resistor, but you have to increase the power handling capacity of that resistor. Normally, you'd use a 1/4 watt resistor for an LED that draws 20mA of current.

For practical purposes, unless you have some specific need to wire them in parallel with one resistor, and know how to calculate the proper resistor value, it is best to:
1) use pre-wired LEDs with resistors already soldered on
2) wire in series

The main problem with wiring them in a long parallel string with a single resistor is that it requires an odd-sized resistor. You can't just use a 1/4 watt resistor on a string on 20 LEDs because the extra current draw would make that resistor dangerously hot. The odd-sized resistors are expensive and not as readily available as common sizes.

For a series circuit, here's the optimal number of LEDs without using a resistor:
4 in series (blue, green, white, uv - blacklight)
6 in series (red, yellow, orange)

Reminder: when calculating for use on 12 volt automotive systems, we must actually calculate using 14.5 volts, because a healthy alternator will pump out more than than 12 volts when the engine is running (or revving).

This is a handy tool: https://www.oznium.com/led-resistor-calculator

And as always, if it doesn't work, try licking it icon_wink.gif
Zaixon

Joined: Jan 27 2008
Posts: 74
Location: Ft. Lauderdale, FL


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 5:39 pm

cool thats exactly what i needed to kno, thanx for yer help
Zaixon

Joined: Jan 27 2008
Posts: 74
Location: Ft. Lauderdale, FL


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 5:45 pm

also 1 more question

Does the resistor need to be directly after the led or can i have wire extension between the resistor and the led
mx107marlin

Joined: Aug 12 2007
Posts: 3095
Location: Fairborn, OH


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 7:17 pm

You can have an extension, although most people unless they have a specific application, will put the resistor very near the LED, for ease of memory... if you have a wire between them, that wire is now part of the LED and cannot be cut and still used in 12V applications.
Zaixon

Joined: Jan 27 2008
Posts: 74
Location: Ft. Lauderdale, FL


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 7:22 pm

ya i got ya, just tryin somethin new with led's, thanx
mx107marlin

Joined: Aug 12 2007
Posts: 3095
Location: Fairborn, OH


Are you sure you want to delete this post?
  
Post Thu Feb 14, 2008 8:12 pm

No problem... just let me know if you have any other questions...
The time now is Thu May 24, 2018 8:01 pm
Page 1 of 1