Go Back   RCCrawler Forums > RCCrawler General Tech > Electronics
Loading

Notices

Thread: Led and resistors

Reply
 
LinkBack Thread Tools Display Modes
Old 05-21-2019, 06:37 AM   #1
Newbie
 
Join Date: Mar 2019
Location: Hughesville
Posts: 35
Default Led and resistors

Can you wire multiple 5mm LEDs to one 150ohm resistor? Or do you need multiple or a bigger resistor?
Kweez is offline   Reply With Quote
Sponsored Links
Old 05-21-2019, 06:51 AM   #2
RCC Addict
 
Join Date: Jan 2016
Location: california under the rock im crawling on
Posts: 1,858
Default Re: Led and resistors

if you are wireing multiple lights to the same circit you dont need a resister if you run off a 6v bec just wire them in sieries they efectivly act as resistors all by them selfs just have extra bulbs on hand just incase you blow a few
ferp420 is online now   Reply With Quote
Old 05-21-2019, 07:03 AM   #3
Quarry Creeper
 
Join Date: Jan 2019
Location: Calgary
Posts: 474
Default Re: Led and resistors

Use something like ledcalc.com to figure out all your resistor needs for LEDs.
Xx Losungen xX is offline   Reply With Quote
Old 05-21-2019, 09:21 AM   #4
RCC Addict
 
Join Date: Jan 2016
Location: Kelowna, BC
Posts: 1,012
Default Re: Led and resistors

Quote:
Originally Posted by Kweez View Post
Can you wire multiple 5mm LEDs to one 150ohm resistor? Or do you need multiple or a bigger resistor?
There's too much info missing to give you a good answer as is. As was already mentioned there's led resistance calculators you can use that will help you figure this out.

If you don't have the specific info for your LED's and you cant find it online, you can roughly assume that clear LED's want 4V and draw 20mA, red LED's want about 3.5V and draw about 20mA.

Single LED's:


Multiple LED's:
QuesoDelDiablo is offline   Reply With Quote
Old 05-21-2019, 10:15 AM   #5
I wanna be Dave
 
Join Date: Jul 2005
Location: North Idaho
Posts: 3,184
Default Re: Led and resistors

I can do the math, have done the math, don't want to do the math...

This is why I buy Common Sense LEDs, they have a very wide voltage range and come prewired with resistors.
Greatscott is offline   Reply With Quote
Old 05-21-2019, 12:24 PM   #6
Custom RC Electronics
 
heyok's Avatar
 
Join Date: May 2007
Location: Vancouver, BC
Posts: 2,290
Default Re: Led and resistors

Don't be lazy Use one LED per resistor.

This will walk you through it all.
How to wire LEDs
heyok is offline   Reply With Quote
Old 05-21-2019, 02:02 PM   #7
Rock Stacker
 
Join Date: Mar 2019
Location: Canada
Posts: 59
Default Re: Led and resistors

One led per resistor only works if they are wired in parralel. If you wire in series you want to limit the current with a single resistor for the string.
The resistor in either case depends on the voltage supply, the voltage drop of the led and the led current rating.
If you have a 12 volt supply and a led that drops 4 volts, you have a 8 volt difference. If the led was to be limited to 80 ma. You would need a (v=ir) 8/.08 = 100 ohm resistor. To limit to 20 ma you would need a 400 ohm resistor.
If you have multiple LEDs then add their voltage drops together and make sure your supply is higher. Then just pick a resistor that gives you the current you need.
If you go with high current LEDs then a constant current led driver would be better.
Alka is offline   Reply With Quote
Old 05-22-2019, 07:53 AM   #8
Newbie
 
Join Date: Mar 2019
Location: Hughesville
Posts: 35
Default Re: Led and resistors

Alka I was thinking that about only needing one resistor when running in series. Thanks for the knowledge. I'm using a prewired light kit and adding light to it. So hope fully the 8
extra lights won't hurt.
Kweez is offline   Reply With Quote
Old 05-22-2019, 02:08 PM   #9
RCC Addict
 
Join Date: Jan 2016
Location: Kelowna, BC
Posts: 1,012
Default Re: Led and resistors

Quote:
Originally Posted by Alka View Post
One led per resistor only works if they are wired in parralel. If you wire in series you want to limit the current with a single resistor for the string.
The resistor in either case depends on the voltage supply, the voltage drop of the led and the led current rating.
If you have a 12 volt supply and a led that drops 4 volts, you have a 8 volt difference. If the led was to be limited to 80 ma. You would need a (v=ir) 8/.08 = 100 ohm resistor. To limit to 20 ma you would need a 400 ohm resistor.
If you have multiple LEDs then add their voltage drops together and make sure your supply is higher. Then just pick a resistor that gives you the current you need.
If you go with high current LEDs then a constant current led driver would be better.
Quote:
Originally Posted by Kweez View Post
Alka I was thinking that about only needing one resistor when running in series. Thanks for the knowledge. I'm using a prewired light kit and adding light to it. So hope fully the 8
extra lights won't hurt.

But, from an electronics engineering standpoint you shouldn't wire in series because of the voltage drop across the circuit. Each bulb in the chain gets a little bit less voltage than the last one did. The difference is small, but across led's you can often see the difference in brightness.
QuesoDelDiablo is offline   Reply With Quote
Old 05-22-2019, 07:09 PM   #10
Quarry Creeper
 
Join Date: Jan 2019
Location: Calgary
Posts: 474
Default Re: Led and resistors

Quote:
Originally Posted by QuesoDelDiablo View Post
But, from an electronics engineering standpoint you shouldn't wire in series because of the voltage drop across the circuit. Each bulb in the chain gets a little bit less voltage than the last one did. The difference is small, but across led's you can often see the difference in brightness.
You also wouldn't be using resistors from an engineering stand point.

From a practical stand point, we have limited space for power and even less for a rats nest of wires. Personally I'll use series as much possible too not only relieve those issues above but also, the entire circuits point is to create light, not heat.
Xx Losungen xX is offline   Reply With Quote
Old 05-22-2019, 10:12 PM   #11
Newbie
 
Join Date: Mar 2019
Location: Hughesville
Posts: 35
Default Re: Led and resistors

Awesome thanks. I'm planning on NOT adding the lights to the existing set and stringing another set for rock lights and fog lights. That way it will eliminate the dimmer lights.
Kweez is offline   Reply With Quote
Reply



Led and resistors - Similar Threads
Thread Thread Starter Forum Replies Last Post
PC PSU Conversion- Resistors necessary? Zeus.:God Electronics 7 03-06-2013 05:27 PM
2.2k ohm resistors........ bob1961 Electronics 12 03-31-2012 08:33 AM
motor resistors Lothar13 Redcat Crawlers 3 01-09-2011 05:01 PM
Voltage divider - need some resistors JamboreeTJ Chit Chat 0 02-12-2008 12:45 PM
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 03:17 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO ©2011, Crawlability, Inc.
Copyright 2004-2014 RCCrawler.com