Model Railway Forum

Go Back   Model Railway Forum > Model Railway Construction > Wiring & Electronics


Reply
 
Thread Tools Display Modes
Old 28-04-2018, 07:48 AM   #1
oncomin5torm
Senior Member
 
oncomin5torm's Avatar
 

Join Date: Mar 2018
Location: Little Neston
Posts: 281
oncomin5torm is on a distinguished road
Default LED series or parallel?

As the topic states I am in a quandary about how to wire my LEDs.

I am having 3 LED 1.8mm size with I believe a forward voltage of 3v.

I am putting them inside my station building which has dividing walls.

I am unsure what Is best, as series would be easier I think.
One wire into the building and then one wire out after the 3rd LED.

I'm just not sure if parallel would work better or not.

Thanks in advance.
__________________
Don't try to be a great man, just be a man.
Let history make it's own judgments.
oncomin5torm is offline   Reply With Quote
Old 28-04-2018, 08:02 AM   #2
Rog (RJ)
Super Duper Moderator ;-)
 
Rog (RJ)'s Avatar
 

Join Date: Oct 2009
Location: South Nottm, UK
Posts: 1,618
Rog (RJ) is on a distinguished road
Default

Series is ok but if one fails then the others will fail to light. You only need 1 resistor for each string of LEDs. The total current taken will be the same as just 1 LED.

When wired in parallel, each LED should have its own resistor. Total current will be the sum of the current through each LED.
__________________
If you can't say anything nice about someone, don't say anything.

Rog (RJ)
Rog (RJ) is offline   Reply With Quote
Old 28-04-2018, 09:14 AM   #3
Teedoubleudee
All round good guy
 
Teedoubleudee's Avatar
 

Join Date: Aug 2014
Location: Downham Market
Posts: 3,179
Teedoubleudee is on a distinguished road
Default

As Rog says parallel is better. It also gives you the opportunity to use different values of resistor for each led thus giving varying levels of intensity in different rooms, which looks much more realistic IMHO than all windows blazing away and lighting up the surrounding area.
__________________
If I agreed with you, we'd both be wrong
Teedoubleudee is offline   Reply With Quote
Old 28-04-2018, 10:18 AM   #4
dtb
9C Macclesfield
 
dtb's Avatar
 

Join Date: Oct 2015
Location: Peak District
Posts: 323
dtb is on a distinguished road
Default

Quote:
Originally Posted by Teedoubleudee View Post
It also gives you the opportunity to use different values of resistor for each led thus giving varying levels of intensity in different rooms,
on the basis of this where could the information be found for resistor values etc, to the un-educated like me me a resistor is just a resistor and I for one would be very interested in obtaining more details.
__________________
dtb is online now   Reply With Quote
Old 28-04-2018, 10:45 AM   #5
Steve M
Carcharodon carcharias
 
Steve M's Avatar
 

Join Date: Nov 2012
Location: Rochester, Kent
Posts: 4,142
Steve M is on a distinguished road
Default

This will help DTB.

http://led.linear1.org/led.wiz
__________________
I'm not arguing with you, I'm explaining why you are wrong.
Steve M is offline   Reply With Quote
Old 28-04-2018, 10:48 AM   #6
Flashbang
Administrator
 
Flashbang's Avatar
 

Join Date: Jul 2009
Location: SE UK
Posts: 8,412
Flashbang will become famous soon enough
Default

Try this web site linked below, but you will need to know a few things first.
Input voltage - often 12v DC but can be whatever you have available. LED forward voltage rating also known as Vf. LED rated maximum current also known as If and finally how many LEDs in your circuit.
Link to LED wizard ....SNAP Steve!
Once the resistor value is calculated chose a resistor ohm value of at least the next available ohm rating above the calculated figure and if you want to dim the LED increase that ohm value considerably.
__________________
Broken? It was working when I left it!
Flashbang is offline   Reply With Quote
Old 06-08-2018, 08:01 AM   #7
Annaa
Guest
 

Posts: n/a
Default

High-power LEDs should be connected directly in series!
1, all stringed together, a total of only need to add a resistor current limit, the highest reliability and safety.
2. The disadvantage of paralleling is that the current obtained by each LED is different! Burning a burden on each of the other LEDs is even greater! But the one that burns is still bright!
3, the shortcoming of the series is that the LED burns off a whole string will not light up! ! But it is easy to do the same current for each LED! If the current of the LED does not exceed the rated value, it will not burn normally and the life is very long.
  Reply With Quote
Old 06-08-2018, 08:21 AM   #8
Bunkerbarge
Senior Member
 
Bunkerbarge's Avatar
 

Join Date: May 2018
Location: Mid Lincolnshire in a field
Posts: 312
Bunkerbarge is on a distinguished road
Default

I've been in the model boat world for many years and never known anyone wire up LEDs in series. No-one that I know would dream of it. Varying currents is a major advantage to give different levels of intensity as well as flexibility with future modifications to one or many lamps.

Wiring in series is very restrictive and, as has been said by many already, is much more inflexible and, in case of failure, dealing with the failed lamp will be very difficult to A) Identify and B) repair.

As regards the points by Annaa there should be no danger of any having too much current through them if the resistor has been calculated correctly.
Bunkerbarge is online now   Reply With Quote
Old 06-08-2018, 09:11 AM   #9
Flashbang
Administrator
 
Flashbang's Avatar
 

Join Date: Jul 2009
Location: SE UK
Posts: 8,412
Flashbang will become famous soon enough
Default

The LED strips are a typical example of LEDs in series with one resistor. Usually three SMD LEDs and one SMD resistor per group.

Current saving is gained by series connecting, but as mentioned previously it risks one LED failing and all in that group go out.

I prefer to use a little more current from the power supply and wire each LED with its own series resistor, the resistor value can be set higher to slightly reduce the LEDs brightness.

Which ever method is used there should always be a series resistor in circuit to reduce current. Some will opt to use a regulated current power supply, but most model railway users will grab whatever power source is freely available! However, whenever possible try and use a DC Regulated power supply where the output voltage is maintained regardless of loading.
__________________
Broken? It was working when I left it!
Flashbang is offline   Reply With Quote
Reply

Bookmarks



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
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 Off

Forum Jump



All times are GMT +1. The time now is 12:32 PM.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.