LED'S what are they and how are they used?

Neil Robinson

Neil Robinson

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24 Oct 2009
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That's strange because all the directional LEDs that I have on my battery locos rely on having the wrong current when running in the wrong direction - i.e. the rear LED will have reverse current (and therefore will not illuminate) when the loco is going forwards and vice versa.
If you wire the front and rear LEDs in inverse parallel it'll work fine with the lit led acting as the blocking diode for the unlit one.
It's not really a "blocking diode" as it conducts rather than blocks but it prevents any excessive reverse voltage across the unlit diode.
 
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playmofire

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If you wire the front and rear LEDs in inverse parallel it'll work fine with the lit led acting as the blocking diode for the unlit one.
It's not really a "blocking diode" as it conducts rather than blocks but it prevents any excessive reverse voltage across the unlit diode.
Having looked up wiring in inverse parallel on Google, I am not the wiser. Would you explain this, please?
 
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Sarah Winfield

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I have a Gaugemaster analogue controller which I could use.

Ntpntpntp, initially I didn't know what I could achieve with them. They were very inexpensive so it doesn't matter if I ruin them anyway.

Could they be used as a string of lights along a platform or for lighting sidings? What about lighting a signal box?

They add another feature to my layout.

SW
 
PhilP

PhilP

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5 Jun 2013
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Having looked up wiring in inverse parallel on Google, I am not the wiser. Would you explain this, please?


To use a 'plumbing analogy:
A diode is like a 'flap-valve', it only allows flow in one direction..
So if you put two of these in parallel, but one 'the other way round', you can feed water (electrical current) 'in' from either end, and one or other of the devices will allow 'flow' through it.

If we now imagine by 'elek-trickery' we can make the flap-valve glow, when water runs through it.. Depending onwhich way the water is flowing, one or other of the devices would glow.

Does that help? Or just leave you in a sea of confusion? :)
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
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I have a Gaugemaster analogue controller which I could use.

Ntpntpntp, initially I didn't know what I could achieve with them. They were very inexpensive so it doesn't matter if I ruin them anyway.

Could they be used as a string of lights along a platform or for lighting sidings? What about lighting a signal box?

They add another feature to my layout.

SW
Anywhere you have power, you can have light Sarah.. :):nod:
 
JimmyB

JimmyB

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I know nothing about LED's so having bought some off ebay it would be useful to know how they are used. Would a member help please?

The description is:-

"L12303W Pre-wired 3mm Bright White LED lamp light set 12v~18v
Forward Current 20mA/30mA"

They comprise a 9" lenght of wire with a tiny see through bulb and a resister.

Thanks.

Sarah Winfield
I must ask - If you know nothing about LEDs, what they're used for etc, why did you buy them!
 
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playmofire

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23 Oct 2010
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Having looked up wiring in inverse parallel on Google, I am not the wiser. Would you explain this, please?


To use a 'plumbing analogy:
A diode is like a 'flap-valve', it only allows flow in one direction..
So if you put two of these in parallel, but one 'the other way round', you can feed water (electrical current) 'in' from either end, and one or other of the devices will allow 'flow' through it.

If we now imagine by 'elek-trickery' we can make the flap-valve glow, when water runs through it.. Depending onwhich way the water is flowing, one or other of the devices would glow.

Does that help? Or just leave you in a sea of confusion? :)
To add to the confusion, "Yes".
 
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playmofire

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I must ask - If you know nothing about LEDs, what they're used for etc, why did you buy them!
I'm sure that here Sarah is well aware what she can use them for, just unsure how to go about using them - e.g. power sources, types of power, connecting up.
 
Rhinochugger

Rhinochugger

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27 Oct 2009
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North West Norfolk
If you wire the front and rear LEDs in inverse parallel it'll work fine with the lit led acting as the blocking diode for the unlit one.
It's not really a "blocking diode" as it conducts rather than blocks but it prevents any excessive reverse voltage across the unlit diode.
Ah, understood, thanks Neil
 
dunnyrail

dunnyrail

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25 Oct 2009
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I must ask - If you know nothing about LEDs, what they're used for etc, why did you buy them!
I can see you living to regret that query Jimmy. Had my mind racing all sorts of answers that I will not nay dare not say on here!
 
dunnyrail

dunnyrail

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25 Oct 2009
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St.Neots Cambridgeshire UK
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
25,249
548
North West Norfolk
I must ask - If you know nothing about LEDs, what they're used for etc, why did you buy them!
Sarah loves to live on the railway modelling edge :clap::clap::clap::clap::clap::clap:

There are times when the temptation is just too great :cool::cool::cool::cool:
 
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playmofire

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Is this diagram any help?

View attachment 243238
Well, I guess the small arrows represent light and the black triangles the two LEDs. Guessing further, the resistor is wired to the positive side one LED and the negatives side of the other and at the other end, as it were, the negative of one LED and the positive of the other are wire back to earth(?). But then again, maybe not.
 
Greg Elmassian

Greg Elmassian

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The triangle with the "Bar" is the universal electrical symbol for a Diode... Light Emitting Diode.

The 2 "free" wires go to power, does not matter which is plus or minus... or plus and earth..

electrical current flows like water, has to come from somewhere and go to somewhere, otherwise known as a complete circuit

Here's one with power drawn in...

 
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Sarah Winfield

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I must ask - If you know nothing about LEDs, what they're used for etc, why did you buy them!
At £0.99p for 20 it was worth it to broaden my knowledge and to find out how I might use them. (NVNG)

SW
 
dunnyrail

dunnyrail

DOGS, Garden Railways, Steam Trains, Jive Dancing,
25 Oct 2009
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Is this diagram any help?

View attachment 243238
Understand that now, but not why if positive comes from the resistor end the left hand Led does not get trashed. But will take your word for it and try it sometime on my Maplin Testing gear. Presumably the juice takes the line of least resistance IE the Right hand Led making light on the way?
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
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Understand that now, but not why if positive comes from the resistor end the left hand Led does not get trashed. But will take your word for it and try it sometime on my Maplin Testing gear. Presumably the juice takes the line of least resistance IE the Right hand Led making light on the way?
By George! I think he's got it! :):nod::nod:
 
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Sarah Winfield

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If I take a 9V PP3 battery and connect the wires from my LED (one with a resistor and the other without) to the + and - connectors will the LED light up please?

Similarly if I take a second LED and wire it the same will I then have 2 LED lights, etc. etc.

If I then replace the battery with the DC output of my analogue controller will it work the same please?

I do appreciate I tend to ask quite convoluted questions.

Thanks,

SW

PS. If I then connect the LED's to the rear socket of my Stainz locomotives (bearing in mind I am DCC) and ran LED's attached to wires to each of 3 or 4 carriages will I have then lighted each carraige?
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
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488
Tamworth, Staffs.
If I take a 9V PP3 battery and connect the wires from my LED (one with a resistor and the other without) to the + and - connectors will the LED light up please?
Yes. - Polarity is important!

Similarly if I take a second LED and wire it the same will I then have 2 LED lights, etc. etc.
Yes.

If I then replace the battery with the DC output of my analogue controller will it work the same please?
Yes. But you need to get the polarity correct.

PS. If I then connect the LED's to the rear socket of my Stainz locomotives (bearing in mind I am DCC) and ran LED's attached to wires to each of 3 or 4 carriages will I have then lighted each carraige?
Yes.*

*Though, as others have stated, you really ought to put a blocking diode in the circuit. - Try this with ONE of your LED's as they may not like this too much.