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Author Topic: Help with LED Wiring Diagram, please.  (Read 9537 times)

TCC

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Help with LED Wiring Diagram, please.
« on: February 03, 2009, 02:47:39 PM »

Hi
I'm 'all at sea' over a LED wiring diagram. Excuse the pun.  :-) Back in the day, I got a load of 'LEDS' and ran them in paralel off 2AA batterys in a battery box. I thought my life was simple...

Here's how I originally wired my LEDs, they are 5mm yellow pairs for the searchlights and 3mm yellow, red or green for the mast, bridge and navigation lights. They are wired in parallel.



you may need to open that image in it's own window.

So that'w what i's like now, however, I now need to add a extra pair of s'lights to the aft superstructure (that's 2 units of  2 LEDs = 4 LEDS) Now I would go with yellow again but I now know they make white LEDs so I'm thinking why not do them all again? It's not like they are perefect as is and I'll be disturbing that bridge area in order to alter it to get it right (new info).

I'll also be disturbing my nav lights if I do this alteration. BUT there is some mast/superstructure lights that are now built in and can't be replaced. I marked them as 'fixed' on my diagram. Other than those 'fixed' LEDS, all the rest can change.

What I want is a wiring diagram or help so I can add these extra 4 white LEDS to the set-up... or a new searchlight set-up of 8 pairs (16 LEDS) of white 3 or 5mm LEDS that will ALSO run the excisting yellow 'fixed' lamps. It's the voltage that's threw me as I believe you can't run white/blue with the yellow/red/green as there's voltage differences. That's what's stopped me.

Can anyone help me, cheers.
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wideawake

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Re: Help with LED Wiring Diagram, please.
« Reply #1 on: February 03, 2009, 03:01:03 PM »

Hi TCC

Just a quick question?   Are the 2 x AA batteries rechargeables or alkalines?

Guy
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TCC

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Re: Help with LED Wiring Diagram, please.
« Reply #2 on: February 03, 2009, 03:46:18 PM »

Either... I think I've had both in there. I know what's coming... alkalines are 1.5v while ni-cads are 1.2.

Here's a bigger version of the wiring diagram:

http://s2.photobucket.com/albums/y6/001-spanky/HMS%20LION/?action=view&current=LEDlwiringdiagram.jpg

You have to click the link and it'll take you to an old photobucket account.
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stallspeed

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Re: Help with LED Wiring Diagram, please.
« Reply #3 on: February 03, 2009, 04:12:03 PM »

To work different colours you will have to forsake the 2xAA method.
Red leds start to conduct at ~1.2 volts and the voltage rises as the colour shifts to shorter wavelength.
If you were to wire green and red in parallel,green would not reach full brightness and white won't work as it has a blue led that conducts from 3 volts and above.
You could google : led resistance calculator or wait for someone to chip in with a diagram.

Oh!...careful handling the white leds.They are very static sensitive.
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Rex Hunt

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Re: Help with LED Wiring Diagram, please.
« Reply #4 on: February 03, 2009, 05:25:15 PM »

what voltage power supplies do you have available on board?

Rex
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TCC

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Re: Help with LED Wiring Diagram, please.
« Reply #5 on: February 03, 2009, 07:04:29 PM »

Sorry mate, I think I'll be going 12v from the 6v at present.

Cheers stallspeed, I did search this site and I came back to the thought that I need to do this right first time as all these LEDs will be built into the ship and fittings. So there's no bulb replacment if anything goes.

If I hit a issue, well it'll revert to a model with non-working lights.  <:(

 %) As I say, life used to seem so simple...
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wideawake

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Re: Help with LED Wiring Diagram, please.
« Reply #6 on: February 03, 2009, 07:17:40 PM »

I agree with Stallspeed, I think you need to abandon the 2 cell approach and also start using series resistors with your LEDs.

I'd suggest to start with that you use a 4 cell battery clip supply.  That'll give you 4.8 volts with rechargeables or 6 volts with alkaline cells.   Ideally you need to settle for one or the other.  I'm going to assume 6 volts for the moment.  That way if you use 4.8 volts you'll just get dimmer LEDs whereas if I assume 4.8 volts and you use 6 volts you MAY blow LEDs up.

A few basic facts.    Any LED of the type you're using needs to draw approaching 20mA for full brightness.   The voltage drop across the LED depends on the colour.  Red 2.1 volts, Yellow, Orange, Green 2.4 volts, White 3.3 volts.

The basic idea (but see later) is to include a series resistor with each LED to drop any voltage in excess of what's required.

Taking your yellow ones as an example: with a 6 volt supply you need to drop 3.6 volts (6 - 2.4) at 20mA.   Ohms Law says R = V/I   so R = 3.6/.02

It's handy to know that 1/.02 = 50 so R = 3.6 x 50 = 180 Ohms

So in the simplest case put a 180 Ohm resistor in series with each LED and that's it.

However in your case I notice that some of the LEDs are grouped in 2s and 4s so you could economise on resistors by using one per group of LEDs.  Using the same calculation as above 2 LEDs in parallel will take 40mA total so R = 3.6/.04 = 90 Ohms

For 4 LEDs in parallel drawing 80mA total R = 3.6/.08 = 45 Ohms

If the calculated resistor is not a preferred value then use the next highest one.

If you're definitely only going to use 4.8 volts then do the calculations with a voltage drop of 2.4 volts instead.

The same calculation applies with other LED colours using re-calculated voltage drops.


Also bear in mind that the resistors can be inserted wherever convenient, they don't need to be tight up to the LEDs.  This might reduce the amount of difficulty when modifying the present set-up.


HTH

Guy


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Colin Bishop

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Re: Help with LED Wiring Diagram, please.
« Reply #7 on: February 03, 2009, 07:24:07 PM »

Just another thought but many LEDs can be obtained in 5v or 12v versions these days with built in resistors. Check out the Maplins site. Saves a degree of complication and the 12v ones usually work quite well on 6v for modelling purposes.

Colin
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Rex Hunt

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Re: Help with LED Wiring Diagram, please.
« Reply #8 on: February 03, 2009, 08:08:32 PM »

This page is a fantastic help

http://led.linear1.org/led.wiz

If you are not sure as to current etc.....click on the ? for guidance.

I would suggest at least 2 separate circuits.

1 for red/green Nav lights (similar requirements)
1 for mast lights and bridge light
1 for search lights.

The link above has useful options too, Schematic diagram (techy bit),
wiring diagram (idiot proof if you remember that 'little leg - or stripe- is neg' when it comes to the diode)
and a guide to the appropriate colour coding on the resistors.

If in doubt....go up one on the resistor values...........just means the led will be slightly less bright!

Have fun

Rex
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TCC

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Re: Help with LED Wiring Diagram, please.
« Reply #9 on: February 04, 2009, 02:57:52 AM »

Listen Lads, the sums just go over my head, sorry. Can I give you a set of requirements or gear I'll use and ask what resistors I need?

I'll go with 2 circuits, if I can.

I'll use a 12v gel cell.

I can group my searchlights [16 in total] in 4 units of 4 so I can use 1 resistor per group, or I could group them in 8's? whatever is easiest/best and most 'reliable' [read as long lived], the 4 (or 2?) groups of s'lights are all run in parallel.  Yes, I'll place the resistor well below the lights on the underside of the superstructures as the wiring is already fitted, when I replace them, I'll just be swapping the s'light fittings for new castings and re-soldering the wires.

It doesn't matter how bright they are really, I just want them to light.


The Nav and mast lights.

This is where I'll have the issues, no? It's a 12v battery so I just need the resistor values for each colour, thanks.

I'd go with the 12v LEDs with resistor that colin mentioned but I think the added resistor would not fit in with the above.

Now the 3, 3mm yellow LEDS that are fixed in I can't do anything about... but I can buy new red & green Nav lights... I'm thinking of using Squires. So if one of you lads can advise on resistors and the voltage of each type of LED I need, I'll be sorted, cheers. And don't think I'm being lazy or not appreciative, I've so much other stuff I'm trying to do at the mo that I've just got too much on my plate.


... and I need to do this as I need to get the LED parts list together so I can order my other bits for all the other things that are holding the building up. The LEDs is just one of several bottlenecks.

Cheers lads
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Colin Bishop

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Re: Help with LED Wiring Diagram, please.
« Reply #10 on: February 04, 2009, 09:09:07 AM »

For the red and green ones just buy 12v types - they have the appropriate resistor built in.
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wideawake

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Re: Help with LED Wiring Diagram, please.
« Reply #11 on: February 04, 2009, 09:34:53 AM »

For the red and green ones just buy 12v types - they have the appropriate resistor built in.

Assumimg they aren't too bulky to fit then that's a sensible idea.    I'll do the sums this evening for the other groups unless someone ellse has done so earlier.   Don't have time today due to other things.

Cheers

Guy
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Colin Bishop

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Re: Help with LED Wiring Diagram, please.
« Reply #12 on: February 04, 2009, 09:45:21 AM »

Maplins go down to 3mm 12v LEDs http://www.maplin.co.uk/Search.aspx?criteria=12v%20led&source=15

They are not the only source, model railway suppliers do them too.

Colin
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Seaspray

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Re: Help with LED Wiring Diagram, please.
« Reply #13 on: February 04, 2009, 12:31:00 PM »

Just a thought and not too knowledgeable on Fibre optics.

You couldn't use a Fibre optics, set up, on the boat. From what little I know you need a light source one end and it comes out the other end.

Is there a way to change a white light (input end containing required amount of fibres)....l(output end each fibre to the place and colour required on the model.) 

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andrewh

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Re: Help with LED Wiring Diagram, please.
« Reply #14 on: February 04, 2009, 01:10:03 PM »

TCC
Thanks for the question -
I'm not sure if you have the answer yet so here is my numpty's guide to LED lighting
THIS is totally from a doing viewpoint - theory (which I also know) can go hang for a moment

You have a 12V supply
LEDs light up with 3V - all of them  (they light one way round and don't t'other)
so hanging 4 in series on a 12V supply will light 4 LEDS - any colour, any size, always

3V may be too bright, and may be too much voltage for long term use - So Add another and run 5 in series off 12V

So to go back to your original question - pick off a new 12V supply and connect 4 or 5 whie LEDS in series across it. 
Do not change anything in your diagram

White LEDS are readily available - in pound shops where they are called keychain lights - 2 for a pound or LED torches where 4 or 5 are fittted as "bulbs". 
Viola  - high power white LEDS!
Functional notes:  Keychain lights connect a white (or other colour) LED DIRECTLY across a Li button cell battery (3V or a little more)
Torches may well have the LEDS connected in parallel to 3V - so you may need to persuade them into series connection if you wish to run from 12V.  They will be fine across two pencells - ANY type

Car accessory shops sell very high power LEDS ready for connection at 12V - lots of colours, but more pennies

Please ask any further questions you like till you are happy (and lit up :})

I leave you with a wise ode from Mr FLJ who says:
"the shorter leg
 goes to the neg"
andrew


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wideawake

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Re: Help with LED Wiring Diagram, please.
« Reply #15 on: February 04, 2009, 05:23:56 PM »

Hi TCC

I'll try to offer my take on this  but I'm afraid there is always more than one way of doing things.    If you're definitely going with a 12 volt supply  and changing all the searchlights to white ones (3.3 volts) then as Andrew says, stringinging 4 in series will remove the need for a resistor for that group.   If you can do that during the alterations then that's good.    If not you'll need a resistor for each pair.    If I understand correctly that will deal with the present 6 twin LED searchlights.   The two new searchlights (2 LEDs each) will need resistors unless you can arrange to wire all four LEDs in series again.   In case you can only wire each pair in series then I'll give you a resistor value.   The simple way to deal with the red and green nav lights is as Colin suggests, using "12 volt LEDs" from Maplin.    I've now checked and the resistor is integrated into the package so they're the same size as a standard LEDs and should fit the present housings. 

The fixed yellows will need resistors and I'm going to assume that the easiest way is to fit one resistor per fixed yellow LED.   So this is how I see it

Single Fixed Yellow LED  12 - 2.4 = 9.6 volts 9.6/.02 = 480 Ohms     Nearest higher preferred value is 560 Ohm 1/4 watt

Single red or green LED  Best option is the Maplin 12 volt item.   Otherwise use 560 Ohm resistor as above

Twin White LED searchlight with the two LEDs wired in series 12 - 3.3 - 3.3 = 5.4 volts 5.4/.02 = 270 Ohms   Nearest preferred value is 270 Ohm 1/4 watt

Pair of twin searchlights as above with the pair of (two LED) units wired in parallel 5.4/.04 = 135 Ohms   Nearest preferred value is 150 Ohm 1/4 watt

Pair of twin searchlights (4 white LEDs) all wired in series require no resistor.


Once you've wired each "unit" and its resistor (if required) you can parallel everything up to the 12 volt supply.

I'm sorry I can't post a diagram as such but if you consider each unit in turn, I think the info above should cover everything.  If not ask again  :-)

There are alternatives but I've tried to compromise between the minimum number of resistors and too many cahnges to your present set-up.

HTH

Guy
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malcolmfrary

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Re: Help with LED Wiring Diagram, please.
« Reply #16 on: February 05, 2009, 02:02:25 PM »

Just a thought and not too knowledgeable on Fibre optics.

You couldn't use a Fibre optics, set up, on the boat. From what little I know you need a light source one end and it comes out the other end.

Is there a way to change a white light (input end containing required amount of fibres)....l(output end each fibre to the place and colour required on the model.) 


If al the lights are going to be conveniently sited, optic fibre is good, BUT - it doesn't like sharp corners and the light coming out the end you look at is less than that going in the other.  On the plus side, you only need one source.  Colours can be varied by interposing a coloured gel (paint clear sheet with craft shop glass paint) between the bulb and the optics intended to be whatever colour. 
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Seaspray

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Re: Help with LED Wiring Diagram, please.
« Reply #17 on: February 05, 2009, 05:03:53 PM »

Just a thought. Worth a look into during a slack time or next winter. They looked bright when they were used as house tablelamps.
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TCC

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Re: Help with LED Wiring Diagram, please.
« Reply #18 on: February 07, 2009, 04:07:34 PM »

Just a thought. Worth a look into during a slack time or next winter. They looked bright when they were used as house tablelamps.

That's a good idea... LION has these 3 'fittings' at the rear/top of the rear superstructure and I think they're fighting lights of some kind.



See the question mark to the right? The centre one is directly above that and then there's one either side. To get you're orientation of the ship, the plane of that wall faces the rear and over 'x' turret.

I've had cogarette lighters in the past that had a blue LED in the bottom and it's powered by 3 button cells. And I can get hold of a few of these strands... see where I'm going?

Or if someone can advance another possible explanation of what they are? I'd be grateful. Or if they can identify the 'mounts'? by the question marks... or the gun(s) on the mounts?

She had 4 3lber saluting guns there when built, it then went to 3 3lber and 1 6lber hotchkiss AA gun. [That's probably that 'unknown gun'! and the 'mounts' are probably off the 3lbers which are unshipped... but that's my theorising, I'd love some confirmation.]
Cheers
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TCC

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Re: Help with LED Wiring Diagram, please.
« Reply #19 on: February 07, 2009, 04:53:51 PM »

Hi lads
It's no use, I'm not getting this thing down clearly. I can't split the s/light LEDS up into 4 as I'm hoping to use a white metal fitting as a 'gound' for one of the wires. To be honest, it's a mess. I've now got 3 circuits which will mean 2 switches and a power source each.

I'm open to suggestions. I'm trying to use squires for bits just for the sake of easiness as I have 1 order to go there. But just give me a list of what I need and I'll sort it.

It would be a good idea to separate the s/lights from the nav/mast/body lights.

I'm also looking at GOW and GOR (grain of rice) bulbs, there's some of the latter in white that are 1.5v and there's a 2nd type that are 12v and are 1,8 x 5mm.

My searchlight body is 5.5mm long and 5mm wide. I was planning on drilling them out to suit using the 3mm LEDS. (well the hole will be cast in them.

The prob with all these curcuits is hiding the switches... unless someone can sugges a set-up [read: switch rating] that uses 'Reed' switches? As I can then put a magnet in a hatch and place it upon the deck planks, which is above the reed. Hopefully, the magnetism would travel thru <2mm ply and the 0.75mm planks.

Other than that, it'll be hard attaching a switch under the non-removable deck areas as they're planked. And there seems little good in putting whatever in the lift of superstructures... or is there?

Saying that, I have a few micro-switches... I'm wondering if I could attach in the ship (under the deck) and pull them on with a piece of rigging through a little hole?

A Ha... I may have scope of small rotary switches under a mushroom vent or capstan or a push on/off switch under a hatch with a cover that lifts off.

Tell me, I've placed 17-odd LEDS in parallel off a 2.4 or 3v curcuit, what's wrong with doing that? What are the downsides.
Cheers
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malcolmfrary

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Re: Help with LED Wiring Diagram, please.
« Reply #20 on: February 07, 2009, 06:45:33 PM »

Quote
I've placed 17-odd LEDS in parallel off a 2.4 or 3v curcuit, what's wrong with doing that? What are the downsides.
At 20mA per LED, budget for 340mA.  If its all going through one switch, make sure the switch can handle that switching current.  LEDs are not resistive, which means that unless something else is restricting the current (a resistor, resistance of wiring, internal resistance of the power supply) provided that the supply voltage is enough, they will glow very brightly, then die early.  If the parallel circuit has elements that react at different voltages, one will lose first, this will put an extra load on its mates.
Micro switches worked by a rotating cam are a good idea, even moreso if the cam is on the underside of a bollard.  You could also use a metal screw bearing down on a couple of copper tracks of stripboard.  Turn on and off by winding the screw in and out.
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wideawake

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Re: Help with LED Wiring Diagram, please.
« Reply #21 on: February 07, 2009, 07:08:18 PM »

Hi TCC

What Malcolm says about by parallelling lots of LEDs up is spot on!   Inevitably they'l all have slightlydifferent characteristics and if one blows there's a good chance of a domino effect  :((

The ideas for hidden switches are excellent IMHO.   Another way is to hide them under removable fittings like hatches or boxes.

WRT the searchlights then surely you're in one of the positions I outlined earlier.   4 LEDs using the fitting as a common negative effectively lets you either drive each one separately with its own resistor or (better) allows you to join the positive wires on the LEDs and use a resistor calculated (see my previous post where I did this) to drive 4 LEDs.

HTH

Guy
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TCC

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Re: Help with LED Wiring Diagram, please.
« Reply #22 on: February 08, 2009, 12:41:16 AM »

Hi Lads
Thanks for staying with this.

I'm with you on the 'if one blows, the power that that would have used is now going to the remaining'. But is that the same even if in parallel? I suppose so, yes?

Right, I'm clarifying it a bit.

2 curcuits: one for the mast/nav lights and one for the s'lights.

The former will have to be non-12v LEDS as that's what is built in. So I'll replace the nav lights with ordinary LEDS in red/green. I'll just need the rsistor for a 12v circuit, thanks.

Now for the s'lights? If I have 4 lights in 2 WM fittings, how can I make each fitting a gound? I may just need 5 mins to think about how to do them.

Cheers
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malcolmfrary

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Re: Help with LED Wiring Diagram, please.
« Reply #23 on: February 08, 2009, 11:35:37 AM »

Quote
But is that the same even if in parallel? I suppose so, yes?
Especially in parallel without something to limit current to the individuals.  The series resistor can go anywhere in the circuit, battery side, ground side, in the case of LEDs in series, between LEDs.  Just cut the wire and insert the resistor.   
In series, one blows, they all go out.  The exception is Xmas tree lights - usually the bulbs are designed to short out when they blow, so the rest glow a bit brighter for a time.  When a few have blown the fused one dies and disconnects that chain.
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