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Author Topic: Lighting to,illuminate the layout  (Read 555 times)

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Offline sprogman

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Re: Lighting to,illuminate the layout
« Reply #15 on: September 11, 2017, 04:03:12 pm »
Just be careful that the lights have current limit resistors and are not relying on the internal resistance of the batteries when used as supplied.

Offline Josiebenn

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Re: Lighting to,illuminate the layout
« Reply #16 on: September 11, 2017, 08:14:47 pm »
At the moment, and in a test rig,  I have 7 of these book lights (each demanding 50mA) all connected in 1 x parallel group , all receiving 3v (the 10 mark) from a Gaugemaster Combi (which could give a max of 12v) and they are all shining like full moons.  Just as if they were still battery powered.  And dimming nicely from 0-10 on the dial.   

I added them one by one and they all simply lit up as I did so.    Any concerns, as this seems to have simplified the theories, which now puzzles me.  I will divide them into 2groups as they need to be spread out around the track, but this does seem to be a working set up.  They seem happy little lights Are they?

 Cos if no-one else says Oi! Don't!  Stop! I will just get another Combi and bosh bosh bosh. 


Offline ntpntpntp

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Re: Lighting to,illuminate the layout
« Reply #17 on: September 11, 2017, 08:29:27 pm »
@Josiebenn   what puzzles you? You have them in parallel and they're all working as you want.  Have you put a voltmeter across the supply - is it around 3V?

Personally I'd still rather connect 4 of them in series for 12V, and run 2 groups of 4 in parallel (yes you would need to buy another light). That way, if you accidentally crank up the controller output you won't immediately fry the LEDs.  Also you'll have more control over variation of brightness. Of course, a "12V" controller may actually output higher than 12V, depends on what it's supplied from.

Sprogman's comment about checking if there is a current limiting resistor is also a good idea.

Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline Josiebenn

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Re: Lighting to,illuminate the layout
« Reply #18 on: September 11, 2017, 08:49:07 pm »
Hi ntp3.  Fair enough.   Bear with me, if each lamp on batteries wants 3v, is it because they are all in parallel, that 3v is enough for all at once?    Being a first year amateur  at model railways, and nearly 68!  I can't recall all of my school days electronic lessons. 

I will be splitting the two groups as you suggested and will get one more for the full 8.   I have a moving coil voltmemeter, and I have measured what volts are pushing out for each dial mark. So I know at the 20 mark(not 10 as I said earlier) the output is 3v. 

No idea where I would look for  a current limiting resistor.   I will probably put a physical stopper at the 3v mark  on the new controller. 

Many thanks for your advice, (and everyone else too), this little exercise has been a lot of fun.   

Offline ntpntpntp

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Re: Lighting to,illuminate the layout
« Reply #19 on: September 11, 2017, 09:34:09 pm »
Hi ntp3.  Fair enough.   Bear with me, if each lamp on batteries wants 3v, is it because they are all in parallel, that 3v is enough for all at once?

Yes. With a parallel circuit being a bit like a ladder, each "rung" gets the same voltage across it.

Because your controller is typically going to output 12V maximum (it might be a bit more or less depending on the supply to the controller), it seems safer to string 4 of your lights in series so that they share 12V between them (ie. 3V each which is what they need).  Then have a second identical string of 4, but connect that in parallel to the first so it also gets 12V across the string.  This way you won't have to worry about putting a stopper on the controller, you will just crank it up to maximum  (or maybe a little less if you want the lights not quite so bright).



« Last Edit: September 11, 2017, 09:54:29 pm by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline MalcolmAL

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Re: Lighting to,illuminate the layout
« Reply #20 on: September 11, 2017, 09:59:08 pm »
Experimentally, I have already converted 1 of them
Did your conversion involve peering inside it or just clips on the battery terminals ? If you looked inside it did you notice a resistor in series with the wires to the battery holder/terminals ? (battery operated led banks dont usually have one I dont think )

How much did it cost ? ie. would it be a sad loss if you destroyed one :) ?

The reason you are being asked about current limiting resistors (or battery resistance) is  that without such a limiter the LEDs can fail quite soon/rapidly if the controller is turned up a bit high,   however if there is a resistor in series then the it will be a more gradual failure mode giving you time to notice and get it turned back down pdq !
« Last Edit: September 11, 2017, 10:05:20 pm by MalcolmAL »

Offline Josiebenn

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Re: Lighting to,illuminate the layout
« Reply #21 on: September 11, 2017, 10:51:09 pm »
Inside where the batteries nestle, i soldered tails onto the plates that take R and B wires to the circuit board.   There were two small black thingies that would be diodes or resistors.  Not sure which.  Then connected the lot in parallel and powered them up.   Nice row of moonlight. 

Npt3 suggests spreading the volts and avoiding inadvertent overload by having g two series groups.   So, more fun coming. 

Offline Bealman

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Re: Lighting to,illuminate the layout
« Reply #22 on: September 11, 2017, 11:48:12 pm »
Hi all, thanks for all replies, apology to Bealman down under.  When people say Folks, we limeys assume they're Americans. 


That's ok, Josiebenn. No offence taken. I'm actually originally from Durham, not far south of you.  :thumbsup:

Themadhippy's circuit seems to be an elegant way of obtaining a variable supply.
« Last Edit: September 11, 2017, 11:49:15 pm by Bealman »
Vision over visibility. Bono, U2.

Offline Josiebenn

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Re: Lighting to,illuminate the layout
« Reply #23 on: September 12, 2017, 08:17:10 am »
Hi, ex Durham eh? Well well well.   Hexham is my nearest town.  Happy rolling!

Offline Bealman

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Re: Lighting to,illuminate the layout
« Reply #24 on: September 12, 2017, 08:21:12 am »
Cheers! Getting off topic a bit, but I assume the Roman Wall is still there.... used to go on school excursions there.  :beers:
Vision over visibility. Bono, U2.

Offline Josiebenn

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Re: Lighting to,illuminate the layout
« Reply #25 on: September 12, 2017, 08:30:00 am »
Being a  World Heritage site/sight, it is still as the locals over the centuries have left it, 75 miles of waist height stones.   English Heritage would like to build a full size reconstruction, (at my and others urging) but Unesco won't let them.  It has to remain and be kept pure. 

It is a huge tourist draw, a new visitors centre has just been opened on the Military Road at Twice Brewed, and Vindolanda is now swooning at finding a cache of well preserved Roman Swords.  All there to be googled. 

Offline Bealman

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Re: Lighting to,illuminate the layout
« Reply #26 on: September 12, 2017, 08:51:06 am »
Cool!  :beers:
Vision over visibility. Bono, U2.

 

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