LED help! Layout lighting shuts off after 1 minute.

[DrStroganoff]

Hello guys.   I need some help/advice with my layout lighting.    I've spent the last day or so reading the myriad of topics on LED lighting, and I feel like I'm struggling to understand the basics.  I'm very much a novice in this area.

 

I've just finished building my Metcalfe station,  in which I have installed 4x LED's (one in each 'room'),  plus 3 platforms lamps.   These are wired in parallel to a copper tape bus under the baseboard.   This is powered by an old Hornby trainset controller.    I must say, when I powered up the lights for the first time, I was most pleased with myself that it actually worked!   Fast forward 1 minute and the lights just powered off.     If I wait a little while and power them back up,  they work for 30 secs to 1 minute and shut down again.

 

 

 

Here is the copper tape bus:  (Ignore the brown/green wires, they are the power bus/track droppers)

 

 

And here is the controller:  (Note the lighting is connected the 12v DC output,  NOT the 16v AC)

 

 

One thing I have learned from reading this forum today,  is that I probably need some kind of resistors in there somewhere.   Any advice in this area would be v much appreciated.

 

The 4x LED's in the building are rated 12v / 20mA   (info taken from the ebay listing.)      And all I know about the lampposts is that they are rated 12v,  I'm only just now realising that they aren't LED's. (?) 

 

I had figured that if I just bought lights that were rated 12v,  that I could just power them easily with a 12v dc controller.    As usual, I was wrong...   So I'm hoping that you knowledgeable folk can offer some advice.

Thanks for taking the time to read.

 

 

 

Edited June 18, 2021 by DrStroganoff
Edited punctuation.

[SamThomas]

I'm assuming that there are resistors closer to the LED's themselves ?

 

Otherwise, the connected load is too much for the feeble Hornby controller & it jkeeps cutting out.

 

Before connecting a more powerful supply make sure that there are current limiting resistors in cicruit otherwise you may blow the LED's (you don't get another chance with LED's).

[DrStroganoff]

18 minutes ago, SamThomas said:

I'm assuming that there are resistors closer to the LED's themselves ?

 

Otherwise, the connected load is too much for the feeble Hornby controller & it jkeeps cutting out.

 

Before connecting a more powerful supply make sure that there are current limiting resistors in cicruit otherwise you may blow the LED's (you don't get another chance with LED's).

 

Hi Sam,  thanks for the reply.

 

No, there are no resistors.   Like I said,  I am a novice in this area unfortunately!

 

OK, so the controller is cutting out due to too much load.    I don't have a more powerful supply,  I'd like to use this Hornby controller if possible.   

 

So, will I need a resistor for each LED,  or is it possible to just put one at the start of the circuit?    Thanks.

[AdamsRadial]

If they are grain of wheat bulbs in the lamp posts they will be getting a bit greedy.

 

There is a quick and dirty method of limiting the maximum current drawn from the controller, and that is by putting a small bulb in series between the controller +ve wire and load. Let's say you want to limit the total current drawn from the controller to 1/2 amp. At 12 volts, 1/2 Amp means 6Watts of power, so put a 12V 6W bulb in series and that will then limit the current to the remainder of the lights and Leds to 1/2 Amp.

 

It will obviously cause some reduction in the light being emitted, but the Leds are less likely to be as affected as the grain of wheat bulbs.

 

[SamThomas]

13 minutes ago, AdamsRadial said:

If they are grain of wheat bulbs in the lamp posts they will be getting a bit greedy.

 

Sorry, I missed the bit about the platform lamps not being LED. Blessing in disguise really as they stopped the LED's from blowing !

 

Personally, I would fit a resistor to each LED & run the whole lot at around 9volts.

[Il Grifone]

12V Grain of wheat bulbs are usually 50mA (may be 75mA - check how hot they get!), so are taking 300mA or so by themselves. The cr puny Hornby controller should be capable of this, but.... It's voltage regulation is likely to be poor as well so the output could be higher than 12V.

 

I bought some allegedly 12V street lights from China several years ago. At 12v, the bulbs got hot enough to melt the plastic!

 

A test meter is a good investment (cheap from the Far East - I bought several at 3€ each).

Edited June 18, 2021 by Il Grifone

[AdamsRadial]

13 minutes ago, Il Grifone said:

The cr puny Hornby controller should be capable of this, but.... It's voltage regulation is likely to be poor as well so the output could be higher than 12V.

Just a thought, but using the controller to supply what are in effect resistive loads might be part of the problem? Motors are closer to reactive/inductive than resistive load.

Edited June 18, 2021 by AdamsRadial

[Il Grifone]

It would depend on the internal workings of the controller. I have a feeling that the Hornby unit uses a thyristor circuit, but I could well be wrong.

 

I have a different Hornby controller (part of a job lot IIRC). It is resistive, but has a very temperamental bi-metallic strip as a cut-out IIRC and cuts out after a few minutes use.

[DCB]

I reckon its the power unit's overload cut out, probably a polyswitch, the continuous load is too much for it.   

I would be very careful here, maybe try connecting to the variable (track) output and adjusting the setting so the lights are a lot dimmer.  Hopefully this will remain within the cut outs comfort zone.  If you substitute a more powerful controller then the whole damned lot might go pop.   LEDs also pass more current as they warm up so backing the power off a tad as they get warmer might also help.   At least trying this won't actually cost anything

I can only assume the LEDs are "12volt" LEDs with built in resistors otherwise with your circuit the building light LEDs would go pop and never work again before the platform lights came on.   A moment connected to 12 volts and most LEDs flare like a super nova and die.

 

[DrStroganoff]

1 minute ago, DavidCBroad said:

I reckon its the power unit's overload cut out, probably a polyswitch, the continuous load is too much for it.   

I would be very careful here, maybe try connecting to the variable (track) output and adjusting the setting so the lights are a lot dimmer.  Hopefully this will remain within the cut outs comfort zone.  If you substitute a more powerful controller then the whole damned lot might go pop.   LEDs also pass more current as they warm up so backing the power off a tad as they get warmer might also help.   At least trying this won't actually cost anything

I can only assume the LEDs are "12volt" LEDs with built in resistors otherwise with your circuit the building light LEDs would go pop and never work again before the platform lights came on.   A moment connected to 12 volts and most LEDs flare like a super nova and die.

 

 

Hi David,  Yes, they are connected to the track output of the controller.   I did try dialling the knob down as low as possible, but I chickened out of leaving it on too long as I didn't want to risk burning them out.  

 

Another question guys...   Would using a 6v battery as a power source be an option?

 

Thank you everyone for the responses.  To be honest,  I'm struggling to process it all.    I'm a bit confused, as I'm sure I've read many threads on here where the advice has been "Just use an old trainset controller" for powering lights!  

 

 

1 hour ago, SamThomas said:

Personally, I would fit a resistor to each LED & run the whole lot at around 9volts.

 

Sam,  to make sure I understand your advice correctly...   You would fit a resistor to the 4 internal LED's,  but not to the 3 platform lights?     And by running at 9v,  would I achieve this by dialling the controllers dial down to say 3/4 power?

 

I must apologise guys,  I meant it when I said I'm a novice!

[SamThomas]

10 minutes ago, DrStroganoff said:

Sam,  to make sure I understand your advice correctly...   You would fit a resistor to the 4 internal LED's,  but not to the 3 platform lights?     And by running at 9v,  would I achieve this by dialling the controllers dial down to say 3/4 power?

Yes, that's correct except that I would not use the old controller. If you run the platform lamps at around 9 volts they will look more realistic, run coller & last longer.

 

You could use something like this (plenty of power for many more lights too) ;

 

https://www.ebay.co.uk/itm/313222101652?hash=item48ed7dfa94:g:mBgAAOSwxUFfYw7P

 

 

[Dungrange]

The Hornby controller that you've photographed looks to be an R985.  My understanding is that this unit simply acts as a rectifier and voltage adjuster and there is a separate AC power supply that plugs into this.  I think these have a different code and there have been a couple of different input power supplies sold with the R985 in the past.

 

Somewhere on that it should give an output voltage (probably 16 V AC) and also a power rating.  This will either be shown as Watts (W) or Voltage Amps (VA).  If you divide the power rating, by the output voltage, then you'll know how much current you have.  For example, if the transformer is rated at 8 Watts and outputs 16V AC, then it can supply half an Amp (or 500 mA).

 

I agree that it sounds as though the current being drawn by all of your lights (LED and bulbs) is greater than the current that the power supply can handle and it is shutting down.

[DrStroganoff]

@Dungrange    Thanks for that info,  I've been able to work out that the Hornby controller can supply approx 800+mA , so it should be able to power about 40 LED's  (Much more than I'll need).

 

I *think* I am getting somewhere now!     I've had a friend come take a look this morning, and he seems to think that the LED's I have used are self-resisting.    So now I have disconnected the lampposts from the bus, and the Hornby controller seems to be fine just powering the LED's inside the buildings.  

 

So I'm thinking I might have a lighting bus just for LED's inside buildings, powered by the Hornby controller.    Then do a separate bus for the grain of wheat lampposts,  and power them at 9v using the power supply that @SamThomas suggested above.

Thanks again everyone.  Hopefully I'm heading in the right direction with this.  I shall report back!  :-)

[Phil Mc]

I’ve had an instance where I’ve wired LED’s in parallel for internal lights in buildings, and got an unexpected issue.

 

I’d got warm white, bright white, red, and blue LED’s, all from the same supplier, and all with the same power usage details.

In one particular building I was adding them to, I went through the same procedure as I had done previously, which was solder in one light, then do a quick test to check all was well before adding the next light….etc.

Blue light in first, check, all ok, warm white in next, check, all ok, bright white in, check, all ok, another bright white in, check, all ok, red in, check…..only the red light lit !

Disconnect the red, check, all the others work fine…red back in, same issue !

So a blue one went in its place, check, all ok.

 

Just glad I used them in that order. If I’d added the red one first I could have been faffing around for ages trying to figure out what was happening !! 

 

cheers,
Phil.

 

 

 

Edited June 19, 2021 by Phil Mc

[AdamsRadial]

In case it helps, although LEDs must be run from a DC supply, grain of wheat and other filament type bulbs will run on AC.

[Il Grifone]

LEDs are semiconductors and their voltage drop (relatively constant in the range 2-3 volts) depends on their colour*. Their brightness depends on the current drawn but varies little (at least  to the human eye). A 1kohm resistor is usually used with 12 volts (330 ohm for 5 volts) which will give a current of about 10mA (above this the brightness increase is low - diminishing returns.

 

* Red about 2V, blue and white about 3V - individual LEDS even of the same colour can vary. Connected in parallel without series resistors (don't) the lowest voltage will light and the others won't light or at least dimly.

 

Real lighting is a lot dimmer than LEDs or even grain of wheat bulbs (try scaling up the power 76.2 x 76.2 x 76.2!)

 

LEDs can be connected in series, reducing the series resistor to compensate (not to zero).

 

Add the voltage drops and subtract from the supply voltage, V=RI then gives the series resistor value. Set I = 10mA and then choose the nearest preferred value (it's not that critical).

[DrStroganoff]

On 18/06/2021 at 14:29, SamThomas said:

Yes, that's correct except that I would not use the old controller. If you run the platform lamps at around 9 volts they will look more realistic, run coller & last longer.

 

You could use something like this (plenty of power for many more lights too) ;

 

https://www.ebay.co.uk/itm/313222101652?hash=item48ed7dfa94:g:mBgAAOSwxUFfYw7P

 

 

 

Sam,  I was just thinking of ordering one of these, as per your recommendation.   Two questions though:

1. How would I connect this to the lighting bus ?     
2.  On the ebay listing,  which version do I get?   72w 9-24v   or   60w 3-12v

Thanks in advance!  :-)

 

Edited June 28, 2021 by DrStroganoff
Added a question!

[SamThomas]

On 28/06/2021 at 12:12, DrStroganoff said:

 

Sam,  I was just thinking of ordering one of these, as per your recommendation.   Two questions though:

1. How would I connect this to the lighting bus ?     
2.  On the ebay listing,  which version do I get?   72w 9-24v   or   60w 3-12v

Thanks in advance!  :-)

 

Sorry about the delay as I've been away.

 

The 60w one will be fine.

 

If you cannot find a connector just cut the plug off - the cable may be a screened  one - the positive will be the single core one.

[sagaguy]

3v LED lighting from Layouts4u range including coach lighting.

 

                           Ray.

[PatB]

One of the useful aspects of the tech revolution is the vast surplus of old wall-warts of various outputs, leading to an almost infinite supply of small power sources, available for free from friends, family and ones own stash, or for pennies from any junk/charity shop. All nicely marked with output voltage and max current rating. Very handy.

[kevinlms]

9 hours ago, PatB said:

One of the useful aspects of the tech revolution is the vast surplus of old wall-warts of various outputs, leading to an almost infinite supply of small power sources, available for free from friends, family and ones own stash, or for pennies from any junk/charity shop. All nicely marked with output voltage and max current rating. Very handy.

Yes, as long as one knows how to correctly read them and what the ratings actually mean, especially regarding protection from over voltage on your device.

 

As for using computer power supplies (often advocated here), the ratings for these are quite scary and will fry much model railway equipment, without a hiccup, let alone a fart.

[PatB]

11 hours ago, kevinlms said:

Yes, as long as one knows how to correctly read them and what the ratings actually mean, especially regarding protection from over voltage on your device.

 

As for using computer power supplies (often advocated here), the ratings for these are quite scary and will fry much model railway equipment, without a hiccup, let alone a fart.

True. Attention to overcurrent protection is important if using computer PSUs, but needn't be over-complex. 12V bulbs, polyswitches, fuses and mechanical circuit breakers (depending on preference) are all cheaply and easily available. 

 

However, in the context of the thread, I was more thinking of stuff like phone chargers, small printer and scanner supplies and the like. A quick rummage through the discarded tech drawer suggests that typical maximum outputs are between 0.5A and 1A at whatever voltage, so not too frightening, but ample for running most accessories. As they're essentially free, it's not a major problem if you need to plug 3-4 of them into a gang socket to run several individual items. In such a case their lowish outputs assist in avoiding high currents anywhere.