Lighting

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I have purchased some lights for the station and depot yard on my layout, but what would you recommend to power them?

I have an old Hornby analogue controller, the one with the two switches rather than a dial, would that be fine? Sue the analogue control is only 12V, which should be OK for powering lights?

Cheers CSK
 
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hairyhandedfool

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12v is fine for lighting, but remember that LEDs will need a resistor in series, I'm using the uncontrolled 12v dc output on my old HM2000 controller for the lights.
 
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I am a bit unsure on the resistor, I have about 10 lights I plan to wire together for my main platform, and connect them to the old Hornby controller I mentioned previous, what is the exact setup I need to do (Yes, In idiot terms would be great, not a whizz with lighting)
 

Nym

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LEDs drop a spesific voltage across them but this voltage drop does not set the current to flow through them (ususally), you need to pick a resistor that will take into account these voltage drops and then sets the current of the circuit.

The typical forward bias for an LED is between 1 and 3 volts, so if you have a resitor in series with this, it will be dropping 9 volts across I don't have the foggiest what you want to be driving your LEDs at, that varies on the specification, but you can use Ohms Law to decide on a suitable resistor value.

If you wanted to be fancy you could set up a current control mirror to drive your LEDs without dropping a load of voltage across lots of resistors, but then you're dropping it against a transistor instead.

One can use this simple equation stolen from wikipedia, but it won't be a perticularly efficent setup if you use that directly.



You would be better providing me slightly more detail and the spesific LEDs and I can work something out for you, or, (not to sound horrid) but think of how you can set up an array of LEDs with rows of them in series to drop about 8 or 9V then drop the remaining 3 or 4 across an appropriate resistor, and run sets of LEDs in series like this.

PS: Typical LED currents vary between 5mA and 50mA, (Power LEDs can run up to about 320mA)

http://en.wikipedia.org/wiki/LED_circuit <<This page may be helpful.

This page will be MUCH more helpful...

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

Select your source voltage appropriately (12V) the diode forward voltage should be listed in the datasheet, pick a current you're comfortable with, 20mA should be fine, but have a look at the datasheet for your LED and pick somewhere in the flat reigon just before it curves up on the graph (where a big increase in current only warrants a small change in light / voltage, that is your saturation current, avoid this area), select the number of LEDs in the array and ask to view the output as a wiring diagram, very helpful little page.

NOTE: Changing the voltage on your source (if possible) will allow dimming with a resistor controlled circuit.
 
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Nym

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Well, I don't know on them because there is no datasheet. There seems to be an internal load resistor but I can't tell you for certain how to set them up.
 
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Thanks for your help anyway, I have a good idea what I'm going to try and will see how we go.
--- old post above --- --- new post below ---
OK, so this is what I have done.

I wired 2 of the lamp post together and connected them to a standard Bachmann controller, the lights could be dimmed and were reasonably bright.

I have now wired all 10 into my station platform and they are all wired in sequence, obviously they are now very dim, but still just about lighting.

So my question is, what do I do from here? is there any way I can run them all from the same Bachmann controller and get them to be bright? Or am I going to have to buy another form of power?

(As I mentioned before, I'm a novice with this side of modelling, so please go easy on me, lol)
 

hairyhandedfool

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If you change the wiring from 'in series' to 'in parallel' the brightness should be better.

so....

-----O------O-----O-----

Becomes....

. . . . +-----O-----+
. . . . | . . . . . . . . |
-----+-----O------+-----
. . . . | . . . . . . . . |
. . . . +-----O-----+

If you see what I mean.
 

Heinz57

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I tend to find that the old Hornby transformers don't give enough juice for multiple lights.

Personaly I use a Gaugemaster 16V AC transformer, which is more than up for the job. Although to get the best results with your lights it would be best to convert the AC to DC (Not that hard though, just a few diodes and a capacitor or two). Alternativley, Gaugemaster also have a 12v DC transformer, which are also up for the job.

Using one of these power supplies leaves you room in the future to expand your lights, because no doubt when you've got the 'bug' for it you'll want more and more lights!
 
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