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

John S

John S

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It is indeed true that their is no recognised convention for the resistor connection, a good habit, methodology and easily remembered is to connect the resistor to the "source", so in the case of a DCC Decoder the Function Outputs are Negative, connect the resistor to the Cathode, for other DC sources and Arduino's connect the resistor to the Anode.

I mention this is passing, having had to sort out on numerous occasions the "rats nest" of wiring from decoders to lights, where the "installer" has used the DEK + as the Common to connect the resistors to, and hence some Led's end up with two or more resistors and some with none!
 
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S

Sarah Winfield

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You really are Gentlemen!

And the lord said "let there be light, and there was light and you could see for ****** miles" :)

There is a flat on the side without the resistor. No coloured wire just a transparent sheath but I do have light.

SW
 
S

Sarah Winfield

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OK, thanks to those contributors and I'm more knowledgeable about LED's and have had one light up.

What are grain of wheat bulbs please? How do they differ from LED's?

SW
 
Gizzy

Gizzy

Railways, Aviation, Caravanning....
26 Oct 2009
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What are grain of wheat bulbs please? How do they differ from LED's?

SW
They are just very small bulbs, or incandescent lamps as us Electronic Engineers like to call them. Bulbs are plated in gardens.... :D
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
24,245
207
North West Norfolk
OK, thanks to those contributors and I'm more knowledgeable about LED's and have had one light up.

What are grain of wheat bulbs please? How do they differ from LED's?

SW
The name comes from the shape and size - usually a slightly smaller diameter than most common LEDs, can be bought quite cheaply pre-wired, but tend to only give you a nice warm yellowy light - more representative of a 1:1 electric lamp or loco light - but as with any traditional incandescent lamp, will absorb more power. A string of LEDs on a PP3 battery should last many hours before you need to change the battery. In fact I would go so far as to suggest that a string of LEDs would be better with a traditional PP3 than with a re-chargeable one.

The small ones are commonly 5v (don't ask how I know) so will need a resistor for most model railway uses :nod::nod::nod: - but say you have a caboose with two or three lights, then one resistor close to the power source will do for all three lights (assuming that you wire them in parallel). Not worth going down the route of wiring in series, that'll give you C******** tree light problems :confused::confused:
 
Greg Elmassian

Greg Elmassian

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Sarah, while incandescent bulbs and LEDs both make light, they work, and must be configured differently.

Incandescent bulbs work on voltage, and running them over voltage will burn them out quickly, and conversely, dropping the voltage will make them significantly dimmer and yellower.

LEDs work on current, and you control current differently, normally with a "dropping resistor" which will control the current through the LED. LEDs are about the same brightness no matter what the current. You can dim them a bit, by dropping the current a lot, some DCC decoders will pulse them on and off to get dimmer. Overcurrent transforms LEDs to DEDs.

Greg
 
ntpntpntp

ntpntpntp

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ntpntpntp

ntpntpntp

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S Sarah Winfield As well as "grain of wheat" bulbs you will also come across "grain of rice". I've always thought of / understood the rice bulbs to be smaller than wheat and/or a different shape (rice being more elongated). Both types simply have their wires exiting the bulb at one end, there's no bayonet or screw fitting.
 
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Martino

Martino

Kit bashing, The UK narrow gauge, The GWR, Aviatio
I have been reading through this and Greg’s website, all of which is very helpful. I was going to say illuminating, but decided against it.....

Anyway, i have been lighting some buildings on my railway by dismantling some solar garden lights. I have installed the LED and its circuit board, with a battery holder in a clear container inside the building. Wires are then run to the solar panel on the gutted garden light, which is then located out of sight, but in a sunny spot (its Florida here, so we are the Sunshine State). This all works well for a building that requires one light source.

Now, I fancy having a number of lights (LEDs) around my main station. I dream of the odd signal light, possibly some platform lights and two or three lights in buildings. I’d like to run this off one solar panel (probably located out of view on the top of a nearby fence or tree) and a single rechargeable battery. Now, what sort of difficulty will I encounter? How big a solar panel will I need? What size rechargeable battery? What type of LEDs? Etc., etc.
Yes, I know I’m being a numpty and probabaly exceeding my knowledge level considerably.

I also don’t have track power - and like the idea of the lights coming on at sunset and running for a while in the evening.

Am I being over ambitious?
 
Greg Elmassian

Greg Elmassian

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No, and most solar units you find will probably have a charging system set up for a 12v battery.

The cool thing is you can calculate wattage and amp hours, and so you can size your panel.

You should be able to run 3 LEDs in series off 12v, so 12 volts at maybe 10 milliamps per "string" of 3 LEDs.

So wattage is volts times amps or 12 x .010 or .12 watts per set of 3.

So figure out the lights you need, add the watts up and then look for a solar panel that can generate that, and then get a large enough battery to run at night that can be charge fully in the shortest days.

That would be my advice.

Greg
 
Martino

Martino

Kit bashing, The UK narrow gauge, The GWR, Aviatio
No, and most solar units you find will probably have a charging system set up for a 12v battery.

The cool thing is you can calculate wattage and amp hours, and so you can size your panel.

You should be able to run 3 LEDs in series off 12v, so 12 volts at maybe 10 milliamps per "string" of 3 LEDs.

So wattage is volts times amps or 12 x .010 or .12 watts per set of 3.

So figure out the lights you need, add the watts up and then look for a solar panel that can generate that, and then get a large enough battery to run at night that can be charge fully in the shortest days.

That would be my advice.

Greg
Thank you Greg, that’s very useful. I’m grateful.
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
24,245
207
North West Norfolk
No, and most solar units you find will probably have a charging system set up for a 12v battery.

The cool thing is you can calculate wattage and amp hours, and so you can size your panel.

You should be able to run 3 LEDs in series off 12v, so 12 volts at maybe 10 milliamps per "string" of 3 LEDs.

So wattage is volts times amps or 12 x .010 or .12 watts per set of 3.

So figure out the lights you need, add the watts up and then look for a solar panel that can generate that, and then get a large enough battery to run at night that can be charge fully in the shortest days.

That would be my advice.

Greg
With a surname of 'Watts', I was once told that .........

My father was Volts, my mother was Amps, so that's how they got little Watts :nerd::nerd::nerd::nerd:


................. scarred me for life :mask::mask::mask::mask::mask: