LED Lights

i have just got back from my local garden centre, and they was tipping the display load of led outdoor lights, so i had them! freebies, love it well there is no transformers with them, is there any way i can rig them up to run off one transformer, i have no idea as this was just a random freebie lol so at worst i can use them as ornaments lol they was 40 quid each to buy but have about 6 or 7 for nothing :thumb:

 

Well done, stroke of luck there.

You need to find out what voltage they need, and how much power they consume. Armed with that info you will be able to pick up a suitable power pack from loads of sources.

Does it say anywhere on them what their power requirements are? (often printed or labeled onto the casing in some inconspicuous place).

 

LED's use very little current, and also will work at a very low voltage. However they can then be connected in a variety of combinations. Unless you can figure this out, or since you have 5 sets, wish to use trial and error there is not really a lot you can do. You also have to ask yourself why did the garden centre throw them away?

 

Trial and error is never a good option when plugging things into the mains. Fair enough the mains side will easily cope, but the output side could overheat very quickly if overloaded. As there is only a laquer coating on both the primary and secondary coils, an overheat on the secondary can melt the coating on the primary, causing it to short out. The result? Fire hazard.

 

Who said anything about the mains? I didn't

I actually said

no mention of the word mains is there?

As for your description, you theory is true but in practice it is unlikely to happen since the wire will melt, not to mention you should never try and power LED's from an A.C source because they are a D.C. device.

I would also like to point out that I also said [quote="water-garden]You also have to ask yourself why did the garden centre throw them away?[/quote]

 

Dawn was asking about transformers. Transformers generally (but not always) plug into the mains. Unless you have another AC power source kicking about, there'd be no point at all trying to get a transformer for it as transformers wont work with DC.

Also, you are right that in the event of a short circuit or over current, the wire would melt at some point, but that means a lot of heat, enough to melt and then ignite plastic.

 

they was getting rid of the lights as they was end of line and not having no more of them in so the lights was useless to them, all lights seem to say 12v have one transformer at home and all lights work nicely, just wondered if there was something that can save you buying one transformer for each light?

worst comes to the worst then at least i have some free ornaments for garden lol as they look really nice

 

W G said,

Your right in this instance but the statement isn't strictly true as a general statement they can used on A C of equal voltage but the current limiting resistor voltage would need to be adjusted to achieve the same brightness,I have a set that run off A C wired through resistors.

 

pics we need to see these lights won't help with the connecting but we'll see how nice they are :grn:

 

As they are 12v, you could very easily go all eco on us. Wired to a 12v rechargeable battery (like a car battery), a 12V 13W solar panel, and a diode (often built into said solar panel). The batter powers the lights at night, and the solar panel tops the battery up during the day.

Or, if you just wanted to keep it simple, a bit of wire splicing and a suitable 12V DC power pack would power the lot. On the one transformer you have does it tell you either the maximum current or max watts?

No argument from me, we were talking about transformers, not potential dividers. Perhaps it was me reading to literally.

 

if i could transform them into solar it would be even better as i can use more of them, would this be easy to do

 

I am not wishing to cause an argument but its a fact that an LED requires DC to operate correctly. To use them on AC is not good as you shorten the life span because AC is alternating current. Since it is oscillating at 50hz, that means that a LED connected to AC will in fact flash because it can only light up on half of the AC cycle, Which is why it should only be use on DC.

But, back to the solar panel question.
A rechargeable battery will be required, as will a voltage regulator and a solar panel not to mention a photo transistor or similar to turn them on when its dark. The solar panel would have to be above 1 Watt.

This is where the "problem" comes in, solar panels above 1 watt are costly (around £40 ) You canâ??t use a 1 W solar panel as you need to run the electronics and charge the battery.

Small 12v power supply to run all the LEDâ??s cost about £10. No contest.

 

You need something like this:
http://www.sunshinesolar.co.uk/khxc/gbu0-prodshow/SS5W.html

A 12v rechargeable battery, which you could get for next to nowt from your local scrappy, and enough cable to wire it all up, and a switch which you could get from your local Maplin for a couple of quid.

[/quote]

For a single LED, yes AC would be a bad idea, but if it is an LED array, it really depends how they are arranged. Arranging two LEDs 'back to back' so that one lights on the positive phase and the other on the negative would do no harm to either LED.

It is very common practice for LEDs to be supplied with a pulsed current (albeit in DC). It enables the LEDs to be pushed significantly beyond their rated nominal current for the duration of the pulse, effectively increasing the light output without compromising the life of the device (of course in real terms you don't get extra light, you just take advantage of the way our eyesight works, with us unable to detect flickers above about 30Hz ). LEDs are the device of choice for pulsed light because unlike incandescent bulbs, their light is not based on anything heating up (and expanding). High speed data links via fibre optics use LEDs as they can achieve a very high pulse rate (bit rate in digital terms) without compromising their life.

Anyway, this is turning into an electronics debate, and we're on a gardening forum, so that's it from me on the subject

 

Yes it is going off topic, but having two LEDs back to back is just that, two LEDs back to back. Same amount of "harm" but to two LEDs instead of one. As you said pulsed current is using DC current, so there are "no flowers in your vase" on that one.

Back to solar panels.

Nice link.(no, really, it is) Its about as much I thought (ok, £5 less) but a battery is still required, (Better off spending a few ££ and getting a decent one than trying to find a "scrappy") and the electronics are still required.

A suitably sized power supply is around £10 (even £20 its still cheaper and better)

Thatâ??s is the main "problem" with electric solar panels, nice in theory, but as you can see, "expensive" in practise.