I am looking for a AC Adaptor
Model: JT-12V3000 Input: 230-240v AC 50Hz Output: 12VAC 3000mA Max: 36Va
It is for the lights in my garden i have two lots and after switching it all around it appears one of my AC adaptors is broken. I have google searched but have no idea where to get one from the connection from the lights is a small two pin.
Any help/Suggestions greatly appreciated.
None of the off the shelf ones from Maplin are beefy enough to replace that, really it looks like all the original adapter is, is a cased transformer ...
How about hacking up an old car battery charger?
ohhhh.... forget that - probably be made to output at a higher voltage....
-- Adrian C
Is Adrian C the forum comedian? dont give up the day job eh!?!
get yourself a 50w 12v halogen lighting transformer.
NT
Ha! Thought that would come upon me one day...
Fame at last ;-)
I think its only "AC" as AC adaptors are cheaper than DC - lights work just as well off AC as DC unless there are things like triacs (dimmers or electronic switches) involved which is probably not the situation in your application.... so that opens up the options a bit....
Anyway, to my point....Aldi (maybe Lidl) have a 13 volt 5 amp DC ( 65 watt) adaptor coming up soon at about a tenner and Ithink this might have been for low voltage lighting as well and this would give you a tiny bit more voltage to counter line losses and plenty in reserve.
I am going to get one, even though I haven't a use for one at the moment, as this seems a useful buy....
Anyone comment about line / load regulation and the AC / DC issue?
Hope that helps,
Nick
filament lamps dont care what you feed them as long as the rms voltage is right. 13v or 13.6v on 12v bulbs is too high and will lead to short bulb life. Filament bulbs are fussy about that.
NT
Hi,
Thanks for the reply - been trying to find out what voltage car "12 volt" bulbs are actually designed to work at and wondered if you knew ?
With alternators producing voltages variously around / between 13.8 and 14.0 V DC (and that is plus or minus tolerances !) which don't seem to blow car bulbs too often, I wonder if they are actually "nominally 12 volts but actually designed for 13.8" or the tolerance is actually quite wide.
Thanks,
Nick
12.0V across a battery indicates there is only around 30% charge remaining. Fully charged, it is around 12.8V (see:
Alternators regulators can control the output to around 14.4V, or more at low temperatures, to charge the battery in a reasonable time if it is deep discharged. Car alternator regulators are designed to clamp the voltage at 14.2V +/-
0.4V. Ordinary filament lamps cope with this (OK, at a reduced life) whereas, for example, a LED lamp must have something to accommodate the voltage swing without the battery + alternator driving too much current through it.
Hi John, Thanks for the reply ...
I had thought that around 13.8 to 14.0 was the "target area", and the "12 volt" bulbs were actually designed to work at about 13.0 volts after taking into account the various losses in the cabling, connectors switches etc.
I do usually fit heavier wiring via heavy duty relays to the headlamps on my vehicles ( halogen bulbs) and this results in a reduction of the volt drop of around 1 volt or a bit over - the extra whiter light is quite noticeable and I don't seem to change bulbs any more often.
I would have thought LED lamps at 12 volts with limiting resistors say for
15 mA, would not worry at all if 14 volts appeared and they then were getting around 18 mA or so passed through them - just a touch brighter - many have a max continuous current of 30 mA or more - and some are pulse driven at much higher currents from a regulated source..Anyway, it is interesting to read that car voltages are apparently a bit higher than I had thought..
Thanks for the reply
Nick
Most car bits are designed to work at 13.8v as this is the voltage that the alternator 'settles' to.
Filament lamps in cars don't need a long life anyway. The operating life of a car is only around 3000 hours (that's the figure manufacturers tend to use when specifying the required life of parts which they don't normally expect to have to replace during the lifetime of a car). Most lamps used in cars operate for only some small portion of the time the car as a whole operates. IME, headlamps are the main lamps which routinely fail, and even then, I've probably only gone through about 4 bulbs in nearly 100,000 miles, which is probably about 3000 hours. However, they are only used a small part of this, perhaps 25%, so we're looking at a lamp life of something in the order of 250 hours. Things like dashboard lamps are probably well underrun in comparison to headlamps, and if they have a life of
1000 hours, chances are you are not going to see any failures during the life of the car (and I haven't).
yep, wot e said. They will run at alternator output voltage minus wiring Vdrop, which is well above 12v. 12v car electrics are not 12v.
NT
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