12V halogen bulbs - ac or dc?
JohnO
I have some 12V garden lights that I want to control with a
microcontroller but can't see anywhere whether they need dc, ac or
don't care. Anyone know?
Cheers
JohnO
whoisthis
<92646b96-b986-485a...@e13g2000pra.googlegroups.com>,
JohnO <john...@gmail.com> wrote:
Dont care.
In houses a transformer is the cheapest method of getting 12v, however
cars also have 12v halogens. All they are is effectively a filament that
gets very hot.
greg
Ah.. but the filament construction is different for AC or DC, most
likely find seen they were from garden lights then the are 12 AC, seen
you want to use a microcontroller, still use the transformer you got
with the garden lights, but use some interface relays driven from the
controller.
JohnO
> whoisthis wrote:
> > In article
> > <92646b96-b986-485a-9102-f88e4841e...@e13g2000pra.googlegroups.com>,
> > JohnO <johno1...@gmail.com> wrote:
>
> >> Hi All,
>
> >> I have some 12V garden lights that I want to control with a
> >> microcontroller but can't see anywhere whether they need dc, ac or
> >> don't care. Anyone know?
>
> >> Cheers
> >> JohnO
>
> > Dont care.
> > In houses a transformer is the cheapest method of getting 12v, however
> > cars also have 12v halogens. All they are is effectively a filament that
> > gets very hot.
>
> Ah.. but the filament construction is different for AC or DC, most
> likely find seen they were from garden lights then the are 12 AC, seen
> you want to use a microcontroller, still use the transformer you got
> with the garden lights, but use some interface relays driven from the
> controller.
Thanks. Its for lights at the driveway gates. I have 12VAC and 12VDC
already for the gate controller and always planned on using a relay
for the light power.
Cheers
JohnO
Richard
Are they really halogens or just incandesent?
There are craploads of garden lamps that claim halogen but the lamps
dont run hot enough for it to actually matter.
If you run a typical halogen off DC then allegedly eventually all the
filiment migrates to one end, but the ones I have done it for years
without ill effect using a PC power supply for lamps on my workbench -
and I have the voltage on it up at about 13.5 so they are definatly hot
enough that they should be doing what they should as far as halogen cycle...
JohnO
I'll open one up and check. Are 10W halogen same or brighter than 10W
incandescent anyway?
whoisthis
<557b55bd-ab5f-4451...@j32g2000yqh.googlegroups.com>,
JohnO <john...@gmail.com> wrote:
Yes, there is less energy in the Infrared area and more in the visible.
Richard
>> If you run a typical halogen off DC then allegedly eventually all the
>> filiment migrates to one end, but the ones I have done it for years
>> without ill effect using a PC power supply for lamps on my workbench -
>> and I have the voltage on it up at about 13.5 so they are definatly hot
>> enough that they should be doing what they should as far as halogen cycle...
>
> I'll open one up and check. Are 10W halogen same or brighter than 10W
> incandescent anyway?
Quite a bit brighter - more of a benifit is the whiteness of them.
But in garden lights the voltage is so erratic with cabledrop etc the
ones I have used have been way down in temperature - yellower then a
normal mains incandesent - only getting 10.something volts at the
fitting with 11.something at the transformer. Those were rated at 10 I
think and were baseless bulbs that just pushed between metal in the
fitting. Like some brakelights and car dome lights use but lower
wattage. was a while ago now - took them out when I removed the garden..
JohnO
Yeah. The power to the gates is 12VAC nominally. The cable run from
the transformer to the gate controller is long - over 20m. However
there are 3 taps off the transformer so I can go to 15 or 18V at the
transformer if required to cover any voltage drop by the end of the
cable. It's all regulated inside the controller anyway.
PeeCee
news:92646b96-b986-485a...@e13g2000pra.googlegroups.com...
JohnO
Personally I don't think there is much difference in powering your garden
lights from AC or DC.
What I would like to suggest you consider is to connect the bulbs in series
rather than in parallel.
Yes you will have to up the voltage to suit but you will get even brilliance
from each bulb.
The overall brilliance can be conrolled by managing the current or voltage
applied at source.
For example say you want 10 bulbs.
12v for each bulb x 10 = 120Volts applied to the 10 bulb serial string for
maximum brightness..
Source yourself a 230 : 120 transformer and drive the primary from a phase
controller.
Some of the kits on this page may suit:
http://www.siliconchip.com.au/cms/search/index.html?scope=&keywords=motor+controller
If the idea is for the lights to be on or off then the microcontroller can
just drive a relay.
Note the secondary of the transformer only has to have a current rating to
match one bulb.
Best
Paul.
whoisthis
"PeeCee" <ab...@local.host> wrote:
VERY BAD idea.
For a start once you go above 50V then it becomes a job for a registered
Electrician.
Next, if one bulb blows then they all go off, finding the faulty bulb in
a series circuit is a Pain.
Also, if a bulb blows you will effectively have the full voltage across
the pins, this can present a danger.
Stick with 12v and do a ring feed if needed.
greg
Or just make the wiring bigger!, BTW the rules changed a while back, 50
VDC, 120VAC. But as soon as you go to 120V then you will have to enclose
the bulbs in suitable fittings that wont let the water in.
Stick to 12V so much quicker easier and cheaper.
JohnO
>
> TV mast Amps use AC just for this reason.
Good on ya Woger. Cheers for that.