1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Use 12v Halogens with a Dimmer?

Discussion in 'Home Cinema Building DIY' started by Goof, Sep 14, 2003.

  1. Goof

    Goof
    Standard Member

    Joined:
    Oct 14, 2002
    Messages:
    752
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Scotland
    Ratings:
    +2
    I was wondering if anyone knows if it's ok to use low voltage halogens (usually 12v isn't it?) in conjunction with my dimmer switch?

    I read someone else on this forums saying he didn't think you could do it as the step-down transformer is already acting much like a dimmer switch, but he admitted he didn't really know and this was an educated guess.

    So, does anyone know for sure?
    TIA :)
     
  2. Cool-hand

    Cool-hand
    Member

    Joined:
    Jan 5, 2002
    Messages:
    2,105
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Portsmouth / Middle East
    Ratings:
    +77
    Hi

    You can use a dimmer switch with the 12v halogens but the transformers that supplies them has to be rated dimmable.
    It should clearly state this on the transformer. They usaully are all made dimmable these days as its quite big business for DIYers, but do check first.

    If the lights were installed quite sometime ago you may need to buy a special LV dimmer swith (an electrical wholesaler will advise) which has different electronics on the control circuit (its also 2 to 3 times deeper than a standard dimmer switch) so chasing out you exsiting box is highly likely too.

    Either way you need to check the trannys to see if they are dimmerable, if theres no writing on them the chances are there not.

    Rgds

    S.
     
  3. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,753
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,906
    Yes you can dim low voltage halogens.

    There are dimmer switches available (from places like Maplin and B&Q) that are specially rated for use with LV transformers. They are specifically labelled as such.

    Maplin also sell lighting transformers which, they say, are suitable for use with ordinary dimmer switches.

    Personally, to be on the safe side, for most of mine, I used both 'dimmable' transformers AND LV-rated switches. They all have LV-rated switches.
     
  4. Goof

    Goof
    Standard Member

    Joined:
    Oct 14, 2002
    Messages:
    752
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Scotland
    Ratings:
    +2
    Thanks Nigel and Snowman, I haven't actually bought the downlights yet but was just trying to get them cheap as possible, and the low voltage seemed to be generally cheaper.

    Thanks! :smashin:
     
  5. fancyabrew

    fancyabrew
    Active Member

    Joined:
    Dec 29, 2002
    Messages:
    332
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Plymouth
    Ratings:
    +12
    I'm just debating whether to go for LV or mains downlighters myself for my lounge. Anyone got any ideas on the pro's con's etc. Mains bulbs seem to be around 3x the price of LV bulbs
     
  6. Goof

    Goof
    Standard Member

    Joined:
    Oct 14, 2002
    Messages:
    752
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Scotland
    Ratings:
    +2
    I caved and got some mains voltage halogens - got a nice 3pack brushed aluminium for £20 from Homebase.

    I noticed the LV ones online were cheap at places like screwfix.co.uk but they didn't come with bulbs (which ended up making them the same price).
     
  7. pwafer

    pwafer
    Standard Member

    Joined:
    Sep 15, 2003
    Messages:
    48
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    Kent, United Kingdom
    Ratings:
    +1
    In the UK, we use LEADING edge dimmers mostly. They can also be called INDUCTIVE.

    Transformers should be labelled "suitable for inductive or leading edge dimmers" and you should use dimmers that are labelled "suitable for LV or inductive loads"

    However, with all 'domestic' level dimmers, the dimming devices used (the TRIAC) will be 'cost effective'

    The new influx of GU10 Mains Voltage Tungsten Halogen (transformer free) lamps has highlighted some drawbacks however. As with all filament lamps, when they blow you get a very short period of time where essentially the load goes SHORT CIRCUIT. This normally trips the feed circuit breaker or fuse. This short stresses the TRIAC immensely and if a heavily over rated TRIAC isn't used, then it will fail after a period of time.


    Paul.
     
  8. Gary Lightfoot

    Gary Lightfoot
    Well-known Member

    Joined:
    Apr 6, 2001
    Messages:
    12,143
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Surrey. UK.
    Ratings:
    +1,954
    I use some 240v lights from Argos - the small recessable ones that go in the ceiling. They dim OK and work with remote dimmers too. Quite cheap IIRC.

    Gary
     
  9. Goof

    Goof
    Standard Member

    Joined:
    Oct 14, 2002
    Messages:
    752
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Scotland
    Ratings:
    +2
    Just caved and bought a remote dimmer too gary :D
     
  10. fancyabrew

    fancyabrew
    Active Member

    Joined:
    Dec 29, 2002
    Messages:
    332
    Products Owned:
    1
    Products Wanted:
    0
    Trophy Points:
    18
    Location:
    Plymouth
    Ratings:
    +12
    What sort of clearance around main voltages downlighters do you need, as I know they get pretty hot.
     
  11. Gary Lightfoot

    Gary Lightfoot
    Well-known Member

    Joined:
    Apr 6, 2001
    Messages:
    12,143
    Products Owned:
    0
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Surrey. UK.
    Ratings:
    +1,954
    The ones I got say about 6ins from any combustable material, and I did a test using some plasterboard and rockwool.

    I put a temp sensor right on the lamp and put the rockwool on it to see if it would burn should some drop onto it. The temp went above 200c IIRC (the temp meter only went that high) but the rockwool charred a little but didn't burn (it's meant to be fire resistant). I left it like that for around 8 hours and nothing burst into flames so I was quite happy to have them in my ceiling. They've been there well over two years now with no problems. :)

    Gary.
     

Share This Page

Loading...