12v MR16 lights, help problems

[casamena]

Hi i have 6 robus bathroom lights that run off a 12 v transformer. The problem is that after around 10 mins they start to dim and and then hardly any light is ammited. a live swith wire comes from a jb goes to a pull switch, then the transformer input is wired to the neutral and switched live at the jb, then the lights are looped to the output on the transformer. these have recently been installed, could this be a transormer problem? i have a multi meter so can check the voltage output on the transformer and at each light. thanks..

 

[ekmdgrf]

It does rather sound like your transformer is on the blink. Would certainly be interesting to see a before and after with a multimeter. It maybe a 12V system but please show it the respect that it deserves. In particular, don't short the probes otherwise you'll likely need a new transformer eitherway...

 

[PrenticeBoyofDerry]

Who installed it/them? I suggest you get them back, unless it was yourself, then the question would be, did you calculate the output of the transformer was suitable for the duty it has to serve.

 

[winston1]

Are they run off a 12v transformer or an electronic switch mode supply?

You cannot measure the output voltage of the latter with a multimeter. The frequency is too high.

 

[casamena]

did you calculate the output of the transformer was suitable for the duty it has to serve.

just had a look at the transformer its rated at 35 - 105 watt, the person who put the bulbs in says they we're 40 watts equalling 240 w load oops.
i'm going to install 6 x 7 watt l.e.d bulbs (42 watts). still using the 35 - 105 watt transformer without causing over voltage for the l.e.d . or would you still suggest using an l.e.d driver ?

 

[PrenticeBoyofDerry]

I would personally go down the driver route for LED lights, it will help optimise the lighting output.

 

[casamena]

I would personally go down the driver route for LED lights.

just found these
http://www.tlc-direct.co.uk/Main_Index/Lighting_Menu_Index/Lamps_and_Tubes_Index/MR16_Led/index.html

 

[PrenticeBoyofDerry]

The manufacturer claims no driver is required, who am I to argue?

 

[casamena]

The manufacturer claims no driver is required, who am I to argue?

just as long as your reaching the minimum wattage value, i thought they were a good price compared to screwfix allthough these wouldnt rech the minimum wattage so will get the l.e.d driver too.

 

[winston1]

did you calculate the output of the transformer was suitable for the duty it has to serve.

just had a look at the transformer its rated at 35 - 105 watt, the person who put the bulbs in says they we're 40 watts equalling 240 w load oops.
i'm going to install 6 x 7 watt l.e.d bulbs (42 watts). still using the 35 - 105 watt transformer without causing over voltage for the l.e.d . or would you still suggest using an l.e.d driver ?

So it is not a transformer then but a switch mode power supply (transformers don't have a minimum load). May not work with LEDs.

 

[casamena]

did you calculate the output of the transformer was suitable for the duty it has to serve.

just had a look at the transformer its rated at 35 - 105 watt, the person who put the bulbs in says they we're 40 watts equalling 240 w load oops.
i'm going to install 6 x 7 watt l.e.d bulbs (42 watts). still using the 35 - 105 watt transformer without causing over voltage for the l.e.d . or would you still suggest using an l.e.d driver ?

So it is not a transformer then but a switch mode power supply (transformers don't have a minimum load). May not work with LEDs.

a switch mode power supply does have secondary windings but are they not used primarly for Dc/Dc converters for industrial control. only ever seen transormers labelled as linear power supply. it was this one http://www.wickes.co.uk/invt/162383

 

[winston1]

[/quote]
a switch mode power supply does have secondary windings but are they not used primarly for Dc/Dc converters for industrial control. only ever seen transormers labelled as linear power supply. it was this one http://www.wickes.co.uk/invt/162383[/quote]

Switch mode power supplies are used in anything from phone chargers, TVs, to industrial control as you mentioned.

That Wickes item is not a transformer in spite of their description. It is a switch mode power supply supplying a regulated 12 volt equivalent at a high frequency AC.