Converting a vehicle lamp into a household light.

Hello . 
Converting a vehicle lamp into a household light.
I have a mains to 12 v adaptor bought from Argos .

Powers  up fine and there is a steady 12v to a car headlight bulb holder . 
So no concern with any of that .

However as soon as the 12v 40watt car bulb is put into the bulb holder the bulb will flash with a slow weak light. 
Any idea why ? 

Thanks

The power supply is not powerful enough.

It's a 40W lamp so will need 40W of power out from the power supply which is a little under 4 Amps.

I am willing to bet your power supply cannot provide that much power.

You are on the right lines but will need a more powerful 12V power supply.

Thank you for reply. 
Sorry I should have said the transformer/adaptor is rated at 4amps and in-line switch is 6.

Would a 6amp transformer be what I need?

Is it a tungsten filament type car lamp? 

These have  a low resistance when cold, the resistance rising as the filament heats up.  Hence you need more than the 40watts briefly to start the lamp, a phenomena known as a, "switch on surge" .

It's likely that the electronics in the supply unit you have is switching off to protect itself from the surge, then trying again to start, giving the effect you describe.   

Using a six amp supply unit would probably solve the problem but I wouldn't guarantee it.  If you can find a Non regulated PSU, or one that's just a transformer, as you don't need DC fro a tungsten lamp, that would work.

Alternatively could you use an LED lamp?  That would need some improvisation to physically install, but would use much less power. One sold as suitable for either car side light use , or traficator use if you want it brighter may suit.

I have two tripods in need of suitable lamps. I was thinking of purchasing a couple of car 6” headlights for the purpose. My question is, can car headlights be used on my tripods and plugged into the mains electricity supply? 

Graham Croucher said:

I have two tripods in need of suitable lamps. I was thinking of purchasing a couple of car 6” headlights for the purpose. My question is, can car headlights be used on my tripods and plugged into the mains electricity supply? 

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only if you want to blow them up! You need a transformer to convert from 240V to 12V. This would also need to earth the metal parts provided everything is class II insulated.

I convert old telephones to table lamps. Transformer is Class II, mains cable is double insulated, lamp is 12v LED 2watts, cable from transfomer to lamp is single insulated as this is only carrying 12v

Do you ever lift up a table lamp to your ear by accident when a phone rings.