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/diy/ - Do It Yourself

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2044233 No.2044233 [Reply] [Original]

Hello.

I recently fixed pic related.
Its an old design lamp my dad bought in the 80s.
I would like to switch the 12V 35W incandescent lamp with an led one.
I went for a generic 12v 3W led and its scorching hot.
The lamp has a 220v to 12v coil in the base. How do I take down the wattage provided by the coil?
Is there any way to mod it for it to safely use a led bulb?
Thanks

>> No.2044261

diy welder use the number of coils to change amperage, but that is dc; might be worth a look. bushcraft welding has lots of how to's for electrical gigery

>> No.2044263

>>2044261
Now that I think about it, the current inside the lamp is ac, the coil's work is just dropping the voltage from 220 to 12v. I have the feeling I might as well take out the coil and use an external transformer...
Fishing for ideas

>> No.2044264

If that lamp converts 220VAC to 12VAC then an LED bulb isn’t going to work. You need a small circuit to convert 220VAC to 12VDC and control the amps too.

>> No.2044267

>>2044264
Pretty much what I said. Use a low power plug-in transformer to provide 12VDC directly to the lamp.

>> No.2044272

>>2044264
And why is the lamp working anyway with 12ac? Shouldn't it turn on and off at 50hz?

>>2044267
What I feared. Any idea where I can buy something that I can hide inside the base of the lamp?

>> No.2044275

>>2044272
Incandescent bulbs take a small amount of time to stop glowing when the voltage reaches 0, and by the time it starts to cool down the polarity has reversed and it’s getting 220VAC again. And this repeats 50 times a second meaning our eyes see a steady glow even though the voltage is 220 to 0 in both directions.

>> No.2044281
File: 464 KB, 1600x1600, osram-led-bispina-gy6-35-3-6w-2-700-k-dimming.jpg [View same] [iqdb] [saucenao] [google]
2044281

>>2044275
Understood.

Pic related is the bulb I want to use instead of the incandescent one.
My only question is why is it working (with the only major drawback that its very very hot)?

>> No.2044288

>>2044281
That LED is designed to work on both AC and DC. It has a build in rectifier to convert ac to dc. Temperature doesn’t matter too much so if it works, job done.

>> No.2044294

>>2044288
I figured it out as I read the specs, i feel like an idiot.
Last question, I'll buy you a beer: If i switch the coil with a 12v dc transformator, do I get the same light without the heat? Or it will be exactly the same?