replacing halogen with LEDs in cheap lights?

[TroelsM]

Hi.

I dont know if this is the right place to ask, but here goes:

I have a few (cheap) older light-effects with halogen-lamps (24V/150-250W).
For fun and challenge Im looking at converting those to LED.

I'm going on a low budget, because brand new LED-based light are sooo cheap these days.

I´ve compared a 5year old LED scanner (20W LED) with an 20years old halogen-scanner(250W) and the results are a bit depressing.
Relative measurements of output ( around 1meter, corrected for gobo-size) shows that the halogen is around 5 times brighter.
Thus the LED is only around 2x as efficient as the halogen. - although that specific LED-source is probably not very good, I had really hoped for a larger difference.

You can buy all sorts of cheap LED´s with 10-100W rating, but they appear to be completely useless for this kind of thing because the light-emitting surface is too big to work with standard optics designed for point-source lights.

There are LED´s with a more "pin-point" design, but prices are higher and you need a dedicated driver (Low voltage, high current)

Up until 20W-40W there are these with pretty low prices: (still need a special driver)

For really small effects I´ve had some succes with these 10W motor-cycle headlight and they even have an integrated driver that takes 12V directly.
They make a surprisingly power-full spot thats around 20mm diameter at 20mm distance: perfect for shining onto a 15mm gobo.

Any ideas, hint, thoughts?

Kind regards Troels

 

[almorton]

You've hit the nail on the head with the size of the source - for the large area sources you need to change the optics, since the filament of a halogen lamp concentrates all that output in a relatively small and well defined area, which the reflector and lens train are designed to work with. There is a chap on blue-room who has had some success converting scanners, but he has replaced the optics with a condenser system which is designed to work with a larger source.

 

[macsound]

Some of the COB LEDs you've shown, I've seen on ebay with condensing lenses that mount directly on top of them.
If you're converting moving lights to utilize these, I think mounting power supplies and considering cooling would be the 2 biggest hurdles. Getting the alignment of the light source is super important but trying to consider power and cooling, it makes for a bit of a mounting puzzle