I am using this led to convert an old halogen 250W dj lighting fixture to LED, 25A power supplies are difficult to come by… Is it possible to supply more voltage/current to make it easier on the power supply? I have 250W available at 15A, large heatsink, active cooling (high speed fan + external exhaust duct in aluminum frame). If I keep the temp down can I use some type of ohms law for say 24V / 5A or 8V @ 15A?
Of course there is a constant current driver in there
No idea what kind of lighting fixture you mean. Wide-angle lighting like an overhead lamp, or spotlight style?
If filtered, the output would be a crappy color because LED spectrum is kinda peaky, whereas halogens are smooth. Also, halogen filaments are omnidirectional, and an LED in that kind of fixture throws light only in roughly a hemisphere. And XHPs especially have pretty lousy angular tint-shift, bluer out the front and yellower out the sides.
More details?
Do you want to use a single LED? XHP70.2 is configurable as either “6V” or “12V” while SBT90.2 is “3V”. The exact voltage and current depend on each other and the nameplate voltage is just an approximation. You can not use Ohm’s law to calculate the voltage/current relationship because LEDs are not resistors. You look that up in the LEDs datasheet or find out experimentally.
This is a DJ Lighting fixture known as a “HES Trackspot”, I will be using the Cree or Luminous chip with a TIR Lens of 10°. This fixture uses dichroic glass for filters
Agro - I see people on this forum going well above and beyond the datasheet… If the SBT90.2 is 3V, could I give it 5 or 7V @ 20A? If I keep the thing cool?
But only with a power supply with the correct characteristics. It must be a current source with high enough maximum voltage. If your power supply delivers not more than 20 A when you short it and doesn’t overheat in that situation, it might be usable.
Don’t go by voltage, but by current. And you’d have to make sure it’s kept REALLY cool.
And don’t forget that lots of times, if you’re already “up there”, you can dump 100% more current into an LED, and get only 10% more output. Push it further, and the more current you dump into it, output will decrease. It’s a hill-shaped parabola.
No, you can’t. Basically at fixed current you get fixed voltage. More precisely, voltage depends also on temperature, but as long as your temperature is constant, at 20A the LED will always have the same voltage. And for SBT90.2 at 20A voltage will be somewhere between 3 and 4V. I haven’t seen any tests or the datasheet, that’s why I’m so imprecise.
And I could sign below Lightbringer’s statement - figure out what current works best for you and whatever voltage the LED has at that power - that’s it, you can’t do anything about it really. Except for some multi-die LEDs like XHP70.2 which has 2 clusters of 2 emitters each and you can choose whether to put the clusters in series or in parallel.