Just noticed the new Maxflex at http://www.taskled.com/maxflex.html
O man,…. I was really looking forward for some improvement on output voltage so you could drive 7 SSC P4 @ more than 500mA…
O man,…. I was really looking forward for some improvement on output voltage so you could drive 7 SSC P4 @ more than 500mA…
Any idea when these will be ready to ship?
Wanting to run 2 MC-Es isn't that unreasonable given how close it is to doing that (I reckon on max 28V required output - may even be as low as 26.4V). I suspect it might just stop there - at least reasonable wants would. I take the point about heat disippation, but that surely just requires a good heat path from the pad - something which some of us are doing already.Besides, the moment I support 7 LEDs folk will want 8 so they can use 2 MC-E's... it never ends...
Wanting to run 2 MC-Es isn't that unreasonable given how close it is to doing that (I reckon on max 28V required output - may even be as low as 26.4V). I suspect it might just stop there - at least reasonable wants would. I take the point about heat disippation, but that surely just requires a good heat path from the pad - something which some of us are doing already.
George,
Do you have a recommended potting compound/process? I saw the warning about potting in the tech notes for the Fatman, and don't know that much about potting compounds...
Turning on the thermal protection in the menu system would be a good idea and backup plan to protect the driver.
cheers,
george.
Arctic Alumina epoxy is fine - though rather expensive to use a lot. I'd recommend using a combination of heatsink attached to the thermal pad at the bottom of the PCB (the rectangular gold area) AND AA epoxy (or similar quality thermal epoxy that is essentially non-conductive & non-capacitive) to pot the top of the board (the switcher IC area) to another heatsink attachment. Potting on its own isn't enough - it needs to be used as a path to a heatsink that can move heat off the board and radiate it away.
The potting is required at the higher power levels - say above 1.5W - though it all depends on ambient temperature. If you have maxFlex inside the LED housing and it is 'cooking' then you will have trouble.
Turning on the thermal protection in the menu system would be a good idea and backup plan to protect the driver.
cheers,
george.
I'd probably choose to run at a bit less than 700mA anyway - you don't gain a lot of brightness for cranking it up that last bit from 500mA to 700mA. I think my heat sinking solution of an alu heatsink path attached with Arctic Silver to the heatsink pad would probably work OK for that. Do you really gain much heat dissipation from potting the top (where you have a couple of relatively poor thermal paths in the way) compared to just heatsinking on the pad which has a pretty direct connection to the switch junction?So at 24V x 700mA we have about 2W of heat being dissipated in the switcher. That's close to 80C rise in package temperature. Assume ambient of 30C in the housing (it would be more than that...) and we have ~110C junction temperature... You can see we're pushing the limits already...
Thats on a bike light where hopefully that light level only gets used now and then for downhills... typical usage much less I hope .... Trout, what do you think?Anyway, I've seen others suggesting pushing the thermal capabilities even more within the existing voltage limits - running 1200mA at ~20V to 3 MC-Es wired 2s2p!
Thats on a bike light where hopefully that light level only gets used now and then for downhills... typical usage much less I hope .... Trout, what do you think?
Thats on a bike light where hopefully that light level only gets used now and then for downhills... typical usage much less I hope .... Trout, what do you think?