So i have this older Convoy C8 and an extension tube, and i recently bought an MT-G2.
Now i need a driver.
Here’s some pictures:
Looks a bit scratched with the flash, maybe it’ll end up de-anodized. (still forgot to get that lye from the drugstore…)
Put some copper bits on the MCPCB to get thermal path to reflector.
Obviously this light is too small for a 30 Watt LED, so it could use some extra heat dissipation.
The parts.
Everything fits snugly.
The pill is kind of clamped between tube and reflector.
Reflector pressed down on head (under the bezel) and on MCPCB copper bits.
The big LED hole in the reflector got there by accident.
The base was bent inwards due to pressing to hard on a centring spacer, so i wanted to bend it back with a plastic rod and a hammer, and then the base ring just broke out…
Turned out to be the exact size of an MT-G2 (after smoothing the jagged edge)
Close up of MCPCB, pill and switch.
The pill is a bit low on mass… Hmm…
I think i’ll epoxy the pill in the head eventually, try to make the best thermal conduction to the head.
Maybe make reflector and MCPCB with LED a whole too.
Big square switch from Convoy store, spring heavily braided.
So i’m looking for a driver that can do 5.5 Amperes regulated (constant current)
I’m not sure, but i think the L3 driver from LED4POWER would be good.
It’s 17mm so it would fit.
5.5 Amperes (hit that 3000 LM :P) seems to be good for an MT-G2:
This would be my first 2S build and my first 6 Volts LED build too.
Your advice is welcome.
It’s the LD-3 driver i’m considering. (not L3)
But it’s an expensive driver.
So maybe there are budget alternatives?
LD-3 does have overheating protection, which would be good for this.
Hmm… Those 7135s will get hot though, won’t they?
I mean they will have to burn off excess voltage, which means at 8 Volts they have to eat up 1.2 Volts at 5.5 Amperes.
1.2 x 5.5 = 6.6 Watts of heat.
But i guess the LD-3 will have to do the same.
Okay, i’ll look if i can find a 3.6 Volts zener and a 200 Ohm resistor.
Old school project.
I found a 2013 topic where RMM did the same thing.
Nothing new under the sun…
But he used a C12, which is a C8 with more and bigger cooling fins.
Okay.
Cooling will probably be the main problem with this light.
At 5.5A voltage sag will be significant but the heat will come more from the led than the chips. Heat pollution could be an issue but it’s still the best budget option since there isn’t a 5.5A buck driver in 17 mm size. The LD-3 is the only other real choice but it does give you the option of thermal sensing and control. A Zener modded A6 is a possible choice but not current regulated for higher modes. That is good in that the FET won’t overheat from current but the led heat will be considerable.
Okay, thanks.
I will do it with a zener modded 105c and settle for 14x 7135.
I’m not a fan of unregulated FET divers.
(They’re only fun when the battery is full i.m.o.)
It’s quite a bunch of lumens this thing produces.
Had to re-do the tailswitch and spring to be able to fit 2x 18350 without the extension tube, but all seems well now.
