Osram SFH 4715S on Bergquist 20mm MCPCB - Max Drive Current?

10 posts / 0 new
Last post
shrick
shrick's picture
Offline
Last seen: 6 days 1 hour ago
Joined: 10/15/2014 - 07:15
Posts: 695
Osram SFH 4715S on Bergquist 20mm MCPCB - Max Drive Current?

Can the experienced IR guys help out with the above? What is the maximum drive current? I’m planning on using a Nanjg 105c… I’ve read one should not do more than 1.5 amps, but I’ve heard comments of pushing more?

Thanks!

djozz
djozz's picture
Offline
Last seen: 1 hour 12 min ago
Joined: 09/07/2012 - 17:04
Posts: 10676
Location: Amsterdam

I pushed it harder than 1.5 amps but mine was on a direct thermal path copper board, that sheds heat much better than a Bergquist board. Gmarch made his own ledboard and drove his leds at 3A, but since the led was pulsing there was no continuous heat production. I'm not sure what the current limit is on your board.

shrick
shrick's picture
Offline
Last seen: 6 days 1 hour ago
Joined: 10/15/2014 - 07:15
Posts: 695

Hi djozz. Ok, thanks for your input. I’ve decided to rather go with the noctigon. This will be the first time I use AS Thermal Adhesive – hope it performs ok. Will be looking at +-2.2 amps. Appreciated.

djozz
djozz's picture
Offline
Last seen: 1 hour 12 min ago
Joined: 09/07/2012 - 17:04
Posts: 10676
Location: Amsterdam

shrick wrote:
Hi djozz. Ok, thanks for your input. I've decided to rather go with the noctigon. This will be the first time I use AS Thermal Adhesive - hope it performs ok. Will be looking at +-2.2 amps. Appreciated.

I assume then that you understand that:

1) the solder pads do not fully match, so to get the led flat on the board you have to be sparing with solder paste, use the right amount (squeezing out surplus solder from under the led will not work)

2)the thermal pad is connected to the led+, so with a Noctigon the whole ledboard is not neutral and will have to be electrically isolated from the flashlight body (but I guess that is why you mentioned the ASTh.adhesive)

(btw, as mentioned before: one advice with AS T adhesive: be quick!, before you know it, it is hardened, and then it is glued forever)

shrick
shrick's picture
Offline
Last seen: 6 days 1 hour ago
Joined: 10/15/2014 - 07:15
Posts: 695

Hi djozz. Yes, I’m aware of what you’ve mentioned… Thanks for the tip on the AS adhesive drying quickly. I hope that I get it isolated first time, as you say, will probably not have a second chance! Should it not work out first time, I’ll try to loosen the adhesive with heat, but, lets hope its not necessary. Will give feedback.

shrick
shrick's picture
Offline
Last seen: 6 days 1 hour ago
Joined: 10/15/2014 - 07:15
Posts: 695

Just some feedback on my build

I eventually made use of the Bergquist 20mm MCPCB rather than the Noctigon, for the reason of struggling to get the LED properly reflowed on the MCPCB – it was shorting out, tried a few times and then rather went the Bergquist route, which turned out to work very well for me.

I made use of the brass Convoy C8 pill from Fastech, screwed down with AS5. Driving current was 2.4 amps (measued at the tail). Made use of a Panasonic NCR18650BD, total overkill for the applucation but the highest capacity I had at hand.

Heat was not an issue on the driver at all. If Im not mistaken, this is in contrast with Djozz’s build. Strange. Not sure if the forward voltage on my LED was higher, hard to believe. I unfortunately did not measure this and at the time of writing I was not sure which LED was used by Djozz. My light meter showed quite stable results for around 2 minutes, I did not measure further, this was good enough for me.

I setup the light with 3 modes always starting on high doing around 2,4A on high 1.1 on medium and 0.3 on low.

I gave the light to a friend for testing with he’s ATN Trident Pro4x-2 scope. It did not work well at all. For some reason he tells me the light works best on the low mode? Luckily he also had GEN1 NV Goggles (did not ask the model) which totally blew he’s mind combined with the IR light – worked excellent.

I contacted ANT to hear what there opinion is about why the light does not work as expected with the scope. Unfortunately they are not getting back to me, even after following up twice.

Might it be any of the following. I’d like to hear your opinions if possible:

  • The scope prefers the 940nm wavelength rather than 850nm? Can the scope block out most of the 850nm light?
  • There’s some setting or configuration on the scope we should set which the owner is missing or don’t know about.

Im also thinking on getting some opinions on the hunting forums. Which is the best / most active forums to look into for this?

Hope my feedback helps.

djozz
djozz's picture
Offline
Last seen: 1 hour 12 min ago
Joined: 09/07/2012 - 17:04
Posts: 10676
Location: Amsterdam

I had a heat issue with my led because it was the 1.8V version (the driver had to burn off 2V: times 3A that is 6W). The led you use is 3.6V . (this Oslon has 2 dies next to each other, each 1.8V and there's a version that has them parallel and one in which the dies are in series)

At the time of my build I did not know that there also was a series version which is quite perfect for a common lineair driver, could have saved me the driver heatsink mod, but it was fun making it anyway Smile

 

The rest of your questions are way beyond my kbowledge..

shrick
shrick's picture
Offline
Last seen: 6 days 1 hour ago
Joined: 10/15/2014 - 07:15
Posts: 695

Ok, that explains the heat issue then. Thanks Djozz…

n10sivern
n10sivern's picture
Offline
Last seen: 2 weeks 5 days ago
Joined: 11/09/2014 - 21:37
Posts: 1374
Location: biloxi, ms

I run them at 1.4A

Three tomatoes are walking down the street- a poppa tomato, a momma tomato, and a little baby tomato. Baby tomato starts lagging behind. Poppa tomato gets angry, goes over to the baby tomato, and smooches him… and says, Catch up.

nofearek9
nofearek9's picture
Offline
Last seen: 2 days 1 hour ago
Joined: 07/08/2012 - 08:46
Posts: 1283
Location: Cyprus

any place i can find the old style, non-dtp copper pcbs ?