I can’t test it myself. I don’t have a bare board (only one with the emitter in place) and I don’t have the tools to check continuity.
But it makes sense that there is a thermal path right? As you said you would usually expect to see a chip burn without it.
Hope everyone had a good weekend,
If there are people still reading this…
The factory tests today showed the following temps on the YF chip:
1.5W - 450mA: 65C Degrees
2W - 600mA: 79C degrees
2.4W - 700mA: 85C degrees
Not really, I would expect led burn out with DTP as well, just a little later, DTP only moves heat faster but if it has nowhere to go, you will still cook the led. that is why I asked if you measured the actual current, not what manufacturer say. I’ve burned many leds, and 700ma on a star alone, regardless what kind, sounds like a disaster to me.
If you plan to build 1000 of anything, do not take anyone’s word, always check and recheck things yourself. many times. manufacturers will tell you what you want to hear, so you place an order, then you end up with 1000 parts you can not use.
You do not even need special tool to check continuity, a battery and a bulb, or any other load, that is all you need.
What temperatures have your found your LEDs to get cooked at?
@blwilli said the manufacturer’s recommendation for YingFeng are 50c at 700mA
The spec sheet also says max operating temp is 85C
This chart shows Ambiant Temp vs Allowable forward Current.
It seems like if I aim for about 500mA i can endure temps of about 70C?
Thought it might be helpful if I share a rough drawing of the device.
I have detailed CAD drawings but I can’t share them unfortunately.
But this should give you an idea of where the heat will hopefully be dissipated.
edit - the drawing is cut off at the bottom because the battery cavity and main pcb are taking up space down there.
Oi, I would not do it that way, a recipe for disaster, when hundreds of customers start calling you and telling no uv light coming out, and you have to either refund, or fix at your own expense. BUT good news it, the design is very easy to fix.
Unless you driving the led with under 50ma or so, you never rely on the star alone, you NEED a heatsink of some kind. at 700ma it is a must.
Use aluminum angle profile or a T bar, cut it up, and put up your star with the led on it, it will come out of your airvent 2, with passive cooling and part of heatsink outside, heat will be dissipated, not build up inside. with that cooling you will not need airvent1 or even air cavity unless you need it for something else. use 1/8 or3/16 thick aluminum profile, or if it has to run for hours non stop use 1/4 inch thick.
Also with a target 10-15 cm away do you really need optics at all?
Only finalize design after building and testing few test samples, only then order 1000s of parts cuz when you design something new, you’ll change a lot of things before you get working device. end product usually does not look like original concept, and it is perfectly normal.
thanks @alpg88 for your drawing and idea.
Unfortunately in this case it’s not that simple. But it’s my fault for not showing you how the device looks on the outside.
It’s full of curves and has a streamlined design. Sadly I can’t share it due to possible future issues with obtaining the patent.
I’ve had multiple rounds of prototypes made at significant cost over the past year, so yes I’m definitely trying to nail it before the factory starts manufacturing.
The factory is also responsible for QC, so it’s in their interest to have everything working reliably. They are not UV experts though which is why I’ve turned to the forum for advice.
Like I said I’m abandoning the hopes of running at 700mA and reducing this down to 450mA. I’m still confused though about your experience with killing chips at these lower currents, as even the cheaper chip was able to run for five minutes at 700mA (in a non-enclosed space).
PS- The factory confirmed today that the lM317 is regulating both current and voltage. And there is only one of them! so that is adding to my confusion as well.
If anyone is interested for their own projects, I received a quote back from an independent mcpcb manufacturer. I believe they make the cree boards.
for 1000 of the 16mm board it’s 0.33 usd/unit for aluminium and .39 usd/unit for copper.
