Hello everyone,
I have a bit of an unusual problem with DJI FPV Goggles, which bothers me a lot more than any other. I suffer from dry eye disease. Goggles start the fan at higher speed immediately after switching on, then the fan speed decreases slightly and after less than a minute it spins again at high speed. The air flow is then felt on the eyeballs almost immediately, I immediately feel the pain and with goggles on I can't stand even 3 minutes. This is obviously a major problem, I can't fly fpv.

Nowhere did I find a setting that would allow me to change the fan speed. I have tried that the state shortly after switching on, when the fan speed is lower, is tolerable for me. So I'm looking for some way to reduce the fan speed or just reduce the airflow that hits my eyes.

Please help, this is really serious and it never occurred to me that it could be such a problem.

Thank you for your help.
Momo

Unfortunately there are no settings to change the fan speed or behaviour. Other than hacking up the goggles and installing a potentiometer, the only thing you can really do is to block up some or all of the vents inside the faceplate. Keep in mind that the fan also acts as cooling for the electronics which is why it speeds up and slows down automatically as required, so if you start messing with disabling the fan completely (by cutting the power to it) or adding a potentiometer then you could face other issues with overheating of the electronics.

Unfortunately no way to change it, but try taping up the little fan exhaust hole(s) with some electrical tape, hopefully it doesn't set them on fire?

Guys, thanks for the quick answers. Of course, it is clear to me that the power dissipation at 700 or 1200 mW will definitely be large, on the contrary at 25 mW I would not expect the system to heat up so much. It also cross my mind to seal the ventilation holes, but I haven't tried it yet.

I was wondering if anyone had solved it. If anyone knows what the routes of the air flow inside the goggles are. And to what extent the sealing of the ventilation holes limits the cooling of the output module. The one who has already disassembled it might know. As for the rpm control, I doubt that they are regulated only by the voltage, I assume that there will be some modulation ...

Output power doesn't affect heat much since most of it comes from the P1 chip which runs Linux and does all the heavy lifting like video processing.

Based on a quick look at a teardown video () I'd say it shouldn't be a problem if you tape up the lens ventilation holes as there are other holes inside where the output air can flow. And the fan itself is just over P1 so the part that needs more cooling will just get straight air from it and shouldn't be affected by taping up some of the ducts. I obviously haven't tried that so can't be 100% sure. Try it and see if you can tell whether the fan speeds up or runs at full speed more often, I've never noticed it myself while flying at all.

So some investigation ...
By far the greatest heat is concentrated around the upper right vent. And probably the most important thing I've come up with right now. When the goggles are pressed against the forehead, a vacuum is created, air swells and air is sucked in from below, unless the goggles are pressed against the face at the location of the cheekbones. If, on the other hand, they are pressed against the cheekbones and have play on the forehead, no flow is created inside and my eyes are fine.
So it is clear that the air stream does not go into the googles but is pulled out. So basically all you have to do is have a gap at the top and it's fine, but then it will shine inwards from above, which is not the solution.

(19-May-2021, 06:04 PM)fichek Wrote: Output power doesn't affect heat much since most of it comes from the P1 chip which runs Linux and does all the heavy lifting like video processing.

Based on a quick look at a teardown video () I'd say it shouldn't be a problem if you tape up the lens ventilation holes as there are other holes inside where the output air can flow. And the fan itself is just over P1 so the part that needs more cooling will just get straight air from it and shouldn't be affected by taping up some of the ducts. I obviously haven't tried that so can't be 100% sure. Try it and see if you can tell whether the fan speeds up or runs at full speed more often, I've never noticed it myself while flying at all.

Thank you for the video fichek. I forgot about the processor, it's true that it's warming up all the time.

Thanks again for the video. From video Part 1 and Part 3 (from 13:40 especially) it is quite good to see how ventilation works in goggles. The turbo fan blower sucks in air at the blades and blows out at the outlet, which is located below the upper right vent of the goggles. This corresponds to the very warm air coming out of it. At first glance, it seemed that the upper left vent was fake, after watching the video, it is clear that it is just blinded, after opening it will probably be normally functional.

And now the key problem, the blower does not suck directly, but from the interior of the googles, because the upper left vent is closed. As I understand it, air is drawn in through the three upper vents and through the two lower vents inside the mask. One would think that when all these holes were covered with tape, air would not flow inside the mask. But this is not true, the air is drawn through the space around the lenses. Subjectively sealing the holes in the mask with tape will not help at all. The mask does not fit around the nose and air can be sucked in through the gaps.

So I see it as follows:
- I would not reduce the speed of the blower, it heats up quite a bit and it needs a lot of cooling
- on the upper contact lining of the goggles it is necessary to add some air-cushioning, which will allow the air to be sucked in from above directly into the upper three ventilation holes inside. This is not a very good solution, but probably fast and functional for some time
- to make holes from above in the goggles frame, I really don't want to do that
- disassemble the googles and remove the blind of the left upper ventilation hole, which is located substantially above the blower blades.

WHAT do you think about it, maybe I forgot something.

Today I disassembled the goggles to get to the top plate with the top vents. The linked video helped a lot. The first photo is the original state, it is a screenshot from the original video, where you can see how the left vent is closed (in the photo the plate is turned upside down, the right is left and vice versa). The holes look exactly the same, there is a metal mesh, which is attached to the plate with molten nipples. The left hole is covered with a piece of plastic cover, which is self-adhesive and is also secured with smaller molten nipples. The second photo shows that I removed the nipples with a sharp razor blade and peeled off the plastic cover. I glued it to the small plastic bag if I wanted to put it back later. The last photo shows the reassembled goggles, where it can be seen that both vents are now open.

The result is as follows:
- the air flow in the face plate has decreased significantly, but still some remains, this amount of air flow is acceptable to me, I will see in long-term use,
- if, in addition, the inner three holes above the lenses are blinded, the air flow is almost non-existent,
- the amount of air flowing from the upper right vent is now greater when the left vent is open, this results probably in better cooling,
- if I close the left vent hole with my finger, the flow rate from the right upper ventilation hole decreases a bit and at the same time I immediately feel pain in my eyes,
- Well, maybe it works.