white IRIS...cooler IRIS?

Posted by Dan McKenna on September 3, 2015 at 7:21pm

I needed to take some video around noon and was getting high HDOP

The IRIS was sitting on the ground for about 5 minutes and when I went to unplug the battery

and reboot noticed that the top was hot.

I normally fly a dawn and just before sunset and found if my house is warmer than out side

 get a better start up and less drift if the Iris is outside for 15 minutes before powering up.

Just an observation that now is a ritual with me.

It just seems that if the top of the iris was white the electronics would be cooler in the day.

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Replies

  • Jimmy Oliver September 6, 2015 at 10:32am

    I could 3D print a white one if I could find the files. 

    • Joe Whiteside > Jimmy Oliver September 6, 2015 at 10:39am

      I'd buy a white top shell, the uv out here in sunny southern California gets way up there during the summer months.

    • Ben Norris > Joe Whiteside September 8, 2015 at 7:30am

      why not just spray it white? non metallic

  • Dale Greer September 5, 2015 at 7:07pm

    A white top might help, but for air cooling I added some spacers for the three screws that hold the top on. I got some 10 mm screws and 5 mm nylon spacers. Probably would be better to use steel standoffs, but the spacers and screws work alright.

    I did my first flight with that setup today. It was 98F in Dallas at 5:30, so high ambient temperature but not a lot of radiant heating. Looking at the logs later, the barometer says cabin temperature got up to 48C (118F) for the first battery. On subsequent batteries it started at about 50C (122F) and decreased to 49C (120F) towards the end, so it seems like air cooling is working pretty well.

    Previously I was getting temperatures up to 53C (129F) in similar circumstances, and 56C (133F) with more direct sunlight at around 3PM, with ambient temperature of around 95F. I'll fly it earlier in the day tomorrow to get more direct sunlight. My hypothesis is that there's going to be some radiant heating effect that will heat things up past 50C, despite the air cooling provided by the spacers.

    Also, the barometer altitude closely tracked GPS altitude for the whole session. In the logs, I did notice some air pressure effects when changing directions. I was testing out some new hardware, so I was doing a lot of flying back and forth, and side to side, in a regular pattern. This showed as sinusoidal variation of barometer altitude around the GPS altitude, but in constant flight, there was no constant offset, and the barometer variation didn't cause any erratic flying.

    • DavidFolts > Dale Greer September 5, 2015 at 7:36pm

      Good test Dale - was not able to do testing today...rained often here in Houston area.  The ESC unit also heats up...and it sits opposite the Pixhawk/PX4 on the underside of the frame plate.The heat seems to rise up thru the side vents in the main plate, and in a motionless Iris, I suppose its supposed to exit out the vents over the aft end of the Pixhawk, or out the rear of the upper cover.

      So, my plan, if I ever get to it, would be to open more vents in the lower half and mount an exhaust fan on the right rear upper aft opening. A bit tight there, but I can string the power leads along that existing wire "harness" perhaps from the rx if I get a 5v fan.

      My present challenge is getting my DIY CHDK trigger cable/circuit working.

    • Dale Greer > DavidFolts September 6, 2015 at 9:38pm

      I flew again today, and now I think I was wrong about my temperatures. I'm getting a lot of spikes and dropouts in my data, so the scaling was messed up in Mission Planner. When I zoomed in on parts without spikes, the temp is more like 44-46C (111-115F), which is much better than I was getting before.

      Now I just need to find out why I'm getting these spikes. Is it the crappy HK Pixhawk, or my crappy installation of it? In any case, they don't seem to affect the flying at all.

    • DavidFolts > Dale Greer September 7, 2015 at 8:53pm

      Compatible Pixhawk from HK?   Hmm, does anyone know where 3DR sources their Pixhawk manufacture?  In their own plant in Tijuana? or China?

    • Dale Greer > DavidFolts September 5, 2015 at 8:40pm

      That sounds like a good idea. Some like this little 17mm guy? Or here's a 20mm one.

      And it just so happens I've been trying to get a CHDK trigger working too! The intervalometer is a decent fallback, but I bought the dang cable, I want it to work. I've never figured out how to test it though, I mean, I'd like to be able to do some kind of test mode, where it would just give me a signal in the comfort of my living room, so I wouldn't have to fly my Iris+ and then see if it worked.

  • Ray September 4, 2015 at 10:10am

    I like the fan idea... How about adding a couple of vent slits fore and aft (or on either side) and a tiny low voltage fan?

    • DavidFolts > Ray September 4, 2015 at 11:30am

      That's where I'm headed Dan...just need to find the right tiny 12v fan...the one used on the oDroid single board computer should suffice.

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