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Feb 21, 2020, 06:46 PM
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Thinking about developing sub 250g cinematographic drone


Hello RCGroups! When I first got into the hobby back in 2015, it was a lot of fun! I left for some time but periodically updated my drone as parts broke and needed to be replaced/upgraded. I started out with an Arduino with MultiWii, mounted to DJI Spinwheel frame with a Basecam gimbal. At the time this was the state of the art for DIY drones, although now we these tiny highly integrated FC's running betaflight/cleanflight/baseflight/INAV for all the small racing drones! Impressed but also a bit frustrated with the rapid developments and obsolescence forcing me to constantly upgrade the FC, I switched to the more mature Ardupilot platform running on a PixHawk clone with a Storm32 Gimbal with a Yi 4K+ actioncam.

Sadly, it seems as regulations around the world have gotten quite restrictive and I am "out of the loop" with the state of the hobby, both in terms of legality, but also in terms of good entry-to-mid range gear and parts for DIY builds. Currently I see a bit of a gap in the hobby for small lightweight cinematographic drones. The DJI Spark and Mavic are very impressive but are very much proprietary platforms. I want to see a more open platform that allows more experimentation and tinkering. Of course to make a very small and reliable drone platform, one has to give up things like modular design, but that's fine since I have the ability to design custom PCBs and electronics. Small is no problem for me lol.

My thought is to design an ultralight that can fly with 1 or 2 Sanyo 3500mAH ncr18650ga cells, can pair with whatever the most popular TX is right now (Ideally running some version of OpenTX) that also supports telemetry over the same link, and utilizes a small camera module, although this will either require extensive hardcore hacking (reverse engineering a typical smartphone CSI camera sensor) and use of an FPGA or a big SoC to interface it, or signing an NDA to get the technical data package from a company, which is very unlikely. If I can get this figured out, then I can build a miniature gimbal around the module and really get the size and weight down!

Questions for the community:
  • Is there much if any demand for such a product? No worth pursuing if there is no interest!
  • It sounds like 250g is the upper limit for most parts of the world before stupid crap like registering are required.
  • What TX do you guys recommend? My FlySky FS-T6 is an unreliable piece of junk. The i6 looks like a good budget option but I want something that is practically designed for OpenTX, is less flaky, and work on a standard that's isn't expected to go obsolete. (I want to integrate a receiver, gimbal, telemetry, and FC all on one PCB)
  • I think Lithium-Ion cylindrical cells are a very good choice, Unless there are higher energy-density flatpack Li-Ion (commonly but erroneously referred to as "LiPos.)
  • Are there any good open-standard digital FPV systems? I know DJI has a decent locked down system
Last edited by Power Max; Feb 21, 2020 at 06:54 PM.
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Feb 21, 2020, 08:09 PM
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Quote:
Originally Posted by Power Max

...I am "out of the loop" with the state of the hobby...
There is a class of micro quads called Cinewhoops, and all the major manufacturers have been releasing them for some time now.
Feb 21, 2020, 09:39 PM
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Originally Posted by benz11
There is a class of micro quads called Cinewhoops, and all the major manufacturers have been releasing them for some time now.
Correct me if I'm wrong, but is that just a 5" racing quad with a GoPro strapped to it? It probably isn't under 250g, and they don't have gimbal stabilization, although the expert fliers get pretty good shots despite this!
Feb 22, 2020, 10:38 AM
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Just google "cinewhoop" and see for yourself. They are not 5" racing quads. They are MICRO quads, with the vast majority under 250g. They don't have every feature you list, but they are cheap.
Feb 22, 2020, 02:24 PM
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Originally Posted by benz11
Just google "cinewhoop" and see for yourself. They are not 5" racing quads. They are MICRO quads, with the vast majority under 250g. They don't have every feature you list, but they are cheap.
OK, maybe not 5 inchers, my point is still that they are not doing everything I would expect. I will probably end up take a COTS (Commercial Off the Shelf) unit and modify it for prototyping. Achieving my feature set on something sub 250 may be difficult and I wonder how much on an issue wind and environment will pose, since smaller quads get pushed around a lot easier.
Feb 24, 2020, 07:28 PM
Ground Pounder
Grab a used Sky Viper brushed quadcopter, equipped with a GPS and running ardupilot. Can't recall the name off the top of my head. You can probably do some engineering around their little FC. Some folks have managed to fit it with brushless motors and ESCs. And then you could maybe remove their so-so Wi-Fi camera and hook up something like a RunCam Split Nano and a small video transmitter.

Sky Viper also made a couple indoor quads that still run Ardupilot. I don't think either of them uses GPS but one has a camera and some kind of optical flow sensor of some kind. Again, using ardupilot opens up a ton of options.

If you can use their existing frame, it would probably go a long way to keep the weight down. And there are some really good, really lightweight brushless motors and ESCs you can use for a power plant. The biggest limitation is that the receiver is built inbto the board but I *think* you can do a simple mod to make it work with Spectrum transmitters.

Just a thought.
Feb 24, 2020, 11:04 PM
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Originally Posted by BorisTheSpider
Grab a used Sky Viper brushed quadcopter, equipped with a GPS and running ardupilot. Can't recall the name off the top of my head. You can probably do some engineering around their little FC. Some folks have managed to fit it with brushless motors and ESCs. And then you could maybe remove their so-so Wi-Fi camera and hook up something like a RunCam Split Nano and a small video transmitter.

Sky Viper also made a couple indoor quads that still run Ardupilot. I don't think either of them uses GPS but one has a camera and some kind of optical flow sensor of some kind. Again, using ardupilot opens up a ton of options.

If you can use their existing frame, it would probably go a long way to keep the weight down. And there are some really good, really lightweight brushless motors and ESCs you can use for a power plant. The biggest limitation is that the receiver is built inbto the board but I *think* you can do a simple mod to make it work with Spectrum transmitters.

Just a thought.
It's an interesting approch, I am turned away by the fact they use those in-runners and noisy and inefficient gears with "those" types of propellers, but I suppose that's the cost of keeping the weight down. I wonder how the Mavic Mini manages to do so damn much with only 249g!

At $40 I'd just buy first and reverse engineer it but it costs almost $200 and looks to be an older product that isn't carried anymore sadly.

EDIT: seems to be the first listing I found had buying options on amazon starting at $170 but there seem to be many variations and versions and $70 is the more common price. Might be worth a shot, though I have doubts about its payload capacity
Feb 26, 2020, 02:03 AM
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Quote:
Originally Posted by Power Max
It's an interesting approch, I am turned away by the fact they use those in-runners and noisy and inefficient gears with "those" types of propellers, but I suppose that's the cost of keeping the weight down. I wonder how the Mavic Mini manages to do so damn much with only 249g!

At $40 I'd just buy first and reverse engineer it but it costs almost $200 and looks to be an older product that isn't carried anymore sadly.

EDIT: seems to be the first listing I found had buying options on amazon starting at $170 but there seem to be many variations and versions and $70 is the more common price. Might be worth a shot, though I have doubts about its payload capacity
Sky Viper Journey (also called 2700 I believe). Target sells them for $100 new apparently. It may not be super capable with brushed motors, but it is possible to mod it for brushless ESCs and motors. Something small, between 11xx and 13xx should be plenty for a sub-250g machine. Look for something with a low kv and use as big (but lightweight) of a prop as possible with it. Mavic Mini prop is weird but tip-to-tip, it's about 12cm (4.75 in). The other Sky Vipers that use ardupilot are Scout and Fury but they have different features. Scout has camera and "surface scan" (sounds like optical flow) but no GPS; Fury has no camera and no GPS but does have "surface scan". You can probably find used versions on the bay or elsewhere pretty cheap.

The reason I suggested you try to use the Sky Viper frame if you start with their electronics is the weight savings. The Mavic Mini is basically a hollow shell with electronics, a lot like the Sky Viper quads. The geometry of the plastic provides enough stability. The extra weight DJI allows for the pins and springs for the arms is surprising to me, along with touches like wire sleeves. The gimbal is genuinely tiny and the camera is mostly supported on very thin plastic. Clever designs for keeping weight down but using geometry for strength. Sky Viper doesn't have all of that, but their frames seem to be rigid enough to fly. I wouldn't want to crash any of the lightweight stuff. Well, I don't *want to* crash anything...

Also, there will probably be some threads about the Sky Vipers over at ardupilot.org. Maybe not a lot though -- those guys tend to buy more "serious" equipment, like $300 flight controllers and $400 frames. but hey, there will likely be some knowledgeable folks there.

Good luck!
Mar 10, 2020, 04:01 PM
Multirotors are models too!
Find a way to reverse hack a DJI Mavic Mini???
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