Cheapest FPV mini-quad

Having two mini-quads I've have managed to get a few spare parts that never got used laying around. Additionally I have a full FPV250 frame that I bought only to get the landing gear for another mini-quad. To get use of those stuff I decided to try to build a mini quad as cheap as possible.


Parts

Even cheaper

These are parts that you could use to get an even cheaper build but I chose not pick something a little bit better or a cheaper product has arrived after I ordered the parts.

The Build


Motors and ESCs


I always intended to solder the motors wires onto the ESCs. Surprisingly the ESCs are constructed a bit differently than what I'm used to with the wires soldered onto the center of the board instead of the edge. As a result the motor wires were to short and it took some extra fiddling to get it right.

ESC with cables soldered into the center of the PCB

The motors are mounted using the new motor adapters the comes with the FPV250 frame from HobbyKing. They work great but I managed to break a screw while attaching them. Hopefullt this does not indicate future problems.
I attached the two front ESCs with transparent heat shrink just to give a bit illustrative feeling. Now I can should people "how" those ESCs work.

Motors and ESCs mounted and connected to the power distribution board.

Electronics visible through the heat shrink


Receiver and flight controller

I decided to use a single-wire capable receiver with the CC3D using the S-BUS system. This is one of the reasons I go with higher priced CC3D instead of a Naze32 or the ultra-cheap KK boards. 

Single-wire capable FASST receiver

To make the installation more compact I removed the servo connectors on the CC3D and the receiver and soldered all the wires directly.

Receiver without the plastic case

As I was removing the servo connector pins from the receiver I managed to break away the soldering pad. I tried to fix this by soldering signal cable directly to a surface mounted resistor on the circuit but didn't succeed. 

Receiver with only the necessary wires soldered and wrapped in heat shrink

Instead I had to use the PPM output to connect the receiver to the CC3D. But it turned out it works quite fine.

Receiver and CC3D installed on the frame

Video system

I picked the cheapest camera I found for this one with a few basic requirements, size and focal length. I really love the wide angle I bought for my last build, it gives a strange feeling at first but when you get used to it is really nice to see so much more of the surroundings. The choice fell on a $27 board camera. I could have found a cheaper one easily. 

Camera and camera mount assembly
Instead of using a telemetry system, which is expensive, I will install an OSD to monitor battery voltage. This is the cheapest one I found. I intended to do this mod to get RSSI displayed on the OSD but I fear it might bright noise passed the LC filter so I saved that for a later build.


Super simple mini OSD
I built the classical LC filter to remove/reduce any ESC noise that might interfere with the video signal. I also removed the connector pins from the OSD to solder cables directly instead. I get more and more into soldering and start wishing they would sell more stuff unsoldered.


LC filter and liberated OSD board

The OSD board is actually quite large. They could definitely have made it smaller. I built a kind of stack together with the LC filter to make them fit together nicely.


LC filter, FPV power distribution and OSD in one

Some heat shrinking to keep everything and double sided tape to attach it.  I used an old wire to secure it. Usually I would use a cable tie of course.


OSD and LC filter mounted on the frame
I installed the camera where it should be and the video transmitter together with a pigtail cable under the top plate of the center cage. I got so carried away that I forgot to take any more photos.

Result


This is the finished frame, except for the antenna that hasn't arrived yet. I will try flying it with the included whip antenna anyway just to see how bad it really is.


Cheapest mini-quad

And the CC3D china clone that everyone says is crap, it's really kicking it!

Specs

Average current: 6.5A
Weight without battery and mobius: 353.3g
Total cost: 204 USD








10 comments :

  1. What do you use to actually view the FPV feed? Maybe I missed it on the parts list.

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  2. I'm using the RCV922 AE goggles. I didn't include the remote control and the video receiver in the build specs as you would probably have this equipment already when building a multi rotor like this one. Of course, the price tag would be significantly different if I would...

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  3. Alright. Thanks man! Any recommendations for transmitters?

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    Replies
    1. I started out with a Spektrum DX6i. It was an excellent choice for a first transmitter and would recommend it still. For a cheaper option, go with the Orange T-SIX which has essentially the same functionality.

      Later on, if you get caught in the hobby, you'll need to upgrade, but by then you know more about what you need and want from your transmitter.

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    2. By the way, this build includes a FASST receiver, it will not work with a Spektrum transmitter.

      Delete
  4. This comment has been removed by a blog administrator.

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  5. One last question, where did you get the battery connector and why do you have to remove all the pwr/grn wires from the esc's besides one. Does that identify it as motor 1?

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    Replies
    1. The battery connector is an EC3. You might want to use a XT60 instead since most batteries comes with XT60 nowadays. You can get those connectors at any vendor.

      The ESCs all contain a "BEC" which is a 5V voltage regulator. If you connect multiple regulators in parallell bad things can happen such as fire and magic smoke. This is not a generic truth but a recommendation and I've seen the consequences of it. Because of this you cut all pwr wire but one. The last one provides 5V to the flight controller and the receiver.

      The ground wire is cut to avoid ground loops. The ground wires, including the power ground from battery to ESC is all connected directly to the battery. The finer, like the servo wires, also passes through delicate circuits like the flight controller and/or the receiver. Cutting the ground wire to the ESC avoids the risk of having excessive current/power passing through the flight controller circuit when the ESC is pulling a lot of power to the motor from the battery.

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  6. One last question, where did you get the battery connector and why do you have to remove all the pwr/grn wires from the esc's besides one. Does that identify it as motor 1?

    ReplyDelete
  7. One last question, where did you get the battery connector and why do you have to remove all the pwr/grn wires from the esc's besides one. Does that identify it as motor 1?

    ReplyDelete