I wanted to share my quad transport slash storage slash FPV groundstation for some time already..

Ordinary tool box, the biggest one from 3-in-1 special offer pack, €15.99 in local hobby store:

When opened, my quadcopter is folded inside with batteries, charger etc:

Plan is to have also the RC transmitter in the same box, there is still room for it. I will have to make some divider for it so it does not get all destroyed while being transported in a car.

This is how the copter looks unfolded:

I have used flamewheel clone arms, some plywood (will use carbon fiber but I did not bother for now..) and aluminium square tube for the fuselage. The tube is drilled to save weight. Flight controller is in the mid section inside the fuselage.

The unfolded arms are not locked in place on the picture so it looks a bit wobbly, but in fact it is quite stiff.. I used bamboo sushi sticks as landing gear to lift the frame so I can mount the camera on the bottom.

The frame is a bit on the heavy side, I will replace it with something lighter when I am in the mood.. But for now it works, and it does not look like flying spaghetti monster..

To the more interesting stuff now: I have used the removable compartment which came with the box to store my FPV gear. The compartment is locked to the lid with two screws and nuts and opens with the lid. While opened, it is held in place by 12AWG wire on the right-hand side:

In the upper-left corner I have 3 antenna connectors - there are hidden 3 separate video receiver modules (cheapo 5.8GHz modules for some 12-14USD excl. postage), each with it's own antenna. There is RSSI comparator which I made using "standalone arduino" - just an Atmega168 chip mounted on prototyping board with 16MHz crystal, some capacitor and hidden spaghetti of wiring. Based on measured RSSI the comparator selects video signal only from receiver with the best quality, and sends only the best video output to the 8inch LCD TV. The TV was some 75 USD from dealextreme, I chose it because google told me that it switches to blue screen only when there really is little to no signal - on picture, the video transmitter was off. Signal switching itself is done by 74HC4052 multiplexer which is controlled by the arduino signal comparator. The nice thing is that it could be scaled up to 8 separate receivers with very little changes - maybe I will do it, once, but for now there was no place on the protoboard anymore :-)There is also composite video-out connector in the lower-left corner, to connect video goggles or recorder.

The whole thing runs of 3S LiPo (voltage on the right LCD). The video modules / comparator / signal selector all work on 5V, so there is hidden UBEC, and it's voltage is displayed on the left LCD. The current consumption is on the analog meter in the middle. It is there only because I really liked how it looks. I have no idea how accurate it is.

The little oled display just shows the measured RSSI values, and which receiver is selected. That is not really needed for the thing to work, but it was quite handy for debugging. You can also see which receiver/antenna is in use by the LED which is bellow the antenna connector. The 3 LEDs flash together while the video transmitter is off.

Picture with antennas - pictured are "stock" omnidirectional whip and flat panel directional linear polarized antennas. 

I will use 1 skew-planar circularly polarized omnidirectional antenna and 2 helical directional antennas, 3 to 5 turns, in an angle of each other so that I will cover wider area, without the need of antenna tracker. If I ever scale it up to use all 8 video receivers, I could combine 1 omnidirectional  with 7 directional antennas of different turn-count to cover 360 degrees around myself. I do not need that for now though..

This is how the wiring looks like:

I know it is a mess, but you don't see it normally :-)

I wanted to make custom PCB to get rid of all the wires.. and maybe I will, eventually. But none of my friends would believe me then, that I made it myself, if it didn't look like a mess of wiring and hot glue :-)   Anyway, normally it is covered and not visible, and there is no stress on the wires, so I do not expect it to fail because of loose wire or connection.

To the end of this post I just want to say thank you all the nice people sharing the knowledge all over the internet - very little of all this comes from my own head - I found tons of material about video diversity receivers (I just don't know why people usually only combine two receivers - one omni and one directional.. the receivers are so cheap and it cost nothing to scale it up a little to get the little bit more land covered), I found many articles about standalone ardino, about video buffers, etc..  I just love the internet :-)

cheers, I hope I inspired someone to try something like this.

Views: 2552


T3
Comment by Richard Boyhan on June 6, 2013 at 2:05pm

Very nice work.  Thanks for sharing.

Comment by Nick Tuttle on June 6, 2013 at 2:22pm

I love it!. Posts like these are the reason I joined DIY Drones! So much good stuff here.

Your quad design is awesome. Very Lean and mean looking!

I have built my ground-station is built out of a smaller toolbox that I just carry batteries and other parts in, but it is a mess! How do you fly using your ground-station? Do you sit on the ground in front of it? I have to find a table the right height to set mine on when I fly, so I am considering redesigning it to be strictly FPV (no battery storage) and for mounting on a tripod. 

I love your solution for diversity as well. I am going through buyers remorse having just bought a system this morning. I haven't looked at it all just yet, but im guessing it would be possible to program the arduino in such a way to drive servos for a tracking system?

You've got me thinking, and definitely inspired. Thanks!

Comment by ondrej kliment on June 6, 2013 at 2:36pm

Thanks :-)

Normally I sit down on the ground with it.. 

Regarding the antenna tracker - yes, it's possible, many people do it also on this site.. I just wanted to avoid any moving parts in the system. I do have telemetry,  but don't use it for any tracker.. just display copter info on android tablet.


Developer
Comment by Mark Colwell on June 6, 2013 at 4:02pm

Nice work, Analog meter ++

Comment by Stephen Gloor on June 6, 2013 at 7:09pm

Any chance of posting the sketch and a wiring diagram?

Comment by Chris Card on June 6, 2013 at 7:16pm

Nicely done.  I love that your quad & gear fit in the box.

Comment by ondrej kliment on June 7, 2013 at 12:26am

@Stephen Gloor: I have changed things here and there during construction on the protoboard, so I don't have any wiring diagram of the actual result..  however, I can only recommend this thread on rcgroups: http://www.rcgroups.com/forums/showthread.php?t=1661980  - his solution is very similar to mine, and there are all the diagrams and sketches there. I borrowed video amplifier circuit from that thread :-)

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