Quadcopters

August, 2015

I have gone from kites and RC airplanes to RC quadcopters, a reasonable progression. Following advice from the net, I got a little Hubsan X4 with built-in 2 MP camera, to learn how to fly. A vid cap from the X4 of a swallow:

This is a fun and forgiving quadcopter. Good education. I lost it twice, the second time forever, so I got another more basic one without a camera to continue my education:

I wanted to be able to fly my little Mobius video camera so after gaining some confidence with the X4, I decided to build a 250mm quad. I got most of the parts from NYPlatform, an eBay supplier in Flushing, NY...

...and a transmitter/receiver and batteries from Hobby King.

Lots of mystery and confusion, as expected since I received boxes of parts with no instructions at all. I was not surprised about that. I knew I would have to learn how to build the quad from YouTube and other web resources. While it is fresh in my head, I will describe the build and the mysteries I encountered.

Here are some useful YouTube videos:

http://myfirstdrone.com/category/tutorials/build-your-first-drone/

https://www.youtube.com/watch?v=OKMOifCn_xA

https://www.youtube.com/watch?v=CNDe6dhKhXo Good contruction tips from Bruce at RC Model Reviews.

https://www.youtube.com/watch?v=EYAW6kVoxHc This video was useful but not directly applicable to my quad since I had a different controller board and receiver...caused some confusion.

August 10. The box of parts, Mr. RC PC board frame, EMAX MT2204-2300KV motors, EMAX 12 Amp ESC's, 4 carbon fiber 5030 props, a CC3D controller board and a connection board:

Here is the frame. How does it go together, in what order do I connect the plates? Where do the spacers and rubber shock absorbers go?

I found a helpful YouTube video showing a similar frame build under a different name. As I assembled the frame I wondered if I should build the whole frame or add parts as I go? Legs on:

At this point I put on the next plate, the one with + - solder points, then start putting on parts that would solder to that plate.

Motors, two clockwise (CW) and two counterclockwise (CCW) motors. Where do they go? I knew each type were across the diagonal from each other, but which is motor 1? Most diagrams I found had them like this, with a CW motor as #1 at the front left (front facing right in this picture):

How to wire the elctronic speed controllers (ESC's)? Here is one in its package:

August 11. There are three wires from the motors and three wires from the ESC's, all black, unmarked. Some sources said it was a "crap shoot," some said it wasn't, some said CCW motor wires had to be criss-crossed, some said they did not. So I wired them all the same way knowing that I may have to rewire some. I figured I would shorten all the wires when I was done anyway. So here is the way I temporarily wired the motors to the ESC's. I matched up the three wires, offset the solder joints so they couldn't short out and covered them with a piece of electrician's tape. The ESC is hiding behind the alligator clip:

Next, how do I mount the controller board? It can be removed from its box (with difficulty due to the tiny screws...) but I want to protect it from the elements.

I drilled out the holes in the box on the drill press, put the controller board back in and mounted it to the PC board using little zip ties:

Here is everything wired up:

I got many hints about where the wires go from openpilot.org, the website behind the development of the CC3D controller. The four ESC's plug into the top of the controller, into positions 1 through 4 (the diargram above shows motor number positions). The other ESC wires are thick black and red power wires, wired to the + and - pads on the PC board. Main battery power wires solder to the + and - pads in the center of the PC board. The battery, I discovered later, had an an XT-60 connector while the parts package had a Deans connector:

I ordered XT-60 connectors but in the interim, I made my own temporary bullet connectors from 12 gauge copper wire:

August 12. None of this was very frustrating, just putting puzzle pieces together. When I got to the controller setup, it got more confusing. The controller came with non-standard colored wires. Only red and black were correct. I found no diagrams for the Hobby King receiver anywhere. The short story, I linked the controller board to my computer using a standard camera to computer usb cable:

Then using openpilot.org, I got through flashing the controller board/updating the firmware, configuring the ESC's and motors(I had to criss-cross the wires on CCW motors), but kept getting hung up trying to set up the transmitter. After changing wire positions to the receiver the 4th or 5th time, I finally got through setting up the transmitter. I tried it out by spinning the motors without props. Working. So I finished assembling the frame, put on the cheap props that came with the frame kit and spun them a little on the workbench:

I taped the battery on and did a flight test.

I gracefully flew the quad into the grass. The second flight ended under the picnic table with two broken props:

OK! It can fly!

August 13-14. I put on the carbon fiber props from the box of parts and I was able to hover the quad for several minutes. With no low-battery buzzer yet (on order) the quad unceremoniously crashed on its side when the battery was low. This is not good for the battery or the quad so I should have waited for the buzzer to arrive in the mail. I should have, but I didn't. After a few more crashes, the quad flew with a definite wobble.I tried securing the frame boards with zip ties to reduce vibration of the controller board. No help. While at the workbench, I also trimmed and resoldered the motor-to-ESC wires, as planned. Here it is with carbon fiber props and cleaner wiring at the motors:

I tried tuning the controller board by changing PID settings. Not for the novice. No help. In fact, it wouldn't even take off after my PID adjustments.Finally, I erased the controller board and set up the board from scratch. This got me back into the air again with no wobble. After a little more practice, I put on the Mobius camera to see how the quad would fly with a little more weight. I didn't notice any change in flight behavior. Here is a vidcap from the first video, noticible "jello" or rolling in the video, but not evident in this photo:

August 15. Here is the transmitter and quad with Mobius attached to the top plate with a 1/4-20 stud and wing nut, plus a little bit of painter's tape for a false sense of security. The battery has a piece of velcro stuck to it on the bottom, secured with a velcro belt. See the new XT-60 male connector on the quad power wires. As shown, with battery and Mobius camera, the quad weighs 611 grams:

Here is a vidcap from the second flight with Mobius, this morning a little higher in the air. The image quality is much sharper than the Hubsan video at the top of the page:

I should wait for a low-battery buzzer and some more flight time before I climb higher. A crash from 50 feet is worse than a crash from 5 feet.

August 16. I received and installed new propellers, springy green nylon? These:

Also above, connected to the battery is a low-battery buzzer, very loud. It beeps when the voltage drops below any set value from 2.8 to 3.8 volts per cell. I tried both the propellers and the buzzer. Flight was noticibly smoother with these propellers. I tried different voltage settings, settled on 3.5 volts per cell in the three cell lipo pack. While testing I found I could fly for 7 minutes before reaching the tripping voltage.

August 17. Another test flight, in the air with green propellers:

I didn't climb any higher than yesterday. Still learning to fly, testing the flight time, testing the buzzer. It seems to work correctly. There is less rolling in the video but it is still present. I must make some kind of anti-vibration mount for the camera.

August 20. Here is a first try at a DIY anti-vibration mount for the Mobius. I got the design from a website called Flite Test:

I got two reels of LED strips for about $8 each on Amazon. Here is the reel of white LED's:

A close up shows the LED's and a cut point every three LED's so you can cut strips of convenient length:

Using the peel-and-stick backing, I stuck a strip of red LED's to a piece of nylon from a big zip-tie and zipped it to the underside of the rear legs. I wired the strip to one of the + and - pads on the PC board on the quad. A test flight showed the anti-vibe mount for the camera needs adjustment. There is still "jello" in the video, too much vibration.

August 21. I shortened the zip ties in the anti-vibe mount, I added white LED's in the front., and I zip-tied the low-battery buzzer to the frame. I used the blue velcro strap that came with the buzzer to double up the straps on the battery. I also replaced one of the propellers that had a couple dings in it. Here it is in the air:

The video is the best yet, with the least "jello" effect, least vibration. I will post interesting video when I get it.

August 25. The vineyard down the street, from the highest flight so far:

Here is a table showing the price of the quad at this point.

250 mm Quad Cost








Item Vendor Cost Shipping
Box of parts nyplatform (eBay) $108.56 $0.00
Hobby King transmitter Hobby King $29.99 $10.93 Hobby King shipping for 3 items

1300 mah Lipo batteries (2)

Hobby King $17.00

Tenergy balance charger Amazon $19.99 $0.00
5 pairs Arris 5030 propellers Amazon $8.99 $0.00
XT-60 connectors Amazon $1.16 $0.00 single use price (pack of pairs for $5.80)
low-battery buzzer Amazon $6.28 $0.00
LED lights, white Amazon $0.25 $0.00 single use price (reel of 300 LED's for $7.88)
LED lights, red Amazon $0.25 $0.00 single use price (reel of 300 LED's for $7.88)





total $203.40


August 26. I ordered parts from Banggood in China, camera, transmitter and receiver. I ordered DIY FPV goggles and two more batteries from Hobby King.

September 2-3. The goggles and batteries arrived on schedule, on September 2. Here are the goggle parts:

Here is a goggle test using a little camcorder for the video source:

Looks sharp to me but the real test will come with the other parts, still in transit from China.

September 6. I learn to fly. Here is a curious red-tailed hawk who came out of the blue to fly circles around the quad:

September 10. FPV parts arrive, receiver (RC832), camera and transmitter (ET200):

September 12. Testing...

It works. The camera (Sony CCD 700 TLV board camera) is wired to the little transmitter (Eachine 200 mw 32 channel), transmits on 5645 MHz to the receiver. I chose that frequency after watching a couple YouTube videos. Channel selection on both the transmitter and receiver is accomplished by pushing buttons. The transmitter has LED's to indicate the channel as seen above.

I had to make one change in the connector to the transmitter. It was wired to power a 5 volt camera, but the camera I got requires 12 volts. The transmitter has a 12 volt terminal labeled "PWR out +" on the label. I verified that it was 12 volts with a volt meter, then pulled the white power wire out of the connector by gently lifting the plastic tab with a small blade screwdriver. This picture shows the screwdriver blade and the tab, and the white wire already moved to the 12 volt position:

Plugged in:

The camera has a crystal in a silver tube sitting on top of the board. It is recommended by some to hot glue this to the board:

So I did, then I zip-tied the camera to the camera mounting board that came with the frame:

I mounted the transmitter through a hole in the top board using the threaded antenna connector. I needed a plastic shim to get it tight:

The transmitter hangs naked since it runs hot. The power connector for the transmitter and camera plugs into the balance connector on the 3s battery. Easy! But it takes the place of the low-battery buzzer so I will have to do something about that.

Time for a test flight. I put the receiver and 3s battery for the goggles in my tool belt. Ready to fly:

After many short and exciting test flights and crashes, my conclusion is that I have to learn to fly all over again. I have to get used to the view through the goggles. It is stable and sharp enough (though not HD like the Mobius) but lacking the stereo depth perception of the real world. I'll learn.

I have a few small repairs and adjustments to make: replace a broken prop, zip-tie some wires, solder dedicated JST power connectors for the transmitter/camera to free up the balance connector for the low-battery buzzer.

September 13. I trimmed, resoldered and heat shrunk the wires on the receiver and goggles to make them self-contained:

I added a JST plug and jack set to the transmitter/camera power wires to free up the balance connector on the battery so I can get my low-battery buzzer back:

Ready for more practice though I'm thinking I should step back and use a LCD monitor like training wheels so I can fly by monitor or fly by direct sight until I get more experience. I am using the Tony Stark method right now, "sometimes you gotta run before you can walk." The problem here is expressed by another Iron Man quote: "I'm not Tony Stark!"

September 20. I continue to practice flying in the back yard. I have tried using the goggles several times but I need better control over the quad so I need more practice. Today, I crashed into the ground hard enough to break one of the legs:

I traced the outline of the leg and the mounting holes onto a piece of scrap aluminum angle and used a center punch to help drill bits find center:

I drilled all the holes on the drill press, cut out the leg roughly with a hacksaw and cleaned it up with an angle cutter with an aluminum cutting disk. Then filed and wire brushed it:

The old leg weighs 10 grams. The alumium leg weighs 11 grams! I bolted the leg on, attached the motor, etc.:

Good as new.Oh, I lost one of the red aluminum legs while flying in the field so I replaced it with a zip tie. Works. After one particular crash, the aluminum leg bent up a little causing slightly erratic flight. I bent it back down, fixed the problem.

September 23. Still practicing. Here is a view to the north near the end of the day: