Syma X1

I thought I’d share a little detail on the Syma X1 quadcopter I picked up as a practice tool and toy from Amazon.  There are 3 models you can choose from but they are all the same except for the vacuum formed canopy.  You can choose from a UFO, a spaceship, or a bee. It is almost purely aesthetics that separates them.  One surprising difference is that Amazon often has different prices for each one (although only by a dollar or two.)  It seems that the bee model is always a little higher priced than the spaceship, with the UFO floating in between the two on a daily basis.  Strange, but there you go.

What do you get for your (approximately) $36?  Well, here is a pic of all the things in the box.  There is a LiPo battery with a USB charging cable, the controller, a manual, spare props, and of course the copter itself.  The manual is pretty challenging.  It is not just that it appears to have been the result of a liberal use of Google Translate, it is that it is missing a couple of extremely key elements.  As you can see if you read the comments on Amazon, the first issue is that the manual doesn’t tell you that immediately after inserting the battery you must put the copter on a level surface.  The gyros only calibrate on initial power up and if you’re holding the thing in your hand (as I and many others have done) it gets a bad idea of what level is and the result is a copter that can’t fly straight.  Second, the transmitter and the copter sync to one another on power up and timeout if you don’t manage to get them both turned on within a second or two of each other.  This results in a bit of a frantic shuffling as you insert the battery in the copter, quickly set if on level ground, then flip on the controller power so it can sync.  However, once you’ve done it a few times you realize that you have more time than you feared and it really isn’t that hard.

The controller takes 4 AA batteries that from all reports will last a long time.  It makes sense, the controller itself is pretty simple and doesn’t draw more than about 5V to power its radio and small set of chips.  The copter battery is a single cell LiPo which yields 350mAh at 3.7V and has an integrated JST-style connector.  It is good enough for about 8 minutes of flying per charge and takes about an hour to charge between flights.  The USB charger is a very simple device that relies on the battery itself to stop charging.  Don’t use this USB charger with other batteries as it will happily keep charging them until they catch on fire.  Like all LiPo batteries, you have to know how to use them safely.  As it is, I have charged this battery a dozen times and never did it get the slightest bit warm and has cut off on its own every time.  I would still watch it carefully though and certainly not leave it charging overnight.

The flight controller on this little toy is overall very well done.  The picture here is hard to see, but it has a simple pair of dual N-channel MOSFETs as speed controllers (the part that transfers digital throttle commands into variable current to the motors), a 2.4GHz radio module (that’s the big silver part plus the A7105 chip to its left), what is described as a 6-axis gyro chip, and what looks like a custom chip that Syma is using to handle the real flight control duties.  I don’t know what this part is, but the firmware in it seems overall pretty good.  Most people have good luck getting the thing to hover easily indoors (no wind) and enjoy reasonable control in most conditions.

How is this to fly?  It’s a great deal of fun.  The controller can operate in Low or High modes which pretty much translates into “less sensitive control” and “more sensitive control”.  It also has a built-in trick which will flip the copter in any direction automatically (this is the strangely titled “Eversion” feature which seems to be a casualty of faulty translating).  Push the right shoulder button, then pull the right stick in any direction and the copter will roll in that direction.  It needs about 2 cubic feet of space to do the trick but because it has altered its momentum you don’t want to do that too close to the ground or people.  Regaining control after the flip is pretty easy so its a safe maneuver in most environments.  I did notice that it was a bear to control in high winds.  Most of that came from the wind resistance of the plastic canopy.  When I removed it I noticed it was much easier to fly.  The canopy also created a surprising effect.  When wind comes at the copter from below (not uncommon when near a building) the canopy acts like a sail allowing the copter to gain tremendous altitude quickly.  In fact, I had it floating at nearly zero throttle more than once with a decent wind gusting up from below.

One great feature of the copter is its weight.  Ready to take off, the thing weighs in just under 70g.  That is super light.  No wonder it can do flips and zip around with easy.  It also means that when you crash you aren’t really likely to hurt it.  I have gotten into the habit of going to zero throttle any time I lose control and even though it has hit the pavement after falling for over 10 feet the device has never been damaged.  It is good to remember Newton’s second law in these situations and that a light copter keeps the force in a crash to a minimum.  I can’t imagine what crashing a 1kg copter is like, but it can’t be pretty.

I have to confess that this is my second X1.  The first one sailed away over my house and was lost.  I sure wish I had some idea where it went, but while I saw it tumble from the sky I was never able to recover it.  I consider it a learning experience – don’t let the thing get too far away or too high.  I also have experienced some strange control interference in a couple of occasions.  99% of the time the device has crisp response, but more than once I found myself wondering why the stick didn’t seem to control the device.  I think this is most likely caused by the relatively weak transmitter in the controller, but it is hard to tell.

I also have to tell the story of how I tested its ability to be a submarine.  I was flying around the back yard and it got too much sideways momentum while I was landing and it slid right into the swimming pool  flipping over onto its back.  At first I figured I had gotten lucky because it was floating on the surface, the canopy acting as a boat.  But as I went to grab it I accidentally pushed the throttle on the controller with my other hand and much to my surprise the submerged props happily drove the little copter right under the water where it sank to the bottom about 4 feet down.  I was frustrated and ran for my pool net.  As I fished it out, I was surprised to see that the little red LED continued to operate and all the way to the surface and even after I shook it to get most of the water off.  I quickly removed the battery and set it on my table to dry.  I was hopeful it would survive and lo and behold, it did! I’ve flown it several times since then with no adverse effects from the dunking.  Now that’s robust design!

Overall, I highly recommend this little toy.  If there is a downside it is that the 8 minutes of flying time goes by too quickly making me wish for more batteries or a faster charge.  I’ve ordered some extra batteries which will help.  However, my next step is to mount a tiny keychain video camera to the copter and fly it around recording to see how that will work.  Check back soon!

Quadcopter: Radio components

In researching the requirements for a quadcopter I found that I needed a real RC hobby radio.  I’ve looked into these in the past and was always daunted by the price of the radios  used traditionally such as those by Futaba and Airtronics.  But, given that I was going to be really getting into these copters I decided to go ahead and spring for a good one.  I started looking around at what others have used and ran across several.  First, the ones I mentioned are still in use, but they’ve moved away from the 75MHz band and analog signaling they have used for years and instead started using 2.4GHz.  And not just that, they now sport spread spectrum, frequency hopping, and digital signals which all adds up to a highly reliable radio solution with tremendous range.  Even the most basic radios have a range of 1.5Km which I find totally amazing.

With that knowledge in mind, I started looking at the various options. There is a good 8-channel setup from Futaba, and the same from Airtronics. Lots of people like Spektrum and Hitec as well and generally they are pretty similar in terms of feature set. They all come in at about $300 and include features such as multi-model memory, touch-screen displays with telemetry, and SD-card slots. But then I stumbled across what is almost an open source radio.  The Turnigy 9XR is an Arduino-based radio using low-cost parts shared with cell phones that are really inexpensive.  This results in a radio platform that costs $50 and takes a JR-style TX/RX module (those are the pieces that actually do the broadcasting and reception.)  It doesn’t have a touch-screen display, but otherwise it is pretty similar in terms of features as the $300 models.  This is the 3rd generation model and others find it works great.  Given its Arduino roots and the ability to run an open source open9x firmware stack, I decided I had to give it a try. And hey, if it doesn’t work out, I can always switch to another brand and re-use the RX/TX module.

I purchased the Turnigy 9XR from hobbyking.com and the Frsky DJT transmitter and V8FR-II receiver for a total of $90.  I’ll let everybody know how it works.

Photo Quadcopter Project

As I said in my previous post, I’m going to chronicle my quadcopter build.  I’ve never done this before so I expect to make some mistakes.  Hopefully I can learn from others and keep those to a minimum while learning lots of things along the way.

The first quad I’ve decided to build is going to be focused on photography.  I’m looking for still and video pictures taken from the perspective of the quad.  I want to try to keep the weight below 1000g total and I think this will do it.  Here is the quad I’ve designed so far and what I’ve purchased:

Frame: Turnigy Talon v2, Carbon Fiber, 550mm, 280g, $50
Why: I wanted a decent size frame to maximize stability.  I’m not interested in aerobatics with this quad, so a big frame is the way to go.  I also wanted to minimize the weight of the frame.  I’ve read the stories of many others making frames from aluminum, wood, etc. and finding they were just too heavy.  Hopefully this will do the trick.
Where: I purchased this frame from hobbyking because they had a great price for a carbon fiber frame ($50) and because I was ordering some other items from them at the same time.

APM 2.5+ ModuleFlight Controller: ArduPilot Mega 2.5+ with , 21g, $180
Why: Ultimately I want a craft that can handle autonomous flight.  While I’m sure I’ll have fun manually controlling the copter I am most interested in building a drone.  I’m looking for a device that can fly itself and take photos/video.  In Jan 2013, this is the controller to use if you’re interested in that.  While there are other controllers that are cheaper, I don’t think any of them possessed the software and community that this does.  The ArduPilot Mega contains an ATMEGA2560 Arduino Mega.  It also includes a ton of useful modules including a 3-axis gyro, accelerometer, high resolution altimeter, magnetometer (aka digital compass), and an off-board Mediatek GPS.  There is an option to deliver telemetry data via an XBee radio module to a laptop but I didn’t choose to buy that yet. I figure that if I want it later, I can always order it as an add-on ($40).
Where: I ordered this from the source – 3drobotics.com.  There is a way to order it for less if you’re willing to do more work in terms of soldering and buying the connectors yourself – rctimer.com has one for $140.

Flight Controller-add on: LV-MaxSonar-EZ0, 4.3g, $30.
Why: I decided to add on the sonar module after reading about how you can use it to let the craft land itself.  The ArduPilot contains an altimeter that allows it to detect its height, however that device is unusable below 10 feet.  In order to fly and land safely a sonar module is used to get accurate height data and allow ‘nap of the earth’ style flight.  That said, I also read plenty of posts about these things not working right all the time.  It seems the device can be noisy in that its data feed contains some bad data while flying over uneven terrain like grass (versus smooth pavement.)  We’ll see!
Where: I got this when I purchased the flight controller from 3drobotics.com.

Motor: 4 x NTM 28-30A 750kv / 140w, 67g each, $15 each
Why:  I wanted motors that were proven but could be had for a reasonable price.  After the props, these parts are the ones that are most likely to break in a crash.  And while I hope I can keep that to a minimum, I know this is going to crash.  I picked these after reading some people being happy with them and using a tool to determine if 4 750kv motors would provide enough lift.  I want to have room to spare in case I wan to put on a relatively heavy camera.
Where: I ordered these from hobbyking.com while ordering most of the other parts.  Luckily these parts were in the US warehouse in Seattle meaning I could keep the shipping costs down (shipping from China is more expensive than I expected.)  I ordered 6 in order to have a couple as backups.  I also ordered the accessory kit which includes the prop adapter (a collet to hold the propeller in place) and mounting brackets and screws.  I don’t have data on the weight of these parts unfortunately.

Electronic Speed Controller: 4x Turnigy Plush 25A, 22g each, $13 each
Why: An RC aircraft requires a speed controller per motor that allows the flight controller to change the speed of the propeller when it needs to.  The idea is simple, but apparently these little controllers are the source of much frustration.  They can overheat and fail and when they do, a quadcopter is going to crash.  While a fixed wing aircraft can glide down if the speed controller fails, a quadcopter can’t, obviously.  The prevailing wisdom is to place these controllers out on the arm of the quad away from the heat-generating devices like the battery and flight controller.  I see that many people like to ensure they are being hit by the propwash in order to cool them.  There is one interesting feature to these little controllers I didn’t expect, and that is because of what they do already they include a regulated voltage output (in this case, 5V 2A) that can be used to power something else (that’s the little plug in the photo.)  For fixed-wing aircraft this is normally a server to control the flaps or rudder, but on a quadcopter this isn’t that useful.  I’m not sure if I’ll use this feature or not.
Where: I ordered these from hobbyking.com but they had to come from China.  They were highly rated by the enthusiast community and also really cheap at $13 from hobbyking so I ordered 5 in order to have a spare.  Even when I factored in the shipping cost, these units were still about 3/4 what you could buy domestically for similar quality.

SlowFly PropsPropeller: Slow Fly 10×4.5 ABS propellers, $0.77 ea
Why: Supposedly these propellers are strong plastic designed for use on electric motors. Of all the things on my quadcopter design this is the one area where I can’t tell much about strength versus weight versus balance in terms of value.  I do know that I will be balancing them when they arrive but given how cheap they are I might also get some locally at a hobby shop rather than order them online in the future.  Obviously the quadcopter needs 4 and I ordered a set of black and a set of red (with extras) so that I can see the orientation of the quad by putting 2 red in front and 2 black in back.
Where: I ordered these with the other parts from hobbyking.com.

Battery: Turnigy nano-tech 2200mah 3S1P LiPo, 187g, $19
Why: I read good things about these batteries and  the run time some are getting from a single 3 cell battery.  I also learned to purchase the nano-tech variety due to the limited swelling during use.  According to one report, a traditional lithium ion batteries can increase in size by 15% due to heat during discharge.  I’m not sure if I will use one battery or two during flight so I ordered 3 while I figure that up.
Where: I ordered these from hobbyking.com because it was in the US warehouse.  If it had not been, I would have been looking for a local source.

My Quadcopter

AeroQuad Cyclone

AeroQuad CycloneI went to the Houston Mini-Maker Faire in January 2013 and for some reason seeing all the Star Wars droid replicas, electric cars, and 3D printers made me want to do something with the Arduino and/or Raspberry Pi I had sitting in my desk drawer.  I was charmed by the 3D printers but I honestly couldn’t figure out why I should build one.  But it was while looking at that hobby project that I found all the work being done on quadcopters and I found myself more interested in that than printing.  And then I happened to see a Nova special titled Rise of the Drones that captured my imagination in a big way.

I’ve always been a fan of RC planes having had them since I was a kid.  I’ve had several in my life including a gasoline powered control line model that was more scary than it was fun and a great park flyer that I still have.  And while I like them I’ve also had trouble with the speed and how fast it can get out of control.  RC helicopters on the other hand, were always more interesting to me but suffered from being more expensive and harder to fly.  At least that is how it used to be.  With modern micro-controllers, digital cameras, and cheap parts like accelerometers and gyros (thanks to the Wii, Sony Move, etc.) this has gotten a lot safer, easier, and opened up a whole new world of possibilities.

APM Planner

I have to admit, it got me dreaming of an autonomous copter flying around the area taking photos and providing a live video feed of its flight as it goes.  All that is possible, but I’m going to take a more measured approach and ease into it.  Sort of.

I know that I want an Arduino-based flight controller.  I like Arduino because it is a powerful modern micro-controller that is relatively easy to code to.  It is designed from the ground up as a real-time control system and that seems perfect for a helicopter.  After checking into it, there are several options that seem very viable.

One that holds great appeal is the MultiWiiCopter.  This project option combines a very inexpensive Arduino board with the insides of a Wii Motion Plus controller.  The Wii component is a very cheap way to get a set of gyros and acceleromters connected to your Arduino.  You can build one for about $50 which will act as the perfect platform for an RC-controlled quad as long as your comfortable soldering the parts (or you can order a board with all the pieces assembled for $93).  However, it isn’t really designed for autonomous flight.  You can add on a GPS/compass and other things but that isn’t what it was designed for.  I might get one of these at some point in order to learn how it works compared to others.

APM 2.5+ Module
APM 2.5+ Flight Controller

The project I ultimately decided to make is based on a project named ArduPilot.  Specifically designed for quadcopters now, ArduCopter is a robust solution with lots of enthusiast assistance in the form of blogs/forums/etc.  It also comes in a great physical package with all the components and easy-to use connectors.  With that in mind, I’ll create another post with all the details of what I have purchased so far, why (at least what my thinking was) and how it is going.