Drones: One year on

On January 2nd this year I took a flight over my neighbors house using a store bought drone (Phantom FC40) and a GoPro camera that arrived as a Christmas present.  I was very happy with the quadcopter and the footage I took.  Then, about a week later, I sunk the whole kit into a lake never to be seen again.

At the time I was pretty upset with myself – I made a rookie mistake and paid for it badly.  But I also reasoned that since I had enjoyed modifying the FC40 I should try my hand at building drones instead of buying them.

One year later and I’ve come a long way learning everything from soldering to PID tuning (don’t ask).

I eventually built two different copters, a quadcopter and then a hexacopter, although it feels much more than that because each of those has been built, rebuilt and upgraded numerous times.  Here’s a quick comparison:

 

	DJI Phantom FC40	F450 Quadcopter	F550 Hexacopter
Transmitter Range	800m	2,000m
Flight Modes	GPS Hold Altitude Hold RTL	GPS Hold (slow and fast) Altitude hold RTL Automatic (programmed) Land Guided (click on moving map) Manual Acrobatic Follow me Circle Mapping
Speed	22mph	~35mph	~55mph
Size	330mm	450mm	550mm
Real Time Telemetry	No	Yes	Yes
Moving map	No	Yes	Yes
Gimbal	2D	2D	3D
Camera Control	Manual	Manual or Fully Automated Point Of Interest Lock
Flight Time	9 Minutes	18 Minutes	15 Minutes

 

But probably the best way to show the difference is to compare two videos taken one year apart.  The video on the bottom was from a year ago with the Phantom. It took two separate 9 minutes flights and was then edited to keep only the best parts.  The video on the top was taken in one shot, no editing and took less than 3 minutes to complete from take off to the fully automatic landing.

In fact this year’s video even made it into the local news, and you can find the full version here.

I’ve learned a huge amount that past year, gained some great friends and had a blast doing this, particularly as my #1 son and daughter were very involved in the build of both machines.

Where do we go from here?  

The drone market is in a phase now where digital cameras were 10 years ago.  Their capabilities are increasing exponentially while prices are plummeting.  Even with how far I have come even the cheapest DJI Phantom 3 would outperform my hex in almost every way and these can now be had starting at under $700.  Just a year ago something with that capability would have cost nearly three times that amount!

For me to build the equivalent of a Phantom 3 Standard would cost around $450 in parts alone, and that is if I use cheap parts sourced from China that would need a lot of time to set up properly.  

Will I still build?  I think the days of building from scratch are over, it just doesn’t make economic sense anymore.  But I will continue to improve the ones I have as a way to learn and experiment.  There’s also talk of teaching kids how to build them as part of a maker space project and that is something I would really enjoy doing.

In the meantime, if you are thinking of getting someone a drone for Christmas, or have one and need questions answered…fire away!

 

 

Building an F450 Quadcopter – She’ll no take the strain Captain!!

I added a gimbal, larger battery, FPV TX and LED lights to Gerry (my daughter’s name for the quad).  But what happens when you add too many farkles to your quadcopter build?

When flying around on a perfectly calm day it was OK, but still lost altitude on runs and would occasionally stall and twitch.  But anything more than a breeze and Gerry was all over the place and a constant assault of wind would actually cause it lose so much altitude that it would crash.

Why is this so?

This picture from the log tells an interesting story – at least it is interesting to me.

Red line is Throttle In (what I’m doing). Green line is Throttle Out (what the flight controller sends to the motors).

Blue line is altitude (graphed on the right).  Time (min) can be seen across the top.

The flight controller has a value (THR_MID) that adjusts the throttle so that the middle on the controller provides enough power to hover.  For example if the quad is heavy then it might take 60% of throttle to actually maintain a hover and this allows the user to still position the throttle in the mid point.  These can be graphed showing the Throttle In (from the transmitter) and Throttle Out (how much power the flight controller is sending to the motors).

The problem is that if the THR_MID is way off then switching between modes that automatically adjust (Loiter, Pos. Hold, Alt. Hold) and ones that don’t (Stabilize) can cause a sudden change in the throttle being applied.

At the 1 minute mark on the graph we can see the throttle is between 40-60% in Pos Hold mode and the quad should be holding altitude.  But on this day it was windy and we can see as the altitude goes up and down and the throttle is bouncing off the 100% mark.  Clearly it is struggling to keep the quad at the right altitude.

Just before the 3 minute mark I switched to stabilize, the Throttle Out drops to the same value as Throttle In and the quad starts to fall…FAST!

I immediately give it full throttle but it’s not enough to stop it hitting the deck in what can best be described as a ‘hard landing’.

I tried again and the quad was really struggling to maintain altitude – you can see Throttle Out bouncing off 100% repeatedly. Despite the APM putting out near 100% the 5 min mark it continues to lose altitude and my desperate application of full throttle does nothing. It hits the deck again and I decide it’s time to go home.

If you were to place a ruler on the green throttle out line and draw a straight line that best fit the data; you will see that it has an upward slope. The reason for this is that the battery voltage is dropping as the battery runs down.  Since motor speed is a function of voltage fewer volts = less lift.  Basically the quad is under powered for the weight it is carrying.

I tried using a smaller battery to cut weight but it still lost altitude, was still twitchy (where it would periodically stop to correct itself) and near the end of battery life it started going up and down in a very odd fashion.

Frankly it felt possessed and I started to wonder about exorcism as a real option!  I later figured out this was because it was starting to start the auto land because the battery was low, but then as it dropped the voltage would climb and back up it would go. 

At home more googling and chatting with friends on Quadcopters (yes, I now consider many of these folks friends) and a possible solution emerged.

The PILOT_ACCEL_Z value is used to tell the APM how fast it can climb.  By bringing this down from 250 cm/s to 50 cm/s it should mean that the APM flight controller won’t ask for more than the quad can give and that should stop it getting confused.  I also properly calibrated the battery so that the auto land didn’t kick in too early, as it was consistently under reading the actual voltage by about 1v.

I took Gerry out for a fly and…what a difference!  Smooooooth flying.  None of the crazy jerkiness that it had before and almost no altitude loss.  It did eventually start to lose altitude but it was now controllable and could be recognized for what is was – a battery that was getting low.  Sure enough each time the altitude loss started to occur the low battery beeper would go off.  I ran through three batteries and walked away with a smile on my face.

So, there we have it.  I now have a quad that flies beautifully and is no longer possessed.  With the smaller batteries flight times are short but the future plan is to upgrade the battery to a 4S  (which can output up to 16.8v) which should mean the quad has enough power that I can start to increase the PILOT_ACCEL_Z rating to give it a little more zip.

*** Pro Tip ***

If you want to know what value THR_MID should be set to, fly in stability mode for a couple of minutes, land and then check the value being displayed in TRIM_THROTTLE.  If it is over 700 you have a seriously underpowered copter.  Under 300 and you are massively overpowered.  

Adjusting your THR_MID value to the same as TRIM_THROTTLE will make transitions between manual and automatic (atl. hold, pos. hold etc.) modes much less troublesome.

Building an F450 quadcopter – After the Build

After our successful first flight it quickly became obvious that having a machine that can fly is just the beginning.  In the weeks that followed there were a number of change, crashes, and not an insignificant number of problems some of which are still not yet solved.

All of this occasionally has me wondering why I decided to build a quad copter instead of just plunking down money and to answer that we need to go back about 10 years to when I took my first tentative steps into the world of websites.  Back then I started a web small business with a friend and the venture lasted about two years before closing it’s doors.

Was I sad that the company closed?  No!  In those two years I had learned far more by doing than I could have learned in the same time at school, and the same applies here.

Each problem is a puzzle to be solved, an opportunity to learn and, as I have discovered, a great way to make new friends.  As I learn I like to give back to the community that helped me when I can and, as such, I plan to memorialize much of my learning here in small posts dealing with very specific subjects.  Much will not be of interest to people, but my hope is that one day someone will benefit from the time it took to put this together.

Pay it forward!

 

Building an F450 quadcopter – Beware Idle Hands

 The first time I ordered something from China it was supposed to arrive in 2 to 4 weeks.  It took 7!

When I decided to build a quadcopter I found a kit on eBay that seemed just the ticket.  The price was good and the seller had great reviews but, unfortunately, they were in China.  Expecting the same delays I found myself nosing around various website the following weekend and came across a ready to fly H100 very similar to the one I was planning to build.

The controller wasn’t as fancy as our build (no GPS) but it down from the regular price of almost $500 to just $200.  

My mind got to reasoning this way.

• The parts aren’t going to arrive for a quite a while, so if I buy this I’ll have something to fly until the other one is ready.
• Having a pre-built one nearby will help with figuring out where things go.
• I’ll be able to upgrade the controller and add a GPS later and can then either have two fully features quads or could sell one (perhaps even at a profit).
• I had a little extra income which would more than cover the cost of this.
• That price was so good…I’d be throwing money away if I didn’t buy one!

After putting it into and out of the shopping cart a few times, I finally pulled the trigger.  Since it was only coming from California it would arrive on Friday…the parts for the build arrived the Wednesday before!  

Not only that but the weather turned nasty bringing wind, ice and snow with the result that the maiden flight of this machine ended up occurring about 5 minutes before the maiden flight of the our build.

Thanks Mr. Murphy – you did it again!

Building an F450 quadcopter – Maiden Flight!

We finally had a break in the weather long enough to get outside and get up in the air!

Before leaving there was some question about which two flight modes I should start with.  Key candidates were Stabilize, Altitude hold and Loiter.  I finally opted for the first two.  Stabilize because it doesn’t rely on anything fancy, and then Alt. hold to make flying a little easier.

The result?  In a word – awesome!  It’s been a while since I was able to fly and it was great to finally get back into the air.   See for yourself.

The F450 has some wobble to it.  Nothing terrible and it should be something we can fix using the Autotune feature of the APM.

S. loved it and wanted to try it out, but was too nervous.  That’s actually good as I would really like things 100% sorted before she does that.  But in the car on the way home she told me she wants a little quadcopter that is all her own 🙂

What a wonderful journey!

I’ve shared my parts list including links to where I bought things in case anyone is interested.  You can see those details here.

Building an F450 Quadcopter – Day 7 – A very low first flight

Having seen one too many videos where the quad flips over on takeoff I was understandably nervous about trying our new baby out.  It seemed that at every turn there were little details that needed to be checked and re-checked.

For example, we checked the rotation of the motors and S. then fitted the props according to their direction.

Later I noticed that we had the exact opposite of what was shown on the APM website.  Our props should have looked like this but were not. So, when S. wasn’t looking, I switched them.  

Fortunately I had woken up that morning with an idea that would allow the quad to fly a little, but not enough to flip over if things go wrong.  It didn’t take long before I had it lashed to our table tennis table and we were ready to try her out!

With S. videoing the first test was a spectacular non-event.  I powered up and slowly increased the throttle until full throttle was reached.  We had plenty of noise but absolutely no lift at all!  Then I realized.  S. had been right all along and I had switched the props which were now pushing it DOWN!

A quick switch of the props and we were back in business.  This is when I thanked my lucky stars that I didn’t trust myself to try it without a safety net.  Every time it lifted up it would go wild and try to flip over.  Fortunately the string kept it in place, but it was all over the place and none of the controls made any sense!  See for yourself!

I checked things over again and realized my mistake.  I had plugged the motors into the APM board with output 1 going to motor 1, output 2 going to motor 2 etc. in a clockwise pattern.  However, as you can see from the diagram above, the ONLY motor I got right was number 1!

Switching the connections on the flight controller had us finally up and running.  It now behaved, didn’t try to flip anymore, and I could lift it up and move it backwards, forwards, left and right.  Forward and backwards was reversed because for some reason the APM sets it up to expect the ELE control to be backwards.  No problem, it just took 30 seconds to change that on the transmitter.

While it seemed to be working it was very twitchy and super sensitive to the controls – nothing like my Phantom which was very docile.  

I posted the video on the quadcopters FB page and our good Samaritan made a comment about how twitchy it seemed. I then found out that the latest version of the Mission Planner software has a sliding scale from 1 to 100 where the higher the number the faster it responds.  Guess where mine was set…yup…100!  I backed that off to 80 which seems to have calmed things down nicely without taking all the fun out of it.

One last thing.  Remember I said that my motors were the exact opposite of the picture on the APM website?  I was under the assumption that it didn’t matter as long as they the same rotation was on the opposite corners.  Turns out that is incorrect and that not having it the right way around is going to cause problems with yaw (spinning on its axis), and possibly more.  So, after some gentle teasing by my friends about not knowing how to fit props, I switched the bullet connectors so that they now all spin the right way.

After all those changes I put it back on the “test rig” and what a difference!  It was beautifully smooth and easy to control.  See for yourself.

So, that it is.  There are still many tweaks to do, such as setting up the battery failsafe and adding LED lights, but really the next big step is to wait for a clear day and take her out.  I can’t wait!!

Building an F450 Quadcopter – Day 6 – Ready to Fly?

Finally the weekend arrived and, with the new flight controller in hand, we could get to work.  S. was at a sleepover again so on Friday I performed the ESC calibration and confirmed that in all motors were finally working!

Unfortunately when I tried to run a normal flight test (minus the props) the double flashing red LED told me the pre-arm checks were failing.

I pondered the problem for a while and then realized the FC was in loiter mode which requires a GPS signal to work.  There’s not much GPS signal reaching my basement!  Switching it to “stabilize” mode had it firing up and we were finally ready to put everything together.

I waited for S. to arrive and we set to work.  She installed the anti-vibration plate, flight controller and radio receiver.  I put the GPS post together and she added the GPS to that.  The post had a little hinge on it and I couldn’t understand why, so when S. asked me which way it should go I told her it didn’t matter.  I figured out later that it allows for lowering the mast for transport.  By pure luck it turned out we had installed it correctly.

We had a hard time figuring out where to put the power module and it ended up awkwardly squeezed alongside the battery.  That might need to be moved if we decide to go for a larger battery in the future.

S. checked the motor rotation, installed the props and then, all too soon, it was ready to fly!  It wasn’t pretty but we were both over the moon with it.

S. had insisted that we set up my phone to record a time-lapse video, which I had to admit was fun to watch.  See below.

Not much to do now but give it a test flight, or so I thought.  With the conditions outside being 13f and 20-30mph winds it looked as though we would have to hold off for now.

To be honest I was nervous about this first flight.  I’ve seen a lot of videos where something small or silly caused the quad to flip and when it happens, it happens FAST!  

I went to bed worrying about that and, as is often the way, woke up with an idea on how to make that first flight almost foolproof!

Next post:  The first flight (why second guessing your daughter is a bad idea).

Building an F450 Quadcopter – Day 5 – Flight Controller Test – FAILED!

After putting the frame together I figured it would be a good idea to bench test the flight controller, ESCs and motors before we actually attached them to the bird.  S wasn’t around so I had to do this sneakily, figuring I would then repeat the process for S once I knew what I was doing.

In theory all I needed to do was hook up the motors to the flight controller, connect to the power module and give it a whirl.  The first question was which way around the FC connector wires go, but a quick question and I confirmed that the white wire goes towards the middle of the FC.  I had the motor order from the APM website and I was ready to go.

I connected the battery, moved the stick to the bottom right which should arm the motors and…nothing!

After some fiddling (and some blind luck) I figured out that I had the throttle reversed on the transmitter.  This video helped me to sort that out.

Unfortunately I now had a bigger problem.  I could arm the motors but only 3 of the 4 would spin.  Motor number 1 (front right and connected to APM output #1) was NFG.

Back to those cool guys on Quadcopters who pointed out that I really needed to calibrate the ESCs.  Oh yes (doh!). Armed with the knowledge that I had missed a step I went back.  But, even after calibration, motor 1 failed to start.

Motor 1 happened to be the one that I had left the power cable connected (for backup) so I wondered if that was the problem.  I removed the wire without cutting it (this time), reassembled and…still nothing on motor 1.

Now we were in full on trouble shooting mode.  I tried starting things and wiggling wires and calibrating the ESCs individually.  Nothing worked.

There is a way that you can connect a computer to the APM and have it run a test on each of the motors.  To do that you need to connect to the “console”, but each time I connected to the console I ended up with spurious characters appearing on the screen and I couldn’t enter any commands.  I tried all of the methods people suggested to get around that and finally came across a post with a person who seemed to have a very similar problem. His problem was solved by replacing the APM flight controller!

I was now starting to think I had a hardware issue.  I tried one last test which was to switch the connections on the APM between motors 1 and 4.  When I started up this time motor 1 (previously not working) fired up fine and motor 4 (previously fine) was no longer working, thus indicating that output #1 on the APM is the culprit.

Since I was still within the 30 day money back guarantee (just) I started a return with the company I bought from on EBAY. I posted this on the FB Quadcopters group and one the most helpful people there – MG – who had been making suggestions and providing encouragement all along said that he would send me a spare APM that he happened to have to avoid the wait time involved in returns and re-shipping,!  No payment, wouldn’t even accept shipping.  Just said to try it out and we can work out what to do once things were up and running.  Amazing!

So, for a short time at least, the fun and games has to stop.  But not for too long – MG’s APM should be here in a couple of days, assuming the snow doesn’t get in the way.

I’m constantly humbled by the outpouring of advice and support the Quadcopters group has provided and only hope that one day I will learn enough to pay it forward.

Stay tuned…we will get this bird in the air yet!

*** Pro Tip ***

The console has now been retired and the motor test functionality moved and can be found under the setup menus in Mission Planner.

Building an F450 Quadcopter – Day 4 – Frame Assembly

My daughter was finally able to fit me into her schedule we had a date for 9:30am on Saturday.

We spent a little bit of time on Friday night trying to work out the best way to piece everything together.  To my surprise the APM 2.6 was too large to fit onto the PDB without sitting on the solder joints, and there was definitely no room for the damping plate.  

After much debate, and taking advice from the FB Quadtopers page, we finally decided there was no option but to switch places and put the battery inside and the APM on top.

Satan’s torture device

First task of the day was assembly of the damping plate.

Let me just say, for the record, the person who came up with the idea of forcing those little squishy balls into those tiny holes on the plates is an agent of Satan.  Getting those things forced through 8 holes without tearing them took almost 45 minutes and included some serious tongue biting to avoid teaching S some bad habits.

Frame assembly

While I was busy cursing the damping plate S. was busy attaching the frame spars to PDB and then flipping it over and starting on the top plate. Blue loctite was used to keep things secure but not permanent.

With that done it was time for us to attach the motors and secure the ESCs to the frame with zip ties.  Pushing in those little bullet connectors was tough, especially after the punishment my digits suffered putting the damping plate together.

Had I been more confident I would have cut the wires shorter before soldering to the PDB, which would have left less slack.  But with some zip ties we were able to make them secure, if not exactly pretty.

At this point we were ready to attach the flight controller, power module and battery and start configuring.  Getting to this point had taken us to 11:30.  I was all for pressing on but S said “No, I don’t want to finish it yet.  I’m enjoying building it with you”.  Awww!

We talked about what the next steps are and how the flight controller works with the ESCs to control the motors.  This was easy for her because we had built a robot with a Raspberry Pi, so she understands that the power cannot all flow through the computer.  We also took a look at the Turnigy 9X transmitter, which is very different from the Phantom one that she has used before.

Noting that the throttle doesn’t spring to the center she asked “How do we make it hover?”

This was a question that I didn’t have an answer for, but a quick look on the Arducopter site and know we know that in loiter or altitude hold mode the throttle just has to be within 40-60% range and it will hold altitude.

For once it is my calendar that is getting in the way.  I have a very busy week ahead and it doesn’t look likely that I will get around to doing anything significant until next weekend at the earliest.

If I’m lucky I will be able to bench test the motors before then.  I might have to sneakily do that before next weekend, as it would be nice to then do that again with S watching and know that it is going to work 🙂

*** Pro Tip ***

Using a pair of bent nose pliers makes putting the little squishy balls in place simple.  I wish I had those the first time around – I could have avoided a lot of cursing.

Building an F450 Quadcopter – Day 3 – Soldering!

One of my first jobs involved soldering RS232 connectors by hand.  I was forever burning my fingers and putting on far too much solder so that I then had to spend time trying to remove it from things that it was not supposed to be on.  That was when I was 16, and I still hate soldering to this day.

So imagine my joy when I discovered that assembling the quad involved soldering about 30 connections (including some to make connectors for another quad).

Since those early days I have learned that the right tools can make all the difference so I bought a decent soldering iron and one of those little helping hands with a magnifying glass.  I also watched a ton of videos on how to solder.

Honestly I dreaded what lay ahead.  So much so that I procrastinated and found all sorts of excuses not to get on with it.  In fact my wife even asked “Are you nervous about this?”  I was.  But eventually, armed with a fresh cup of joe and an audiobook, I got down to work.

An hour later I had surprised myself with how well things had gone.  I had made a charger cable for the Aerosky quad, a battery converter so that I could reuse my Phantom batteries, soldered 12 bullet connectors on the Electronic Speed Controllers (ESCs), and soldered all the ESCs on to the power distribution board (PDB).  Work finally stopped when I realized I needed another XT60 connector and some wire to make the battery connector, which meant another trip back to Cruzin RC where I am now on first name terms with the proprietor.

12 little solders

PDB

With progress halted until the next day because the CrusinRC was now closed I turned to the Aerosky quad.  With the battery fully charged (thanks to my new lead) I performed the controller calibration and installed the propellers ready for its maiden voyage. Unfortunately the weather was terrible (freezing rain) so that was the end of day 3.

The next day provided just enough time to finish the last connector and I am now patiently waiting for my daughter so that we can start assembling all the components. She can definitely be a big part of this once she finally deigns to fit me into her busy schedule.   With a bit of luck I can get on her calendar next weekend…:)