Tag Archives: F450

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
 IMG_1482.JPG  _MG_4923.jpg  20151122_093203.jpg
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!

 

 

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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.

TooHeavy

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’.

sadwalkI 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.

Baphomet-pentagramFrankly 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.

IMG_1653

*** 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.

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Building an F450 quadcopter – After the Build

flight_mapAfter 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!

 

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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!

Aerosky

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!

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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.

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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.

APM RotationLater 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.

basicOne 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!!

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

AssemblyFinally 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.

IMG_1544I 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.

IMG_1556S. 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).

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