Sentinel 1

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My son has been making parts for Sentinel 1 for me, I figured I will start to post those in case people find the useful.

1st post – This is a battery holder for the HobbyKing X666 frame! It works great holds the battery nice and tight and allows you to hold other payload – like a WifiPineapple! 🙂

If you don’t have a 3D printer and want a battery holder, he will print a set for you for $5.



Sentinel 1 drone is my newest project. It is a fully autonomous drone with telemetry. What does that mean? It means I can fly it by remote control OR/AND it can fly a pre-planned mission going to any waypoint or locations that I choose. GPS coordinates, altitude, and the speed between each waypoint can all be pre-programmed OR changed during mid-flight by simply clicking on a google map location the drone will fly to the new location. At that location you can tell it to loiter, or circle the area even train a camera on a specific target. When the mission is complete it returns to the takeoff zone and lands all on it’s own!

Ok, it’s not all working yet and thanks to many open source projects both hardware and software, this project is mainly a collection of parts, ideas and concepts from others all pulled together.

I am hoping to get a 2-4mile round trip range! Not sure if I am close to achieving that yet but it certainly has more power and much faster at climbing and forward momentum than I expected – hopefully not to the detriment of battery life!

I plane to add a few more features: a fully automated “releasable” pin that can hold a platform to carry payloads or can be activated to drop/release an object. The platform is planned to carry a few beers or a Wifi Pineapple (an automated wireless hacking platform – also open source). The platform will also be able to carry, or I don’t know maybe a bottle rocket and ignite the wick on command 😉 —– SO MANY POSSIBILITIES!

My inspiration for this project? Daniel Suarez author of Daemon, Freedom and his newest which I did not read yet Kill Decision which is about a future of swarmed drones!!!


  • Aluminum Frame w/ Fiberglass platforms
  • ArduPilot APM 2
  • GPS
  • Magnetometer
  • Barometer
  • Sonar
  • Gyroscope
  • Accelerometer
  • Optical Flow Sensor
  • 4 Turnigy Speed Controllers – 20amp
  • 4 880kv Turnigy brushless motors2 – 4500Mah 3S Battery (Fly with 1 while charging the other)
  • Turnigy 9x 2.4ghz  9 Channel – hacked to add backlighting and usb to flash with custom firmware
  • Telemetry via 900mhz xbee modules – 3 miles range? – Replaced with 433mhz 3DR Radios – So far no bricking and flawless connectivity!
  • 1.3ghz 800mw Video transmitter / Receiver  3-5 mile range?
  • Video 1/3” CCD – Switching to Gopro Hero HD
  • USB Dazzle DVD Recorder

The Build:

Sentinel 1 is now in it’s 2nd revision with changes to the landing gear and lowering of the center of gravity. Wiffle Balls are being used for landing gear and so far have proved very robust!

Tuning and then more tuning and then more tuning is the key/pain! I am would get things fairly stable and all the parameters tuned and then need to make a structural change and have to retune all over. Mix that in with a few flight and then a crash… then a few more flight and another crash and it takes some time!!!

The Experience:

I have also ran into problems with the XBEE’s getting bricked at least every 5 flights if not more frequently. Although it is correctable, it’s a pain and ends your time slot that you planned to do the tuning. I always feel like “just one more tuning session and I am ready to go to full autonomous testing” and then bam, boom, bang a new delay…

However, after some patience – it all came together! I have now had several successful flights with flawless execution. RTL, GeoFence, Stable mode, Basic missions, auto landings are not perfect. I also recently flown my first test mission with a full 12once can of “beverage”! A complete success in it’s first attempt!

At this point my confidence is up and all has worked nearly perfectly for many flights!

But then….  I have been tuning this for months and adjusting my configuration. Spread the electronics out a little onto the arms and removed the 3rd level tray and cleared off the 2nd level tray so there was nothing on it. I cut some of the ribs out of the 2nd level tray so the GPS has a nice clear shot up. Got tired of breaking the 3DR legs, so I moved to using wiffle balls as landing gear (works awesome – and you can see it better).

I finally had Sentinel 1 (the quad – what you don’t name yours?) tuned. GREAT Loiter, Alt Hold, very stable flight, basic waypoints followed and a solid return home. Auto-Landings never work that great for me and I still like to take control for landings…

I setup the Geofencing. Tested it and it seemed to work well enough doing a RTL when it hit the boundary. I flew a beer can around and all was pretty flawless…

It was around 7:00pm. I began to fly Sentinel 1 fairly aggressively – a little more than my skill set should have let me. I ended up getting it higher and farther in the in the sky than I wanted to be. GeoFence – where did you go??? So I hit RTL like I have done in the past. Only Sentinel 1 decided it was going on a journey of it’s own… It went up higher and higher, while I lost all orientation to which way it was facing. Now to add to the fun — Warning, Battery at 9.2 volts! it was about 200′ up and 1,500′ away! Oh Oh!

I could not get the perspective right and flew it farther away – I switched to stabilize, then loiter and back to RTL – Ahhh good RTL seems to work — 1,947′ feet AWAY!

Warning Battery at 5.8volts! OH NO!

At that point it starts coming down – by the way, over a VERY thick forrest area into a valley. .500 mile away! Warning Battery at 4.7 volts – as it drops below the horizon and disappears into the background view of the mountains and trees into a valley…

I check, and still have a telemetry connection. I then rip through the logs, grab the coordinates, look at the altitude -41′? And see that the quad is very tilted – around 80 degrees…Tree?

I jump into the car and enter the GPS into my iPhone – which keeps correcting to the nearest street! 3 miles by road to then do a 800-1000′ hike to it’s location in the woods. But now it’s getting dark… I get to the location and install a better GPS app for this mission on my phone. I head into the woods with 4 people – hunting for Sentinel 1 – we yell his name, but no one answer – batteries are now dead.

The woods were so thick after 100′ in, that it was dark in there, very dark… Looked for 30 minutes and had to give up! It could have been 5 feet in front of me and I would not have seen it…

Went home and waited for daylight – and waited, and waited slept for 1 hour.. and waited, and waited… what a long night.

Got up at sunrise and headed out with Sentinel 1 – Recovery team Alpha! We brought the Jeep so we could drive further into the woods…

We swept the area and found the exact GPS coordinates – it has to be right here!

AND THEN HANGING IN A TREE ABOUT 10 FEET IN FRONT OF ME – My favorite white wiffle balls appeared! Hanging from a tree branch about 10′ from the ground was Sentinel 1.

The woods were so thick there that you could only see an opening in the sky about 10’x10′ and that’s it, the rest is canopy… How lucky I was…

I give him a hug, carry him to the car and bring him home. A quick inspection, then I put in the new battery — AND IT ALL WORKS! NOT EVEN A BROKEN PROP!!!


Take-aways — DO NOT fly beyond your experience level – do not get over confident – and remember this is experimental – eventually something will go wrong!

Fly safe my friends!

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