## RC Fireworks Ignition System

Hi there 🙂

It's been kind of a while since we published the last article. Actually the topic of this one is pretty cool and can be used for many purposes such as mole hunting 2.0 :D.

So everything started with an idea. A simple idea. "Hey! we should drop fake bombs from our R/C plane!". Then, "Hey, smoke would look great on this R/C plane!", and finally, "Hey! We should launch fake rockets from our R/C plane!" (and yes, we are grown up people with employement... 🙂 )

We started doing it by hand, firing the smoke and the firecrackers with matches just before to take-off. It was nice, but we had to hurry and we could not decide on when the smoke/firecracker should be launched.

# The principle

After looking on the Internet for automatic ignition systems, we came up with our personnal DIY system, which, while not perfect, gives pretty neat results!

There isn't that many options to automatically light a firecracker's wick:

• We can use the principle of a lighter, that is, having an embedded tank of flammable gaz, a system to generate a sparkle, and an automatic valve.
• Or we can use a thin steel wire and put a large current run it so it would become incandescent.

The first solution would involve a too complicated system for the sunday DIYers that we are. Also, we were not sure how it would behave with all the relative wind there is on a plane. We decided to adopt the second method.

To have a reliable and effective ignition system, the key is to reach a temperature that would effectively light the wick, but not TOO hot in order not to destroy the wire or even the plane's battery.

# First version

#### The coil

So we started by using a wire that came from a stranded wire (itself coming from an old computer power supply unit). We took 3 or 3 strands, twisted them, cut around 10cm (4inches) of it and shaped it as a coil around the wick. then, we put our protective glasses, gloves, and put the power. the coil instantly melted, ligthing up the wick! So it worked 🙂

#### The switch

We only had to find a way to put the power when the plane was in the air. That was a tricky question because in an R/C plane even if you have a very powerfull battery that can provide 300 or 400W easily, you still need a switch that will withstand this kind of power. But in a plane you also have the PWM output of servos comming from the R/C receiver. Several solutions here : the most aesthetic one is to buy/design an electrical relay that is triggered by a channel of your R/C controller. but as I said, we where in a hurry to make this plane in the air, so we opted for the most epic switch ever: a servomotor with hot-glued wires on it that make contact when we trigger a channel on the transmittor. Effective, very ugly, that was perfect!

So it worked like this for a few flights, with the obligation of crafting a new coil for each successful ignited firework. kind of boring after a few ones... So we decided to improve a little the system.

# The improved version

#### Basic physics..

I had some steel wire remaining from an old project (a hot-wire cutting table to cut airfoils out of foam blocks). I knew that it could become very hot without breaking by experiment it back then. So we first got some wire, and measured the electrical resistance per meter which was around 10ohm per meter. Let call it Rw.
The resistance of a wire is proportionnal to its length. So we have:

By experimentation, we also knew that a power of around 100W would do the trick : it's enough to provide very big sparks, but not enough to damage the battery and to reduce the autonomy of the plane. So to calculate the length of the wire we need, it's really easy physics :

it's a simple resistive circuitry, so we have the famous

Also the power consumed is given by

Injecting the ohm equation gives us

We inject the very first equation giving us

Only very basic math and physics here. Applying it to our problem gives us (the average voltage on a plane that is flying with mid throttle on 3S is 11V).

#### On the Bixler...

That is a neat result because it allows for a small enough wire to be shaped as we want to make it easier to lock the wick. We decided to cut it in half and put it each side of the Bixler's wing. We cut a can and glued it to protect the wing from the rocket's projections. We also doubled the circuitry with 2 switches to have another ignition system to light up smoke 🙂

Here is an amazing video demonstrating the rockets and the smoke bombs, it also features some night flights with the Bixler 2!

## T-Rex 700L Dominator

Hey there !
It's been a while since the last article... So let's talk about something big this time. something really big. REALLY. The T-REX 700L Dominator, a class 700 (rotor size of about 1.6m, 5kg) helicopter made by Align. If you remember, I started to fly helis with an other Align helicopter, the T-REX 450 Sport V2. We remember beeing very afraid of it when the rotor started to spool up for the first time. Let me be clear, this T700 has NOTHING to do with it.

So, from a technical point of view, this 700 heli is the most advanced version of the T700E, first 700 electric heli made by align of this side. It features the last upgrades of the frame, BL815H and BL855H brushless servos, the 800MX Align motor, a Castle Creation 120A ESC and the DFC rotor head. The stabilization control is done by the new GPro controller (formerly known as 4GX)

The Cyclic BL815H brushless servomotors

The huge 800MX Align motor.. A real monster !

The built is really straighforward and you just have to follow the manual :). Beware to threadlock all the metal-to-metal screws and VERIFY it's well locked ! I crashed because a servo screw became loose... 🙁

The frame beeing assembled

As I said, it comes with the latest "inovations" from Align, so you have two helicoidal gears wich make a really nice sound once in the air 🙂

Close-up view of the motor and servos

Tail and servo tail

View of the implentation of components

As I didn't have (still don't) a High Voltage receiver, I had to think a little about electronics in this bird. This is the wiring I used to power the servos with HV source (2S lipo = 8.4V fully charged), and feed the receiver with a safe 5V.
Electronic wiring

The BEC component is actually in the T700L Dominator kit, good point for Align (again) :-D.

Tail assembly details
One word about the CC 120A ESC. When using lower head speed (<1800RPM), the CC tends to get very hot (above 100°C). This can lead to the destruction of the device. I wanted to put a 1500RPM head speed at first but changed my mind after seeing that. 1850RPM works fine for me. As you can see in the next picture, I put the controller on the rear of the frame, which is excellent in terms of heat because we have a giant propeller above it that helps to cool it down 🙂

Setting the GPro up is really a piece of cake, we can see Align really cared about the ease of use for this device. It comes with a free software for PC, Android and Iphone users! Note that for the phones, you have to buy a BlueTooth device separately.

GPro unit

As I could expect, it flies REALLY well, and the FBL head is quite amazing at all head speeds I tried (from 1500 to 2100).

## The tricopter

Hi everyone!

We have been pretty busy since we got our Ardupilot and setting it up was so easy and fun that we decided that it could be fun to get another multicopter with a  "ready to fly" flight controller, so we would just have to take care of building the frame ! We decided to build a multicopter and use it with a cheap multiwii board from hobbyking 🙂

As great as the Ardupilot is, we didn't want to pay 180$again for a flight controller, and we thought that this time we didn't need a full fledge controller, with GPS and telemetry; just something to have fun with. So we started to look for a cheap multiwii board, and we found "the one" on hobbyking: the Multiwii 328P flight controller. The price of this thing (28$...) is actually pretty insane, and I would recommend this board to anyone who would like to work with IMUs, to track motion and position, not just to power a multicopter! Just plug it into your computer, launch the Arduino IDE, select Arduino Duelmilanove 328 in the board list and you're ready to go! We definitely should have bought something like this when we started to work on our quadcopter, it woud have been so much cheaper than buying the sensors separately and would have avoided so much troubles with soldering/ fitting everyhting on a tiny PCB !

We decided to build a tricopter because we always thought that their flight behavior seemed really nice and we wanted something a bit smaller and a bit more nervous than our quadcopter. Our quadcopter was a pretty standard one, with arms 25 centimers wide, a good size to get stability and space to carry a GoPro and a FPV setup. We decided to make the tricopter is a bit smaller, with motors 20 centimeters away from the center of the tricopter triangle and to use the same Turnigy SK3 1130kv motors as on our quad. They work great and we had 3 motors left, so no need to buy new ones ! And with these motors, the tricopter would have enough power to carry a GoPro 🙂

While we took the "hardcore" approach with our full carbon quadcopter, designing it with CATIA, cutting it with a CNC mill, the tricopter construction was quite the opposite. It took us just a couple of hours to build it from scratch with no real plans. The hardest part was the rear servo mecanism, as it always is with tricopters.

Everything is made of carbon fiber, so it's pretty lightweight and power efficient. We get more than 11 minutes of flight with a 2200 mAh 3S LiPo battery.And it flies very, very well. Tricopters are very fun to pilot, there behavior is really close to an Heli behavior, it kinds of floats in the air and vertical descents can be very fast and stable. The yaw control is obviously much stronger than on a quadcopter so it can be maneuvered easily in very small areas. It carries a GoPro and its case without any problems, so we think it's the perfect toy to play with if you want to film withou stabilization nor FPV!

If you are considering building a drone, you should really consider building a tricopter. It may be harder to figure out how to handle the yaw servo, but it's so fun to play with! Go for it 🙂

A little video where we used the tricopter (80% of the footage)

Stay tuned for more fun with drones and other things 🙂

## New videos/ photos. When a drone goes 250m high

Hi everyone!

I created a new album on my flick'r account : Drones and stuff. I will try to update it frequently with pictures of everything we do 🙂

We also posted 3 new videos on Youtube:

A FPV flight where we reach 250m of altitude with our quadcopter

A peaceful flight near Saint-Benin, France.

A little "ad" for multicopters 🙂

More to come soon 🙂

## The octocopter

We recently built a brushless gimball for our Gopro but our quadcopter became too heavy to fligh safely, so it was time to get something bigger. We first thought about a nice hexa, but we couldn't resist to the appeal the octocopter. We wanted to get enough power to carry a lightweight DSLR such as my 550D, or simply all the FPV equipment we have, plus our Gopro on its brushless gimbal; all of this with a 10 minutes autonomy.

It all went so fast. Add to cart. Pay. Bam, it's delivered. We chose this time not to build the frame ourselves, just to put everything together, and have fun.

We bought this big and cheap octocopter frame from Hobbyking, the X930. The arms are in aluminum and the rest of the frame is made with pretty thick glass fiber.

[notice]THE MOTOR MOUNTS ARE VERY WEAK.[/notice]

If you look at the comments on Hobbyking's website for this frame, you will see that many people (including us) broke several of them while flying. So don't even try to fly with them, they will eventually break. We reproduced these motor mounts in aluminum with our CNC and mounted them under the original ones to get  rock solid motor mounts.

The Turnigy 910kV motors provide plenty of power to lift anything you'll throw at the octocopter. They are controlled by 40A controllers (Turnigy Plush 40A), which are fed by an octocopter power board.We use two 3S 5000mAh batteries in parallel to reach our desired autonomy.

Be careful with this board, it is only certified to deliver 8x10A, which is really low (our motors can take up to 35A). We chose to add a lot of solder on the PCB in order to increase the amount of current it could deliver and it seems to be working fine so far.

We flashed our Ardupilot with the latest octocopter firmware and tried to find the best PID values for the octocopter. It does fly pretty well now but there is definitely room for improvement.

We'll try to fly FPV with it as soon as we can with our new new brushless gimbal (article to come 🙂 ) and we will obviously post videos of it here and on YouTube on our channel.

We'll be back soon 🙂

## The Ardupilot Mega 2.5 : why it's awesome.

After a good run, we decided it was time for our homemade quadcopter controller board to go. Actually, it had to. It started to wobble in the air pretty violently for no reason while flying. We made no change to the program, nor touched the hardware, and since it was working fine before, we figured that it probably came from an electronic problem somewhere in the tons of wires and soldering we made. Pretty hard to "debug"...

So here we were, on 3D Robotics website, ready to click the famous "Add to cart" button. And we finally did click, after a long time of hesitation. It was not that long, in fact. It was a no-brainer. For 180$, you get a tiny assembled PCB with an accelerometer, gyroscope, magnetic sensor, pressure sensor, GPS, current sensor, with completely open-source software that will let you do basically anything you could want to do with any kind of RC model. Not only this works with quadcopters in + or X configurations, it's also made for RC cars, planes,hexacopters, Y6 copters, octocopters, tricopters, and even helicopters! 180$ seems pretty cheap now, doesn't it? 😉

We don't regret having spent so much time on our controller board at all. It was a great experience, it worked pretty well and got us to understand pretty much everything about how these drones fly. We just couldn't make something so small and so well designed ourselves in our garage. Plus, the huge community working on the Ardupilot's software came to something close to perfection, with a dedicated windows program (APM mission planner) that can control every single parameter of the drone, communicate with it in flight via a telemetry module, prepare mission scripts with GPS waypoints and actions to take, read flights logs and export them into Google earth-friendly KML files (and more)!

We ordered the fully assembled APM 2.5 with a Mediatek GPS, and a current sensor. It also delivers with a USB to micro USB cable so you have everything you need to start playing 🙂

It turned out very easy to setup on our existing quadcopter frame. We followed the instructions given on the arducopter google code project and everything went smooth and fast! The steps are the following:

1. Download mission planner and install it (it will also install the Arduino mega drivers on your computer)
3. Start mission planner
4. Choose from the drop-down list the COM port you APM has (check Windows Device manager to find which one)
5. Go on the firmware tab, select the one you want to use, upload it!
6. Press connect and you're ready to configure everything!

The default parameters should be fine for an average quadcopter frame (50cm wide, ~1200kv motors, 1kg). At least they are okay for flying. We lowered a bit the PIDs on ours because it was a bit too nervous but the first flight was still pretty good and the stability in the air was quite amazing, even with high winds!

You can assign any action you want on your radio extra switches and knobs. The most impressive one obviously being the "Auto" mode, where the quadcopter will follow a script of actions the user can write with the mission planer software. Just flick a switch, sit down and let the drone take off, fly to the waypoints you told him at the altitude you told him, and then land where you told him.

Flying has never been so easy! 😀 Also, it is really, really nice to have the return to launch (RTL) feature, which will bring back the drone where your armed the motors. It is a life saving feature, for those of us who put expensive cameras on their drones and don't want to crash them in case they lose the orientation or the video signal when doing FPV. It actually happened to us in one of our first flights. We were about to test the RTL feature when the drone was so far that we couldn't see its orientation anymore. We were already thinking about the "walk of shame" we would have to take with the broken pieces of our beloved quadcopter. But none of that happened. We flicked the RTL switch, and the drone came back home 😀 This feature really is a must-have! It's awesome and works great. We've only played with it last weekend, and even though it was a pretty windy weekend here, we managed to fly up to 80 meters with no problem whatsoever for the drone!

If there should be a conclusion to this article, it would be : buy the Ardupilot. It's great, works with everything, has a big developer community around it, and is actually not that expensive when you think about all the electronics it contains.
We just ordered the telemetry and OSD module so we can go all FPV on it 😉 We are definitely going to play our quadcopter in the weeks to come, and will try to add a nice video to this article (or to a new one) to show you what you can do which such a powerful tool 🙂

## Flashing a Turnigy 9x with an Arduino

Don't you think those programmable transmitters are really expensive ? Well here is one solution to this problem : If you already have an Arduino, some wire, a soldering iron and a litle bit of dexterity, you can have a complete, highly customizable transmitter !

Indeed, some awesome guys made new firmwares for the "well known" Turnigy 9x (a low cost 9 channels transmitter, about \$60). Even better, those projects are opensource and free. What else ? Ok lets start this little hack.

There are numerous projects (TH9X, ER9X, GRUVIN9X, ERSKY9X,..) and the choice is up to you. I personnaly used Open9X because it seems to be the better easy-to-use/fonctiunalities ratio. But before talking about software, lets discuss the hardware. The problem is, how to send the new firmware to the radio ? Actually this is where you'll need to solder a little. It can be pretty scary, but it's not that hard if you have a good iron ;-).

[important]If you purchased a "9XR" version, there is no need to to this hack since it's already done in factory ![/important]

Ok you said goodbye to your beloved radio ? Let's unscrew it ! Note that on mine the screws were really hard to unscrew, and I had unfortunately to destroy one of them. Once i'ts open, you'll first be like "WTF am I doing?". Actually, it's pretty simple. First thing you have to do is disconnect the connector that goes from the front part to the back part. After this you'll be able to separate them. On the front part, locate a "big" chip. It's the heart of this radio, the ATMEGA64. Pretty simple stuff, actually. It will be easy to reflash thanks to the AVR isp (In-System Programming) protocole. You'll just have to add the wire to be able to use that protocole.

You'll need 6 wires for the isp protocole :

1. MISO (Master In Slave Out) known as PDO (Program Data Out) on the chip
2. Vcc (5v)
3. SCK (clock signal)
4. MOSI (Master Out Slave In) known as PDI (Program Data In) on the chip
5. RST (Reset)
6. GND

You can figure out by yourself were you should solder those signals reading the ATMEGA64 datasheet (pin n° 2,3,11,20,21/52, 22/53) but I'll give you a simpler way to solder it : Actually the designer of this board were cool guys, the little pads you can see can be easilly used as entry point to solder your own wires.

Pretty easy, isn't it ? I strongly recommend you to make an interface to the outside of the radio because there are several softwares that allow you to customize your model on your computer and then transfert the result in the radio memory, using this protocole. I personnaly used a DB9 connector. but you can use whatever you want (it must have at least 6 connections). The better place to put this connector is under the radio so your hands won't be disturbed.

Ok you can now close your radio (don't forget to plug the 12 wires connector). Try to turn on your radio. If it works, lets go to the next step!

# Turn your arduino into a AVR programmer

From here, you can use every AVR programmer you want that is compatible with AVRDude (that is, almost every programmer, actually). But I hadn't one and I knew that the Arduino could be used as one. Here is basically the schematics you want (leds are optionnal but strongly recommended. Also, the PCB should not be really hard to design and make).

Note that the reset is tied to Vcc to prevent reset when connecting the Arduino.

Double-check your connections between the ISP and the ATMEGA64, if you don't want to buy another 9X 🙂

The Scketch to upload to the Arduino is located under the examples as "ArduinoISP". This is actually an implementation of a subset of the "STK500" protocole  (learn more here), and therefore you'll be able to use it with Avrdude (which is nice because that's what we need to easilly flash our 9x !).

Pin assigment is given in the sketch :

// pin name:     not-mega : mega(1280 and 2560)</div>
// slave reset: 10        : 53</div>
// MOSI:        11        : 51</div>
// MISO:        12        : 50</div>
// SCK:         13        : 52</div>


[notice]

Because of the ATMEGA64 EEPROM address managment, you have to make 2 modifications : when reading the EEPROM and writing the EEPROM : the code looks like it :


uint8_t write_eeprom(int length) {
int start = here * 2;



and


// here again we have a word address
int start = here * 2;



You have to delete the "*2" since the address is already a byte in the ATMEGA64.

[/notice]

# The Firmware

Just install the Companion9X software that will do everything for you. Just change your programmer option under Burn/Configure... and enter the following :

(The Port is the port representing your Arduino)

Ok, time to flash ! You can download whatever version you want and try all those wonderfull firmwares !

I hope this little tutorial has been usefull for you 🙂 Stay tuned !

## Crash T-REX 450

Hi all ! As we're enjoying a very bad weather for a few weeks now, i'll use this time to share some pictures of my first crash with the T-REX 450. This one was due to the big distance of the heli and a grey sky (I lost the orientation). The crash were pretty bad mostly because I panicked and forgot to stop the engine.. Any way 40€ latter it was back in the sky !

As you can see, the main shaft was bent pretty hard..

All the broken parts..

Stay tuned !

## The T-REX 450 filmed by our quadcopter

We tried for the first time to fly together and that was pretty cool, until Benoit crashed the T-REX... Never forget the idle-up when looping with a collective pitch heli 🙂

For some copyright reasons, you might have to go on youtube to see the video....

We'll surely try again really soon with our soon coming FPV kit 😉

## Align's T-REX 450 Sport v2

Ok, so after flying with our quadrirotor, I wanted a machine capable of doing a more aerobatic flight. So I started looking at CP helicopters. A CP (Collective Pitch) helicoptere is a particulare type of heli that is able to independently move its blades. For instance, the two blades can take a positive pitch which will sustain the helicopter in the air, or it can give a different pitch (Called cyclic pitch) regarding the position of the blade, to make the helicopter move in a particular direction. See this Wikipedia page for more informations about it.

So, after a while, I decided to buy a class 450 heli (rotor diameter around 700 mm), mainly because of the low price of this class and also for the ease of use (and also, it's less dangerous than a 700 with a rotor diameter of 1m50 !). I bought the TREX 450 Sport V2, as the Align brand has a really good reputation among the Internet.

The box arrived 10 days after shipping, and my first impression was : that's a very tiny box !

Everything inside this box is tidy.

Let's open all those sub-boxes, to discover that there is a significant number of parts 😀

One great point with this kit, is that it comes with the electronic (motor, ESC, servos) and i had to add my newly converted to 2.4Ghz Eclipse 7.

Let's now have a look to the assembly. I knew what to expect here has I read a lot of things on the Internet about it. Clearly Align masters the subject and the assembly is really straightforward.You just have to follow the manual. Don't forget to double check if the pre-assembled parts are well threadlocked.

This is clearly a masterpiece, it's beautiful and there is no backslash. the only (related) problem is that the links are tight so you have to lapp the plastic screeds. Here again, it's really well documented on the Internet. On the pictures, you may have noticed that I inverted the main shaft. Be careful or you'll have a big backslash between the frame and the head.

Let's now have a look on the carbon frame assembly.

Nothing to say here, just follow the manual :-)Oh, just, don't threadlock the rear screws (where you insert the tube) as we'll need to loose it to put the tube and adjust the tension of the belt.

Let's focus on the AC assembly. Almost nothing to do here for me as it was well locked from factory.

A little word about the main gear : to adjust the backslash between the motor and the main gear, one tip is to insert a piece of paper between the teeth, so there is around 0.1mm between them, as given by Align.

Last part of the job before the adjustments : the electronic. Just screw the servos, make them horizontal when the TX is at neutral, and it's done ! Also put a little strip of foam between the frame and the gyro to absorb vibrations.

Annnnnnd it's done : it took me two days to do it, but it was the first time I did it ! I think I would take 5-6h now to assemble it again.

Later we'll talk about the first flights, maintenance, and the first crash I had after 50 flights ! Stay tuned 😉