Saturday
Sep152012

GoPro Vibration Dampening using Moongels.

I have been messing with the quadcopter lately and since rebuilding it from the last crash, I decided to take more measures to eliminate or at least dampen some of the vibration I have been experiencing on the GoPro camera.  First I dynamically balanced all the props using a laser from the idea I found on flitetest.

This helped out however I was still getting more vibration then I would like.  I recently heard an idea on thecrashcast podcast where people were using Moongels to dampen vibrations.  Moongels are a product marketed towards drummers who want to eliminate some of the excess ringing on their drums.  I decided to give this idea a try.

I must confess,  I lied took the cheap way out as I didn't use use actual moongels, but rather used those sticky toy things you often find at grocery stores in the front where they have all the candy/toy dispensors for kids.  As I understand it, this is the same material used in moongels.

Here is how I did the assembly.  Meet Roswell,  Roswell is going to sacrifice himself for the better of FPV video everywhere...

 The next thing I did was to make a separate plate to hold the gopro mount itself, I then sandwiched the pieces of the toy between the new plate and the plate on the quad.  I also noticed the buckle for the go-pro had more play in it then I would like, so I used some small pieces of electrical tape to make it fit tighter...

Here is the finished result ready to fly!

 

Lastly, the results.  I made this before and after video to illustrate the difference.  I feel this improved things greatly,  see for youself...

 

 

Friday
Aug172012

Arduino Speed Test

Just for funsies, I had this idea in my head to try to see if I could measure how fast the Arduino Uno can process a very simple loop of code using an oscilloscope. For this experiment I wanted to toggle a pin on, then turn it off while turning another pin on, rinse, repeat.  Basically toggle 2 pins off and on opposite of each other.

For the first part of the experiment I wrote the following code...


void setup() {   //Setup routine (runs once)
  pinMode(5, OUTPUT); //Configure I/O pin 5 as an output
  pinMode(6, OUTPUT); //Configure I/O pin 6 as an output      
}

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(5, LOW);  // turn off pin 5
  digitalWrite(6, HIGH); // turn on pin 6

  digitalWrite(6, LOW);  //turn off pin 6
  digitalWrite(5, HIGH); //turn on pin 5
}

 

The code above ensures that neither pin is on at the same time as the other.  Using the Arduino's digitalWrite commands, I had to use a line of code to turn one pin off before I could turn another on.  Here is the screenshot from the scope,  the yellow signal trace represents pin5 and the blue trace is pin 6.  The measurements displayed are for the channel associated with Pin5.

 

 

So a few interesting take aways,  the maximum frequency is ~51kHz, I feel this is rather slow considering the Arduino is running at 16MHZ.  The other interesting point is the +Duty% is roughly %25, this makes perfect sense considering the code is 4 parts and pin5 being only represents 1 out of the 4 lines of code, so the math works.  The last thing is the massive overshoot, the waveform peaks at 6.6V and undershoots to -.4V.  This seems extremely "loose" considering it is supposed to be 0-5V.  I am running this board off of 12V power supply but the Arduinos onboard regulator should regulate the operating voltage down to 5V, so I am not sure what to make of this.

Moving forward, I read a chapter in the "Arduino Cookbook" that explains how to set digital pins directly by accessing the bare metal on the chip via its hardware registers.  I have read that this can lead to speed increases by as much as a factor of 30.  So,  I decided to run the experiment again.

With this new code, being as I was manipulating the hardware registers directly, I no longer had to "waste" a line of code to turn a pin off,  I could toggle the states of up to all 8 pins on PortD on or off with a single line of code.  Here is what the new version of the above code looks like.

 

void setup()
{
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
}

void loop()
{
PORTD = B00100000; //Sets the output of ALL pins on PortD (0-7) to LOW except Digital Pin 5
PORTD = B01000000; //Sets the output of ALL pins on PortD (0-7) to LOW except Digital Pin 6
}

 

 
And here is the new waveform...

So here we have some expected and unexpected results...  First, the speed has dramatically improved,  The measurements indicate a 1MHz frequency.  This was predicted, it works out to be about 19.5 times faster than the previous code, although I am disappointed that a 30x speed increase wasn't realized.  What I did not expect is the uneven duty cycle of the 2 waveforms.  Pin6 stays on 87% of the time while pin5 is only on for the remaining 13%.  This represents the state of the 2nd (and last) line of code in the loop.  My only thought is the MCU needs time to "Rewind" back to the beginning of the loop.  It actually seems like this requires about %75 of the total time to accomplish this in this example.  Were talking roughly 800nanoseconds (or 800 billionths of a second / .000,000,800 seconds), so in most use cases this is negligible.

 

Perhaps if I knew assembly, even more fun could be had, but for the time being, this will have to suffice.  Hit me up in the comments below to let me know what you think.

Saturday
Aug112012

Solder Reflow Experiement

I've been working with SMT soldering for a while now, and up to this point I have been using a conventional iron to hand solder componenets to the board.  I have read about various reflow techniquies used in mass production and most of those use solderpaste or wave soldering techniques.  Wave soldering requires specialized equipment, so for my purposes this is inpractical. 

If I had a decent volume to assemble I could use a solderpaste/stencil technique and do my "pick and place" by hand.  However for the small 1 off type projects I had a thought.  An idea popped into my head on how I could do reflow soldering without dealing with messy solderpaste or special (expensive) equipment.  I decided to test this idea out,  the video below is the results of this test, enjoy.

Thanks for watching.

Sunday
Aug052012

H-Quad: A new way to think about quad-copters.

I have been working on building up an H-Quad.  For all intents and purpose, an H-Quad is no different then a regular Quadcopter in Xconfig, except it has a larger center section to mount loads of electronics.  I finally have just about everything mounted that I would want on it (lights coming).  So now it is just a matter of optimizing it for longer flight times.  There are still many bugs to workout, but I am very pleased with how this bird flys.  Here are a few pictures and video of it in action.

 

 

 

Saturday
Apr142012

Tricopter

So a few people have been asking me about my tri-copter and "how did you make that?"  or "where can I get one".  So I am going to put this little post together to talk about that. For those unfamiliar with the Tri-copter project, here are a few YouTube videos I uploaded of my successes and failures...

 

 

 

Now,  generally there are 2 types of people,  there are those that want to seriously pursue the hobby and are looking for an entry point.  This post is intended for that person.  It is a challenging and sometimes frustrating hobby, but it is also very rewarding as well (just like any hobby).

If you just want a toy on the cheap to casually fly around, walmart & other stores sells cheap little helicopters that will basically fly themselves and have everything you need in the box that range in price from $50-$100.  These are typically of the counter-rotating coaxial kind.  The self stability these machines offer sacrifices mobility, however there are many that recommend even those that are serious out trying the hobby first start with one of these out just to see if it's something they like.  Here is a link to an example of one of these.

Now on to the serious stuff.  Unfortunately when I built my tricopter it I did not document a proper build log, maybe I will at some future point.  My tri-copter is based heavily on the FPV Manuals Delrin Tricopter kit and David Windestål of rcexplorer.se Tricopter designs.  I highly recommend checking out both of those sites as they are the core of my design.  The tri-copter itself can be built pretty cheap depending on how much of a Do-It-yourselfer you are.  If you are a beginner and don't have access to a machine shop or CNC machine (or a jigsaw and an afternoon) I recommend getting the Delrin kit.  This adds $100 to your build costs, but the quality of the kit is top notch.

Here is a photo of my tricopter...

 

So assuming you have decided on what you are going to do for a frame, the parts I used are as follows.  Each item will be a hotlink and I will list the prices.  Another thing to consider,  if you are new to the hobby, you are going to need a transmitter and a lipo battery charger.  I will post a few recommendations below as well.

------------Main Components------------

                                                   Motors (3 Needed):  Hextronik DT-750  $11.60 ea,  $34.80 for 3

                              Speed Controllers (3 Needed): Turnigy Plush 18amp $11.90 ea,  $35.70 for 3

                         Batteries (as many as you want!):  Turnigy 2200mah 3S $8.99 ea

                             Yaw Servo (1 Needed):  BMS-385DMAX Digital Servo  $20.48 ea

Propellers (3 Needed, good idea to get extras):  GWS EP 10x4.7 6-pack  $4.82 ea

                      Brains (1 Needed):  Hobbyking Multirotor Control Board    $14.99 ea (need to be reprogrammed for tri-copter mode)

      Boom Arms, These are just home depot 3/8" Square Wooden Dowel:  $ .98 for 36" length

 

------------Parts Needed to Wire everything up------------

                                                        Turnigy 25mm heat shrink (for escs)   $ .75 ea

                                                                      4mm heat shrink 1 needed:  $ .35 ea

                                                       16AWG Wire RED (3 Meters Needed):  $1.29 ea,  $3.87 for 3meters

                                                      16AWG Wire BLACK (1 Meter Needed): $1.29 ea

                                  10cm Male to Male servo leads 10pack (1 needed):  $4.75 ea

                                                           XT60 Connector 5 pack (1 needed): $3.19 ea

                                                               Battery Strap 3 Pack (1 needed): $4.90 ea

                                              420mm Servo Extension 5 Pack (1 needed): $2.88 ea

                                        Bullet Connectors for ESCs 10 pack (9 needed): $1.59 ea

                       Zip ties (these break a lot get a few packs they are cheap: $ .65 ea

 

Optional: Turnigy BESC Programming Card: $6.95  This is not required, but it will make programming the ESCS a LOT easier,  without it you will likely mess it up (I know I did!).

 

 

Ok, so that is everything I can think (excluding tools such as soldering iron, etc) of you will need to build a tri-copter.  If you are new to the hobby, then this means you probably don't have a transmitter or battery charger.  You will need both of these.  The good thing about these is, a you progress in the hobby to flying other things these will still be useful.

------------Radios------------

I present these to give you an idea the range of products on the market...

Low End Spektrum DX5e Radio + 1 Receiver:  $99.99 (Decent radio, but I don't recommend because it is missing some key stuff you will want as you grow in to the hobby (such as Expos)

High End Spektrum DX7e + 1 Receiver: $299.99 (Decent starter radio,  has room to grow into advanced features)

Even Higher End: Spektrum DX8 (No Receiver included): $349.99

Best (In My Opinion): Futaba 10CHG (Includes 14channel Receiver) :  $619.99 (has a lot of features, probably the last radio you will ever practically need/want to buy)

Insane (The last radio you will ever need to buy) Futaba 18MZHL: $2999.99 (And Yea,  I do not have one of these, lol)

 

------------Battery Charging------------

The odd thing with battery chargers is that most are designed not to be plugged in to the wall, but to be hooked up to a 12v car battery.  This is due to the origins of this hobby being gas planes that you had to take out to a flying field.  Out in the field there is usually no where to plug in.  So if you want to charge these at home then you need not only a battery charger, but also a 12v power supply for the charger.  Here are a few ideas...

------------Chargers------------

Hobby King 10A 6 Cell Charger: $32.96

Hobby king 4x6 Charger: $69.99 (Charges 4 batteries at once)

Here is hobby kings full product line on chargers

 

------------Power Supplies------------

20A twin 12V Power Supply: 29.99

 

What I am using is about 10+ years old,  and has been working great.  There are better options on the market, but I will link my setup for those who are curious.  Certainly do your own research.  As with anything read the reviews..

------------My Battery Charging Setup------------

Power Supply:  Power Force 13.8V Power Supply (No longer sold as far as I can tell).  Here is a picture..

Charger: Poly Charge 4   $87.99

LiPo Balancer Interface (Required for charger that I have): $34.99  4x $139.96

 

So that is basically the rundown of my setup and all my thoughts on what is required to go from nothing to being started in the hobby.  It is impossible for me to cover every question or topic in this one post, if you still have questions or need help, feel free to reach out to me via the contact page or comments below.  Thanks for reading.

For more reading, here are some of my favorite sites.

ILoveFPV

RCExplorer

FPVManuals

HobbyKing

HorizonHobby

FPV Lab (Forums)

ILoveFPV (Forums)

YouTube.com/flitetest