Sunday, October 30, 2011

Some MultiWii links

Got the Arcticopter IV put together with the MultiWii, but couldn't get the MultiWii Conf to talk to the board.  Have to check with Andreas to see what's up with that.

Here's a few links.
Stick Controls
  • lower-left: disarm
  • lower-right: arm
  • lower-left / down: gyro calibrate
  • lower-left / up: accelerometer calibrate
  • up / up,down,left,right: accelerometer trim
Setup Notes

  • sticks should be 1095 / 1500 / 1905 low / mid / high

LiFe battery in Turnigy 9x

 Here's how the 1500 mAh LiFe fits into the Turnigy 9x transmitter.
 It uses the servo-style connector.  From the left, it goes black-red-empty.  I put a sticker in so I won't forget it.
There's plenty of room inside the battery compartment.  I put the wires on the right side.  The cover fits on very easily now!

GoPro FPV Setup (cables)

Output cable is: 2.5mm 4-pole jack
From inside, connections are: ground, video, audio, unused
yellow: video with shield (ground) , white: audio with shield (ground)
connecting to servo plug:

  • two grounds together, to servo black ("ground")
  • video, to white/bronw ("signal")
  • audio: to red ("power")

Two versions of off-the-shelf cables from ReadyMadeRC:

Nice tutorial from RCTestFlight:

Friday, October 28, 2011

The Servo Database

Truly the Internet has everything!  Everything you ever wanted to know about servos.

Wednesday, October 26, 2011

APM carrier for Hawk Sky and related planes

Inspired by the new Bixler Accessory Chassis on diydrones, I thought I would tidy my own setup and make my own adaptation for the Hawk Sky.  I haven't quite finished it but it looks promising enough to write up, and I think something similar would work on other models with a front hatch.

I cut the horizontal top plate using the opening as a template.  I just cut the cardboard "close enough" and then traced the opening directly onto the cardboard.  I used scissors for the cutting.

 I then did the same for the forward and rear risers.  I attached the three pieces with epoxy.  I positioned the pieces on the plane and then spread the adhesive on the front and back joints.  I used enough so that the joint didn't need any extra reinforcing.  Note that the fuselage opening bends down towards the front.  I attached the top plate to the front riser in such a way as to keep the top plate level.
 I tried a couple of different ways to attach the APM.  What eventually worked best was a cardboard carrier  bent to the appropriate size and hot glued to the top plate.

I cut some holes to run wires, see the ABC lights, and reach the reset button.  I attached the xbee and GPS on the top plate with velcro.  I didn't make a GPS mount like diydrones did; if I have reception problem I will do so.
 I uncased the Turnigy 9x receiver both to save weight and get clearance for the battery.  I replaced the standard 3-wire connectors with single wire connectors.  Later I'll get the rectangular 6-way connector and use that instead of multiple single wire connectors, but it doesn't seem to be a problem for now.
 The unit sits on top of the battery.  With the receiver case removed, there's just enough clearance for the 3S 2200 mAh 15C battery.  I velcroed the reciever on the bottom and hang the antenna wire out the side.  That's roughly equivalent to what I've been doing and haven't had a problem so far.  I provided some strain relief for the antenna by hot gluing it onto the board.
AUW for the unit with velcro is 13.3g. Still to do:  put some magnets to hold everything down, velcro or otherwise attach the APM to the lower carrier, and attach the pitot tubes.  I'm hoping to attach the tubes to the carrier if I can.

I'll update later when I've applied the finishing touches and gotten the thing into the air.

Spherical flyer from japan

Amazing spherical flyer from Japan Defense Dept.  350 grams, 42cm diameter, made from off-the-shelf components costing about $1,400.  Hobby King, get busy!

Saturday, October 22, 2011

Thursday, October 20, 2011

Sugru: repairing DX6i charger port

Another note to Sugru about repairs.  This to my DX6i where the charge port had busted loose.

Here's a simple, unglamorous repair that saved me time, money, and the expense of being without a radio transmitter that I use frequently.

The battery recharging port had worked its way loose, due to a crack in the groove that holds the connector in place.  It's a standard sized connector that's available at any local electronics
store, but it turns out this particular piece is a nonstandard size and can only be replaced by sending the unit in for warranty service.

I was actually opening the case each time the unit needed to be charged; in addition to being inconvenient, I was worried that the wires attached to the case would undergo more stress than they were designed for and might work their way loose.

I considered using epoxy, but then the connector would be permanently bonded to the case, and if it ever went bad I would have even more work to put things right.

The sugru worked perfectly; the connector is held very tightly and resists the pressure when the power cable is attached;  and if I should ever need to remove the connector, the Sugro can be easily scraped away with a small blade.

The work took about 10 minutes including opening and closing the case, and I let the Sugru cure overnight before testing, so I didn't have any downtime related to the repair.  I didn't bother making it
pretty since (a) there wasn't a lot of room for my fat fingers, and (b) with any luck it will be many years before somebody has to look at the inside of the case again.  I guess if it ever gets stolen I'll have the perfect identifier -- my fingerprints permanently embedded inside the case!

And the package of Sugru was so much cheaper than the shipping cost of returning the unit to the manufacturer (via tracked mail) I'm money ahead as well!

Thanks again Sugru, you've saved me time and money!

Sugru: repairing macbook feet

I recently bought a package of Sugru.  It's neat stuff and I'm happy with the results, so I sent them a note and picture to their gallery, and reproducing it here.

For some reason I seem to be pretty hard on the plastic "feet" on the bottom of my macbook pro.  I've busted three of them right off and the fourth was looking pretty dodgy.

So, I popped the fourth one off and replaced them with sugru feet.  I used one package of black sugru, divided it into five equal pieces and reserved one piece for an unrelated repair. The remaining four pieces I shaped into chubby "coins" the same size as the original feet.  Underneath the feet the case is open to the inside, and I wanted to be careful not to fill up the guts of the computer by squishing the Sugru through the holes.

Using pressure around the edges gave a nice convex surface and ensured a good bond with the case, in addition to keeping the Sugru on the outside of the case.  After it looked like all the feet were pretty equal, I put a bit of soapy water on a flat tabletop and set the computer down for a second or two to make sure everything was level and the unit wouldn't rock.  I turned the computer over to let the Sugru cure.

The Sugru is working much better than the original plastic feet. In addition to being a lot more sturdy, the grip of the sugru on a desk or tabletop is excellent.

And as a bonus, my macbook pro got much quieter!  I had not realized how much of a loud hum the disk drive made with the missing foot.

Thanks Sugru, I don't know what else would have worked so well!

Tuesday, October 18, 2011

What's a "400" size motor?

I've seen this specification mentioned many times and couldn't ever find out exactly what it meant.  A quick query on rcgroups and all has been revealed!

Here's the original Graupner Speed 400. It was one of the original brushed electric motors when they started to be introduced.

Sunday, October 16, 2011

DragonPlate Carbon Fiber

These guys look like the Leonardo Da Vinci's of the CF world... every possible formulation of CF: sheets, rods, trusses, tubes, core sheet goods, with a gorgeous mirror finish.

Friday, October 14, 2011

Motor Balancing

Not just props, you should balance your motors too:

EasyStar upgrade

(Oldie but goodie... I typed this in and didn't publish)

Here's some notes from Andreas on some mods he has made to his EasyStar.  (It's interesting how we met:  he lives about 5 minutes away from me in our little town; he dropped me a note after reading a comment I had left on  I've worked with one of his old neighbors for almost 10 years!  It's a small and crazy world!)
  • To really make the Easystar fast, you need a brushless motor, esc and lipo. I just used the equipment from the first helicopter I wrecked. Original propeller fit too. With that power I can fly in any wind with no problem. Performance similar to this rocket.
  • This is a full mod-project but I did not find any structural re-enforcement necessary:
  • The Easystar's rudder is too small. Especially once you add more power. I found this credit card trick the simplest and very effective.
  • All hinges should be replaced with real plastic hinges instead of just bending the foam.asdfa
  • Also the center of gravity is often too far aft, even on stock EasyStar. Must add enough weight on nose to make it controllable. So I think it can lift a lot of weight (FPV, more electronics for your autopilot etc).

Update:  I've done all these and they make the EasyStar a very nice flyer.  I changed to a Hawk Sky for the ArduPilot platform.

By The Numbers: LiFe batteries

Lithium Iron Phosphate (aka LiFe, LiFePo, LiFePo4) batteries are most often used in RCLand for transmitters.  They're safer than LiPo, since they don't emit oxygen during rapid breakdown leading to combustion.  Lots of chemical detail on wikipedia.

Here's the model that fits into the Turnigy 9X transmitter.  Use the servo-style connector to plug it in.  Note that there are two ways to plug it in: only one of them works; the other doesn't do anything.

Charge Levels

 1S   3S
3.3   9.9  nominal voltage
2.8   8.4  minimal discharge
3.6  10.8  maximum voltage


You need to set your charge into LiFe mode.  Don't charge in LiPo mode. Bruce has a video here that explains how to do this on a standard 4-button charger. Here's the tldr for a typical 1500 mAh 3S:

Save Data / 01 / LiFe / 9.9 / 1500 / (hold start) / 1.0 / 9.9 / (hold start)
Save Data / pgm number / LiFe / voltage / mah / (hold start) / charge current / voltage / (hold start)

Thursday, October 13, 2011

xbee causing odd servo jittering in APM?

Here's an odd thing that happens in my office.  I haven't noticed it happening in the field.
  • when powered up, the servos constantly jitter
  • jittering seems to be going through the APM... note the period of time when APM is booting and jittering stops
  • jittering associated with 900MHz xbee
  • if the xbee is disconnected, no jittering
  • if I ground the xbee by touching the antenna, jittering stops

I'm curious as to the cause of this; partly to see if there's a problem, fix, etc, but mostly to understand what's going on. The primary practical issue is that the jittering noise seemed to make people nervous as they were looking at the unit.

update:  It seems to be noise from the radio.  There are quite a few postings on this in the diydrones forum.  Applying a ferrite ring on the cable between APM and xbee seems to be the recommended fix.

Wednesday, October 12, 2011

Xoar Props -- big and wooden

Xoar International has really nice big wooden props.  They've got a placeholder on their site for multirotor props.  The OMStudios MikroKopter is using them.

Nice airbrushing

rcgroups maven hance has a nice way of airbrushing superflys.  Cut a template like this, move the two pieces apart, and you can use one piece as a mask for the other.  Check out the article, it's got two ideas for how to use this, with a bonus pic of the charming Mrs Hance!

Tuesday, October 11, 2011

FTDI and AVR cables

Here's a quick brain dump of the differences between FTDI and AVR programming cables.

  • Arduino things use the FTDI adapter.  FTDI is basically a serial/usb converter. 
  • FTDI is a company, their main product is a serial/usb chip.
  • The Arduino boot loader has code to handle the ftdi loading process.
  • Shown is the Solarbotics FTDI basic breakout.

  • The KK Board is more hard-core, non-arduino, "pure" atmel.
  • AVR programmer is used to "flash" the on-board chip memory, like writing an eprom.
  • If you want to take an atmel chip and make it into an arduino chip, you would use an AVR programmer and flash the arduino boot loader.
  • Likewise, you use an AVR programmer to flash the kkboard software onto the atmel chip.
  • Daddy87 has a great tutorial here.

  • "Name brand" AVR programmers are, ironically, more expensive than the HK KKboard .
  • But, lots of cheap vendors on ebay, all based on the open-source hardware design of Thomas Fischl:
  • This one is from ProtoStack.

Sunday, October 9, 2011

cheap lightweight battery for Night Vapor

 One of the things I love so much about my night vapor is how light and floaty it is.  Turn the throttle down, you can't hear the motor, and it just effortlessly glides across the room.

Of course, a lot of this is due to its light weight.  17g AUW with the supplied 70 mAh battery.  Unfortunately, extras of this battery are $5.50 + shipping, and when I originally ordered I think it was closer to $8.00!  So of course, everybody buys the cheaper, larger batteries.
 But, that adds another 2-3 grams to the AUW.  Still it's a fine flyer, but just a little bit more speed is necessary to keep it in the air, and just a bit of the floatiness is lost.  I can compare this out the Concord Model Engineer's indoor fun fly, where a couple of other guys have night vapors.

So, when I noticed that Hobby King had cheap single battery cells, I thought I would try to make my own.
 Here's exactly what I used:

Total cost for 3 batteries: $5.50, $1.82 each.

I've never worked with raw battery cells before, so I was a bit nervous.  It turned out to be no problem... just keep in mind that you're working with a live circuit, don't touch wires together, don't short the tabs with a screwdriver etc.

The battery tabs take standard solder.  I snipped and tinned my wire, and then tinned the battery tab, leaving a proper sized blob to attach the wire.
I then put the cell flat on a piece of wood, and lined the wire up.  Touching the soldering iron to the wire allowed me to mash the wire down onto the tinned tab, making a very nice solder joint.

On two of the cells I make a straight solder joint, so I had the shrink tube on the wire as I soldered it.  Because of this, the wires were a bit longer than I liked... extra weight, and I was worried it might not fit in the plane very well.
 So for the third try, I flipped the wire around.  This is the top battery in the first picture.  This produced excellent results:  the wire was a lot shorter, it ran alongside the battery, and I was able to put the shrink tube on after the soldering, since I could just slip it over the tab and wire, heat it, and trim.

I think I'll resolder the other two cells in the same way.

[update: solved the charger problem using the 1S extension wires from Hobby King.]

 Mini Plug Extention for Micro Battery 10cm (5pcs/bag)

 When soldering, be sure and do one side completely (all the way up to shrink tubing), and you'll have a lot less chance of shorting the battery tabs together.

The completed battery is too fat to to fit nicely in the holder, but a bit of blue tape holds in on nicely.  I might a a tiny bit of velcro as well.  When I flew it for testing, there was a bit more tape than what I'm showing here.
The batteries fly perfectly; slow and floaty behavior restored due to the low weight, and the 20S discharge gives a lot more power.  The original 70mAh cells don't have a discharge rating, but the replacement eFlight 150s are rated at 12C.

I didn't test relative flight times, coz I was pushing the testing between a couple of other activities.  I'm guessing it will be comparable to the original battery, but I'll try it later and update this post.

I've misplaced my little subgram scale, but using my big scale show the following weights:

  • Turnigy 138, 5g
  • Parkzone 150, 4g
  • Original Parkzone 70, 2g
  • These replacements, 2g (I'm assuming the 3rd one was a bit less and would show it on the higher precision scale)
But, using my big scale, the the plane's AUW including the battery drops from 17g to 16g (with no battery, it's 14g).  So, it seems that these replacements are lighter than the original, and could get even a bit lighter if I were more aggressive about trimming the wire.

They fit on the charger nicely... line them up and poke them in with your fingernail,  pull them out by holding on to both wires (not the battery body) when finished.  Note that I have to tip up the third battery to get it to fit into the solder.  When I redo the others, I'll solder on the other side of the battery (if possible?) so that the batteries won't have to be tipped up; but it doesn't seem to be enough of a problem to resolder the one that's already made.

Update: Figured out how to eliminate the shrink wrap.

Turnigy 9x Trainer Mode

Here's some notes on setting up two Turnigy 9x radios in trainer mode.  Thanks to Miki for asking about this and training new RC pilots!

I'll type in a few quick notes now; I'll try to borrow my friend's 9x, take some pictures and maybe a video of trainer mode in action.


  • We'll use "teacher" and "student" here;  The other common terms for this are "master" and "slave".
  • The teacher radio is in contact with the plane.
  • The two radios are attached with a 1/8 inch mono male-male jack.  Student radio turns on automatically when attached.
Student Radio
  • In new model 9x's (the ones with a single antenna), there is a circuitry problem that blocks the trainer port.
  • The simple way to fix this problem is to pop the module out.  The antenna connection is soldered to the main board, so be a little bit careful.  You have 2-3 cm of loose antenna wire.
  • With the module disconnected, the trainer port is active.  I think it's ok to operate in this mode, just tape the module so it doesn't fall out and break the antenna wire.
  • Another solution, but more work, is to solder a resistor into the circuit.  I have not tried this yet, but have my notes on this page.
Teacher Radio
  • Turn on trainer channels [menu / func setting / trainer].
  • You can turn on all controls or just some.  It might be useful for teacher to keep control of the throttle, for example.
  • The settings are confusing.  I will probably make a video, but I think you want to set Off/On mode. When in that menu, pull the trainer switch and you should see the mode switch.
  • In most radios, you pull the trainer switch to allow student control, and let go of trainer switch for teacher to control.
  • Turnigy 9x is opposite!  Must hold trainer switch for teacher to control.  Use this method for mechanical reverse.
Simple Summary
  • Eject the module from student radio.  Tape it down so it doesn't break antenna wire.
  • Make sure "Reverse" has same settings on both radios. [menu/func setting/reverse].
  • Set trainer mode on teacher radio.
  • Attach mono cable to both radios.
  • Test all controls to see if reverse is correct on both radios.
  • Fly!

Saturday, October 8, 2011

Quad Dome from Electronic Goldmine

Looks like these might be nice for a quad hat; also available in red, if you like that HAL look.  Sales page says:

Green See-Thru Super Quality Acrylic Dome-The Electronic Goldmine:

"These domes make great additions to small robots. They are large enough to mount sensors, small circuit boards, LEDs, lamps, etc. underneath. Each dome is 2.83" in Dia. plus a .5" mounting lip. The highest part of the dome (at the center) is about 1" tall. These were made for large projection TVs and came in to us in sealed master cartons so they are in perfect condition. Green See-Thru.

Nice rule of thumb for COG testing

mikeruth @ rcgroups:

A general rule of thumb is on a calm day fly the plane upright and trim it out for straight and level flight at a moderate speed.
Then roll over inverted and see if you need to put down stick input in and how much. This is the tell tale sign of your CG.
3d planes typically will roll over and fly with no input and or climb becuase of the reward CG settings we like for 3D flying.
As you move the battery back, it's going to take less input or in my case require holding some up-stick just to stay level since I like a very tail heavy setup. 

Friday, October 7, 2011

Monday, October 3, 2011

XBee APM Overview

Got the XBee soldered and tested, but forgot to link to the video. Doing that now, and leaving this as a placeholder for all wisdom XBee.

Sunday, October 2, 2011

Oddness in APM mission planner KML conversion?

version: APM Mission Planner 1.0.69

KML export seems to add some spurious locations pointing to an incorrect location.

If you look at the attached google earth screenshot, you can see there appears to be some spurious points in the data path.  The points all go to my house, where I generated the file.  Perhaps APM has set that as the new HOME location and some of the logfile points are relative to HOME?

First test of APM auto mode: Drone Status Achieved!

Hooray!  Finally got the xbee assembled and tested... still seems somewhat miraculous to be logged into to a computer flying around overhead.  Went with Andreas and his friend Reto, (an old schoolmate visiting from Switzerland -- they did their robotics project together), to the park to try fully automatic flight controlled by waypoints.

Had some initial difficulties connecting the xbee.  It turned out that rebooting the vmware windows session on my macbook fixed that problem.  The pre-cached map tiles worked well.

Shiny laptop screen + Full Sun = invisible.... will figure out some boxy thing to provide some shade for the screen.

Video cap of part of the flight is attached below. The waypoints are wrong. Be sure and save the waypoints to a file after you fiddle with them if you intend to play back the log files later.

The main goal was to get the unit in the air, and exercise all the modes.  All of that worked and we finished up with everything intact, so we considered it a great success... Hooray!!

Still need to hook up the magnetometer, pitot tubes, and battery monitor.  But it seems things are so far going not too badly!  Also need to do:  hook up APM to the simulator, build APM from source and fly that.

Notes on reflashing ESC firmware

A couple of random notes about this.  The firmware mentioned is good for multicopters as it supports a very high update rate.  The code is fast, can support a prop speed of 120,000 RMP... yikes!  On the thread, someone notes "Finally that annoying 8kHz whine from the motors is gone, and motors are very smooth."

Very light power distribution

rinatka at rcgroups has an idea for light-weight power distribution for this setup: plush 6a, 18-11 2000kv motor, 5x3 prop.

3/32 styrene tube good for Vapor repairs

ungn at rcgroups has this note on using 3/32 styrene tube for vapor repair.

Build a cheap Champ?

Somebody at rcgroups mentions that you can build a Champ from parts and save some money over getting the complete kit.  Here's the parts page at wholesale trains and my best guess as to the parts needed.

$ 2.99 150mAh 1-Cell 3.7V 12C Li-Po for Ultra micro helis...
$ 1.99 Propeller with Spinner(130 x 70) for Champ, Hobbyz...
$ 2.99 Decal Sheet for Champ, Hobbyzone, HBZ4913
$ 3.99 Main Landing Gear for Champ, Hobbyzone, HBZ4918
$ 7.49 Main Wing for Champ, Hobbyzone, HBZ4920
$ 3.49 Pushrods with Accessories for Champ, Hobbyzone, HB...
$10.99 Gear Box with Motor for Champ, Hobbyzone, HBZ4930
$ 5.99 Complete Tail for Champ, Hobbyzone, HBZ4931
$37.99 Fuselage with Electronics for Champ, Hobbyzone, HB...

Update: Veccstr and leethetreeguy shows the smallest purchase to build a champ:

HBZ4952 - Fuselage with Electronics for Champ, Hobbyzone, HBZ4952 - $37.99
HBZ4920 - Main Wing for Champ, Hobbyzone, HBZ4920 - $7.49
PKZ3907 - Tail Gear Set: UM J-3, Parkzone, PKZ3907 - $2.71
HBZ4931 - Complete Tail for Champ, Hobbyzone, HBZ4931 - $5.99
(skipping main landing gear and prop)
TOTAL: $67.17 shipped to my door.

Some small JST and Molex connectors

From jj604 on rcgroups.

12V DC power stepup module

Input DC 3.5V~10V, output 12V, 1.5A (2.5A max), 26Watt
$5.75, listed here on bay from vendor coldfusionx.

Vendor: ReadyMadeRC

Specializes in FPV.  Good source for Sky Surfer, aka Bixler, and associated parts.