De-spaghettify your craft with MPX connectors

29. May 2014 15:05 by outbackuav in

I you are like me you hate spaghetti.  Not the stuff you eat but the stuff that fills all available space within your fuselage.  There's a lot of solutions out there including one that simplifies conncting several servos in the same spot.

These little guys have 6 poles - so that's VCC, GND and 4 servos or anything that can share the poer and ground planes.

Careful when soldering though, the plastics is soft and melts easily.  The trick is to plug them into eachother when soldering to keep the pins aligned even if things get a bit overheated.

My Bixler has a nifty all-in-one FPV pod which has two connections - a 12V JST and one MPX connector for pan, tilt, APM telemetry data (for the OSD), 5V and GND.

Soldering: no more stage fright

15. May 2014 13:39 by outbackuav in Hardware, Posts

I used to hate soldering, now I love it.  Sometime in the early eighties I tried to make a Centronics adaptor for my Sinclair Spectrum microcomputer.  The soldering was horrible and it never worked and not long after I plonked down $3,500 for an IBM PC clone with two floppy disk drives and no hard disk.  The ESCs in my planes probably have more CPU power than that PC.

My main problem was that YouTube hadn't been invented yet.  Now there's many good soldering videos there, like the ones made by Dave Jones of EEVBlog fame and Bruce Simpson (XJet):


My suggestions are:

  • Get the right gear: if you can afford it, a temperature controlled iron is a must.  It stops your flux (and your work) going up in smoke.
  • Soldering iron tips - use the right size and shape for the job
  • Helping hand: very useful unless you have three hands already
  • Pre-tinning: essential for a good bond
  • Chemist glasses: the best $2.50 ever spent!  I only need the weakest ones but they make a huge difference
  • Start simple with things like cables and battery connectors, leave the micro servo mods for later

When I got my ArduPilot it was of course the cheapo version from RCTimer - which required soldering the pins.  I was terrified of destroying my new $70 baby but it was all over in about 20 minutes.  I almost wished there was more to do.

Trivia Corner:
Why don’t Americans pronounce the ‘L’ in soLder?  Is it the French influence on American English, like the way they say “herb”?

Adruino Controlled Brushless Motor Test Stand

13. May 2014 11:49 by outbackuav in Hardware, Posts

I've tested a few motors using my HobbyKing 7-in-one watt meter to learn the whole which prop/ESC/motor/battery thing.

There's some good videos on this topic notably Ed from Experimental Airlines who did and exhaustive study with some kitchen scales and a watt meter.

Being lazy I wanted to avoid the onerous task of actually writing down numbers and enlist the Arduino to do it for me.

Having done a few Arduino projects I thought an automated test stand might be fun to try.  I'd never output PPM from an Arduino or read from current sensor but how hard could it be?

The main difficulty was outputting the right values for arming, you need to go from something the ESC recognises as low throttle, to high, then back to low.  I tried a few things to work it out including hooking up the ESC to my servo tester to see what the PPM values should be.

Main Components

I did 4 years of woodwork at school so it should have been better than this


Just an Uno I had lying around, no special shields but I have a proto shield that I might use to tidy up things and get rid of the breadboard.

Current sensor

Spare one from my Bixler build - from RCTimer I think.

Thrust sensor

I had an old Phidgets force sensor but I discovered it isn't accurate.  It's intended to just sense force, not tell you how much.  I ordered a some sort of strain gauge on eBay and it never arrived - that's $3.56 I'll never see again.  I have an old kitchen scale that I'm planning to tear down and use if I can find a measurable analogue voltage on it.

In the meantime I've used a spring from and old desk lamp and a slider pot to give a fairly good thrust measurement.  I calibrated it by hanging a cans of beans from it - isn't science wonderful!

Temperature sensor (eventually)

Pointed at the motor to record heating.  This could be good for endurance testing but a high amperage supply from the mains might be better to eliminate battery fade from the results.

.Net Application / Firmata

After feeling a bit confined by the Adruino code limitations and slowish code upload speeds I discovered this excellent bit of code called Firmata which allows you to control a connected Arduino from, in my case, a C# application running on a PC.  I was able to do a lot more (e.g. funky-town user interface including graphs) and luxuriate in object-oriented goodness.

I'm sure that once I learn a bit more about Arduino scripting (or is it sketching?)  I'll be able to structure my code a bit better an dpossibly use a little LED display shield although I do like the graphs.  I might have to investigate using one of those OLED shilds that have the resolution for graphs.

Basically Firmata has a library/DLL that you can call to do inouts and outputs on the Arduino.  Firmata handles the rest - as far as your .Net application is concerned the action is happening locally.

A solution in Visual Studio runs the motor and record the results.  It arms the ESC then steps up the motor incrementally and records the current, voltage, thrust and one day the motor temperature at each step.  Gunna get to grips with GitHub so the code is available.

User interface


The Arduino and breadboard, the breadboard isn't essential, just convenient for connecting the test stand.

Things to Do

  • Make a smaller, neater frame
  • Make a prop guard
  • Do a video
  • Clean up wiring, make Arduino shield
  • Make quick release system for motor
  • Upload the code
  • Spreadsheet creation, Excel, Google Docs, comparison site
  • Vibration sensor?


  • Safety first!   Either make a prop guard or wear eye protection.