Thursday Miscellanea

Some nice airbrush tutorials on RCGroups.  Be sure and look at the first three posts.  More here.  And a store-bought checkerboard stencil.

Cheap GPS hackery here. Very interesting, and it can save on some projects.  Ebay searchage for "U-blox PCI-5S" and "GPS Ceramic Internal Patch 1575.42MHz Antenna 20x20x7mm" about $15 combined!

Servo City has some nice pin crimpers.

Arduino Power Management here.  Using the JeeLib to access the Atmel low level sleep functionality.

Disabling the built-in GPS on APM 2

Andreas sent me a note pointing me to the procedure to disable the APM2 built-in GPS.

tl;dr: the disable pin is adjacent to GND.  Short them with a solder blob.

An interesting GPS guided vehicle.

From LetsMakeRobots, an interesting writeup with lots of code and explanation.

Idea: ArduPilot Differential GPS

Update


Fail... lots of people have thought of this idea and it won't work.


Executive Summary

• Hook a GPS to GCS.
• GCS calculates GPS difference.
• GCS transmits GPS correction over xbee MAVLINK connection
• ArduCopter Stabilize mode gets very fine resolution.

Background

I was just reading the ArduCopter 2.0 docs and saw this:

The quad should stay in a 4-5 meter diameter "circle" around the target position.

I recalled an old TV show where somebody used differential GPS (hereafter DGPS... is that a common name?) to track glacier movement... they had DGPS receivers planted across the ice, and a DGPS transmitter attached to rock.  I recall being impressed that they were able to get 1-inch resolution.

I googled around for DGPS products -- wouldn't it be neat if you could just buy something and have your ArduCopter hover with that kind of resolution! -- but found out a couple of things:

• DGPS seems pretty common in the GIS world.
• the definiton of "highly affordable" DGPS systems was about $15k.  Yikes!
• "portable" DPGS receivers were touted as being easy to carry around by a single person.
• DGPS seems to work by sending the sideband correctional signal over some kind of modem.
• "normal" GPS receivers won't benefit from a DGPS transmitter.

Idea

So, I had an idea for implementing DGPS in the ArduPilot/ArduCopter world.

• Hook up a GPS unit to your ground control station (GCS).  This could be any GPS unit... You could use a hand-held receiver with USB, make a custom arduino-based unit, etc.  The purpose of this unit is to be near the GCS and feed a love GPS signal of the GCS's current position.
• When setting up the GCS, allow an absolute current position to be entered.
• Add a MAVLINK message outbound from the GCS to the plane(s), broadcasting the difference in measured and specified absolute position and altitude.
• When in stable mode, the ArduPilot software takes the DGPS correction into account if it is available.
• Super Precision Stable Mode!

Bluetooth GPS Logger

On Ebay, labelled as "GBTGP-38KM 65CH Bluetooth GPS Receiver+Data logger".

"a high-tech product combines the advanced Bluetooth technology and GPS technology. Through, Bluetooth technology, you can receive and storage GPS data through intelligent mobile phone, PDA, laptop and desktop. Can be used for location,navigation,read the history of track records, and other applications."