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31  Community / Bar Sport / Re: What's with the response to Sandy's victims ? on: November 25, 2012, 12:24:08 am
I'm amazed at how right wing the world is becoming
32  Community / Bar Sport / Re: What's with the response to Sandy's victims ? on: November 13, 2012, 10:57:29 pm
I'd rather have killer storms than killer bushfires...

I'm down in the city and I hate it, but I still go into panic mode for a second when I get a wiff of smoke.
33  Topics / Robotics / Re: Wheel encoder interrupts on: November 13, 2012, 10:31:30 pm
I'm thinking we all need to replace our breadboards or flush them with IPA every now and then!

Been chasing a weird problem that ended up being caused by intermittent contact with a damn pullup!!
34  Topics / Robotics / Re: Wheel encoder interrupts on: November 13, 2012, 03:45:13 am
Why bother with the quadrature encoders?
Just look at one of the outputs from a wheel, you already know which direction it is turning from when you send your move commands.

I was trying this with my Rover 5 chassis and gave up, looking at the 2 outputs from each wheel on the CRO the pulses where pretty close together.
Thing was actually counting pulses per distance traveled, it was no more accurate looking at both outputs than just counting on a single output.

Thing is we are talking about measuring distance traveled, not which direction the wheels are rotating.
35  Community / Bar Sport / Re: Your MOST painful accident/event! on: November 08, 2012, 09:13:37 pm
another one I remembered,

walking along a main road that borders a golf course, I got hit on the side of my knee by a golf ball, 150 metres from the tee.
I thought I'd been shot with a .22, made the same noise a round makes when it hits a rabbit, that and it hurt like hell.
Guy saunters up, says,
"Seen my ball?'
After slight pause,
"Uh, yeah, sorry I hit ya"

And walked away
36  Community / Exhibition / Gallery / Re: Navigation Calculations for Arduino GPS on: November 08, 2012, 08:57:46 am
I was using a topographic map and went to a local trig point, that's government survey data.
But, when I compared barometric altitude, a Freescale MPL115A1, it was pretty close to what the EM-406 read.
To calibrate the MPL115A1, I went over to the Kuitpo AWS, went online, checked the current barometric pressure.
Standing next to the AWS the barometric altitude read the same as the map, as did the EM-406.

I mainly went to that effort because the MPL115A1's temperature reading was and still is, way off.

With my Android tablet, the altitude was spot on, but that uses cell towers to get better data.

Both the Android tablet and EM-406 speed readings are pretty good, I used a straight bit of road and a stopwatch between "mile" posts to check that.

37  Community / Exhibition / Gallery / Re: Navigation Calculations for Arduino GPS on: November 06, 2012, 09:33:21 pm
after a "few" beers I had a go at driving the quad, at night, with my android tablet and the navigation app.
without cell tower assistance I kept "bumping" the verge, with, it was "slightly" better.
not something I'd recommend at speed or if you wanted accuracy.

working out levels for contours in the paddocks seemed to be better, the altitude is way more accurate than position, as is speed.

side by side comparison with the tablet and an EM-406 on an Arduino was interesting, after logging kml files, then plotting them in google earth showed some weird effects of the non-military gps units.
38  Community / Bar Sport / Re: Your MOST painful accident/event! on: October 28, 2012, 10:25:05 pm
Re: Model aircraft propellers and adjusting mixture

Remember when using a PUSHER PROP the airflow will pull your sleeve through, not blow it back.
39  Community / Bar Sport / Re: For Sounding Balloons or Red Bull Stratos: Why not use hydrogen over helium on: October 25, 2012, 09:06:05 pm
That's gung-ho! Making your own hydrogen with zinc and HCl is way more dangerous than getting a cylinder of gas.

When I've built hot air balloons, we've chased them for over an hour, retrieved, refilled, relit and relaunched them!
Some of them covered over 80km in a single flight.

As I mentioned in another thread I've been working on a tiny glider controlled with an Arduino.

Now I live in the city again I've had to stop development for a while, that and summer/fire ban season is here again.

But next winter...
40  Community / Bar Sport / Re: For Sounding Balloons or Red Bull Stratos: Why not use hydrogen over helium on: October 24, 2012, 04:03:18 am
Back when I still had a model aero diesel engine, I was mixing fuel, 20% castor oil, 70% methanol, 10% ether, I knocked over the ether, mopped it up with a rag, left the rag on the bench...

After a while I was feeling a little "funky" and a goof I know open my shed door just as he lit a fag.

I remember this whoosh and boomph, buuga-lugs got blown across the yard and the walls of my shed has a distinct "bow" to them.

Got my first radio control a bit after that and sold my control line engines that couldn't be upgraded to have a throttle.

All the diesels went...
41  Community / Bar Sport / Re: For Sounding Balloons or Red Bull Stratos: Why not use hydrogen over helium on: October 24, 2012, 01:41:58 am
you have to wonder what concentration her bottle of bleach was!

On the turkey farm we used "Oxonia", a mix of 33% hydrogen peroxide and 33% peracetic acid to clean, sanitise and dissolve crud in our drinker system.
That was nasty stuff, even diluted 25:1 it burnt skin and you couldn't wash it off.
The guy who owned the place set fire to a paper water filter with it!
42  Community / Bar Sport / Re: For Sounding Balloons or Red Bull Stratos: Why not use hydrogen over helium on: October 22, 2012, 02:40:56 am
Back in high school, the fire brigade came to refill and test all the extinguishers.
One of the firemen put a few inches of water in a bucket, then gave the inside of the bucket a long burst out of a CO2 extinguisher.
Then got me to touch the surface of the water.

The big fat spark that got me REALLY hurt!!

That was when he told us about the dangers of using a CO2 extinguisher on flammable liquids, gas leak fires or fine powder fires.

This is why you won't find CO2 extinguishers in grain silo's, grain elevators or flour mills.
43  Community / Bar Sport / Re: For Sounding Balloons or Red Bull Stratos: Why not use hydrogen over helium on: October 21, 2012, 08:58:36 pm
I still think this is part of the "bad press" hydrogen got because of the Hindenburg.
Has anyone seen a documentary where a JPL engineer first put forward the theory about the Hindenburg's "skin" as a possible source of it's demise?
Canvas, doped, with iron oxide on the inside and aluminium on the outside, can anybody spell "thermite"?

People were allowed to smoke on the Hindenburg, they just were not allowed to use a naked flame to light up with.

 
44  Using Arduino / Networking, Protocols, and Devices / Re: How do I go from one point to another? (GPS used for my AVG) on: October 21, 2012, 12:18:48 pm
This is where I got my formulae

from the site
Quote
Local, flat earth approximation
If you stay in the vicinity of a given fixed point (lat0,lon0), it may be a good enough approximation to consider the earth as "flat", and use a North, East, Down rectangular coordinate system with origin at the fixed point. If we call the changes in latitude and longitude dlat=lat-lat0, dlon=lon-lon0 (Here treating North and East as positive!), then

       distance_North=R1*dlat
       distance_East=R2*cos(lat0)*dlon

R1 and R2 are called the meridional radius of curvature and the radius of curvature in the prime vertical, respectively.

      R1=a(1-e^2)/(1-e^2*(sin(lat0))^2)^(3/2)
      R2=a/sqrt(1-e^2*(sin(lat0))^2)

a is the equatorial radius of the earth (=6378.137000km for WGS84), and e^2=f*(2-f) with the flattening f=1/298.257223563 for WGS84.

In the spherical model used elsewhere in the Formulary, R1=R2=R, the earth's radius. (using R=1 we get distances in radians, using R=60*180/pi distances are in nm.)

In the flat earth approximation, distances and bearings are given by the usual plane trigonometry formulae, i.e:

    distance = sqrt(distance_North^2 + distance_East^2)
    bearing to (lat,lon) = mod(atan2(distance_East, distance_North), 2*pi)
                        (= mod(atan2(cos(lat0)*dlon, dlat), 2*pi) in the spherical case)

These approximations fail in the vicinity of either pole and at large distances. The fractional errors are of order (distance/R)^2.

I took the Micromega examples and changed the great circle method to the one above.

45  Using Arduino / Networking, Protocols, and Devices / Re: How do I go from one point to another? (GPS used for my AVG) on: October 21, 2012, 12:14:52 pm
Try this site

http://williams.best.vwh.net/

I'm using a Micromega FPU V3 with my GPS/Arduino, so none of my code will do you any good here.

Here is the link to the aviation formulae

http://williams.best.vwh.net/avform.htm

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