Friday Once More

Once more it’s Friday again. Time to do a recap of the week.

Nothing much this week. Having classes, preparing for exams next Monday. Something very interesting about old plane technology. The 747 and older planes were designed well over 30 years ago. During those times, computers weren’t invented yet and some planes were still using valves.

The autopilot system is one of the most advanced system in a plane. It controls the attitude of the plane as well as providing automatic navigation through waypoints on the ground and a whole lot more. So these systems require a lot of inputs from gyros, static ports and pitot probes. These inputs need to be processed mathematically to produce a correct response. But without advanced electronics (processors) they have to find other ways to make those calculations.

One very interesting example is the conversion of a value to it’s logarithm. They actually use an eccentric cam to make the conversion! The value to be converted is fed as a rotary signal to the cam. When the cam rotates, it moves a cam roller and the cam roller’s movement will represent the log of the input! The diagram below will make the explanation clearer.

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Ps is calibrated altitude, which is converted to log Ps using the log cam.

Looking at the diagram above, the symbol on the right of the cam shows a differential synchro. There are 2 inputs and 1 output in this synchro system. Depending on the connection between the synchros, they will either add or subtract the input and the result will be fed to the output in the form of rotary motion! Addition and subtraction are done using mechanical means!

There is another type of synchro called the resolver synchro. This synchro can convert polar (angle and magnitude) to Cartesian coordinates (x and y) and vice versa depending on the construction of the synchro! It’s like a mechanical calculator with moving parts.

All these resolvers and synchros and cams are used in older aircraft mainly for autopilot purposes because it involves calculation to navigate the desired route. It’s very interesting how engineers solve mathematical problems before the invention of the computer. Now if I want to convert a number to log, I may just need to write 1 line of code.

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Visual Studio is a breeze to use when developing applications for Windows Mobile devices.

I’ve gone back to developing applications for Windows Mobile. This time round I’ve been playing around with serial ports and bluetooth. The possibilities are endless on a WM device because it’s not as locked down as the iPhone. It lets you do whatever you want with it. That’s why somehow rather I still prefer the WM platform. If only they make phones as desirable as the iPhone.

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Taking raw GPS data from the GPS receiver through bluetooth and converting the gibberish to useful figures. Look at the first 3 lines after “$GPGGA” and you will find the values that you seek. By the way, you should be able to find my house using the coordinates above.

For more information on the NMEA (National Marine Electronics Association) formatting, click here.

I look forward to a weekend of studying. Continue reading