Scrupuli

blunt essays with sharp points

I have been attacking the problems at Project Euler.net

by Scrvpvlvs
Apr 26, 2011 6:30 PM–… and Project Euler is winning Round 34.

I have been working my way through some fun problems at Project Euler.net. Fun for me, anyway. To solve them takes what Edsger Dijkstra called mathematical engineering: mathematics and programming skills used together.

There are many problems to choose from, from very easy to very challenging. But they all have this in common: though it takes time and thought to analyze each problem, the solution should run on any basic computer in less than a minute.

Which is great! It means that nobody needs a supercomputer to solve these problems: just a PC and the will to learn and succeed.

Which brings me to Problem 34, find the sum of all numbers which are equal to the sum of the factorial of their digits. This problem is eating my lunch.

My solutions to problems 1–33 were sometimes lazy. Yes, some run under a millisecond, or scale to much bigger problems than those posed … but I have also been perfectly satisfied with brute force solutions if they ran under a minute on my old PC.

But, so far, my solution to Problem 34 takes more than 2 minutes to run and its output is rejected by Project Euler for no good reason that I can see. Suddenly I cannot afford to be lazy.

Incidentally, all my solutions are written in Perl. I have, as I hoped, learned quite a bit about optimizing Perl programs that I did not know before.

In case you can’t tell, I am really enjoying this!

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Do it yourself repair of a Panasonic KX-FL511 fax machine

by Scrvpvlvs
Apr 6, 2011 1:41 PM–I solved a CALL SERVICE 3 condition by fabricating a one dollar wire for the fuser unit.

The machine reported a CALL SERVICE 3 condition and recorded a cause distinction code of 01DF, which means the heat roller temperature sensor was still at 23 °C (room temperature) 22 seconds after the heater circuit was energized. The fuser stayed cool to the touch, so I agreed with the sensor.

This could have been a fault anywhere in the heater control system. I pulled the fuser assembly because the moving parts and heater have a high potential for failure.

The multimeter showed the heater circuit had no continuity (bad), but the bulb had continuity (good). So I started removing wiring, and terminal plate wire B came out in two pieces.

The wire runs across one end of the heat roller. In my unit, it was installed wrong and was in contact with the heat roller. Over time, the heat roller sawed through the wire.

I fabricated a new wire because I did not find one in stock. I used bare solid copper wire of slightly heavier gauge than the original.

After reassembling, I cleared the CALL SERVICE 3 using service function 529.

This was my first use of the KX-FL511 service manual. It is a very good, detailed and complete manual. It has some mistakes in the cross references, some poor grammar, and some missing text cut off by the margin, all of which might have been caused by Japanese–English conversion. But it was still so good that even someone like myself who does not normally service electronics can be successful using it.

References

Service Manual: High Speed Laser Fax and Copier: KX-FL511 (for U.S.A.). KMF0304645C1. Panasonic, eBook. 6 Apr 2011. <http://www.eserviceinfo.com/download.php?fileid=38206>

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