Blog entries from June, 2007

Binary marble adding machine

Saturday, June 23rd, 2007 at 2:01 pm

I don’t normally post things like this, but it is just too cool to not post…

An article on Boing Boing linked to an article on MAKE that linked to an adding machine made of wood and marbles by a guy called Matthias Wandel:

Once I started looking at the other things he had made I realised that I had been there before for his other marble machines, his home made pipe organ, the camera made from a flatbed scanner, and his CD changing machine.

The closest I have ever come to anything like these is making a primitive marble machine out of old shoeboxes and carboard tubes split lengthwise. But that was many many years ago.

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The shortest day of the year

Friday, June 22nd, 2007 at 8:39 pm

Either today or yesterday is the shortest day of the year for those in the southern hemisphere. This is ironic as last night my bicycle lights took another turn for the worse.

For the last few months I have only been running one of the lights from the set as the batteries no longer hold enough charge. Last night it faded out just over halfway through my ride home. Half the load only gets a quarter of the original runtime. It is now critical that I address the problem.

The batteries are in two sticks, each with five 1600mAh 1.2V C cells, which (originally) drives the pair of 10W lights at 6V for an hour. If I were to build a replacement battery pack it needs to be rated for at least 3600mAh.

A brief browse through the Jaycar site gives me:

Five cells and the charger (the charger I got with the lights is for NiCad) could be a solution. But is not cheap at $144.72. I have been meaning to find another source, such as a hobby shop with remote control vehicles, but have yet to do so.

When my light faded out on me last night and I was left with just the LED front light I asked myself: What about totally replacing the rechargeable+incandecent lights with LED based lights? For the price of building a new battery pack I could get some decent lights that:

  • are self contained, ie no wires to a battery pack
  • last for weeks on alkaline batteries

But how does the brightness compare?

It is a compelling alternative. One way or another I need to do something. Soon.

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Best meeting for some time

Wednesday, June 13th, 2007 at 10:44 pm

Tonight’s Melbourne Perl Mongers meeting was probably the best meeting for some time.

This isn’t saying that past meetings haven’t been excellent. They have been. In this case a simple change to the seating at the pub mean that instead of the conversation fracturing into a number of small conversations, most of the time all of us, 11 I think, were having a single conversation.

The change? Instead of having the tables arranged in a long line they were arranged in a rectangle that gave more of a round table aspect. We were also located under some lights which eliminated the normal gloom.

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Another block o’ wood (and some other stuff)

Tuesday, June 12th, 2007 at 9:43 pm

Last week I broke the clip on the rear light on my bike. The fortunate aspect of this is that I was forced to mount the Cateye TL-LD1000 I picked up a few months ago.

I had been procrastinating over mounting this light as the obvious solution using the belt clip to attach the light to the loop on the back of my seat bag (where the old light was) has a crucial flaw. It was too easy to detach the light from the clip and I doubted if it could survive even a single trip to or from work. Another issue was that the light then angled downwards at a 45° angle which isn’t very good for visibility. The old light was much smaller and only angled down by a few degrees.

At first I was considering an elaborate bracket to attach the light to the back of the seat bag but by necessity I ended up with a much simpler solution that used a screw, a cable tie, and a roughly shaped block bit of wood:

The components

As well as the belt clip and a post mount the light can be mounted on a rack via some holes on the back of the light. In the drawer of miscellaneous bits I found a screw of the right size that was short enough, had a coarse enought thread to self tap into plastic, and had a domed head. The hole that resulted from breaking the tab off the belt clip was in the correct location to drive this screw into one of the mounting holes to securely attach the clip to the light.

Rear light in place

After I slipped it through the loop on the back of the bag it was a simple matter to shape a small scrap of wood that both fitted in the gap on the back of the belt loop and lifted the light enough to be parallel with the road when secured with a cable tie.

This isn’t as elegant as my previous block o’ wood solution but it has been doing the job. If I find the time (unlikely) I may replace the bit of wood with a better shaped piece of plastic.

The even more obvious solution for mounting the light would have been on the seat post where the reflector currently is. This has two issues: first that it is then obscured by my legs and the bag, and second is that the road rules for cyclists state that a rear light AND rear reflector are required…

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Wednesday != Thursday

Wednesday, June 6th, 2007 at 9:52 pm

I went into the city tonight for the June Web Standards Group meeting.

Small problem. The meeting is tomorrow night.

Despite the page for the meeting stating “Thursday 07 June, 2007”, “June 7th”, and “Thursday, June 7th, 2007” I put it in my calendar for today, Wednesday the 6th.

Unfortunately I won’t be able to make it tomorrow as we are going to dinner for my sister’s birthday. Hopefully I can make the next meeting.

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The power of the command line

Sunday, June 3rd, 2007 at 2:24 pm

Twice in the past few days I have found that my best solution for the problem was command line tools under Linux.

First was some image manipulation:

My mother has been preparing a (physical) album from the digitial photos they took on their trip to China earlier in the year. In order to fit more photos in she was looking at collage programs so she could combine a number of photos into one print that could then be cut up. Unfortunately none of the programs could handle the simple task of combining photos, they all assumed a freeform layout.

The command line solution? The append option of ImageMagick. Once my mother has worked out which photos she wants I will write a shell script to semi-automate the process of appending a pair of images:

convert -append 1.jpg 2.jpg final.jpg

I may even take it a step further and use PerlMagick, the Perl API for ImageMagick, to make it easier to automate more complex manipulations such as cropping, resizing and rotation.

Second was some video manipulation:

I have a set of avi videos that I had been unable to archive as the total filesize was slightly bigger than a single sided DVD-R disc. I couldn’t easily chop the end off each video to reduce the size as the audio was using a variable bitrate as I would first have to convert the audio to a constant bitrate in a multistep process.

The command line solution? Transcode, a suite of command line utilities for transcoding video and audio. The following command converts the audio stream of the avi to be 64kbit/sec MP3 while leaving the video untouched:

transcode -i input.avi -P 1 -N 0x55 -b 64 -o output.avi

I couldn’t detect any difference in the quality of the audio and it had the pleasant side effect of reducing the file size enough for my purposes. A quick shell script allowed me to batch process an entire directory of videos.

Also, these were both installed on my linux box from the command line:

apt-get install imagemagick
apt-get install transcode

It is nice when it all comes together.

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