Looks like a good job. It’s sure to work better than before!

So I have made a little Linux app which can extract scenes from a DVD disc. The camera records each scene as a DVD “chapter”. My application reads a DVD disc and copies each chapter into a separate MPEG file. I’ll publish it here in case anyone else finds it useful.

Downloading and Compiling

I’m just releasing this as source code at the moment. I have tested it under Ubuntu 7.10 but It will probably work fine on any UNIX-based system. You can download it here:

DvdChapterExtract-1.2.tar.bz2 (16k)

You will need libdvdread and libavformat before you compile. So install those:

sudo apt-get install libdvdread-dev libavformat-dev

Next unpack and compile:

tar jxf DvdChapterExtract-1.2.tar.bz2

cd DvdChapterExtract/Release

make all

Usage

1. You need to record your discs in Video mode, not “VR” mode. VR is a Sony proprietary format which cannot be read in a regular DVD drive.

2. After recording your disc, you must Finalize it in-camera.

3. Put the disc into the DVD drive on your PC.

4. Launch the DVD chapter extract tool like so (assuming /dev/scd0 is the name of your DVD drive).

./DvdChapterExtract -d /dev/scd0

It will extract each chapter into a separate file called chapter001.mpeg, chapter002.mpeg and so on. These can be loaded directly into any video editing software.

The camera also tags each chapter with some meta-data such as the date and time the scene was recorded. I have not yet figured out how to read that data.

Before you start, preheat your oven to 180°.

The Apple

• 850g Apples (I used “Pink Lady” apples but any kind would probably do)
• 2 tablespoons Brown Sugar

Core the apples, cut them in half or quarters and slice them with the skin still on. Mix the sugar with about 50ml of water and put it with the apples in a pan. Stew until soft.

The Crumble

• 175g Plain Flour
• 100g Brown Sugar
• 125g Butter
• 100g Oats
• ½ teaspoon Cinnamon

Put the oats into a food processor and lacerate them into small pieces. Then dump in the rest of the ingredients and process until it is well mixed.

Put the stewed apples into a baking dish. There was some liquid left over from the stewing, I did not drain it.

Then sprinkle the crumble over the top. Do not pack it down, you want it light and crumbly.

I baked it for about 50 minutes, it was OK but that was probably too long. Next time I’ll try about 30 minutes.

Serve with whipped cream or ice cream. You’ll get about 12 serves from these quantities.

They are so proud of it.

This solder paste stuff is pretty toxic. Perhaps I’m going overboard here but I thought some rubber gloves would be a good idea.


To apply the paste, I just squirted it on the board. It kinda went everywhere at first until I got the hang of it. Next time I’ll get a smaller tube and perhaps a smaller nozzle. I fixed it up as best I could using a toothpick and cotton tips. It took quite a lot longer and was much more messy than I anticipated.


Next comes the pick-and-place. I got most of my parts from Digi-key who send them out as “Cut tape” which is pretty convenient, you just peel the backing off the tape until you get the quantity of parts you need and the rest are left still attached to the tape so you don’t lose them in the carpet. I positioned the parts with tweezers since most of them are incredibly teeny.

My board includes both surface-mount and through-hole components. I just placed the SMT stuff at this stage because I need the back of the board to be flat for heat transfer.

Now for the fun bit. I put the loaded board onto the pan cold. Then I increased temperature to around 100°C. I left it at that heat for a minute to get everything nice and warm. Then I cranked up the heat to maximum (in my case, 175°) until the solder melted. It was magic to watch. Everything just blobbed into place. Even components which were not exactly positioned right pulled themselves into line.

After a slow cool-down over 5 minutes, I examined the board. Everything looks good to my eye except for some pretty major bridging between the pins of my ARM chip. I’ll leave dealing with these to part 3.

In the end though, I’m pretty pleased with the result. Not bad for my first try!

The idea is to use a frying pan or toaster oven to perform solder reflow for SMT circuit boards. I decided to use a skillet thinking that a toaster oven would melt components since it heats both top and bottom.

I managed to find the perfect thing. A pre-owned 9″ electric skillet from the Salvation Army shop for $3.

Believe it or not, this device is not a precision instrument. The temperature dial is simply numbered from 1 to 10. The first thing I need to do is get some idea of what actual temperature this thing gets to.


So I need to do a scientific experiment. Firstly I put some oil in the pan and stuck in a thermometer (the fork is to hold the probe in the oil). Then I turned up the heat slowly making a note of the temperature. Finally I graphed the result. Here are the results in degrees C. That cheap little temperature knob is surprisingly linear.

1. Element not energized
2. 30°
3. 46°
4. 65°
5. 90°
6. 105°
7. 125°
8. 140°
9. >150°
10. >150°

The last two entries I could not measure since the thermometer only went up to 150°C, but by extrapolation I get 155° and 175°. Yes I did this on paper, it is much quicker than using Excel!

I am now ready to use this thing for solder reflow.

At first I found I could make some rough face shapes just by pouring the mixture into the pan but to make the more advanced shapes, I had to make a stiffer mixture and used an icing bag to squeeze it out. Mine aren’t as good as Dave’s.

FYI, my pancake mixture is:

• 1 cup self raising flour
• 2 tablespoons caster sugar
• 1 egg
• 3/4 cup milk
• pinch of salt

Just mix it all up, it’s pretty simple. Even my kids can do it.

Here’s some pictures. You can all laugh at our bed-hair!

Thanks for the inspiration Dave!

Today we made “Comet Balls”. We saw something similar to these at a school fair and Kai really wanted some. So I got some tennis balls and some long colourful socks to make the tails (I could only get toe-socks. Long story, don’t ask. They do look cute with the little toes on the front though).

Making them couldn’t be simpler. Just shove the tennis ball into the sock and secure it with an elastic band. Kai could do it all by himself.

You can throw them quite well when you hold the tail and twirl them. We played a game where Kai and I would try to throw them into a bucket at a distance of two metres. Here’s some photos:

Since digital cameras are sensitive to infra-red light, you can simply point your remote at the camera and you will see the flashing of the infra-red beam on the phone’s screen, digital technology making the invisible visible!

After dragging it home and powering it up, I saw that the panel would light up, the buttons seemed to work but there was no sound coming out so I opened it up. It was certainly a mess inside (and out). It was filthy with mud and it looked like some cockroaches had been breeding in it. Fortunately, there was very little corrosion on the circuitry so I felt I had a good chance of getting it going.

First thing I did was to take it completely apart and wash all the plastic parts such as the case, buttons and keys with lots of hot soapy water.

After reassembling it, I had a poke around. By connecting some headphones to a wire and probing around the circuit board, I could work out that the sound was being generated but didn’t make it past the main amplifier chip, an LA4558, it seemed to be blown. I had a look through some parts suppliers catalogues but could not locate a replacement for this chip.

No matter because I had a stereo amplifier module surplus from an old project. I got this amplifier ages ago from WES just down the road at Ashfield for about $12 from memory. It is a 5W RMS per side, class A stereo amp. Total overkill for this job but what the hey. I simply bypassed the blown-up chip and fed the signal through the amp module. It has a little hiss, no doubt due to my sloppy wiring or incorrect impedance matching but is really loud when you crank it up.

I screwed the amplifier module down to the metal keyboard frame which makes a handy-dandy heatsink and it is good to go. Not bad for a couple of hours work, a free Kawai MS710 keyboard/synth! Maybe I could circuit-bend it in the future, we’ll see but for now, it makes a great toy for my kids.

So I decided to do something about it.

Instead of expensive AAA batteries, it would definitely last longer on AA cells. Four cells would also supply a higher voltage than three and so give greater output power. First thing to do is void the warranty and take it apart.

Then I simply grabbed a 4xAA battery holder and soldered the wires in place of the existing 3xAAA battery compartment. I loaded up the batteries to see if it would work.

Ah, but it didn’t. The activity LED did not light and after a few seconds I could smell the familiar aroma of burning silicon. After very quickly removing the batteries, I had a closer look to see what was up (apart from the main chip being very hot).

Turns out I had relied on the colour-coding of the wires and connected my positive to the red wire and the negative to the black wire. After all, that is the standard right ?

If I had checked more closely, I would have noticed that whoever assembled this thing had used a red wire for negative and a black wire for positive !

After I stopped swearing, I connected my battery positive to the black wire, and negative to the red wire. My engineer mind was screaming “noooo!” but I did it anyway. After that I tested again and it worked! I was very lucky the chips had not been fried by my earlier mistake.

Finally since the battery holder would not fit inside, I glued it to the underside with some hot glue. After testing I was pleased to note that the range was much increased. I can use it while leaning back on my lounge and I don’t have to carefully aim it anymore. With the larger batteries on the case, it should be quite a while before I need to change them.

You’ve probably seen this one before, the idea is to move a hoop along a bent wire without touching the wire. If you touch the wire, a buzzer sounds and you have to start again.

We built ours out of an old plastic box which once contained chocolate. A wire coat hanger was the main component. I cut off a few inches of the coat hanger to bend into a loop and used the rest to make the squiggly wire. The ends of the wire were bent into tight loops through which I put small bolts to secure it to the box.

The electronics and battery holder were simply glued to the inside of the box using hot-glue which is really an incredibly useful substance.

After I soldered a flexible wire to the loop, Kai put some bicycle handlebar tape around it to make the grip. For strain relief on the wire, I used a cable-tie.

The end of the wire is a yellow “safe zone” which was made simply by wrapping electrical tape around the wire to prevent electrical contact.

The noise maker

I didn’t have a buzzer handy but I did have a 555 timer chip so I used it to build an oscillator and connected that to a small piezo speaker in keeping with my principle of using whatever parts I’ve already got wherever possible.

Much has been written about the 555 timer IC. I have wired mine in the classic astable mode. The values of the components are not at all critical, the formula below shows how to compute the output frequency from the component values. The 100µF capacitor was added to provide a little sustain so that the sound is less “scratchy” when the wire is touched lightly.

Of course, if you are not a complete nerd, you would probably just get a buzzer.

Formula to calculate the output frequency

The result

I was going to paint the box but my wife (who is an artist) said “Noooo! it looks so post-modern in clear plastic with the chocolate label still on it” – so it has stayed un-painted.

This has cost me $0. It is built completely from parts I have found around the house. I like the challenge of trying to use what I have and this project completely achieves that goal. Here are some more photos:

After butchering the back panel, I neatened it up a bit with a hand-held hacksaw blade and a metal file. After that, I vacuumed the case out thoroughly to make sure there were no metal shavings inside.

As you can see, the bigger motherboard fits now. Removing a large chunk of the back panel allows the connectors for the keyboard and other ports to be accessible.

Unfortunately, the CPU cooler sticks up too high so I could not fit in the PSU. However, I am a computer nerd and always have plenty of odd spare parts lying about such as a Micro-ATX PSU which fitted in just nicely after I drilled a few new mounting holes.

Once I put in the hard drive, CD-ROM, PCI cards and everything, the box is getting rather full but it does all fit.

And here it is in my server room – uh, I mean server cupboard. It’s running a PIII 667 overclocked to 750MHz with 384MB of RAM and a 250GB hard disk. Debian Linux of course (if you have been reading my blog, you must realise by now its my favourite OS). And it is all working great. After all, it has just served this web page to you!

Now all I need to do is enter the new machine into the Linux Counter.

I have been pondering the best way to add some over-current protection to prevent damage to the batteries in the event of a short. A colleague suggested I try a Polyswitch – he even donated one for this project (thanks Ian!) thus saving me about $2.

This device is also known as a PTC fuse and is commonly used to protect loudspeakers. When a certain current is reached, it will trip and go into a high-resistance state until the current is removed. You can see a photo here of the device dropping the current to 120mA despite a dead short across the battery. The trip current is well over an amp so it does not affect normal operation of the board. Neat.

First I found an old piece of MDF from my shed and cut off a bit about 10″ by 6″. Then I bought some screw eyes from the hardware shop. I already had this bunch of colourful clip leads.

To build it, we drilled some 1mm pilot holes and then screwed in the eyelets with a small washer under each one. Kai loved having a go of a power tool even if it was only a little battery-powered Dremel. The wire from each part gets clamped under the washer as the screw eye is tightened. I used some pliers to screw the eyes in nice and hard so the wire will stay clamped.

I have soldered a current limiting resistor in series with each part. I used 100Ω for each of the LEDs and a 15Ω ½ watt resistor for the motor. These values were arrived at by guesswork, experimentation and whatever I could find in my parts box using the time-honoured principle of “Whatever works man”. I used a little hot-glue to hold the parts in place.

I attached the battery holder to the board with some velcro so it can be easily lifted up to change the batteries.

And here’s the finished product. I still do not have any kind of over-current protection for the batteries. I guess it won’t be long before the child tries to connect the battery terminals together and kills them. I’ll see what I can come up with in the future but for now we are having too much fun to bother about it.

I spent about $2 all up to buy a packet of screw eyes. Everything else came out of my junk box. That is my driving philsophy here. Just use what I’ve got, otherwise, I may as well have spent $50 on a store-bought electronics kit.

The board contains 4xAA batteries, 2 LEDs, a momentary push button and a DC motor. Kai can make up circuits by clipping the clip leads onto the eyelets. I have left some room on the board so we can add other bits on in the future. Its simple and fun enough for a four year old.

Related posts

Kid Type

UPDATE – Adding current protection

Analogue electronics is not really my thing, I’m much more a digital person but when I found a design online for The #3 Standard WoggleBug by Grant Richter, I just had to build one.

First I built the circuit on some veroboard. This thing is controlled by a bunch of potentiometers, there is no keyboard and certainly no MIDI!

Then I was wondering what to make for an enclosure. My friend Jasper found an empty CD spindle and you know, it was just crazy enough to work.

To create the control panel, I got a CD-R and messed it up a bit with a blowtorch. I mounted the knobs on this and glued it to the central shaft of the CD spindle. A little more glue and the whole thing was assembled inside the spindle.

Here is the finished product. As you can see, the cover of the CD spindle makes a handy travel case.

If you want to hear what it sounds like, Click here for an MP3 (1MB). Okay, this is not a pure recording, I have added some drums and a couple of effects because this thing sounds really rough and is almost impossible to control. You’ll have to imagine me twisting the knobs frantically while you listen.

Anyway, I had fun building it and that’s what makes me happy.

I also learnt how to use ProTel so I could draw up the final circuit properly. Here’s the result. Notice that I’ve got it down to just one chip now, the little PIC is doing everything. It can directly drive the LED and the MIDI output. I’ve used multiplexing to enable it to drive the 7 segment display and read all the inputs. The PIC’s built in timer keeps everything running accurately, all in all, I’m very pleased with the result.

I threw it into a box and its done! You can see in this photo that I also added a second MIDI output.

Since I last did any work on this project, I have upgraded my PC to a Duron 900 and have installed Windows 2000. I am most impressed with the stability of Win2K, I rarely have more than two crashes per week as opposed to about three times a day under Win98.

However, Windows 2000 will not run the NOPPP software which I have been using to download code into the PIC. I suspect the way ports are accessed in Win2K is not backward compatible with Win95.

To cut a long story short, I have found the Linux version of NOPPP works just fine so I’m using that instead. gpasm is a free compiler for the PIC which runs on Linux so I’m all set to continue development without using Windows.

I’ve redesigned the thing again and got rid of the buffer chip. I’m driving the MIDI output directly from the PIC and it works fine. I’ve used a 7 bit bus arrangement to allow all the inputs to share the same I/O pins as the LED display.

One little hitch was the discovery that the big red illuminated push button needs 12 volts to light up. But I’m running everything off 5 volts. So I’ve made a little adapter out of a small piece of veroboard so I can substitute a LED. I tellya these modern LEDs are so bright! I nearly blinded myself messing about with it.

One thing I had a lot of trouble with was understanding the MIDI signals. I couldn’t seem to find much documentation on them. I had to do a lot of trial-and-error and also use my CRO to analyse the signals coming out of some MIDI equipment. Here’s what I found:

MIDI works by current, not voltage. The receiving end has a 1k input impedance and the sender is expected to put a 5V voltage differential across this which produces a current of 5mA. Current flow is indicative of a logic 0. No current flow is a logic 1. There is no current flow when the line is idle.

A fairly standard way to implement a MIDI output is to tie pin 4 of the DIN plug to 5V and pin 5 to your digital output. This forms a hardware inverter so you can use normal logic levels in your circuit.

The data rate is 31250 bps +/- 1%

Another confusing thing is that nowhere is it described how the serial data is sent. The literature will tell you that there is 1 start bit, 8 data bits and one stop bit. Great, just like RS-232 I thought. Well no, it’s not anything like RS-232. The start bit in MIDI is a 0, the stop bit is a 1 and the data bits are sent in reverse order. All perfectly fine but I had to discover this myself.

The firmware is now over 1000 lines and is almost finished. I’ve just got to figure out how to store the BPM setting in the internal EEPROM and it’s done.

Another problem I’ve come across is the Potentiometer voltage ramp arrangement has turned out to be not very accurate, the reading varies wildly depending on voltage, temperature, current and just about any other variable you can think of. After wasting a lot of time with it, I’ve decided it’s just not a suitable method for setting the speed.

So instead, I’ve got myself a rotary encoder. This looks like a potentiometer but it’s actually a binary counter which increments as you turn it. It has detents so it won’t drift once you turn it to a specific position and is generally much more suitable for this role.

Of course, I now have to modify the software to read it.