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Today I was given the smoke machine that we tried to use at a gig a few months ago where it tried to burn down the hall. Thankfully it only burnt a hole in the floor a bit.

So I am going to try and repair it as the only problem seems to be with the heat exchanger(Al structure fully melted and in a puddle in the bottom of the case) and somewhere in either a relay that controls the heating element or the temperature probe. My gut feeling is that the temperature probe is to blame and hopefully I can find a way to test it(perhaps with the oxy-acetylene torch from school). When checked with a multimeter the temperature probe gave a reading of between 0 and 3 ohms at room temp (about 30 degrees C) and a voltage reading of 0V(2000mV scale). If it were a thermistor I would expect the resistance to be somewhat higher and if it were a thermocouple I would expect a higher voltage(from a little reading on Wikipedia).

Here is a good overview where we can see the piping that was inside the heat exchanger and the Aluminium that made it up all spread out.

A view with the heat exchanger unit removed from the case.

The nozzle(I did mangle it pretty badly when trying to remove it and appear to have shorn through the silver solder(?) that held it onto the end of the smoke pipe.

The heat exchanger module. Here you can see the coils of pipe to carry the fog juice, the horizontal heating element and the puddle of solidified aluminium from when it overheated.

Just a quick picture to remind me which way to connect the temperature probe. It appears to be polarised which makes me think it's a thermocouple. If it is a thermocouple and a wire has broken from repeated heating/cooling cycles then that may explain the lack of voltage and the lack of voltage would explain the amount of heat applied to the heat exchanger when it overheated.
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Here are the photos as promised yesterday. I apologise for the quality but my iPod 4G was pretty much the only camera that functions reasonably well and reliably.

 The basic overview. The tag in the back right corner is a repair tag from when grandpa got it fixed at some stage.

 A view of the screen, keyboard and mousepad. the screen and keyboard should be re-usable but I'll need to find a new mousepad and buttons.

Some views of the bottom. At bottom with all of the removable sections partly removed. Clockwise from top right there is the CDROM drive, HDD bay, Floppy/Zip drive bay.

Here all of the removable modules are removed. Bottom left we can see the modem module with broken ribbon cable from a previous teardown I did.
 Here is the backplate with (L to R) VGA out, RS-232, 2xUSB, proprietry breakout plug, RCA video out, S-Video out, Printer port.

 2.5" HDD bay.
 CDROM sitting on top of HDD bay to get some angle on the front.
 Zip and Floppy drives side by side on top of HDD on top of CDROM, once again for some angle.
 A close up of the connector. Should be pretty easy for me to put in my own connectors.
 The where the battery was. It's a pretty big hole and a raspberry pi would probably fit in this space alone. Maybe some other pluggable module... Perhaps a replaceable CPU/RAM module or something.
The battery in all it's brick-like glory. It doesn't work as a battery anymore but if I did want to I could probably re-pack the original cells... Perhaps even increasing the capacity. :)

If you want any more detailed pictures or info post a comment and I'll get some for you. Write comment (0 Comments)
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This is a post I was going to make a little while ago about a fairly basic project to get me into Amtel's AVR microcontrollers... I had some problems with the internet on that day and have only just rediscoverd the draft that was saved :)

So I'm not happy with the stock electronics for the Nerf Stampeed. Using a 7 shot clip you can easily fire away all of your darts and still not hit anything. Also the 6 D cell batteries are a pain to replace and are massively heavy.

The solution:

Put a small microcontroller such as an Amtel AtTiny of some description, replace the current power switch with a 3-way switch to allow selecting between:
-Full Auto(Stock Setting)
-Burst(fires 2 or 3 darts at a time)
-Semi-Auto(fires 1 shot but automatically re-cocks)

Some way of displaying the number of rounds fired in battle and the battery level should be easy to set up. If I can find a way to differentiate between different magazines then a readout showing how many are left in the mag. would also be useful.

A display like this only needs an SPI interface, everything else can be controlled with digital I/O except for reading the battery state, the best solution for which I don't quite know right now but will probably need an ADC channel.

This is a fairly quick flowchart I did up showing the basic functions that will be called and when... not quite up to drawing a flowchart to show exactly how each function works... but I figure this is a start.

If you want to know why I did up a flowchart for this just ask me to put up the Qt code and flowchart that I taught myself and wrote in 1 week or so... the flowchart was about 2.5m high when printed so small it was barely readable... Originally I was trying to work it all out in my head... doesn't work that way... not like the simple little things they wanted me to do flowcharts for in my sfotware design and development course...
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Finally I've decided what to make my next new project. A DSO... This oscilloscope will be housed in the case of an old laptop that was given to me a while ago by my grandfather after they got a much better one. From memory it's current specs are in the vicinity of: 400-500 MHz processor(Pentium?), 64MB RAM, 4GB 2.5" IDE HDD, broken mousepad, decent screen (will run up to 1024x786?), came with win98, struggles to run cron, X11 and a window manager(twm?) on top of a CLI Ubuntu install.

All this will be replaced allowing me to start from scratch... I will probably keep the keyboard and screen, even if I have to set up an AtTiny or similar to get the interfaces in a format I want. At this stage looking at using an ARM processor or SoC. The CDROM bay will be replaced with pluggable modules with a digital interface to the main board allowing me to change and upgrade input channels or make a computer controlled function generator/DSO that can be controlled from any computer (Running Linux of course :) ). At this stage to allow remote control ethernet/WIFI is planned with an interface probably built from Qt. As well as being remote controllable the oscilloscope will be locally controllable, with the bootloading being handled by coreboot with a linux kernel payload.

I want to be able to use this to help me debug amateur radio rigs up to the 40m band to start with. The pluggable ADC modules allow me to improve if I need better frequency/accuracy. Basic features will include :
-Local control to allow full functionality as a normal DSO.
-Updatable firmware so new features can be implemented.
-Miniumum 50MHz bandwidth for initial product(excluding prototypes).
-Network connectivity to allow remote monitoring.
-Possibly battery, to allow monitoring in locations with limited power outlets
-Using only free and open source tools to design and sharing the designs as open source(github?)

Hopefully soon I'll get a picture of the laptop in it's current condition so you can get an idea of how much space internally I have to work with :) Write comment (0 Comments)