About Me

I've been taking things to bits, and making things ever since I can remember, starting with dismantling knackered alarm clocks and watches and helping my dad fix the car. Now I have a well-equipped workshop and have aquired lots of new skills, so I can make better stuff. When they first appeared, I became involved with personal computers, and these and developments in electronics have increased the scope of the things that I can do. Just recently retired, so O yes, now I can make all sorts of stuff.....

Thursday, 31 January 2013

December/January update

Hmm, so much for my plan of writing something on here every month.  Xmas got in the way a bit, so there's no big stuff to talk about this time, but lots of small things occurring

The first is the Raspberry Pi.  I got one of these as a present from Jon a while back, and although very interesting, it had a couple of shortcomings that made me park it for a while.  For those who don't know, its a credit-card sized computer which runs a proper Linux operating system with a proper windows-like user interface - its a bit slow compared with your average desktop PC, but fast enough to be usable.  I planned to use it as a means of running a house monitoring screen.  The intention is to have it display a calendar and task list; a news headline ticker; plus showing the status of various devices around the house - doors open/locked; inside and outside temperatures; whether lights are switched on or not and a bunch of other stuff. The Pi is small enough to be tucked away either behind or inside a PC monitor, which can probably be persuaded to provide it with power as well.

I have an arduino computer running quietly in the engine room which switches lights and the vent system on and off, monitors temperatures, doors, and water controls, and collects all this status data and squirts it into the server.  Up to now, that is as far as it has gone, although my plan was to have the server collate the data and then feed it to a web page that the Pi would read.

The problem was the Pi only has a HDMI video output, or composite video.  The spare screens that I have are all PC monitors, and none of them has HDMI, and although one has a composite video input the picture quality was so bad that text on the screen was pretty much unreadable.  I'm not about to buy a new screen just for this, so the Pi went into a drawer while I thought about it for a bit.

You can buy HDMI to VGA converters - however, they are big-ish, need mains power, and cost the thick end of a hundred quid, so for all these reasons they are a non-starter.  A recent trawl of ebay turned up a cable adaptor for a lot less dosh, and although all the boffins state that its not possible to do the conversion like this (because HDMI is digital and VGA is analogue) I also noticed that a couple of the big electronics sheds were selling what looks like the same thing for around £30.  My chinese pals would sell me one for a little under four quid, including free postage so I thought I would risk it. 

Chinese VGA to HDMI adaptor
Around three weeks later it arrived, a nicely made device in Apple white.  I plugged it into the VGA lead, reconfigured the Pi to speak out of the HDMI port, and hooray! - not only did it work, but the display is crisp and clear with easily readable text.  I have read some doomsayers on the web shaking their heads and claiming that the power requirements of the adaptor will burn out a diode on the Pi if used for long periods ('she canna take it, Captain'), and they may be right, but for now it makes the Pi a usable device again.

In a sudden burst of enthusiasm I dusted off the old visual basic skills, and wrote a bit of code that collects the data from the arduino, displays it on a screen and stashes it in a text file for later access by the web page, which is still to be written.  My copies of VB - both v6 and VB.NET - won't run on the Windows 7 environment, so I tried downloading the latest VB.NET express version from Mr Microsoft.  Hoo boy.  Not only are my programming skills rustier than I thought, but Mr Microsoft has taken the superbly simple and easy to use VB environment and turned it into a programming monster, much more complex and hard to follow, and with online help and examples that make it even more 'ard and 'orrible. I took the easy option and loaded VB6 on to the Windows 2003 server where it runs quite happily and wrote the code on that.

More to come on this next month, I now have to build the web page and find ways to import Google calendars and task lists, and add a scrolling news ticker.  The Pi browsers are more restricted than those that run on Windows or PC linux, so this is going to be another challenge.  Where did I put that copy of Dreamweaver...?

Next:  audio cassette tapes.  I spent a lot of time a few months ago scanning all our old photographs on to the PC, and decided I would do a similar job with the hundreds of cassette tapes that I have collected over the last forty years.  I bought my first Philips portable cassette machine in 1969, had a big Akai open reel machine as my main music generator until around 1980 when I bought a Technics M14 cassette deck.  The quality of the Akai was better, but the cassettes were much easier to use (I've never seen a car stereo that can play open reel tapes) so the Akai was sold and all music from then on was played on the Technics deck.  CDs arrived and blew away the tapes for quality, and slowly the tape deck was used less and less, eventually being consigned to a cupboard with its massive box of tapes.

Rather than just bin the whole lot, I thought I would copy the tapes that were worth saving on to my music server.  To my surprise, the tape deck still worked after a bit of cleaning the dust out of some of the switches to cure a slight hum on one channel, and althought some of the tapes were a bit sluggish the whole thing worked.  Downloaded the most excellent Audacity free software, hooked it up to the PC and we were off.

Amazingly it worked very well, although a bit tedious - have to copy every track in real time, so a 90 minute tape takes errrr.... 90 minutes to copy.  I finished copying all of the tapes I wanted to keep and was idly skimming through some of the others when the deck died.  All the electronics were working fine, but it seemed like a drive belt had either snapped or was slipping too badly to continue.  I briefly thought about trying to fix it, but a) you can buy these machines for a fiver on ebay or at a boot sale, and b) the whole idea was to get rid of the whole cassette tape thing, so why would I want to revive the old girl?

I can't bear to throw away stuff just like that, so I stripped it down for parts and turned the rest into a small pile of of plastic and metal.  That old deck had been a good friend over the years, played endless hours of music in around six houses on two continents, so I was sorry to see it go, but the way forward is digital, so adios amigo.

Next, some new stuff - the Whizzcopter.  Sean introduced me to the idea of multicopters a while back - for those who don't know these are helicopters with several sets of rotor blades, and while flying a helicopter (either real or a model) is fiendishly difficult and requires you to have at least five hands and three feet to keep the thing in the air, multicopters have an on-board computer that takes care of most of the crash prevention gymnastics.  The brains of the device revolves around a set of electronic gyro sensors which detect changes in attitude, and the computer automatically corrects by speeding up or slowing down the propellors.

Sean is keen on a quadrocopter with four rotors, but I have decided to build a tricopter.  The tri is a bit more complex to make, as it is steered by a tiltable back rotor, but it uses less power (so increases flying time) and costs less as there are less bits involved.
The completed frame
I made a start of the build of the frame this month, using mostly bits that I already had in the workshop - 10mm alloy tubing for the arms, 4mm rod for the bracing and some fibreglass sheet for the central platform that hold all the clever bits. Made extensive use of my little milling machine to make the motor mounting plates and to drill holes in the central platforms at exactly the right angles and spacings.

Fly cutting one of the motor mounts
Drilling the centre platforms on the rotary table
The arms seemed a bit too rubbery for my liking, and I assumed that with all the weight in the centre that a heavy landing would probably buckle the arms, so I braced them underneath with angled alloy rods.  It may not be pretty, but its certainly very rigid.  The whole thing weighs in at around 450g, and I reckon the rest of the bits will bring the flying weight up to around 850g.

The steerable motor mount plate - it will be tilted with a servo
I've just ordered the motors and speed controllers and a few other bits, should arrive by the end of this week. The remaining parts are mostly out of stock so I will order them later, watch this space.  Sean has started his build as well, and Jon has just received all the bits for his:  I can see this developing into a bit of a competition.....

Hot news now on the coffee front as well.  We have had a Krups fully automatic bean-to-cup coffee maker for around 12 years, and it has worked hard and been great for all that time.  Recently it started getting very confused, grunting a lot and flashing its lights in ever-more bizarre patterns, and consuming coffee beans without actually giving me a cup of the stuff.  Although it cost a lot originally, the business bought it for us and its earned its keep several times over, so it had to go.

Extensive searching on t'internet to find the best replacement - believe it or not, you can pay several thousand pounds for these machines, but I suspect that mostly what you pay for is the name on the front since the mechanics of making coffee from beans ain't that hard.  We settled on a De Longhi machine at a reasonable price and we've been running it in over the past few weeks.

So far it looks good.  It makes a good cup of coffee, it has adjustments that the old Krups never did, and it seems to be well made.  If it lasts as long as the old one did, I shan't complain.

Last thing this time is some long overdue work on the kart.  I still need to do some more research, but it looks as if my oversteering problem on the way out of corners is actually the result of understeer on the way in - too much steering lock to get the beast to turn results in a sudden loss of grip at the back as soon as the front starts to grip and the inside rear wheel lifts. I've noticed this especially when driving in the wet, where there is absolutely no grip at the front at all even on full lock, followed by instantaneous massive oversteer, followed by a close encounter with the scenery.   It may NOT be my crappy driving after all (well, not entirely anyway).

Fixing the understeer is a bit of a trial and error thing, so I've made a start in the meantime on other stuff that needs doing.  So far I've straightened the front bumper bar (pushed down on the last outing with the sudden arrival of the crash barrier); changed a front wheel bearing that was leaking grease; taken the undertray off and beaten out the many, many dents (another result of too many off-track excursions), and straightened the steering column which hasn't been straight since the major collision some time ago that left tyre skid marks on my steering wheel.  The lower steering column bearing is completely fooked, so a new one is on order, can't put the undertray back on until this is replaced as the tray gets in the way of the spanner.

The other major task is to try to clean all the crud out of the exhaust, which is almost certainly stealing some of the power, especially at full throttle.  I've been told that leaving it full of  caustic soda for a while will do the trick so I'll give that a try first.  If it needs to be scraped out, we have a problem, as the various bends and turns make it impossible to get any kind of scraper inside, and the only other answer I can think of is a wire brush on a flexible shaft with the ol' power drill attached to the end.  Whatever I do, its going to be pretty filthy, so I'm not looking forward to it much, but the only alternative is a new exhaust at over 200 quid, so I'll take the filth, thank you very much.

Next month there should be more progress on the Pi; the whizzcopter should be pretty much finished if not actually flying, and the kart should be back together and we should have done a test session to try out the handling changes. Can't wait!