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| Thursday, December 17th, 2009 | | 10:46 pm |
Making Things
Today, I sent off my proposal for the 2010 Maker Faire in Newcastle. I should find out in January if I've been accepted. It'll be the same Compukit UK101 exhibit as last year, plus some new goings-on with the Arduino and maybe some other 8-bit chips. Meanwhile, I have acquired an STM8S Discovery development board for the ST Microelectronics STM8 CPU. It was less than a fiver from Farnell. I'm considering an LPCXpresso from NXP, too, but of course that's a 32-bit ARM chip. In the lab, I have put together a 40-bit LED display based on five 8-bit shift registers (74HC595). At Dorkbot Bristol, I worked with David Henshall on a wire-bending rig that ended up featured on the Make magazine blog: http://blog.makezine.com/archive/2009/12/curious_wire_bending_machine.html | | Wednesday, November 25th, 2009 | | 11:26 pm |
FreeCycle Overload
I've been doing a lot with the Bristol FreeCycle mailing list recently. Now, the majority of stuff on there is out-grown children's toy and clothes, and household stuff. But every so often, computer parts and suchlike turn up. It all started with an iRiver MP3 player, 40Gb size, with no charger. Then I got a couple of in-car power amplifiers, although I wish I hadn't (see later). Next came a rather good 19" CRT monitor from Bedminster, which replaced one that had been getting flakier and flakier on me. In one evening, I made a trip to collect some squares of slate, a PC speaker/subwoofer set and a 400W PC power supply. Finally, all from one generous FreeCycler, I received a FireWire web-cam, a Bluetooth headset and a 21" CRT monitor. But it hasn't all been acquisitions -- I have a PC case, an Apple 17" monitor and some photographic printing paper which are destined for new homes. Now, the sorry tale of the MP3 player and the amplifier. As far as I could tell, the only fault with the iRiver was its battery -- no surprise there. The machine can record from a mic or line input as well as play back, which I thought was rather useful. Then I got the two dud in-car power amps and set about fixing them. The Pioneer one had a very obvious fault in the DC-DC converter that supplies +/-40V to the main amplifiers. Fixed that, all powers up and things start to work. So I connect the MP3 player to act as a signal source. Fatal move. The amp has something bizarre going on which gives a DC offset of about 12V on the inputs, which promptly blasts the output stage of the MP3 player. So, that's dead and the amp is no further forward. I was kicking myself all the way down the road for not checking before connecting it. Other FreeCycle stuff has been more productive. The FireWire web-cam works, although I'll need a package called Coriander to get it running on Linux. The Bluetooth headset is charged up, and OK, but has a broken mic boom. Well, that'll most likely end up in an old GPO phone handset anyway. And last night's pickup of a 21" Mitsubishi Diamond Pro 2070SB monitor has resulted in a 2048x1536 display on the Linux box. With the second monitor attached, I get an additional 1600x1200 screen, and with Xinerama, they merge into a single desktop. I've been doing some major rearranging upstairs, which has resulted in the landing, bedroom and computer room being clear of odd items of junk left laying about. This is partly due to a couple of things going into the loft, but mainly due to the HP 7550 pen plotter moving from spare bedroom to the computer lab, which a much more sensible place for it to be. Then, with a lot of moving around in the spare room, I've been able to get all those odd little items tidied away in there. Result: I can walk around the upstairs without having to dodge past things. | | Wednesday, November 4th, 2009 | | 5:18 pm |
This Old Amp
On Monday, via FreeCycle, I acquired three rolls of thermal cash register printer paper. Well, they're just the ends of rolls, but there's plenty enough on them for testing the printer that I got way back in February. It's a Citizen CBM1000, with a serial interface (25-pin D-connector). Tuesday evening is Dorkbot hack evening, and I took the printer along. I rigged up a USB-to-serial gadget to use with the Compaq Presario 3000 that I fixed previously (broken USB socket). All went well, and we were able to demo the little printer making text, graphics and barcodes. I've done a bit more to the code now, so that it exercises more of the printer's functions, and so that it prints a correct JAN-13 EAN barcode for a can of Heinz Curried Beans, 200g size. I'd been playing with a Yamaha DD-5 electronic drum machine that someone from Dorkbot had picked up in a car boot sale. It has four rubber drum pads that I resorted to striking with wooden spoons. With it rigged up to the hi-fi amplifier, it sounded OK and certainly generated the various rhythms that it has built-in. Strangely, it has only a MIDI-out socket and no MIDI-in. But the drum synth was only passing through, on its way to another Dorkboteer on Tuesday evening. On its way back, was a much more interesting piece of electronic music gear. I picked up a very fine old amplifier from the Dorkbot hack space, to take over to the Uni for someone there to mess about with. He's interested in using a real, electromechanical reverb spring instead of the modern digital reverb units; the old amp has such a reverb spring. So I now have it set up in the lab, belting out 1980s synth-pop, in mono, from a CD player (most of my CDs are 1980s music of some sort). The amp is an HH MA100, which is a ten-input mixer/amplifier. The inputs are in five pairs with individual level and tone controls for each pair, plus a reverb button. Then there's a master volume, "presence" control, master reverb control and on/off switch. Inside the amplifier, it's all cable-laced wiring looms, which was a surprise until I found the date codes on some of the parts. This amp was made in 1974! And it still works perfectly, with not even scratchy pots. But the best feature, though a little beaten-up, is the front panel. It's a perspex panel (you can still buy replacements) which lights up all the way along with a gentle greenish-blue light. It has an electroluminescent panel behind the control knobs (the pot shafts pass through holes in it) which just makes it all look superb. Later, I'll play "Love Will Tear Us Apart" by Joy Division, and I'll be instantaneously zonked back to a Westfield College disco in 1984... | | Monday, November 2nd, 2009 | | 12:48 am |
Compact Discs
I realised that I have several CDs on my shelf that are 20 years old. Not CDs of 20-year-old music, but CDs that I bought in the 1980s when I lived in London. Some may have been from the Virgin Megastore on Oxford Street, back when it had a CD pressing machine in the basement, behind a glass partition. And I've been listening to them with a 30 year old Pioneer amplifier and my 30 year old Sennheiser headphones. | | Sunday, November 1st, 2009 | | 1:42 am |
Another EV Tale Of Woe
I've had another disappointing trip in the City-El electric bubblecar, with the batteries failing once again just as I arrived at the charging point at Cabot Circus in central Bristol. I was very gentle with the throttle all the way down there, and I was able to take the shorter route now that Filton Avenue has re-opened. But the car still didn't manage to travel the 10km/6.5 miles successfully. I think the batteries may be the cause of the trouble, so I'll do a proper capacity test as soon as I can get a voltmeter rigged up to record the voltage over time. And as if that wasn't enough, the throttle pedal microswitch failed when I was half-way home, getting a recharge at a friend's house. Fortunately, I was prepared for that eventuality with some tools and a short length of wire. So now I have a temporary repair that's wrapped in gaffer tape.  I've replaced the mouse on the ThinkPad with a new one. It still has a PS/2 interface, though, because the machine only has one USB socket, and that's best left open for things like the Arduino and the memory stick. It's been a stressful two days here, while the builders were fixing the roof. The damage and deterioration was much worse then I'd thought, and worse than the roofer had thought at first. But with the scaffolding up, they stripped off the tiles, removed the battens and replaced the felt layer. There were a couple of birds' nests up there too, which they removed. Then with seven new battens and ten new tiles, it all went back together again. So I now have a roof that will be good for the winter, but I also know that the rest of it will need maintenance next year. | | Thursday, October 29th, 2009 | | 10:55 pm |
Fixing Things
I've been trying to tidy up the house a bit recently, and have had limited success. One of the things I've dug out from under the piles of miscellaneous crap is the video camera stand. It's an Elmo EV550 AF "video presenter", which means that it has a video camera (PAL) that can be used in much the same way as an overhead projector. It has lights both below and above the subject area, and it has a rudimentary video mixer that can accept two external video signals. The camera is auto-focus, with a zoom and with controls for inverse video and a monochrome mode. But, the reason I have it is (of course) that it's broken. It was shipped without any packaging, and was dropped en-route. The camera head broke off the arm that supports it, one of the upper lamp units broke off, and the camera's zoom stopped working. Some time ago, I fixed the lamp and partly fixed the camera attachment. The zoom function, however, was a puzzle. The camera made a sound like a geared motor was turning, but the image did not zoom. Nothing for it but to open up the camera head and make a visual inspection!   It turned out to be a complex assembly of PCBs, connectors and motors all built around the lens and sensor itself. The jolt that broke the other parts also disengaged the zoom motor from the ring gear that's located around the lens. I undid the motor fixing screws, reseated the motor, re-engaged the gears, and reassembled it all. So now I have a working zoom lens, but the camera head is still not reattached to the arm. I'll do that next, and then take it along to Dorkbot and try it out on the video projector there. The 802.11g CardBus card in the Compaq laptop gave me a bit of trouble the other day. In the Uni library, it singularly failed to connect to the wireless network. All sorts of error messages in 'dmesg', to do with dis-associating from the access point. But then, when I tried again from the coffee bar area, it worked absolutely fine. As it happens, I normally use the wired connections in the library and the wireless only when I'm elsewhere, so I should be OK. The major step forward today, though, is that I have at last got a roofer to have a look at my ridge tiles. He's spotted a number of problems with water getting in, and faults in the felt layer, so it's going to be a more complex job than we first thought. But I have to get it done, so we'll get the scaffolding up and get on with it. | | Monday, October 26th, 2009 | | 9:58 pm |
To the Micro Maker Faire in Wales
The pole-mounted camera project has progressed to the stage where we can use it to take a few test shots (see below). It's by no means finished, as I'd like to add a few features for better control of the aiming of the camera. For the video camera, this will be a fairly straightforward video monitor and a cable connection. For the stills camera, another method will be needed.  I've been messing about with chargers for the 12V lead-acid batteries in the City-El. So far, I've concluded that I need to charge them to about one volt more than I previously did, i.e. just over 45V. I found this by a careful reading of the Trojan battery data sheets, where they specify an extra 5mV per cell, per degree Celsius below 27°C. They actually specify it all in degrees Fahrenheit, though, and base it on 80°F. The big Compaq laptop now has a 32-bit PCMCIA (CardBus) card for 802.11g wireless networking. It's a Belkin card, and it loads up firmware each time it's inserted into the machine. That firmware comes via a small program that extracts it from the Windows driver binary files. All seems to work OK. The trouble with the PS/2 mouse on the ThinkPad turned out to be in the mouse itself, not the laptop. I helped out Jon from the Dorkbot group the other day, by getting his N8VEM machine running. It's a Z80 microcomputer with static RAM, EPROM and some I/O chips on a Eurocard-sized PCB. The reset circuit wasn't working properly due to a misplaced component -- a resistor in place of a capacitor. Once we'd fixed that, the machine started up OK and ran CP/M. Jon gave me an audio compressor/expander/noise gate, which I'll be setting up with the microphone preamp. It's a DBX model 266, and requires balanced line-level signals. The Suzuki Cappuccino is running well, having made the trip to Colchester and back for mum's birthday. I modified the radio to accept a line-level input from the MP3 player, which made the trip a little less monotonous. I have acquired an Anglepoise lamp from FreeCycle, which I will modify to hold a microphone. With a bit of luck, I'll get it to balance properly. Should also be possible to un-do the modifications later if I want to restore it to a working lamp.  Finally, I have been busy with Dorkbot activities, mostly in preparation for the trip to Cardiff for the " May You Live in Interesting Times" festival. I made up the larger bike wheel, with bigger amplifier, bigger speakers and a bigger battery pack. The two days at the Chapter Arts Centre in Cardiff went very well, although I did need to reconnect some of the wires on the larger wheel after they got snapped off (needs more cable ties). Photos of the "Micro Maker Faire" are here, here and here. I shot some video of the event, but haven't had a chance yet to do anything with it.  | | Wednesday, October 7th, 2009 | | 12:15 am |
A Moderately Successful Day
Today, I went over to the Uni to get on and do some stuff. I've been over there before, and spent all day getting nothing done. I've also stayed at home and got nothing done. But today I was firm with myself and gritted my teeth and ordered the CAN-bus AVR microcontroller modules that I need in order to make an autonomous robot vehicle. I refrained from yelling at myself, or kicking myself around the room, because I was in the library, and that kind of thing is frowned upon -- even in the modern university library where we have group study areas where students hang around nattering and where every so often someone's mobile phone rings and the first thing they say is "I'm in the library" and then carry on with the conversation. But in addition to ordering the parts, I took the big Compaq laptop to the Uni. After all, I'd soldered the new dual USB socket in, making all four USB ports usable. It worked well both on the Uni's wired network and on the wireless system in the coffee bars (using a USB WiFi gadget). I tried out the el-cheapo Tesco in-ear headphones, too, which were fine. There was quite a bit of setting-up to do, like getting the pop-up blocker exceptions right in Firefox (some Uni web pages have pop-ups that you need to see) and getting Adobe Flash and the essential Flashblock add-on installed.    The camera pole mount is progressing, although not yet ready for "first light". The last photo, incidentally, also shows the new living room rug. Yesterday, I acquired a 12V leisure battery charger from FreeCycle, although I'm wondering if that was such a good idea, because it was offered as "faulty". It's a Zig X-2 and can charge at 10A, which is more than the usual car battery charger. It's a switch-mode design, and quite lightweight as a result. This evening was another Dorkbot Bristol hack session at Hamilton House. We messed about with the Arduino music synthesis code, rigged up a bigger amplifier and generally made plans for the trip to Cardiff (end of October). I brought the big amplifier (a car booster amp) back with me to make a mounting arrangement that will clamp onto a bicycle's front forks, along with the pair of speakers. This will be used with the larger bike wheel to make a bass version of the music synthesis gadget -- we thought that the bigger wheel ought to make lower notes, like, say, a double bass compared to a cello. | | Saturday, October 3rd, 2009 | | 12:49 am |
Rickshaw Motoring In Somerset
Since my last posting, I have sent the scrap metal on its way to be recycled, via the local "civic amenity centre". Why that can't just call it a tip, like everybody else, I don't know. The garage door insulation is now in a heap at the back of the garage, pending a better way of fixing it up. I got fed up with fighting my way through it as it hung forlornly down from the underside of the opened garage door. The living room rug is making a huge improvement to the living room. I still have a few items to send to FreeCycle, and of course I have much too much junk lying around the place. But the idea of using the rug to mark out a junk-free space seems to be working. The Orange SPV smartphone is now SIM-unlocked thanks to a program I downloaded off the internet. No, really, it worked just fine and unlocked the phone with no problems. The phone itself is great, although I wish I could get it to accept infra-red communication from the old Nokia. It seems the only way to back up or copy data from the "Contacts" database is by installing Outlook on the host PC -- which I would prefer not to do. Maybe I can get IR communication working with a laptop, and transfer data that way. Oh, and I've installed a reverse Polish calculator program on it. I've reinstated the simple op-amp based constant-current circuit that I made a few months ago, to use as a battery charger. So far, I've used it on some NiMH cells that I got from Lidl, a couple of NiCads that were in the cordless phone handset, and the NiMH battery pack for an old Canon PowerShot A5 Zoom that I was given because they'd lost the proper charger. I'll no doubt use it again for the Roomba battery (NiMH, 14.4V) and the cordless drill (NICad, 18V). Had a bit of a problem with the big IBM Thinkpad A21 at the Uni the other day; the PS/2 mouse stopped working. The LED in the mouse just flashes about once a second, and does not move the cursor. Not sure if it's the mouse or the port on the laptop. Anyway, will need to use the USB mouse instead. Must get on with soldering the USB socket in the Compaq, too. Today, I went to Brean in Somerset to see a truly bizarre electric vehicle. It's the Electraction Rickshaw, made in 1976. It has front and rear bench seats (lap-belts in front only), no roof, no doors, no speedometer (no instruments at all in fact) and runs on twelve 6V lead-acid batteries. Well, it's supposed to, but the rear brakes are dragging so much it hardly goes at all, certainly with hardly any range. I do hope the owner gets it fixed, because I'd love to take another ride in it! Finally, in an attempt to actually make something instead of just thinking of all the things I want to make, I have started on the pole-mounted camera that Phil and I discussed last week. It's not very sophisticated, and may not even need an electrical system, but it should be a fun way to get some unusual camera angles. | | Tuesday, September 29th, 2009 | | 11:06 pm |
Charging Batteries
It's been a funny few days, but the funniest thing is that the days are not really getting started until nearly lunchtime. I really must find a way to get myself awake in the morning and get out and do something. On Friday, I successfully drove the City-El to the electric vehicle owners' meeting at the charging points in central Bristol. But it felt like it only just got there, with little energy left over. The trip back was easier, though. I'm wondering if the additional battery drain of the long climb up the hill at Filton is part of the problem. We'll see when Filton Avenue is reopened. Saturday was Bristol Linux User Group meeting day, and I took the Cappuccino (via a friend's, who wanted to see the car and then come to the LUG). As it turned out, we had as many Arduinos as Linux machines. On Sunday, I popped over to see ![[info]](http://l-stat.livejournal.com/img/userinfo.gif) k81ng and aminorjourney and helped to clear out the garage. Amongst the stuff, we found a NiCad cordless drill, but no charger. I have now got it working again by improvising a connector and charging up the 15-cell battery. I'm considering modifying it to have a white LED light and maybe a MOSFET speed controller. The garage clearout turned out a number of Prius parts too, including a couple of Denso current sensors, which I'd like to get working in the City-El.  I've also charged up the lithium-ion battery in an Orange SPV, aka the HTC Universal smartphone. It's a Windows CE based phone with two built-in cameras, one for stills and the other for video calling. If I can get the phone SIM-unlocked, then that'll make a good replacement to the aging Nokia 9110. All the FreeCycle items have been collected, leaving me with a bit more room in the house. I've also been given a rug for the living room floor, which turns out to be not only just the right size, but also a pleasant colour scheme. It makes the "sitting" area of the room much nicer. The insulation that I applied to the inside of the garage door has fallen off, which is disappointing. It's supposed to be held on by double-sided sticky foam pads, but I suspect that they'll only dry up in time and fall off, even if I can get them to stick in the short term. So, I may need to devise an alternative fixing method -- I'm considering a sort of zigzag pattern in strong cord, rather like shoelaces. My attempt to charge up a Roomba battery (12 cell, NiMH) has been less successful. It seems to have at least one cell with a bad case of self-discharge. But opening it up will have to wait for a triangular "security" screwdriver bit. Today, I helped aminorjourney with the arrival of a yellow G-Wiz electric car, and then headed for the Uni. The evening was taken up with more Dorkbot activities. Tomorrow, I need to get on with more Uni stuff, but also a trip to the tip to dump the accumulated scrap metal from the garage. | | Thursday, September 24th, 2009 | | 7:18 pm |
Petroleum Spirit
The big news of the day is that the Suzuki Cappuccino is back on the road again after three years spent dormant in the garage. It needed two new sills, two new tyres, two new brake disks and a number of other small repairs. The repair turned out cheaper that I had originally been told, because the repairs to the inner sills didn't need the expensive repair sections (steel pressings), which were also difficult to obtain. The repair was also quicker than I'd been expecting, and I got the call yesterday to say that it was all done, when I'd been expecting a message about delays. That meant I had to rush ahead and get insurance arranged, so that everything was ready for today. This morning at about 7:30, I got a wake-up call from aminorjourney, and we were off to Fishponds (in her EV, of course). We arrived, checked the car over, grabbed the MOT certificate, and headed back to the DVLA office. We arrived there twenty minutes before it opened (at 9am) so we made a detour to B&Q. I was the ninth customer of the day at the (newly refurbished) DVLA office and rapidly came away with a neatly printed tax disc. I was back home before 10am, awaiting another call to say that the welding work had been primed with a protective coat of paint. That call came at lunchtime, and I set off on the 581 bus back to Fishponds. So now I have a valid MOT, insurance, a tax disc and a working petrol car! And I have to get used to the noise, vibration, gear-changing and smells of a petrol car again. In fact, driving the Cappuccino makes the City-El seem big in comparison. Oh, and I've already tried to get the Cappuccino into reverse by flipping a switch on the dashboard, like you do in the EV. In the garage, I have tidied up and installed the insulation on the inside of the up-and-over door. I've also sealed up a huge gap between door frame and wall, with mastic. This evening, I must offer a few items on FreeCycle to complete the clear-out. Meanwhile, back at the MSc, I have had a frank meeting with my supervisor and he's basically told me to just get on with making the autonomous car work by any means I see fit. Carte Blanche, in fact. So I don't need to go and meet up with the guy who's designed a PIC-based CAN-bus node. But I do need to design my own CAN-bus system based on the AVR chips. I can't say I'm proud of myself for being so anti-PIC, but at least things are moving again. Oh, and the Uni has moved the deadline back again, to May 2010. | | Saturday, September 19th, 2009 | | 11:43 pm |
EV Tale Of Woe
It's been a while since I posted an update here, so there's quite a bit to catch up on. I have gained a Compaq Presario 3000 laptop, with Pentium 4 processor. It's been a bit beaten up, with a broken USB socket and knackered battery, but it runs Slackware 12.2 and can drive an external monitor as a second X Windows screen (or as a single wide desktop using Xinerama). Shame it has no serial port, and the PCMCIA slot won't recognise non-CardBus cards. But I've fitted a new NVRAM battery, desoldered the USB socket, and got a new one ready to go in. Well worth fixing up, overall. The Dorkbot Bristol project for Staging Sound in Bath was a big success. We had two modified BMX bicycle front wheels, with Arduino microcontrollers and reflective opto-sensors attached. They played generative music via speakers fixed to the handlebars. The music was synthesised directly by the Arduino using the AVR chip's PWM facility. At the end of the day, we paraded through Bath playing musc as we went, accompanied by the other circuit-bent instruments that had been made during the day. We'll be doing it all again in October for a festival in Cardiff. Meanwhile, I've made a number of improvements to the PWM synthesiser and also made a small CD-sized version of the wheel for desktop testing. A photo of that version was featured on the Make magazine blog.  I've continued to run about in the City-El electric bubblecar, with the new set of Crown lead-acid batteries. But the other day, just as I was about to drive into the car park (and hence the charging points) in central Bristol, all the lights on the instrument panel went out. That can mean only one thing: the DC-DC convertor had shut down. That, in turn, meant that the battery voltage had dropped below 22V (normally 36V). I crawled the car into the car-park but it couldn't make the climb up the ramp to the charging point. Fortunately, I got there (after a short pause) by using another, less steep, ramp. So now it was charging, but I had to get it home -- after dark with the additional drain of the lights on. As it turned out, with a couple of charge-ups from friends en-route, I got it home OK.  So now I have an EV that can't make the 10km/6.5mile trip to town, let alone get back again without a charge. Something must be wrong, but what? I checked a number of possible causes, without finding anything conclusive. I think that, on that particular evening, I hadn't fully recharged the batteries before setting out -- but that still leaves me with a marginal 6.5 mile range. There must be something else wrong. Which led me to wonder if the brakes were binding; the front wheel's brake drum is usually hot after a run, but nowhere near as hot as a petrol car's would be (the Suzuki Whizz-Kid had binding brakes once). Then I finally realised that, given the much smaller amount of energy in the EV system, the hot brake drum was surely a bad sign. I carefully checked the City-El manual and found nothing in the diagnostics section for brake troubles. But in the section for the brake pedal, it mentioned a 0.2mm clearance at the master cylinder, and an M6 threaded adjuster with lock-nut. Now, an M6 thread has a pitch of 1mm, and I undid it nearly two turns before any clearance showed up. So I think it was nearly 2mm too far in at the master cylinder and definately binding at the wheel cylinder end. I've had the car over two years, and it's been bad all that time. Crap. I have now lost all enthusiasm for the Masters degree. I have passed, with good marks, all the taught and examined modules. But I have completely come to a halt with the project work, which is based on an autonomous vehicle with a CAN-bus for sensors and control. All I have to do is get a CAN-bus working with a few sensors, and controlling the vehicle's motor and steering, and then write it up. The deadline is in November. But no, I can't get started. Crap again. But one positive thing has happened this week. With a lot of help from aminorjourney, I have taken the DEC TU77 reel-to-reel magnetic tape drive from my garage to The National Museum Of Computing at Bletchley Park. It has been taking up space in my garage for twenty years, and has only been powered up once in that time. It's a huge rack of vacuum pumps, compressors, fans, motors and electronics that was originally connected to a PDP-10 at King's College, London. At TNMOC it looked small next to the big ICL machine, the Elliot 803 and the air-traffic control radar system.  Since shifting the TU77, I've been able to make some rearrangements in the garage and put up some of the storage and tool racks. I've had those since March but only now done anything with them. Tonight, I also gave away a load of bubble-wrap and other packaging materials via FreeCycle. | | Sunday, August 16th, 2009 | | 10:23 pm |
Oh What A Busy Few Days
Wednesday started with a meeting with my Masters project supervisor. All went OK, but I'm still finding it hard to get properly motivated. Rest of the day spent following up on that and preparing for the Dorkbot Hack Day. The theme is "mobile music", and that leads to Arduinos running music-generating code. Also a trip to the UWE library in search of circuits. The main thing to do on Thursday was to get the Farnell order sent off. I got a selection of stuff for Dorkbot, as well as some TL071 op-amps for the microphone preamp. That was done by 2pm, easily in time for the parts to arrive the next day. Thursday evening was a pre-Hack Day meeting for Dorkbot Bristol, at the Watershed. I took the City-El electric bubblecar, did a few errands and purchased some parts from Maplin. Also got some balsa wood (3/8 inch thickness) for use with drawing pins for circuit-building! Friday morning and sure enough, the parts arrived. All good and ready to go for Sunday. Trip to Cabot Circus in the evening for sushi with friends. Discovered last thing in the evening that I'd ordered programmable unijunction transistors (2N6027, 20p each) instead of unijunction transistors (2N2646, £2.50). So that'll mean a slight change to the circuit to get them working as oscillators. Saturday was the occasion of aminorjourney and k81ng's civil partnership. Friends and family arrived from far and wide. I was acting as photographer for the day, too. All went very well, the weather was sunny and the day ended with everyone tired but happy. Sunday was Dorkbot Bristol Hack Day. I hadn't really left myself enough time to pack up the stuff I needed to take, which meant a last-minute rush and a few things left behind (nothing vital). The trip down to Stokes Croft, with the car fairly heavily loaded, gave me doubts about making the return trip without charging. So, to be on the safe side, I ran over to Cabot Circus again for the charging bays. In fact, I'm wondering if the trouble is actually poor instrumentation in the car rather than actually using up the batteries after less than seven miles (they were at 36.6V before charging). As for the Hack Day, we had circuit-benders working on the spoils of a trip to the Bradley Stoke car boot sale, we had simple oscillator circuits made on balsa wood and drawing pins, we had an Arduino tapping out rhythms on a bank of solenoids and we had my project, an Arduino generating music based on trigger pulses from an optical sensor. I wired up the sensor initially to an LED, which revealed that it needed patches of light and dark surfaces about 25mm in size. Shiny metal bulldog clips also worked, but had to be accurately aligned with the sensor. We decided to use black felt pen on white paper, and keep the blobs over 25mm. Ultimately, the sensor will be attached to a dismembered bicycle. Meanwhile, the Hamilton House lift had failed. It was forlornly trying to close its doors, but sensing a ghostly obstruction every time. We had to stage an escape via a roundabout route that brought us out at the Gloucester Road side of the building, instead of coming out at the car park side on City Road. Getting back in was more convoluted, requiring someone on the inside to open one of the inner doors for us. Suggestions were made that a tunnel could be dug, avoiding the razor wire and by-passing the searchlights and guard towers (for the full effect, imagine somebody whistling the theme from The Great Escape). Back at the Arduino, I took the existing delay-based code and made it respond to the logic state on Digital Pin 2. Now, we got a new note whenever the sensor was triggered. A swiftly applied paper disc on the bicycle wheel was followed by some equally swiftly applied gaffer tape to fix the sensor onto the bicycle forks. Finally, we had a working Arduino program and a working opto-sensor, set up on the bicycle wheel with an amplifier and a battery. You could spin the wheel and get the Arduino to play a new note each time the dark spots passed underneath the sensor. Success! After another Great Escape back to the car park, this time with three other escapees carrying the tech gear, I loaded up the bubblecar and made a silent exit. The trip back seemed to go better, leaving me with 37.2V on the batteries. I made a minor repair to the sunroof by replacing a bolt that had fallen out the day before. | | Monday, August 10th, 2009 | | 7:23 pm |
Amplification and Volt-metering
I have finished constructing a balanced microphone preamplifier. The circuit that I used is here: http://sound.westhost.com/project66.htm. The only changes I made were in the choice of transistors (ZTX214 and ZTX300) and the use of switched resistors for setting the gain instead of a potentiometer. When it's set for full gain, it's a little noisy but the mic signal is very strong. Medium gain seems to be a good compromise, at least with my PC's "line in" port. Which, incidentally, is far from a noise-free signal path. Will be interesting to try it out on a better quality sound system. The actual construction is captured for posterity as a time-lapse video, shot with a Mini-DV camera, an IEEE-1394 interface and 'dvgrab' on my Linux box. I set it to grab every eighth frame, which makes the playback run at eight times normal speed. I had to find a 60W filament bulb for the work light, to avoid awful colour shifting problems with the CCFL. Once I've got the video file onto YouTube or Vimeo, I'll post a link. So now I'm back on the expanded scale voltmeter for the bubble car. All attempts to fix up the old Tandy multimeter have failed. It's got a flaky connection somewhere deep inside (it's two PCBs full of CD4000 series chips and a DVM chip, sandwiched together). My original plan to use a fine 80mm square Simpson panel meter has been thwarted by the fact that there just isn't room behind the panel on the charger for it to go. I have, however, found a smaller 100uA meter which I have fitted with LEDs for illumination. There is room below the ammeter for that one, and I have found the right zener diode to make the circuit work. | | Sunday, August 9th, 2009 | | 12:00 am |
It's All About Cars
Well, it's about electronics and software too, but mainly about cars. Firstly, there is news about the City-El, my electric bubblecar. I wrote earlier about getting it through the MOT test and running it on a temporary set of batteries. I have now, with a lot of help from aminorjourney, purchased three new Crown 12V 105Ah batteries and installed them. Since then, I've taken the car to the charging points at Cabot Circus (twice), to the Tesco's in Bradley Stoke and to UWE. None of these trips have been long ones, so I still haven't determined the overall range. I've been monitoring the pack voltage fairly carefully, although I have now removed the Tandy multimeter that was fixed to the dash with Velcro. It was reading 0.6V too high at around 40V, which is enough to make it useless for the purpose of monitoring charge. If I can get it recalibrated, I'll reinstall it in the rear of the car, next to the charger's ammeter. I have a good circuit for an expanded scale (analog) voltmeter that would read 30-45V, so I may fit that, if I can find a good mounting arrangement. I'd also like to fit a charging indicator light and some night-time illumination for the ammeter. The high-level brake light continues to annoy, mainly by falling off. As part of the stuff I'm doing for Dorkbot Bristol, I have connected a MIDI keyboard to my Linux machine, and a MIDI synthesiser module. It's a Roland CM-32L, which I bought at a car boot sale a few years ago. It turns out to have a good selection of rhythm sounds, which will be useful for the Dorkbot project. One of the City-El trips was to Bradley Stoke, to collect a FreeCycle item: a set of PC speakers and sub-woofer. Now, I was told that it was broken, but the fault went deeper than I expected. First of all, the volume control for the subwoofer was broken -- snapped off at the PCB level. I fixed that by soldering six short wires to it and resoldering it to the PCB. Then, I found that the main on/off switch (on the main volume pot) was broken, so I by-passed that (it didn't actually switch the mains off anyway). Then, the pots were so worn that they acted like carbon microphones. But the most odd thing was that the sub-woofer just didn't respond to low frequencies. It peaked at about 75Hz, when tested with the fine HP 3310 Function Generator. I traced the circuit of the crossover filter and changed a pair of 0.068uF capacitors to 0.47uF, and suddenly it worked down to below 5Hz. That actual speakers seemed to be OK. The power amplifier chip turned out to be a Philips car radio amplifier. Monday was mainly about making videos of electric cars, namely the Mitsubishi Miev. Quite by chance, we discovered an ideal site for a secret lair, not far from Chippenham and apparently abandoned. The gatehouse had a very derelict but distinctly 1930s look to it. There were vast areas of concrete, derelict industrial buildings and hints that it may have once been something to do with the water supply system. Once safely back in Bristol with the precious footage, we discovered that my recent Linux upgrade (to Slackware 12.2) had rendered my FireWire interface useless. This led to general gnashing of teeth and recompiling of all sorts of obscure packages. It's fixed now, though, and I'm about to embark on some soldering, while simultaneously recording every eighth frame of the video onto a DV file on the Linux filesystem. The result will, I hope, be a speeded-up version of the build process -- inspired by Mythbusters. At UWE, I was given a batch of Acorn RiscPC Model 700 machines, with StrongARM upgrade modules. But they were all fitted with strong brass padlocks to keep the covers closed. Well, they looked strong but actually succumbed to drilling out really rather easily. Inside, they all have leaky clock batteries, but are otherwise OK. I've only tested one so far, but that one worked fine. Running it was a glimpse of a lost civilization from 1996... Finally, yesterday I contacted the new Suzuki main dealer in Bristol and arranged to have the Cappuccino picked up (on Tuesday). So, today I fitted the new battery (I got that at the same time as the City-El batteries), put some petrol in, and started it up. Started first time, too! Again with help from aminorjourney, we cleaned the car, removed the cobwebs, pumped up the tyres and generally made it ready for its repairs. Having checked the MOT failure note, it turns out that the Cappuccino has been in the garage for three years, not two years as I first thought. | | Saturday, July 25th, 2009 | | 10:08 pm |
Colchester and back for the last time
I have now made the final trip for Colchester and back, at least for the time being. Mum is in the nursing home and the flat keys have been handed back. Colchester FreeCycle was a great help with clearing the flat, as was Nicole's charity shop. We also sent a few items to the auction salerooms, which will have been sold by now. I did bring a few final items back with me, but they were mostly things like a jar of coffee, the kettle and a mug. Couldn't resist a visit to Aldi, where I acquired a suction-base vice for six quid. While I was in Colchester, though, we had the excitement of a huge scrapyard fire, which sent up a pall of smoke that was visible for miles around: http://www.heartcolchester.co.uk/article.asp?id=1412676So now I can concentrate on my own stuff for a while, without the distractions of worrying about mum, the nursing home and the flat in Colchester. This means that I will be doing more with electric vehicles, the Arduino microcontroller, the ARM microcontroller, the robotics Masters degree and Dorkbot Bristol. Speaking of which, I'll be building a mobile musical gadget for an art festival in Bath, to which Dorkbot has been invited. I'm thinking of doing some type of physical interface to a sequencer or rhythm box. Amongst the things I brought back from Colchester was a toy musical keyboard, a kiddie cassette recorder and a pair of (broken) karaoke microphones. I just can't resist this stuff! | | Wednesday, June 24th, 2009 | | 10:56 pm |
Colchester and back again
Another round trip to Colchester, more successful this time. Mum is set up in a nursing home and the flat is getting a lot closer to being cleared out. I have the family photos here now, as well as mum's toaster and a few bits and bobs. The trip was made less tedious by the handy "AUX IN" socket in the car, which connects a portable music player to the car's stereo amp. I called at Maplin's while I had the chance, and acquired screened cable to repair a pair of 35-year-old phono leads. That repair is now done, and the leads are ready for use again. Also made up an XLR cable for the old Shure 588SA dynamic microphone, in preparation for a home-made balanced mic preamp. I already have a functioning electret mic preamp made from a dual op-amp, which sounds OK. But the big news is with the electric bubblecar, the City-El. Last week, with a little help from friends, we got it to the MOT test centre in Staple Hill and it passed a Class III test (that's the class for three-wheelers). We then got it back home and I set up insurance. Having got the cover note, it was off to the Post Office for a tax disc and now it's back on the road. I've done a few short test runs today, gradually working up the range. Maybe tomorrow I'll attempt the Bradley Stoke charity shop run (much shorter on foot, that one). I'm still running it on a mixed set of used batteries, so the range could be anything from a couple of miles to maybe ten miles. | | Wednesday, June 10th, 2009 | | 11:40 pm |
Colchester and back
Over the last few days I have been to Colchester to visit my mum and try to make arrangements for her future. Not altogether successful, after a false start and lots of frustration. I did make a start on the clear-up at the flat and also visited the grave of my grandfather and grandmother. Meanwhile, back in Bristol, I have acquired two new manhole covers and a garage door insulation kit. | | Monday, June 1st, 2009 | | 11:05 pm |
More ARM success
I've now added the all-important LED to the ARM chip, and made it flash. It's a yellow one. More importantly, the code resides in Flash ROM and starts up as soon as power is applied, which is much more like the AVR chips that I'm used to on the Arduino and elsewhere. Now I'm going through the rather long process of reading the chip's user manual before attempting very much more coding. One thing I'll need to master is setting up the clock PLL (phase-locked loop) so that the chip runs at the highest possible speed. Sunday's car boot sale yielded an Evolution MK-7 MIDI keyboard and a later version of the Mashed game for PS/2. Still no sign of any fine old 8-bit computers, but there was a Commodore Amiga with a selection of games. | | Sunday, May 31st, 2009 | | 12:19 am |
ARM Success
I went ahead and reinstalled Slackware Linux on my main dev machine, upgrading from 10.0 to 12.2. Then I built two versions of GCC as a cross-compiler: one for Atmel AVR, one for ARM. Also got the X Windows config set up for a 1600x1200 desktop, although for the moment the PS/2 mouse isn't working (I've plugged a USB mouse in temporarily). Then, it was back to the soldering iron to finish off the prototyping board with the ARM chip on it -- actually an LPC2103 from NXP (the old Philips Semiconductors). The chip has 8k of RAM and 32k of Flash ROM, plus all the usual I/O ports, timers, and so on, and runs at 60MHz. It's programmed via a serial boot-loader that's built into the chip during manufacture. There's a free Flash programming tool called FlashMagic, but that only runs on Windows and isn't open-source. I downloaded the Linux equivalent, 'lpc21isp' and compiled that. Finally, with the hardware done and all the software ready to go, I couldn't put off the crucial moment of switch-on any longer. Following the excellent tutorial at Alexey Vyskubov's site, I connected it up and programmed the chip. And it all worked! So now I need to understand the special run-time startup code and figure out how to put the C program code into ROM (the initial test program puts it all in RAM). Then, it'll be time to connect up some of the usual Arduino-style peripherals like an LCD and maybe a PC keyboard. In other news, I went over to see aminorjourney and made an appearance on EVcast episode 240. Current Mood: accomplished |
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