• Metabo. Mmmmm…

    metabo-logoI am often banging on about the rubbish products out there on the market but there is a beacon of hope. Metabo. Mmmmm… Lovely German made products.  They cost up to four times as much as equivalents but they seem to be reliable and they are a joy to fix. Windings are all nicely sealed, brushes designed to protect the commutator, wires are nicely routed and secured, construction that is simple for ease of servicing, and parts are that readily available.

    We do a bit of work for a company that gives their angle grinders a real hard workout. Usually it is only the switch or brushes or power cord that fails but I did have one recently that had a stuffed armature and field coil.  To be fair, and they do put in protection against it, what may have happened is that a stray metal fragment probably got caught up inside the angle grinder.  Anyway, the field coil was not to badly priced but the armature was expensive.  The repairs would have cost about two thirds of the cost of a new one.

    I have not checked out how the switches actually fail but they have rubber seals all over them to keep out dust.  I was not to keen on the push-in method of connecting solder covered wires to it.  Solder and connections is often a bad match but in this case it seem to be reliable.

    Metabo. Mmmmm…


  • Another crappy CFL

    I was sitting at the dining room table a few weeks back when the light level changed a bit.  I did not think anything of it at the time but a little bit later there was that distinctive smell of overheating electrical equipment.  After checking out all of the electrical things in the area I remembered the change in light level.

    Yep, sure enough, another one of the CFLs had failed in the dining area lamp and emitted the electrical stench.  I have blogged about these things before and this time it is an Elite branded lamp.  It is not as if the lamps are in an enclosure that causes the heat to build up.  I think that they are just really crappy products.


  • To state the obvious…

    I had to laugh when I came across this bit of Korean made gear:

    P1040539

    Check out the handle.  It has got the word “handle” embossed into it!  I don’t know why they felt that they had to do that.  It is even more odd when you consider that the rest of the gear is covered in Korean language rather than English.

    Now I can’t read Korean but a circuit is a circuit in any language.  After pulling it apart I could see that it was just an autotransformer with a number of switched taps coming off it.  There was also a voltage meter, front panel plug (Asian style), current overload switch, and back panel  output terminals.  It is obviously used in an application where the mains voltage needs to be varied for some reason.  The company website is at http://hanilsys.co.kr but without trying a Google translation I could not read it.

    The electrical inspectors would have a field day with it.  Firstly, autotransformers are a bit dodgy because if the common connection of the winding goes open circuit the full voltage is applied to the output regardless of its control setting.  I don’t really know how the regulations pertaining to autotransformers would read for a bit of gear like this.  Secondly, the metal case was not earthed, which is a complete no-no here in New Zealand.   Also, the screw terminals on the back carrying the controlled mains voltage are not completely enclosed, and that will not pass muster.

    Needless to say the thing is now in the scrap pile waiting to be recycled.


  • A new old phone

    My phone started playing up earlier this week.  Every time I tried to make a call or check my voice mail the phone would shut down.  As a good technician I did some basic tests.  I tried rebooting it (removing the battery) and  I gave the battery a good charge up.  None of it helped.  It was almost as if the transmitter output stage had a short and when it powered up it caused an internal supply voltage to dip below the reliable operating voltage.  Anyway, as much as I  would like to repair it and discover the failure mode I decided to replace it.

    It so happened that my partner, my one and only, and my favourite person at the moment (actually these are all the same person and I think that those descriptions have applied for quite some time!) had a spare smartphone.  She was only using it as an alarm clock.  Gee!  And I was only recently blogging about consumption!

    So I now use a smartphone to take my calls.  I am glad that at least my phone is smart!  Maybe it help me get through the day a little easier?

    The old phone will go off to the Starship Foundation mobile phone recycling programme, a worthwhile cause for many good reasons.

    a lot of mobile phones
    The swirling tide of discarded mobile phones.
    Image: Huffington Post


  • Compact fluorescent lamp failure

    I replaced yet another compact fluorescent lamp (CFL) in our house last night.  I have been meaning to track our personal MTBF of these things because they seem to fail all too easily – well before the service life of at least 6,000 hours.  I actually ended up putting in some standard incandescent bulbs in as replacements although they seem to fail prematurely as well.  This time I have kept the receipt to monitor the lifetime of the new bulbs.

    I took the failed lamp to the workshop to investigate the failure mode, along with my small collection of other CFLs that had failed.

    A Woolworths Essential CFL along with a complete one.
    A Woolworths Essentials CFL along with a complete one.

    First up is the Woolworths Essentials CFL.  I think I tried to complain to Woolworths about these things but I never heard back.  I don’t think there is any data on their lifetime available from Woolworths.  After taking the lamp base apart I discovered that one of the lamp filaments was open circuit.  There was also quite noticeable deposition on the inside of the tube. This deposition is probably tungsten that had boiled off the filament.  There are two capacitors on the circuit board that are probably polyester greencaps which are now quite a dark colour indicating that they had built up a lot of heat.

     

     

    A dismantled Philipd Geni CFL.  The venting of the capacitor is not very obvious at this angle.
    A dismantled Philips Genie CFL. The venting of the capacitor is not very obvious at this angle.

    The next one I inspected was a Philips Genie 11 watt model.  I gave it an initial test to see if it was actually blown (it was in my to-do pile for some time). The CFL tube gave a brief flash at switch on in the same way that some incandescent do when they blow.  After taking this one apart I found that the the mains filter capacitor (4.7μF at 400V) had almost vented.  Capacitor failures due to venting (caused by a build up of internal pressure during overheating due to the ESR) are a common fault in switched mode power supplies.  These power supplies operate at frequencies in the order of 20 kHz so if they have poor quality capacitors the heating due to ESR is significant (Ohms Law, ripple current, heat dissipation and all that). Heating due to ESR is much less at a 100 Hz ripple frequency so the failed capacitor must have had a really high ESR value.  The capacitor is one of the cheap brands that come out of China so it’s failure is no surprise.  As for the failure mode I can only guess that the capacitor ESR slowly increased, the lamp may have somehow shut down due to over temperature, and then when I turned it on from cold the high ripple voltage caused the switching transistors to fail by both being in conduction at the same time.  Someone has reverse engineered the electronics of some CFLs and you can check out the circuits on this page.

    Ecobulb and original packaging.
    Ecobulb and original packaging.

    The last one I looked at was from Ecobulb, a New Zealand company, although the lamps themselves are manufactured overseas of course.  Given the lack of debris and signs of heat discoloration his one did not look like it had had much use.  The switching transistors had shorted and an RFI coil was open circuit.  The coil essentially acted as a fuse.  My guess is that this one failed because it was used on a dimmer circuit.  Hmmm, that gets me thinking about the design of the electronics in these CFLs.  There is no reason why the designers could not have put in a low voltage cutout in the circuit.  Oh, silly me that would cost extra and affect the profits!

    Eventually I hope to wire the whole house for 12 volt lighting and then use 12 volt LEDs in all of the lamp fittings.  This is a much more elegant, versatile,  and efficient way of lighting.  Single step down transformer (switched mode of course), ease of battery backup, ability to hook into PV panels would be a few of the advantages   I’ll keep you posted.

    Incidentally, Interwaste do CFL recycling and I think they actually pioneered fluorescent lamp recycling in New Zealand.


  • Electric pencil sharpeners – what next?

    I have asked the question of how much technology do we really need in a previous post.  I now have to question the need for electric pencil sharpeners.

    Why bother with electric pencil sharpeners?
    Image: Wikimedia Commons

    So what is hard about sharpening pencils? What is wrong with the low tech options of a hand cranked model?  Even that is overkill in my opinion.  The small hand operated type works just fine.

    An electric pencil sharpeners needs all sorts of materials that need to be mined,  transported, refined, transported again, manufactured into the final product, shipped around the world, and then purchased by the customer.  And what happens to it when it is at the end if its useful life?  It should be recycled but at present that is not likely to happen here in so-called clean-green New Zealand.  An electric pencil sharpener also contains embodied energy, a proportion of which will be from fossil fuels.

    So here we are, squandering the future of Earth on unnecessary items such as electric pencil sharpeners.


  • How much technology do we need?

    Now I am no luddite – that is obvious since I repair and own all sorts of high tech stuff – but I have to question just how far do we go with all of this electronic technology?  Most of us are buying and using it so we obviously want to have it.  But do we need it?  Is it being forced on us by seductive marketing and the pressure of keeping up with the Joneses?

    What prompted these thoughts was my discovery here on our roadside of a discarded vacuum cleaner hose (of all things) from some unknown brand of machine.  I was interested to discover that it had a remote control with three buttons built into the hand piece of the hose.  As an electronics tech my professional interest was aroused.  My first thought was how does it interface to the vacuum cleaner?  Does it have a set of contacts on the hose end?

    It turns out that there were no wires or contacts at the vacuum cleaner end of the hose.  So I unclipped the bezel surrounding the buttons – a simple matter of of using a small screwdriver as a lever in a slot on the bezel edge – and a circuit board assembly dropped out.  It had some water damage but I could see that it was a little battery powered RF transmitter and a bit of control circuitry. The buttons still work because the LED comes on when they are pressed, and the battery is reading about 2.5 volts.

    Is it useful?
    Is it useful?

    If I had the actual vacuum cleaner I could have repurposed the remote control into something else.  Unfortunately it would probably have a very poor range because it only ever has to transmit the length of the hose and it is only powered by a CR2032 cell.

    So all this effort has been put into designing and manufacturing this little gizmo to improve the owners vacuum cleaning experience. Or has it? Just how useful was it over its short lifetime?  Given the materials and the unsustainable energy that went into making it, that these things are not likely to be recycled, and the relatively short useful lifetime of vacuum cleaners, it all makes a mockery of environmental protection.


  • Don’t snort your crushed microwave oven

    NOTE: Some information contained in this post is incorrect.
    See the comments for further information.

    Here is a little bit of advice.  If your microwave oven is crushed into a pile of dust and shredded metal you should not snort it up your nose.  Bits of it are poisonous.  The magnetron, which generates the microwave energy, has a sintered ceramic insulator that is made from beryllium oxide.  During use it is inert and harmless but if it is crushed and the dust is inhaled you can get berylliosis, an incurable disease of the lungs.

    There are other electronics items that contain beryllium oxide as well as other nasties, so to be safe make sure all of your e-waste is recycled.  Here at Ecotech Services we can fix or safely recycle your microwave oven of course. Or we can recycle just the magnetron. And other types of e-waste.  Give us a call.

    The pink section just below the waveguide at the top is made of beryllium oxide.
    Image: Wikimedia Commons.

    [Edited 13 August 2015]


  • Cheap and dangerous rubbish

    While browsing my filing system (also known as the office floor) I came across a news item from 2013 about a real dodgy Chinese knockoff of the Apple iPhone chargers.  A Chinese women was electrocuted when she answered her Apple phone.  Now you cannot get electrocuted from an iPhone of course because it runs on extra low voltage (ELV) but it was plugged into a charger at the time.  This suggests that the charger, which was not Apple branded, did not have any isolation between the mains power and the ELV output.

    Credit where credit is due and while we can easily criticise Apple for all sorts of things they did the right thing by offering their replacement chargers at a discounted price in many countries, including New Zealand.

    It was not the first time that phone chargers has caused electrical shocks and there was another case in China soon after the fatal one mentioned above.  As a technician I am very interested in the results of any investigation into dangerous phone chargers but a quick poke around the internet did not bring anything to light.

    Designing a charger that gives sufficient isolation between the mains voltage and the ELV output is not rocket science! Insulation, isolation, testing, compliance etc are all important things.  So come on manufacturers get your act together!

    UPDATE: Yep, sure enough, these crappy chargers don’t have enough isolation between the primary and secondary (amongst a whole lot of other problems)!  This is a video from Dave Jones over at the EEVblog who did a teardown of two of them:

    EEVblog #388 – Fake Apple USB Charger Teardown

    No Description


  • Electronic pest control

    This is a little off topic but as an electronics tech who is keen on conserving the many endangered species I occasionally ponder the use of electronics technology to do the job of controlling predator numbers.  Here in New Zealand there are a number of really bad mammalian predators, the stoat being one of the worst but rats, mice, feral cats, and possums add to the problem.

    The use in New Zealand of the mammalian pesticide 1080 (sodium fluoroacetate) is really contentious and the media have recently been banging on about the by-kill of the kea, a unique, endemic, clownish, intelligent alpine parrot.  It is a valid concern but the pest problem is really bad and 1080 is the most cost effective option.

    goodnature trap
    A goodnature trap mounted in position on a tree.
    (Photo copyright by goodnature)

    One of the newer mechanical technology methods of trapping stoats and possums is a pneumatically operated skull crusher developed by goodnature.

    It looks like a really good idea and because it only needs to be checked once a month it is a more cost effective way of controlling pests.

    I want to go a step further and have a completely automatic trap for all pest species that never needs to be maintained.  A big ask you may say. Well I say that if we have flown to the Moon, to Mars, and sent space probes to beyond our Solar system (and I say that we have to all of you Moon landing conspiracy theorists) surely we can trap a few animals in the bush.

    So how would it work?  Since facial recognition software is now old hat it will be easy to develop species recognition software.  So all we need to do is to mount a camera in a trap and when the target pest is recognised some method of killing it is activated (perhaps mechanical but I like the idea of electric shock).  A trapdoor is then opened and drops the now dead pest on the forest floor.  The trap will then reset itself for the next baddie.

    The trap could be powered by a solar panel, although this will not be very effective under the shady bush canopy.  Maybe the weight of the pest as it falls out of the trap could be used to drive a small generator?  Hmm, maybe not.  Could be prone to mechanical failure.  Modern electronics can be made to run on the smell of an oily rag so powering the trap may not be too much of an issue.

    One problem is that the trap could be stolen by some nasty individual that thinks it might be worth a bit of money.  There was a case last year some time where a very expensive and specialised wildlife monitoring camera was stolen from a remote part of a protected area here in Christchurch city.  As well as being a financial cost it set the scientific work back a bit.

    I like delving into the realm of “conservation technology science fiction” and I have been dreaming up a few scenarios.  We could employ a fleet of airborne drones with image sensing for pests and lasers deployed to zap them.  Hmm, that sounds quite feasible to me.  How about an army of nanobots that swarm over the land to seek out pests and then somehow kill them?  And then dismember them into individual molecules rather than having the carcase left behind to disrupt the ecological balance.

    Now we really are talking science fiction! A bit like Michael Crichton’s book Prey.

    Image from The Lens Flare
    They are coming….!
    Image from The Lens Flare.