Computing stuff tied to the physical world

Posts Tagged ‘Teardown’

TD – New Solid State Disk

In Hardware on Jun 5, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

After the recent server troubles (scroll down a bit), I had to replace one of the 500 GB Hitachi drives in the Mini.

I decided to switch to a 128 GB SSD for the system disk, with up to 6x faster transfer rates:

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It came with an interesting USB-to-SATA adapter included. Which looks like this inside:

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And on the bottom:

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(sorry: no teardown of the SSD, it’s probably just a bunch of black squares anyway!)

The scary part was replacing the disk in the Mac Mini’s “unibody” Aluminium case – as explained on YouTube.

But I definitely wanted to keep the server setup in a single enclosure. First lots of disk formatting, re-shuffling, and copying and then I just went ahead and did it. The good news: it worked. The system disk is now solid state!

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I had hoped that the most accessible drive would have to be replaced, but unfortunately it was the top one (when the Mini is placed on it feet) – so a full dismantling was required – look at all those custom-shaped parts:

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The other thing I did was to add an external 2 TB 2.5″ USB drive, to hold all Time Machine backups for both these server disks as well as two other Macs here at JeeLabs. This drive wil spin up once an hour, as TM does its thing.

Summary: the JeeLabs server now maintains a good up to date image of the entire system disk at all times, ready to switch to, and everything gets backed up to an external USB drive once an hour (these backups usually only take a minute or so, due to the way Time Machine works). All four VM’s get daily backups to the cloud, as well as now being included in Time Machine (Parallels takes care to avoid huge amounts of disk file copying).

That means all the essentials will be stored in at least three places. I think I can go back to the real work, at last.

There’s plenty of room for growth: 8 GB of RAM and less than half of the system disk space used so far.


TD – LED flashlight

In Hardware, News on May 22, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

Today’s episode will be a short one, it’ll become clear why halfway down this page…

This is a little bargain LED flashlight, nothing to it really:

DSC 3228

Three AAA (not AA) cells, a toggle button, 24 + 4 white LEDs, and that’s it. Press the button once, and the 4 LEDs on the side turn on, press again to light the 24 on the top, and again to turn it off.

Quite a bright light BTW. The 4 LEDs draw 190 mA, with 16 it rises to 270 mA. That’s perhaps 4 hours of use with 16 LEDs before the batteries run out.

The circuit is as ridiculously simple as can be – one 4.7 Ω resistor and a switch:

DSC 3229

That “metal” reflector is actually plastic with a chrome finish. The PCB is one-sided, no doubt to lower the cost:

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(it won’t take much bending to create a short with that top wire!)

Using Ohm’s law (V = I x R), we can deduce that the LED’s forward voltage is 4.5 – X = 0.190 x 4.7 – in other words, X = 4.5 – 0.190 x 4.7 = 3.6V. Note that the light intensity will vary considerably with battery voltage and that this lamp won’t work at all with 3 AAA EneLoop batteries which only supply 1.2V to 1.3V when fully charged.

The reason I’m opening up this trivial little gadget is not to marvel at the deep electronic engineering that went into it, but to show how custom plastics and a custom case makes something quite practical and nice to the touch. The top and bottom have a rubbery feel to them. The bottom has a little plastic hook in it, which can be folded out.

The bigger news today is a bit of a mess, unfortunately.

Last night I decided to upgrade the JeeLabs server from Mac OSX 10.7.3 to 10.7.4 – that update had been out for a few days, worked fine on two other machines here, so it seemed safe to apply the update to the server as well.

It failed.

This server is connected via wired Ethernet, and I usually only look at the GUI via a VNC-like “Screen Sharing” mechanism built into Mac OSX. It works well, because that connection is re-established even when the machine is in an exclusive “Updating…” mode, so you get to track progress even while the system is busy replacing some of its own bits and pieces. No screen needed, even though part of admin interface sometimes uses the GUI.

Last night, the server failed to come back online. Which is a major hassle, because then I have to move it to another spot to hook up a mouse, keyboard, and monitor to see what’s going on. Never happened before.

Trouble is (probably), that I turned the darn thing off forcefully. I knew that all the VM’s had been properly shut down, and I heard the characteristic reboot “pling”, so I thought it was waiting for a GUI response… or something.

Then the trouble started. Hooked it up, did a restart: no go. So I restarted it in recovery mode, and did a disk check/repair of all the disks. Guess what: the startup disk with all VM’s could not be repaired… whoops!

Time to kick my backup strategy in gear. I have two in place: local hourly Time Machine backups to a second drive, and daily backups for all VM’s to the cloud.

To make a very long night story short: the local hourly backups are fine, but they do not include the VM’s (whole-file backups of a VM disk every hour is not really practical). And the daily backups? Well, they are indeed all there – I can get any day in the past 3 months back, for any of the 4 VM’s. Awesome.

But Turnkey Linux does things a bit differently. Very clever in fact: it only backs up the minimum. The Linux Debian packages for example: these are not backed up, but re-installed from some other source. The rest is a well thought-out mix of full and incremental backups, and it all works just as expected.

Except that my VM’s are about two years old now, and no longer the latest base images used by Turnkey Linux. No problem, they say: you can get the latest, and then recover your own stuff on top of that.

So I spent about 6 hours trying to work out how to get my VM’s back up from the Amazon S3 storage. No joy. I can see all the files being restored, but the result is not a working VM. At some point, package installs & updates hang, with either udev restart problems or bootdisk image generation problems.

And now the crazy bit: the JeeLabs weblog + forum + café sites are all back up again (phew!). I restored from Time Machine to a freshly freed disk partition, and restarted the Mac – it’s alive! Right now, the server is running from the new disk partition, but with the 4 VM disk images still on the damaged partition. So apparently they did not get any damage, although the Mac file system structure on that disk seems to be hosed.

I’ll spend some time thinking about how to clean up this mess, and how to avoid it in the future. The good news is that I lost no data – just a lot of time and some hair. Yikes … this really was uncomfortably close to the edge!

The moral: test the backup strategy regularly. It can still break, even when not changing anything!

Update – All systems are “go” again.

Update 2 – Final diagnosis: one of the 2 internal disks was getting too hot, leading to intermittent failure, so it was hardware after all – unrelated to the 10.7.4 software. And it was probably all my fault, because I placed a (fairly warm) router on top of the Mac Mini. I’m going to replace the failed system drive with with an SSD.

TD – Soldering iron

In Hardware on May 8, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

Today, I’m going to take a quick peek inside the soldering iron from Conrad, which was suggested as low-end soldering option for a first toes-in-the-water electronics toolkit:

Opening up the base is trivial, just remove 4 screws after taking off a couple of rubber caps:

DSC 3123

On the right: the AC mains feed, with 2 live/neutral wires and the green/yellow ground.

On the bottom: again 2 wires plus the green/yellow ground (as crucial safety feature).

First thing to remark is that there is no temperature sensor in the soldering iron. In other words, this is an adjustable unit, but it’s not temperature-controlled – the 150..450°C scale around the rotating knob is bogus.

Just removing the knob and a washer around the potmeter is enough to examine the board up close:

DSC 3121

A couple of resistors, caps, an inductor, and a little transformer – that’s all. Oh, and a little TRIAC in a TO-92 housing (just beneath the transformer). Here’s the other side:

DSC 3122

A plain single-sided low-cost PCB. No surprises here – this is a very low-cost unit, after all.

So how does it work? Well, it’s basically a simple dimmer. But instead of dimming an incandescent lightbulb, it dims the heater coil inside the iron. The way this works is that the start of each AC mains cycle gets switched off – and then only after a specific time does the TRIAC start conducting. The whole circuit is essentially an adjustable delayed pulse generator, synchronized to the AC mains zero crossings.

Here’s what it looks like on the scope (as measured via a differential probe for isolation):


The entire AC mains cycle is 20 ms (50 Hz), half a cycle is therefore 10 ms, and in this mid-range setting, each half of the sine wave is switched on after about 5 ms, i.e. halfway into the sine, at the peak voltage in this case.

Does it work? Sure, turning the knob will definitely adjust the tip temperature – but not very directly. Instead of a feedback loop, we merely control the amount of power going into the iron, and assuming a fairly steady heat dissipation, the iron will then stabilize more or less around a specific temperature. Just like a lightbulb, such a circuit will “dim” a soldering iron just fine this way.

The only drawback is that it’s not tightly controlled. When using the iron and pushing it against a thick copper wire or a big copper surface, the iron will cool off. Real temperature control requires a feedback loop which senses this change and counteracts the effect by pushing more power in when needed.

For simple uses, the crude approach is fine, but if you plan to solder under lots of different conditions (through-hole, SMD’s, PCB ground planes, thick copper wires) then a more expensive type might be more convenient.

TD – Solar light

In Hardware on Apr 24, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

The other day, Ard Jonker pointed me to this item available at the Dutch Lidl stores for €12.95:

DSC 3066

A solar LED light you put in the floor outside, which automatically lights up when it gets dark.

It’s about 14 cm in diameter, and 6 cm deep – let’s have a look inside:

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A solar cell, with two white LEDs, held in place by two screws yearning to be removed:

DSC 3075

The red leads connect to an on/off switch which can be accessed from outside. The batteries are 800 mAh, according to the specs, and look like standard replaceable AAA cells. The PCB has a chip on the other side:

DSC 3076

Hey – not bad, two NiCad NiMH’s and a little chip to drive the LEDs. This could easily accommodate a JNµ!

The DIP-8 chip in there seems to have logic for turning the LEDs on only when it’s dark (weak solar cell voltage, I assume). It does a bit more though, as this scope trace of one of the LED shows:


Probably some sort of charge-pumping, to drive the LEDs beyond the 2.5V supplied by the batteries. The power consumption is about 9.5 mA, so these lights should last through the night if there is enough sunlight during the day to fully recharge the batteries.

Neat. This could make an excellent power source plus enclosure for a JeeNode Micro, but note that the big metal ring is essential – it presses the glass and rubber seal tight against the rest of the enclosure “cups”.

TD – Infrared Remote

In Hardware on Apr 10, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

Steve (@tankslappa) recently sent me two spare IR remotes he had lying around. Very joyfully and gratefully accepting his generous gift, I decided to tear one down to see what makes these things tick:

DSC 3043

Frightfully little, I’m afraid. Just a single SOIC-20 type IC! Marked “DUSUN021” and “1003” (3rd week 2010):

DSC 3044

The switches are custom-designed, using a silicone mat with buttons, each of them holding some sort of little carbon-lined conducting pad. When pressed, they connect two traces on the PCB and that’s it!

Oh, wait, the other side has two more components and some simple battery clips:

DSC 3045

The electrolytic cap just helps the battery supply power for IR LED, I presume, while the other component is a cap 3.45 MHz resonator, and part of the frequency-generating circuit.

Here is a scope trace of the emitted IR light when pressing a single button:


This was picked up with an AMS302 light sensor, BTW. You can see the two pulse trains, i.e. the button press gets repeated twice. Perhaps not as easy to see, is the fact that “ON” is not represented by a simple IR pulse, but by a pulse train. This allows the receiver to filter out noise and random pulses, by filtering and detecting pulses only when modulated in this way.

As you can see in the zoomed-in section, the pulse train consist of turning the IR LED on and off at a 36 KHz rate.

This is within the detection range of the TSOP34838 IR receiver, as used on the Infrared Plug, even though that receiver is optimized for 38 KHz modulation. Don’t be put off by the term “modulation” in this context, BTW – it simply means that the 38 KHz frequency used to drive the IR LED is turned on and off in a certain pattern.

Each key has its own pattern. This remote appears to use the RC5 protocol. Here’s a snapshot of one keypress using the TSOP34838 chip, which detects, demodulates, and then outputs a clean logic signal:


I’ve enabled the tabular pulse search listing, which gives us information about the encoding used by this remote:

  • 829 µs for a short “OFF”
  • 953 µs for a short “ON”
  • 1738 µs for a long “OFF”
  • 1752 µs for a long “ON”

Decoding such a pulse train is fairly easy, and as you can see, the component count for such IR transmissions is extremely low and hence very low-cost. Which also explains the popularity of this system!

PS. I’ve switched to light oscilloscope screen shots as a trial. The colors are not as pronounced, but it seems to be a little easier on the eyes. Here’s the same info, in the dark version as it shows on-screen:


TD – PC Power Supply

In Hardware on Apr 3, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

Well, not a very “deep” teardown, just opening it up and looking inside a conventional 400W PC power supply:

DSC 3003

When turned on, but not powered up, the power cunsumption is a substantial 2.8 W. IOW, that’s your computer when turned off. But the nasty surprise was that even with the mechanical switch in the off position, it still draws 0.04 W? Oh well, the sticker says “2006”, so let’s assume things have improved since then.

Here’s the top view inside:

DSC 3004

Two large heatsinks with two fans blowing air across, the bottom fan is on the outside of the case.

These caps scare me, I had it powered up briefly, so I’d probably get a jolt if I were to touch them now:

DSC 3005

Two small transformers in there, on the right. And here are three more:

DSC 3006

One last toroidial one in where the main circuitry appears to be – note the one-sided PCB with jumpers:

DSC 3007

And that board at the right is filled with varicaps, etc – noise and surge suppression, no doubt:

DSC 3008

Found a schematic of a 200 W supply on this website:


Go to the website for the full-size view. Looking at the number of transformers, this supply is probably similar. The basic idea is simple: generate a high-frequency AC signal, and feed it through some transformers for galvanic isolation and to produce the much lower voltages at much higher currents. A high frequency is used i.s.o. 50 Hz because transformers are more efficient that way. There’s a feedback mechanism to regulate the output voltages.

The TL494 chip (which is not necessarily the same as used in this particular supply) is the heart of a PWM Power Control Circuit, which seems to drive it all. It generates pulses, and varies the ON-time as a way to regulate the generated output voltages. I think.

What I never understood is how you can regulate multiple voltages with what looks like only one feedback loop. In the schematic, the +12 and +5 V outputs are brought together as a single regulating signal through 2 resistors. What if the power draw from those 12V and 5V sections differ widely over time?

Anyway, go to that website mentioned earlier to read more about how it all works. I’m sure it does since there must be hundreds of millions of these on the planet by now…

Update – This particular unit will turn on without adding 10 Ω resistors, as sometimes suggested for lab use of such PSU’s. Voltage unloaded is 3.39V, 5.18V, and 11.99V, so close enough – with a little extra to compensate for wire losses. Big downside for lab use of such a “raw” PSU, is the nearly unlimited current that will flow with a short-circuit – guaranteed to vaporize lots of things! One solution would be to add basic current sensing and MOSFETs to switch off when pre-set values are being exceeded. With proper dimensioning, the added current drop need not be more than perhaps 100 mV, so the generated voltages would still be “in spec”. The + and – 12V would make a nice ±10V supply for analog experiments with dual-supply op-amps, for example.

TD – Cost Control

In Hardware on Mar 20, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

Over two years ago (gosh, time flies), I reported about a low-cost AC metering device called Cost Control:

It seems to be available from several sources, not just Conrad and ELV, under different brand names. Not sure they are identical on the inside, but the interesting bit is that they transmit on 868 MHz and seem to go down to fairly low power levels as well as all the way up to 16A:

DSC 2976

So let’s have a look inside, eh? Here’s the back side of the PCB:

DSC 2971

No much to see, other than a thick bare copper wire, which probably acts as the shunt resistor.

The rest appears to be built around 3 main chips, two of which are epoxied in, so I can’t see what they are:

DSC 2970

Flipping this thing over, we can see the different sections. I had expected a special purpose AC power measuring chip, but it looks like this thing is built around a quad LM2902 op-amp:

DSC 2972

Note the discrete diode soldered on the flip side – the topmost solder joint looks pretty bad!

The rest of the analog circuitry and the MPU of some kind running at 4-something MHz is here:

DSC 2974

The 24LC02 is a 2 Kbit I2C EEPROM, for the node ID and some calibration constants, I presume.

And here’s the wireless transmitter, running off a 16 MHz crystal:

DSC 2975

Being 16 MHz, it’s a bit unlikely that this is a HopeRF RFM12B (or its transmit-only variant), alas. The blob at the center bottom goes to an antenna wire on the other side of the board.

Would love to be able to decode the wireless signal (1 packet every 5s, very nice!). Either that, or find out how they are measuring the power from 1..3600W – the remote actually displays in tenths of a Watt.

PS – See also this forum discussion about decoding.

TD – KAKU remote switch

In Hardware on Mar 13, 2012 at 00:01

Welcome to the Tuesday Teardown series, about looking inside the technology around us.

Today’s episode is about the “KlikAanKlikUit” remotely controlled AC mains switches, a.k.a. KAKU.

I’m going to look at two different units, the older/smaller/cheaper PAR-1000 supporting 16 different addresses, and the newer YC-3500 supporting up to 256 different addresses and switching up to 3500W:

DSC 2956   DSC 2955

Here’s the PAR-1000, once opened (you need a TX9 torque screwdriver for both units):

DSC 2957

There’s a .22 µF X2 cap as transformer-less power supply, in series with a 100 Ω resistor (hidden in black heat shrink tubing, bottom right, next to it). According to this calculator, you can get up to 12.2 mA out of that, when using a bridge rectifier (which is under the cap, using discrete 1N4007 diodes).

The measured power consumption is 0.58 W. Note that due to the way these transformer-less power supplies work, this power is always consumed, whether the relay is turned on or not.

There’s an interesting post-production “mod” in this unit, on the relay, i.e. top middle in the above image. After removing the tiewrap and glue, this interesting part emerges – in series with AC mains:

DSC 2960

I’m guessing some sort of overheating protection for the relay, a PTC resistor?

Here’s the copper-side of the PAR-1000’s PCB, with what looks like lots of solder flux residue:

DSC 2959

And here’s the YC-3500, in a slightly larger enclosure and using a relay which can switch up to 16A:

DSC 2958

Same 100 Ω resistor but beefier 0.33 µF X2 cap, bringing the maximum current to 18.2 mA. Measured power consumption is 0.81 W – what a waste for an always-on device which is merely switching another device!

Here’s the underside of the YC-3500’s PCB:

DSC 2961

Both single-sided non-epoxy PCB’s have SMD’s on one side and through-hole parts on the other, but the amount of solder on the SMD side suggests to me that everything has either been soldered on by hand or glued on and wave-soldered. The extra solder on the left increases the PCB’s current carrying capacity, BTW.

These 433 MHz units respond to simple packets using the On-Off-Keying (OOK) protocol. There’s no way to control them directly, other than via RF – and even if there were, there would be no way for a home automation system to know their state since these units are receive-only. The relay is off after power loss. There’s an LED to indicate the actual on/off state. The choice of 24V relays is wise – needs much less current than 5V and 12V ones.

Note the 433 MHz antenna – a single loop of copper wire in one case, and a loop plus coil in the other!

Tuesday Teardown

In Hardware on Mar 6, 2012 at 00:01

Welcome to a new initiative on this weblog: a weekly series about taking something “interesting” apart and peeking under the hood. I’m calling it the Tuesday Teardown series, and since they’ll all be tagged “Teardown”, that link you see will bring up all posts, accumulating as we walk down this path.

The idea is to look at some neat existing technology and find out how things were engineered, which is after all often a highly creative process, reflecting the outcome of a lot of problem-solving and deep insight about the design and production of all sorts of products. Since this weblog is all about creativity, technology, and exploration, it seemed like an obvious fit to look at how “stuff” was made.

This series of posts is also a departure in that I’ll be passing the microphone to guests once in a while. There is plenty of technology – both excellent and awful – to be able to keep this weekly topic alive for a long time… if you have suggestions, would like to contribute a complete story, or simply want me to translate or do part of the writing for you – please get in touch!

To start off, here’s a little dive into an amazing piece of engineering: a vintage-2005 Apple Power Mac G5 (2x 2.5 GHz PowerPC, each dual-core), which a friend and I recently took apart, after it had suffered a catastrophic breakdown – as you’ll see.

Here’s the shiny new Power Mac, as presented in the marketing brochures (it’s about 50x50x20 cm):

Powermac g5       Overview featurette expansion 20100727

The interesting bit is that at the time, these CPU’s were hitting the limits of personal computer cooling capabilities, yet Apple wanted to really keep noise levels down. As a result, an elaborate set of cooling zones was created, each with quiet cooling fans operating independently and adapting to demands.

I wasn’t really interested in the top part (drive bays and expansion slots), or the middle part (motherboard and memory expansion). I wanted to see the CPU cooling solution:

DSC 2923

This is an oblique top view of the cooling unit, sitting on top the two CPU boards – which are separate from the big motherboard (no doubt easier to service and upgrade this way). The whole unit looks and behaves like a mini car radiator, and indeed, it uses what seems to be the same sort of thick blue-ish liquid coolant (glycol) as you’d put in your car (or your fridge, as cooling blocks).

The whole Power Mac can draw over half a kilowatt, and no doubt quite a bit of that goes to these CPU’s when maxed out. Since all of it ends up as heat, this really is an impressive feat of engineering.

Trouble is… after a few years, things tended to fail. In a pretty ugly way, in this case:

DSC 2927

Massive leakage. Taking the board with it, to the point where the solder joints got corroded:

DSC 2926

Interesting detail – look at the immense number of capacitors on there. Here’s the other side:

DSC 2925

Oh, and this isn’t a run-of-the-mill double-layer PCB either – check it out:

DSC 2930

Even 7 years later, “awesome” only barely covers the level of engineering that must have gone into this.

PS. I also extracted the power supply, rated 600W, to see whether that could be re-used at JeeLabs somehow. But the PSU didn’t really like me – my first attempt at powering it up beyond the default standby state produced fireworks inside and a smelly puff of smoke. It probably needed a certain load to function properly. Oh well.