SSD als externe Festplatte

Ganz neu: Die mit Speicherbausteinen ausgestatteten Festplatten(SSD oder Solide State Disk). Sie sind unempfindlich gegen Stöße und Stürze, schnell, stromsparend und klein. Dafür ist der Preis leider noch etwas höher als bei externen Festplatten mit der alten Technik sich drehender Scheiben. In Zukunft wird diese stromsparende Technik bei externen Festplatten aber eine immer größere Rolle spielen.
Immer mehr Käufer legen sich eine externe Festplatte mit Audio- und Videoausgängen zu (Multimedia-Disks). Damit ist es möglich, Filme und Musik direkt von der Externen Festplatte auf dem Fernseher wiederzugeben. Und das dank HDMI und Full HD in ausgezeichneter Qualität.
Im Heimnetzwerk beliebt: Sogenannte NAS (Network Attached Storage). So eine externe Festplatte wird direkt an Ihren DSL-Router angeschlossen. So können Sie von jedem Computer im Netzwerk auf die externe Festplatte zugreifen, ohne das immer der Computer angeschaltet bleiben muss, an dem die externe Festplatte angeschlossen ist. Und bei Bedarf können Sie sogar über das Internet auf Ihre Daten zugreifen.
Externe Festplatten sind ausgereift, bekommen von den Herstellern wie Western Digital (WD), Freecom, Seagate und Lacie immer mehr Extras spendiert und erobern sich so immer neue Nischen und Anwendungsbereiche. So wird man auf seine externe Festplatte bald nicht mehr verzichten wollen und auch nicht verzichten können.

I, and others, have our doubts about wether this video is a fake stunt, or a true story. It is true that the Fonera overheats, much more than would be expected from a consumer-electronics product, but to the point of causing physical damage to the plastic case?

The heat problem

Heat in electronics mostly comes from dropping voltage by converting current into it, in our case, the voltage regulator in the Fonera drops 5V to 3.3V at 500mA, resulting in the dissipation of 850mW. That’s right, we are dumping 850mW right into the atmosphere in the form of heat. This brings the operating conditions very close to the maximum ratings for this regulator, which has a maximum rated thermal resistance of 90ºC/W, my calculations put the operating conditions at 88ºC/W. Additionally, the wireless section of the Fonera is also converting a lot of energy into heat.

The measurements

After I finished my tests, I got a comment from Pobletewireless, regarding his own measurements of the heat problem, which are shown in very cool thermographs (no pun intended!) – much nicer than my rather rudimentary method.

I measured the temperature of the Fonera using a thermocouple connected to a Fluke 123 Scopemeter via an 80TK thermocouple module. The thermocouple was placed in between the heatsink and RF shield, the case closed, and the Fonera powered, as can be seen in this picture:

After 10 minutes operating normally, the temperature had risen to an average of 72ºC, with a peak of 80ºC.

The second batch of measurements were performed drilling four small holes to allow the thermocouple into the casing, the locations are shown in the following picture:

Maximum temperature at one corner was 43ºC. Next, an attempt was made to melt the white lid of the Fonera, by exposing it to a high temperature airflow from a paint-stripping gun, and at the same time, applying slight pressure from below. The thermocouple was used to measure at which point the plastic became maleable, and deformation started. At around 100ºC, the plastic was soft enough that a solid object could change its shape – this is in line with ABS plastic thermal properties, which state a deflection temperature around 100ºC, depending on specific material composition.

As the deflection point test resulted as expected, the lid was then exposed to an airflow at 280ºC for two minutes. The result of this exposure is shown in the pictures below:

It’s obvious that some deformation has taken place, with discoloration and charring on the point where heat was directly applied. However, the front side of the lid had mostly retained its shape.

Conclusions

The Fonera does indeed run very hot, much hotter than it should, if anything, for the good of the internal parts. Electronic components are sensitive to heat, with maximum ratings given by each manufacturer in terms of storage and operating conditions. The higher the temperature, the lower the service life of any given component. Some are affected more than others, most notably, electrolytic capacitors have a high sensitivity to heat, as it can evaporate the electrolyte quicker, causing it to fail. The capacitors in the Fonera are made by Taicon, a taiwanese manufacturer, and are max-rated for 105ºC. From the datasheet [PDF], at this temperature, the capacitor will fail after some 2000 hours, around 83 days. Following Arrhenius’ Law, and since the area around the capacitors was found to be at around 52ºC, their expected life would be 7800 hours, or about 325 days – what a coincidence, almost a full year, after which your warranty has expired. Comparing the Fonera to a Meraki Mini, one realises that there is a serious design flaw, as apart from the Mini having a switched-mode regulator, the wireless section shares exactly the same design as the Fonera. The temperature measured outside the casing of the wireless section indicates that the junction temperature of the components inside has to be ridiculously high. So, one conclusion is that the Foneras will eventually fail due to overheating, and it will probably happen sooner than later.

On the deformation / melting video – in my opinion, it’s not real. At least, it couldn’t have happened without the Fonera reaching temperatures around the whole casing that would have caused some components to blow up (for example, the capacitors). The Fonera could not have undergone such an extreme temperature, and still function as shown on the video. The temperature gradient between the heatsink and one corner of the case is almost 2:1, thus, to reach a deformation temperature of say 200ºC at the corner, the heatsink must have been running at 400ºC! A final bit of evidence – the sticker. If you look closely at the video, the sticker on the bottom of the Fonera looks almost unscathed. Here is a picture of what it looks like after applying a 250ºC airflow for 30 seconds, which causes the plastic to deform:

Obviously, a more prolongued exposure would have damaged it even more. In all honesty, I would love to get more details from the guy who made the video, as it stands right now, I’d call it a hoax.

To recap a bit, the problems are random reboots of the keyboard, disconnections of keyboard and mouse, erratic mouse behavior (including spontaneous motion of the cursor), and repeated keystrokes after the keyboard has not been used for a few minutes (resulting in things like “aaaaaaaafter the news…”). In all, a very frustrating and annoying experience, for a rather expensive combo. Logitech seem to acknowledge the problem, but I have not yet seen any form of update that could fix this, and my theory is that the problem cannot be fixed with a simple software update.

Declaring the keyboard and mouse defunct, I performed an autopsy, which revealed a few interesting facts (details after the jump):

• The Bluetooth dongle has a very very strange RF design – it uses a normal groundplane meander PCB antenna, but then it has a copper-wire loop antenna on top.
• Dongle and keyboard use Bluetooth chipsets from different manufacturers (CSR and Broadcom), in theory interoperable, in reality…well.
• The touchpad uses a very crappy sensor design, which explains the lack of responsiveness and uselesness of the scrolling controls.

Let’s start with the dongle. Below are a couple of photos of the opened device, the first with the loop antenna in place, the second with it removed, showing the meander. If someone with better RF knowledge than me can explain why this makes sense, I would be grateful. The design of the loop itself is wrong for 2.4GHz, having a wire length about 10 times larger than what would be required given its size.

The dongle uses a Broadcom BCM2045 chipset, with a 4Mbit flash memory onto which the firmware is loaded. The meander is a PCB track designed for 50ohm impedance, coupled to the chipset via a normal inductor-resistor-inductor matching network. Noticeable is the lack of baluns or filters, I’ll have to check the datasheet (if it’s publicly available) on this aspect.

Let’s take a look at the keyboard, starting with the touch controls. These are built into the keyboard as a separate module, linked to the main control board with a flat ribbon cable, and consist of three main pieces – the PCB and touch sensors, external case with printed cover, and a plastic support with built-in LED light pipes. The controls are made with a layer of gold-plated copper, printed on the underside of the PCB, and on the top side lives the control chip, made by Synaptics (who also makes touchpad systems and other stuff).

The principle by which these type of controls work is capacitance changes. When you place your finger near the sensor, a capacitive effect takes place (using the air and any other material in between as dielectric), which can be measured. It is very small, but enough to give an indication that a finger is present. There are a few rules that one must follow when designing such touchpads, as any interference in the capacitive effect can have negative results on the ‘feeling’ of the controls. Namely, ground planes have to be carefully controlled, and usually placed away from the sensor area, the sensors have to have a minimum size in order to be effective, and any trace routes from the sensor pad to the control IC have to be kept tight, avoiding cross-overs and other disturbances.

I am not familiar with the Synaptics chip, but I have worked with Quantum Research QProx devices, and I cannot see how the physics of capacitance could be avoided in either case. The MX5000 design violates all these rules. The sensor areas are irregular, with a gaping hole in the middle to allow for LED light to pass through, there are ground planes all over the PCB, the tracks meet and part at various spacings and passing right next to ground planes. The biggest joke seems to be the ’sliding’ sensors for the volume and zoom. These are depicted on the face of the keyboard as smooth analog paths, as if one could go from minimum zoom or volume to maximum by sliding the finger to each end of the vertical scale. The truth is that to change the volume in any significant way, one has to repeatedly slide the finger along the whole path of the scale several times, and in some cases, the detection doesn’t work. You end up looking demented, rubbing away the side of your keyboard repeatedly! As is shown on the photo, the sliding scale has only 7 distinct sensors, thus giving you a maximum of six detectable steps in either direction (each step is signaled by the triggering of one sensor, then the one adjacent, determining direction of finger travel). It would be a bad idea to place the whole volume or zoom range on a scale of six steps, and so they settled for the crazy-monkey-rubbing-keyboard action instead.

The next two pictures show the PCB inside the plastic assembly that houses the faceplate. Notice how the cutouts allow for light from the LEDs to be piped towards the labels and icons.

And finally, the last part of the broken equation – the Bluetooth module on the keyboard. It uses a CSR BlueCore3 ROM, which is cheap but cannot have its firmware modified after the die has been printed, meaning whatever bugs you had in the device will be there forever. Again, the module uses a meander antenna. Now, I am not too familiar with the Broadcom chipset, but I have worked with CSR chipsets quite a bit, and know they provide a balanced antenna output, this means that to use an antenna such as a meander or chip, you have to go through a balun. I don’t see a balun on the MX5000’s module, and so it appears they have attempted to balance the antenna with another set of meanders, which can be seen between the chip and the large main meander in the picture below:

Again, this design doesn’t seem to be the best in terms of RF performance, specially when you have a large inductor nearby (L1).

Conclusion? Don’t buy one of these, if you want to go wireless, get one of the non-Bluetooth (some also work at 2.4GHz) keyboard/mouse combinations, and I would still say get a Logitech, as they make some very good ones, such as the MX3000. I’ve always used Logitech, but the MX5000 has been a real lemon.

With the current Fonera, you cannot access devices on the wired side of the network (such as a SAN drive or printer) from the wireless side, be it using the public or private SSID, you are effectively NATted from your own network. A LAN port would solve this the same way as it is done in higher quality devices such as the Linksys WRT54 series.

What really surprised me was to see that these routers have already been shown by Accton, the OEM that manufactures the Fonera on their website for a few weeks. Check out these links, datasheets in PDF available, for a white-label Fonera, a Fonera with LAN passthrough, and what looks to be the Fon Liberator, having a USB port and BitTorrent client built-in! Martin Varsavsky recently put the release date of the Liberator back a few months, originally scheduled for Christmas 2006, citing technical difficulties.

Now, either Accton wants to score a goal taking advantage of the publicity offered by Fon, or Fon didn’t pay an exclusivity fee for the design of these routers, or both. One million routers by 2010 is nothing by asian manufacturer standards, but they do allow buyers to secure exclusive designs. Copies could still be found, but not as prominently and by the same manufacturer making their own.

I wasn’t sure that Accton was the designer behind the Fonera, and gave Fon the benefit of the doubt of actually having developed something themselves in the electronics field, but now it seems clear that Accton is the designer of the hardware platfom, so there wasn’t that much development by Fon after all (the firmware was created by the hackers behind DD-WRT and OpenWRT).