Zds Project Log

These are the built-in controller knobs of the Scythe chassis fans. They are set to minimum speed and taped into upper front corner out of the way:

Assembling the parts starts with routing the front panel connector cables properly. They will be sandwiched between motherboard and motherboard tray, so rerouting them pretty much means detaching the motherboard:

Motherboard and the hard drive installed. As you can see, the chassis is just high enough that motherboard clears ODD on top and HDD on bottom:

Motherboard and the hard drive installed. The hard drive clears the motherboard by just few millimeters.

The stains on the southbridge tell that this motherboard is already on it’s second life. It served originally my personal desktop machine, but I poured white wine over it on certain party, and +12V voltage sensor and one of the DIMM slots stopped working.

Now that the previous motherboard of this machine broke, I gave it another try and was able to wash it clean. Literally wash - I removed all detachable parts including CMOS battery, washed it under tap water, dried with hair dryer and let it dry for 24h before connecting again. And lo and behold, the fourth memory slot started working. Another 70€ saved!

Hard drive mounts to aluminium sled with plastic rails. The two aluminium sleds also double as case bottom and feet:

The SATA cable for ODD is routed under the motherboard like front panel connectors. The SATA cable needs to do a tight turn - needed to be very careful here to not place too much stress to motherboard SATA header:

Opening the right side panel we see that there’s not much there. No space for anything, and thus no holes either:

Except this one, for screwing ODD in place. Notice also the steel inserts for motherboard standoffs - this is a quality case, and it shows. Aluminium is not good for screw threads, it breaks too easily and it has lot of friction. Steel inserts make sure the threads are easy to use and last some use and abuse:

One of the downsides of the M4A78-EM motherboard is that it has only two chassis headers. But it’s a solid budget motherboard otherwise, can’t get everything for just 70€.

Notice also the clearance between motherboard and ODD tray - not too much space wasted here either:

In this revision of M4A78-EM the other chassis fan header is awkwardly between IO panel and CPU cooler. This might work for cases that sport case fan in back next to IO panel, but it’s very bad for this build. Interestingly enough, on my newer M4A78-EM the headers are in a bit different locations, better, if you ask me. Different revision, I guess.

Quality case often come with details you didn’t know to ask, but which help you build better machine. And here’s one: an extra PCI slot cover. There is some amount of room behind the ODD, but not enough breathing space for anything that generates heat, so SilverStone engineers added this slot there:

The USB PCI backplate cable is *just* long enough. Remember it needs to go between motherboard and VGA card, which requires an additional turn.

Here you can also see both ends of the ODD SATA cable, routed behind the MB:

Graphics card in place. This was the only “oops” on this rebuild: on the previous motherboard, M2A-VM, VGA slot was one spot higher, on M4A78-EM it’s one spot lower.. meaning the graphics cooler fans sit very, very close to the hard drive cages.

Do note that the fans face to different directions - this is intentional. At first they blew both away from the VGA card, but that heated HDD to uncomfortable levels, so I switched it around. This hurts GPU temps a tiny amount, but very little in practise, and helps HDD a lot. And because HDD dislikes temps over 40C, while GPU can handle up to 95C, shifting some thermal load from HDD to GPU is a good deal:

This S shaped piece of acrylic is the only totally custom part on this build, and plays a crucial role:

These black tabs are rubber foam; expensive and heavy, but very good at vibration insulation. Attached with hot glue.

The air guide (the S-shaped piece of acrylic) installed. The purpose of this is twofold: First, it directs air from the front fans towards the CPU/PSU intake area and second, it keeps the cables from the non-modular PSU out of the way of the said airflow:

The air guide friction fits between front panel connector PCB and case border, with help of the rubber foam tabs:

Air guide and PSU in place. The PSU is 380W model from SeaSonic S12II series. It’s 80Plus certified and one of the first sub-400W 80Plus PSUs on market back when it was bought. And 380W is already too much for this system, but because everyone and their dog believes bigger is better this was the best fit I could find.

Air guide and PSU in place, cables in their almost final places. As you can see, there’s a lot of spare cabling to store, and this is where the custom guide really shines:

All major components in place:

Tape was used to keep power and SATA cables out of the way. The borders and corners of the case have quite a lot of room for cables, you just need something to hold them there:

The Fanmate 2 controlling VGA fans was routed to the back of the case. If you do tricks like this, keep an eye on the power ratings - the reason why I was able to pull it off is that I used small (92mm) low power fans. Anything larger would go over the max rated power supported by a single fanmate:

Here you can see the bottom of the case and the HDD caddies. They are machine aluminium extrusions that also form the feet of the case. Now that the VGA fans are blowing almost against the case floor, I’m thinking of machining a fan vent to the empty HDD tray. I just need to make sure the structural strength of the case is not compromised:

The bottom of the case and the HDD caddies. They are machine aluminium extrusions that also form the feet of the case. Now that the VGA fans are blowing almost against the case floor, I’m thinking of machining a fan vent to the empty HDD tray. I just need to make sure the structural strength of the case is not compromised.

Overall view of the completed innards. Some of the cables look like they’d be in way of airflow, but trust me, none of them actually are:

Finished!

Completed system, from front. To get idea of the size, the front grille is almost exactly the size of 2*120mm fans. You can actually see the hub of the top fan through the mesh:

It’s small and pretty, but does it perform? Yes. By stressing the system with EVE, the most consuming task she suspect her system to, we got CPU temps a bit past 60C and GPU temps a bit past 65C. When you weight in the HDD being below 35C, the system works very well thermal-wise.

It’s also quiet. Not silent, seeks of the random 7200rpm 500G WD drive are audible if the room is very quiet and you can hear medium band whoosh of turbulence when you go closer than 30-50cm of the vent on the left panel when room is otherwise quiet. However, the left panel will face to the wall, not to user, so the perceivable noise is lower. In practice the easiest way to check if the system runs is to look at the blue leds on the front, or their absence, so I consider this very successful build.

The graphics card is AMD Radeon HD3850 cooled by Arctic Cooling Accelero S1 with two 92mm Nexus fans installed on it. As we anyway need to strip the whole machine to pieces, I swap the fans and clean the heatsink:

Turns out the cleaning and swapping was indeed a good idea. In conditions like this the fan bearings will break over time, however good fans you use:

The Accelero S1 leans to the graphics card PCB with plastic standoffs seen in the middle, we need to clear then when mounting fans:

To run both VGA fans from a single Zalman Fanmate 2 I soldered together an Y splitter:

The fans are mounted by two layers (remember, we need to clear the plastic standoffs) of double-sided tape on each four corners and zip ties on two opposite corners:

Graphics card cooler with Y splitter but with not zip ties yet:

The Accelero S1 overhangs the graphics card PCB by hefty amount. Luckily this is the direction where we have plenty of space in SG03:

And now we are in this stage, as advertised:

Next and last page: putting it all together.

After the case is stripped and cleaned, it’s time to prepare the parts. Here’s a preview of where we are heading in this part, all the parts ready to be installed:

The clearance for CPU cooler in SG03 is 82mm, and the PSU on top of the CPU area can be installed two ways; intake facing either the side panel mesh or the CPU area. In the previous generation of this system CPU cooler was Zalman CNPS8700 NT, a heatpipe flower where stock fan blows towards the motherboard and PSU was installed to draw air through the side panel.

Zalman is known for creating amazing metal parts for their coolers and then pairing them up with lousy fans that are hard to replace, and CNPS8700 NT was not an exception. The fan was mediocre to begin with and after half a year of usage it started to produce annoying rattling noise even when undervolted. Most likely trying to suck air just 5-10mm from the solid back of the PSU put too much stress to bearings of a fan of questionable quality.

So, in this generation I am using Scythe Big Shuriken, a short but wide cooler that has received high praises on SPCR:

The dimensions of the Big Shuriken are almost optimal for SG03, as cooler height is limited, but due to supporting regular µATX boards, width is not an issue:

Big Shuriken comes with unique 120*10mm fan which is really, really thin:

Cleverly the fan mounting clips seem like they’d accept any open-cornered 120mm fan. This means you can use thicker fan, if you have enough clearance. Per my guesstimate 15mm or even 20mm fan would still fit SG03.

The fan was installed blowing away from the motherboard, because that way it works to same direction than PSU fan, meaning the fans work in tandem, instead of fighting against each other. Obvious downside is that PSU now breathes pre-heated air, but on the other hand PSU fan has to rotate less to move similar amount of air, because CPU fan creates positive pressure for intake side of it.

Bug Shuriken installed on the Asus M4A78-EM motherboard:

The Big Shuriken still clears all power circuitry and standard memory modules with flying colors. Memories with tall heat spreaders need not apply, tho:

Next page: Preparing graphics card for installation.

In this post I explain and show building a quiet gaming PC inside SilverStone SG03. This is generation 2.5 or 3 of this particular machine, so some component choices reflect that.

The system is used by my better half, who mostly uses it for playing back video, surfing, word processing and EVE. I wanted the system to be quiet and utilize standard components, she wanted it to be small and stylish. While you can build mini-ITX gaming machines these days, they still carry hefty premiums and often need to cut corners on things like IO connectivity and power delivery. So, a case that can fit µATX motherboard, ATX power supply and gamer graphics card without being any larger than it has to be to fit those was needed. And SG-03 fitted the bill.

The images link to gallery where you can view all the images from this build and see larger-sized versions of them. License: CC, Attribution, Share-alike, Noncommercial.

Assembled system from left side:

Assembled system from back:

As you can see, the case is really small for µATX case: 360*312*200mm (H*D*W). Power supply sits on top of the motherboard, which seriously restricts the height of CPU cooler. However, graphics card has almost as much room than in mid-tower case - the width and height available for it are decent. Super-long cards might be a problem, but the AMD Radeon HD 3850 used here fits with room to spare.

The system from front, as first assembled:

The SG03 ships with one case fan, 120mm SilverStone one. I complemented it with Scythe SY1225SL12VBL, a 120mm fan that sports blue leds and comes with integrated speed control. Fan speed can be adjusted from 800 to 1600 rpm. Because she liked the leds, I replaced also the stock SilverStone fan with another Scythe unit.

Hub of the Scythe SY1225SL12VBL showing rated specs:

The system from front, with fan grille removed for dust cleanup before proceeding to install the latest generation:

I’m a bit suspicious about filters that are this open (ie. not filter cloth but coarse-grained plastic mesh), but judging from the amount of dust collected in the filters after year of use they indeed have some merit.

To be continued on next post.

I recently got me a Mamiya/Sekor 135mm f/2.8 lens with M42 mount. Turned out the outmost edge of the aperture ring reached farther back then the M42 threads -> the aperture ring was in a way of properly mounting the lens to the EF adapter and when mounted, the aperture ring would not turn. Thus I had to machine away a bit.

The DSLR I am using is Canon EOD 450D, and I am mounting the M42 lens with passive M42 adapter.

Here’s the lens before the operation:

Taped up the lenses to protect them from the metal dust:

I used Dremel router mount table to keep the cutting disc precisely on the desired level:

The router table worked very fine here. As you can see, the removed part stayed in one piece despite of being just fractions of millimeter thick - sign of the cutting disc staying put as it should:

The lens after the operation:

The image magnifies the deepness of the cut; the shiny, cut section is actually less than 1/20th of millimeter below the inmost surface of the aperture ring. If it was sanded down and painted black, you would have to strain to see it was cut.

Because this comes to my own use and you can’t really see the cut part when the lens is mounted, I did not sand or paint it; I only filed down any sharp edges.

Here’s the lens mounted after cleaning up the dust. It’s just as desired; the gap between mounting adapter and the aperture ring is around 0.25-0.4mm, just enough for the aperture to turn smoothly but not having to cut out any more metal than absolutely necessary:

I installed Gallery again tonight, so image spammage in this blog will now come to end.

If you want to see images I publish, please direct your browsers to http://www.iki.fi/zds/art.

Background

All modern CPUs (AMD Athlon 64 and Intel Core series to name the most popular) support functionality called “CPU power scaling”. This means that when the CPU is not doing anything, ie. is sitting idle or doing only some light work, it runs at lower clock speed and lower voltage than normally. When CPU is loaded, the speed is adjusted accordingly so that you get the full power to your hands.

So in essence, the point is to reduce the speed of the CPU when the speed is not needed and call it back as soon as there is something to do. Makes sense, doesn’t it? The sad thing is.. you need to do this yourself, because by default this functionality is disabled. This post goes to explain how.

Case: our home server

As nowadays our home server is the only piece of electronic hardware that run 24/7 in our apartment, I have had a project on reducing it’s power consumption. Surprisingly move from power-hungry (at it’s time) Athlon XP to more power efficient Athlon 64 X2 did not help much. I guess the motherboard itself, Asus A8N-SLI Deluxe, and its NForce 4 chipset consume too much and balance for the more energy-efficient CPU. Then again, now the gigabit ethernet runs on PCI Express bus, machine has 2G instead of 256M of main memory, there is four hard drives instead of three and naturally the dual-core CPU has at least three times the horsepower compared to the old one, so still running at almost the same AC power is not that bad in the end.

Now, to the benefit of all the potential googlers and to help my own memory, follows a brief description of how I got the power saving enabled and how I checked it actually works.

Hardware
OS: Ubuntu Linux Hardy
CPU: AMD Athlon(tm) 64 X2 4600+
Mobo: Asus A8N-SLI Deluxe
Memory: 4G DDR-400 total
PSU: Antec 350W, bundled
Hard drives:
ST3120022A Seagate Barracuda 7200.7 120G
WD3000JB-00KFA0 Western Digital Caviar SE 300G
ST3160023A Seagate Barracuda 7200.7 160G
WD6400AAKS-00A7B0 Western Digital Caviar 640G

Results
Without CPU performance scaling enabled: 124-131W AC on light load/idle.
With CPU performance scaling enabled: 110-116W AC on light load/idle.
Saving: 14 to 15W AC.

In this particular case the savings are not tremendous.. I really should look into replacing the PSU with a modern one. But still, 15W 24/7 is energy wasted.

Notes: the hard drives are not the definitely most quiet models available, mostly because I buy server hard drives when some old ones fails and thus I want something that’s available right now, right here. Still all of those four drives running on hard surface are easily drown by the sound of quiet 92mm and 80mm fans keeping the CPU and chipset cool.

Seeing how the CPU runs
This applies to both Linux and Windows: Go to http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_871_13118,00.html and download the AMD Power Monitor. Install it and run to see your CPU speed and voltage:

What you want to see is to have the voltage be reduced to 1.1V and clock speed to 1GHz when the machine is idle and then check that it rises back to full speed (like 3200MHz and 1.4V) when machine is loaded. Especially the voltage reduction is important - clock speed increases power usage linearly while core voltage increases power usage to second power or more.

To install the Power Monitor to my Ubuntu box I first installed Alien by running

apt-get install alien

as root. Then I downloaded the Power Monitor rpm (tagged RHEL 32-bit in this case) and used alien to create .deb of it:

alien PowerMonitorLinux-1_0_4_118-RHEL4-External.bin.rpm

Then installed the resulting .deb:

dpkg -i powermonitorlinux_1_0_4-1_i386.deb

And finally ran the Power Monitor itself:

amdpwrmon

Note that this is X program - so you need to have X support. In my case I ran it remotely by running and X server on my Windows box, but you can naturally run it locally, too, if you have X running.

Necessary drivers

To actually install the CPU scaling support I followed this tutorial: http://ubuntuforums.org/showthread.php?t=248867. It should work equally for Debian, too.

Since I am running stock Hardy kernel, 2.6.24 derivative, the necessary modules were already compiled with my kernel, so I needed just to make sure they are loaded at every boot and then configure them to save energy by enabling mode ondemand.

The rather long downtime is over. Expect updates real soon now - I have hundreds of photos from various projects waiting to be posted..

I have for some time longed for a tool that would run in both Windows and Linux and be able to test the raw speed of the network between two endpoints. Now, half accidentally, I ran into this thread: Slow Gigabit Network - Win XP. And there it was: iperf.

With iperf I found that the bottlenecks were the actual pieces of software doing downloads, not the network itself. I managed to pull some 300+ megabits per second over TCP with gigabit link between nForce gigabit NIC and Netgear PCI NIC, and 700+ megabits between the said nForce NIC and Realtek TRL8111B integrated on Riitta’s Asus M2A-VM motherboard. Satisfactory to say the least.

Strongly recommended.

This is just a quick report to help friendly googlers.

We today disassembled a Lifebook S7010 to examine problems in the cooling fan. Unfortunately after opening it we found nothing in the cooler we could have fixed, tho the thermal paste was in bad shape and we changed it; hope it helps the cooling somewhat.

However, when assembling the system back we got it working but the backlight was not working. Suspecting broken inverter we tore the machine back apart but as we had not touched it, we found it strange to have broken it.. The problem was solved when I screwed back the screws securing the D-Sub external VGA connector to the chassis - after fastening them the backlight worked like new.

Seems the inverter is grounded with the screws that also hold the VGA connector in place. Talk about kludge..

One nice side-effect in my LED lighting system is that it makes my plants grow sideways, not upwards. Naturally this is not what everyone wants, but for me it suits very well.

On September I finally had time to cut my yucca. I literally cut it, to four pieces, and sealed the upper ends with plant wax. Now that it has had some time to adjust, the bottommost part has started to make new branches, and not just one, but four!

This is so nice change to the one long upward-reaching trunk with leaves just on the top.

The same effect is seen on my chilis:

The Interweb and people who understand plants told me this has to do with plants sensing if they are neighbouring another plant or a rock, ie. do they have to outgrow their neighbour or not. More specifically the red:infrared balance is what matters; the bigger that ratio is towards the red light, the more the plants will branch and grow sideways.

This is also very nice, as I’d love to have them bush-like, not tree-like. Much rejoicing ensued!

As the UV LEDs were 7-10 times as expensive as the red and blue ones, I switched them off and ran the light with just blue and red LEDs for five days:

Again fluorescent tube is on the left, LEDs on the right. One could argue that the plants turned a bit less this time, but as they grow all the time it is hard to say for sure. Also there naturally was less light output, too, this time as the UV LEDs were lacking and blue and red LED count stayed the same.

Nonetheless, it seems blue and red might be sufficient alone, which cuts more than half off of the LED cost.

This time I dug into territory of plant lighting. Early summer I got some young chilis from IRC acquaintance of mine and, well, three of five were still alive when autumn fell and it was time to check how I should have grown them in the first place.

The most obvious thing lacking was light. During the summer they did ok’ish just with sunlight, but during the rest of the year there’s not much sunlight to speak of here in Finland. Time to go artificial.

I already knew most of the plant lights just produce unnecessary heat and make plants look good, but do not help the plants grow. Quick dig into the Web confirmed this.

From http://www.bonsaifi.net forums I got what I was looking for: some hard data on what wavelengths chlorophyll actually uses (from Botany Online):

To put the long story short, I bought a E27 form factor compact fluorescent tube optimized for plants (info via bonsaifi.net again) and ordered some 400 leds of proper wavelengths from China and it was time for soldering and comparison.

The reference light is branded as “Megaman” and has a spectrum that looks like this:

The leds came from Chinese company branded as HB. They are the only Chinese manufacturer I am yet to find who sell small quantities directly to customers and who have English web page with prices. The delivery was very fast and service was good, earning my warm recommendation.

As UV and deep red frequencies are hard to come by and/or expensive, I took leds in 1:2:2 proportion on wavelengths of 402nm:455nm:639nm. The UV ones (402nm) cost four times the deep blue/red ones, so I took a chance and hoped this combination would work.

The combined electricity usage of the led light is around 20W and this is how it looks in action (never mind the casing, or lack thereof, its just in prototype stage):

The light is actually nowhere close to white, it’s red-blue-violet to a human eye. Whatever white you see there is just camera sensor having difficulties. The plant leaves look dark blue in that light as expected - there is no green light to reflect away, just wavelengths the leaves absorb and use.

And here is a combined image showing the LED light passing the real test with flying colors. On the left is the fluorescent tube light, on the right the led one; time difference between the two shots is five days:

Introduction

In computer enthusiast circles thermo-electric Cooling Modules, or TEC modules, or Peltier elements and best known for their use in keeping overclocked monster CPUs cool, or getting below the ambient without compressor equipment. In extreme overclocking TECs are usually asked to pump as much heat as they can and are operated near 80% of the maximum wattage they can move. They have however a lot more uses than that, and in this article I am diving into completely other part of their range of usage.

The TECs have an important property I am going to take advantage of: the less you ask them to do, the more they can do per given amount of power. This means that if you have TEC rated for moving 172 watts of power at maximum (Qmax 172W) and you ask it to move 150 watts, you need to throw in a lot more than the 150W to get it done. But if you ask it to move 30W, it might need only 10 watts of power to do it, thus having Coefficient of Performance of 3.0: moving 3 watts per watt consumed.

In theory this should mean that if your TECs are clearly more powerful than the component to be cooled and you run them seriously undervolted, you should get the component kept cooler than without TEC, without changing the other parts of the cooling system.

Test setup

To validate this theory I first used Kryotesc, TEC system calculation software provided by Kryotherm, one of the leading TEC manufacturers. By varying parameters I ended up having considering overrating Qmax 7-8 times being a good compromise for efficient cooling.

So I acquired a DRIFT-0,8 TEC module from Coolputer. It’s rated for Qmax 172W and 24.6V. This means I can seriously undervolt it using just the pre-existing ATX power lines, +5V and +3.3V. Here’s the test equipment in group portrait:

The other components are 1ohm/100W power resistor, el cheapo two-sensor thermometer, 50×50mm piece of 3mm aluminium flat, passive heatsink used to cool Pentium Pro and old Enermax ATX power supply. Part of the test but not in the picture are two small active coolers.

The power resistor was connected to +5V line, which theoretically should make it produce 25W of heat. In practise the regulation of the power supply and resistance of the wires lowered this figure quite a lot.

I did not use any thermal compound, so to get comparable results without TEC I used the aluminium flat in place of it:

The thermometer sensor was taped to the resistor and we were good to go.

Three sets of configurations were tested: Just the resistor with heatsink and aluminium flat for comparison, and heatsink, resistor and TEC running at 3.3V and 5V (nominal).

On the batch of runs I tried using the passive heatsink (originally used to cool my Pentium Pro 180 CPU), but while it showed expected results, it was way too prone to changes in the environment. It was hard to get it to stabilize even to within a whole degree of Celcius.

The next cooler to try was an old tiny aluminium heatsink with a 40mm fan, possibly from some 486dx100 CPU. I reasoned that despite of the small size it should easily beat the all-passive heatsink, but the smell of overheated electronics soon signalled I was terribly wrong. The fan seemed to have worn out and the cooler had lost even the smallish cooling power it had once had.

After letting the parts to cool down a bit I brought in what I think is fairly new chipset stock cooler. With aluminium flat the setup looks like this:

And with TEC:

Caveats

In the end the results I got are to be considered preliminary, as while measuring the setup and running tests I found several weaknesses in my testing methodology:

1) The inherent (and pre-known) weakness is that as the resistor is not insulated in any way, inevitably fair amount of heat moves to air without going through our test heatsink assembly.

2) The test PSU, old 230W Enermax ATX one, seemed to have exceptionally bad voltage regulation. It is rated for 20A for 5V line, but by no means I could run the resistor and the TEC module from it without voltage dropping to 4V or below. This means the heat load was smaller than hoped for and that the results between different setups are not that comparable, as the TEC load affects also the heat generated by the resistor.

3) The low resistance of the resistor itself (1 ohm) combined with bad voltage regulation means that there’s no way to measure the heat generated precisely, as even the wires from the PSU cause resistance in the same order of magnitude. Even putting the measuring equipment to the loop affects the system noticeably, so margin of error for the results is quite high. In the final run I hooked the resistor and the TEC module to the ATX motherboard connector, not the molex ones, to get a bit more stable voltages.

4) The thermometer used in these tests is cheap and is pretty certainly not calibrated. However I have all reasons to believe it is consistent, ie. given the same real temperature it shows always the same reading. And as temperature delta and differences between deltas in different setups are the relevant things, I don’t think this weakness really skews the results.

5) The experiments should be done in a space with more constant airflow and temperature conditions.

Results

With all these disclaimers, here are the numbers. Ambient temperature was between 24 and 28 degrees during testing.

First of all, the C/W numbers for TEC setups are there just to get some idea about the cooling performance between these three setups. You can *not* extrapolate these results linearly. Second, the CoP numbers are just estimates, as it is not known how large portion of the heat gets transferred to air without ever going through the TEC. The first CoP value sets the upper limit by assuming that all the heat would go through the TEC and the second, more realistic but more vague number calculates the CoP assuming 80% of the heat goes through the TEC.

As you can see, at least these results show the same pattern the simulator does: both TEC setups beat the reference aluminium flat and TEC running at 3.3V does better job than the same TEC running at 5V. This is due to better CoP, so less extra heat is produced and thus heatsink has to do less work.

What this mean in practise is that you can get your chip run cooler *with the same heatsink and fan* if you employ TEC properly. You can extrapolate the rating of the TEC(s) needed by multiplying all the parts with the same multiplier: if you for example double the heat load, you need to double the rating of the TECs and double the efficiency of the heatsink to keep the temperature the same. All other means of linear extrapolation are doomed due to non-linear behaviour of the TECs.

Also in practical applications you want some intelligent circuitry to run the TEC(s), so that they do not accidentally put the chip below the dew point and thus risk condensation occurring. One way to do this would be to harness a microcontroller to monitor the temperature and PWM the TEC to keep the cold side at the same temperature regardless of the load. As TECs need quite a lot of power and they do not like PWMing, you need to chain some hi-power transistor to keep the microcontroller circuitry from frying and hi-capacity capacitor in between to even out the voltage. Needless to say, if you are not familiar with these concepts, ask someone who is to help.

Further work

First of all, the TEC and the temperature source should definitely be fed from different PSUs to rule out the possibility of the TEC load affecting the thermal load. Second, the thermal load should be better insulated so that we’d have clearer idea about what exactly is the thermal load we are coping with.

Third, it would be interesting to hook up two TEC modules electrically in series and physically both in parallel and in series and see how that compares to a single one. Simulations with Kryotherm software indicate the electrically series physically parallel configuration should yield even better CoP, but it’d be nice to get that validated myself.

Yesterday I bought some aluminium-capable blades for my jigsaw, a drill press and router. Unluckily I didn’t have time to pick up my aluminium sheets and rest of the week goes into long weekend snowboarding in Lapland and preparing for it.

But on the bright side, I’ve made some progress on the case shape front:

The rightmost is my vision per today, middle one from Sunday and leftmost from Saturday. Definitely getting better.

The clay model did it’s job - it helped me to see which parts worked and which did not, resulting in a sleeker model. Huzzah.

But I better get the shape fixed soon, as I do not want to cut 130€ worth aluminium into something that does not satisfy me :-].