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Filed under: General — Thomas @ 11:07 pm

11:07 pm

Every time I am watching a DVD and am being forced to sit through these stupid legalese warning pages (don’t you absolutely HATE it when you get criminalized exactly when you are doing everything legally ? Why do I get these stupid anti-piracy trailers every single time I go to the cinema and pay to watch a movie ?), I am completely baffled as to why “they” specifically chose to add “oil platform” to the list of places where you’re not allowed to see the DVD in group.

I mean, seriously. In French, the words “plate-formes petrolieres” take up almost a complete line of the twenty they’re showing. Who writes this stuff ? Who thinks “oh dear god, we almost lost millions of revenue by not excluding the oil platform people ?” Who gets the extra Christmas bonus for getting those two words in there ? What do the tens and tens of oil platform workers think about this ? And more importantly, do they even care ?

In unrelated news, the Buffy “smashed” episode probably has my favourite all-time love scene. Buffy and Spike duking it out, tearing a house down, and suddenly, bam. They get into it as the house collapses around them. The foreground noise cuts out, so you don’t hear any of the house collapsing, just their noise, and the moodsetting music. Nicedly edited.

Fedora 18 part one

Filed under: Fedora,General — Thomas @ 12:10 am

12:10 am

Yesterday, I was wondering if there shouldn’t be a new Fedora out by now and if it would fix a bunch of my current GNOME 3 annoyances.

So I checked, and lo and behold, the final release date was yesterday! Excellent.

Let’s do some completely unscientific scoring this time around. In part one, it’s bound to get ugly because you always run into the negatives first when doing an upgrade.

First challenge was finding the torrent links for the full DVD. Apparently the DVD is now a well-hidden option, and the torrent even more so – I had to google for it, I couldn’t find any links on the download site. -1 and -1. I appreciate that there is a small CD with a live installer and everything, but I have to upgrade 3 computers in total so I prefer to download once as much as I can – although it’s likely all of them will need to upgrade gazillions of packages soon after.

The second issue: after booting, by default it gives you the second option – test media and install. I didn’t realize that, and just hit Enter. Then anaconda starts counting something without telling you what it’s doing, at which point I figured it would be a media check as it was really slow. But if you hit Esc to abort it, you get dropped into a rescue shell, instead of just continuing. Err, OK. I don’t know if anyone out there really uses or prefers the media check option, but I never do.

Reboot, make sure to go up to select the first option (which, really, should be switched to the second if you’re not going to default to it ?)

-1 for being confusing and defaulting to wasting my time.

This is the first anaconda that is actually full-screen on my laptop, nice. +1

The first impression of anaconda is that it looks good and it looks very GNOME 3-y. Not entirely sure I like the ‘things popping up on my screen as anaconda presumably checks stuff’ without telling me, because there’s potential for getting it wrong (-1), but I’ll accept it for now. Definitely liking that it figured out my network connection automatically, if NetworkManager is behind it then I’ll be darned – yay for NetworkManager! (+10 alone for that one, so NetworkManager pulls out slightly from minus infinity.)

Date & Time, since you now can rely on network possibly working maybe you should look me up by IP as a sane default instead of New York ? Network Time was on by default, but no. No points for or against though.

On to partitioning. I’ve always used a custom layout. The new dialog scares me a little; I checked “I don’t need help” but the only option forward is ‘reclaim space’, so I’m not sure it’s not going to do anything bad to my drives. -5

On the next screen, I see a tree with New Fedora 18 Installation, Fedora Linux 15, Fedora Linux 16, and Unknown. I typically have two or three root partitions so I can test different Fedora versions and fall back to older ones when I’m upgrading. It’s a little confusing to use the tree, but basically I figured out how to go through the Fedora Linux 15 config and get it to move the ones I wanted to use to the New Fedora 18 Installation. I definitely see the potential for this being easier to use than the old way but it needs a bit more documentation or tooltips or explanation to make it really feel safe to use. Maybe it would help too to have a final overview page when finishing partition so you can confirm that it looks like it’s going to do the right thing. -1 for the confusion, but +5 for finding partition info from all my roots.

It’s a small touch, but it’s nice it’s asking for your root password *while* already installing packages. Makes it a little faster to get it done. +3 guys! I’m wondering if it couldn’t do more of that – your time zone config for example ?

The redesigned anaconda really looks nice, and fits in well with the GNOME 3 experience I’m now used to. Gutsy move, but this is going to pay off in the long run. +10

After waiting for the packages to install, I clicked Reboot, and it dropped me in a text mode that said [terminated]. oh well, nothing’s perfect I guess. -2

On a hard reboot, I got greeted with a reasonably nice GUI that had managed to pick up my old boot options – even the Windows partition I have on this machine. +5 The text looked ugly and stretched (-1), but it could have been worse.

Firstboot starts and greets me first with a big white square around my cursor (-1), and then the nice-looking GUI. Firstboot asks me for date and time info again, not sure why. Maybe an oversight. -1

And then we’re on to the login screen. And it definitely looks nice! +5

Logging in. Being told there are updates. Holy crap – 218 updates – for a release that’s a day old. Does the word ‘release’ mean anything anymore? -5. Seriously, freeze that crap for a few days, only real security issues or facepalm bugs.

My updated failed to process – because I had installed the rpmfusion rpm and it doesn’t have the GPG key. Yet again, by default updating packages fails completely when anything in the config is not working, instead of at least getting me the updates that can be installed, in the name of, you know, security. -10 because this is a persistent attitude problem for yum.

Create some missing symlinks, and the upgrade can continue. So I leave for lunch.

And when I come back, I am greeted by some kind of lock screen. It looks pretty. (+3) It’s like a video game, those arrows. Yes, that’s it – it reminds me of when I pretend to be Batman in Arkham City and I’m on a mission and it’s telling me to glide down in the direction of the three floating arrows. Except, it’s not actually acting like a lock screen – when I click it, something happens and I go to a user selection ? It looks like I got logged out behind my back ? Really ? Is it doing some kind of automatic logout after upgrading ? I hope not, that would be horrible as a default. No clue what happened. -5

I log in again, and recover my vim sessions that got so brutally killed.

I start running the install commands that are part of my general upgrade checklist. In the meantime, I check out this rumour I heard that Fedora 18 installs with kernel 3.6 by default but the one day old upgrades install 3.7, so I run rpm -qa | grep kernel.

Oh my. It’s spewing db errors halfway through the query. Three times in a row. Contrary to popular belief, rpm is really robust, and you really need to do evil things to get it to corrupt, like drop your hard drive or kill -9 during package installs. But here it just fails simply querying, presumably for the first time in my experience it can’t handle querying while installing ? -5

After letting it sit there and install some more, I get that lock screen again. I click it, and some arrows flash. Maybe I’m supposed to drag it up or something ? But before I can do, the screen flashes, and I’m back to the login prompt. Oh, so even worse – this new lock screen crashes my whole desktop somehow ? Ouch. -5

Evolution forgot my sort settings (per folder) and 3-pane window. -3 for making me suffer through having to sort every single folder by date, descending again (really, is unsorted a sane default to anyone ?)

The lock screen looked cool at first glance, but after what feels like lifting up the door to my garage four times today already it’s getting on my nerves. -3 Same with the ‘pressure-triggered’ notification area, which is starting to cause pain in my hand on my laptop, and I never have that kind of trouble. I wonder if these things got designed with a console joypad as an interface, where you could accept that pressure-triggered actions make sense. -3 for sucking and another -3 for making me think originally that it looked cool until I actually had to use it.

My first login as a ‘fresh’ user (I don’t mount my real home until I’m sure all the basics work ok) is very zippy and GNOME 3 looks tidier. +5

However, my second login, with my old user, takes a good 30 seconds before anything at all appears beside the desktop. I don’t know which dead weight I’m dragging along from before, but this upgrade is not liking it one bit. No feedback whatsoever on what’s going wrong though. -3

Total score so far: -13.

It didn’t pull back to breakeven, but don’t despair – now that the basics are done, it’s bound to get better in the next part.

(editor’s note – see if you can tear this whole article to pieces by pointing out a counting error in the score, cleverly invalidating my already unimportant opinion!)

dEUS week

Filed under: Music — Thomas @ 4:08 pm

4:08 pm

For some reason this week turned out dEUS week at home in Barcelona. Ripping the deluxe edition of Worst Case Scenario that came with the DVD, I finally watched the ‘Time is the state of my jeans’ documentary about the album.

So I thought, why not go the whole hog, and use some dangerous pirate site to download the Belpop special about dEUS, and get through all of it.

The contrast between these two documentaries was very revealing.

The first one focuses only on the album, with interviews of the band members together, and they turn out very different than in the second where people were interviewed separately. In the joint interviews, you can see how Tom’s controlling side comes out and talks over the other people; maybe I’m reading too much into it, but you even see some of the band members bite their tongue and being reminded of why they left the band in the first place. It doesn’t paint as nice a picture of Tom.

The second documentary makes him look a lot nicer. They seem to actually show bits of the other interviews to each member, so they can still react, and usually it ends up with loud laughter. The stories are better too, the second documentary goes more in-depth. The international stars make a comeback experience, which I guess is unavoidable.

It’s fun to see the history from before the first album, and it reminded me of the first time I saw them – a little festival 20 km from my house in the sports room of a school, where they were the last band before headliner Nemo (who had just released their debut). dEUS in its early days was sloppy but dangerous – when you see the live recordings of that period of Suds & Soda for example, they mess up one of the two notes in the riff, mess up the rhythm and the phrasing, and so on.

The second documentary is full of funny moments. My favorite is when Rudy Trouvé talks about the EP after the debut:
“Tommy thinks that my sister = my clock really (long pause) made sure that a part of the audience tuned out. I think so too (starts giggling evily)”.

The Belpop documentary is definitely the better one of the two.

The bonus disc for the WCS deluxe edition is a nice collection of stuff I painstakingly collected at the time, just in time for our current music consumption culture. Kinderballade, their only dutch-spoken song (and one of my favourite tracks they ever did) was on a hard-to-find tribute album, probably made around my sister = my clock because the sounds are so similar, but beautifully done. Their b-sides from that album are plentiful and excellent.

The one answer neither documentary answers is the question I’ve always had about the debut album – why did the English version have a different tracklist ? For me, Via will always be followed by Let Go. Yeah, maybe Right as Rain is a better song, but it’s not right in the flow of the album. Same for Great American Nude – an amazing song, but after the 50 second splinter bomb of shake your hip (the real ending of the album to me), the only thing that fits is the completely atypical dive bomb djingle. Great American Nude brings the energy back up instead of doing something out of character to go back to the opening track. I just have no idea what was wrong with the original release.

I hope to get off planet dEUS by next week, but an album like this that hit when I turned 18 is going to be in my head forever. They were, and still are, an excellent band.

Here’s hoping that two years from now the WCS gang gets together again to play the album together. Come on Rudy and Klaas, give it a think.

After so many years, I also finally appreciate a track like WCS (First Draft). I used to hate that song, but today it’s one of my favorites. Time is the state of my jeans is as good a definition of time as time is what turns kitten into cats.

Fedora 16 upgrade

Filed under: Fedora — Thomas @ 2:03 pm

2:03 pm

A new Fedora, a new decision on which machines to upgrade. Usually I try to stagger the three machines I use most – my work desktop, my home desktop, and my laptop. I had updated work machine and laptop to F-15 when it came out, and kept my home desktop at F-14.

I actually have two or three root partitions on each of those machines, and I typically do a fresh install on a separate root, so I can try things, poke around, and make sure everything I will need works. When I do the install, I don’t mount my /home partition, because I don’t want to have the new version upgrade things for me on my user config.

I have a pretty long checklist by now that I go through on each install/upgrade, installing the packages I use a lot, setting up specific configuration, copy over ssh keys, …

I actually liked F-15 a lot, and though GNOME 3 has its issues (which I still want to document in a separate post), I overall enjoyed the experience. At home, I noticed myself using the windows key or moving my mouse to the top left corner expecting something to happen.

That is how you know you really are ready for GNOME3.

So I thought, what the heck, let’s get to upgrading all of them. I started with my laptop, as usual. That mostly went fine, except for hurdle number one. My laptop actually has /home encrypted. And I did not add it to my custom layout in anaconda. So, the system dropped me in a rescue shell after booting. It took me quite a while to figure out that I had to copy over /etc/crypttab from the old system. After that, things worked again.

Arguably, hurdle #1 may not be Fedora’s fault. Maybe normal users don’t encrypt home drives, or use custom partitioning like I do (although on a few fedora upgrades this saved my bacon when it turned out certain things I needed didn’t work in the new Fedora, like VMWare)

And yes, GNOME 3.2 is a slight improvement. Enough to make a difference at least. All the usual applications seem to work, so I can now mount my old /home directory.

That’s when I ran into hurdle number 2: the default uid/gid numbering change. My thomas user now was 1000:1000 as opposed to 500:500 on all my machines before Fedora 16.

In this day and age, I still have to shell it up to fix things like that:
find / -uid 500 -exec chown 1000 {} \;
find / -gid 500 -exec chown :1000 {} \;

If I had less shame I’d tell you how embarassing it is if you do this for a few users on your system, and start thinking “let’s put this in a for loop”, and because it’s already 1 AM you start doing things like
for a in 0 1 3; do find / -uid 50$a -exec chown 10$a {} \; ; find / -gid 50$a -exec chown 100$a {} \; done
Note how I got the number of 0′s wrong in the first find, and how I actually forgot the : in the second. You can imagine how amusing it is to fix the effect of those commands.

But I’m a shameful person so I won’t tell you about this bit. Instead, suffice it to say that this took a long time.

Ok, so now /home is mounted on the laptop, and for the most part things worked fine.

On comes the weekend, so I turn to the home machine. I tend to keep the work machine for last, because I don’t want to spend work time on fixing distro problems. And I usually take a whole weekend to upgrade at home. The home machine turned out to be more of a problem. I ran headlong into hurdle number three. You see, there is this new thing called GPT for your partition table, and it is now the default, and it means that fdisk will no longer work, and now you should use gdisk (which sadly is not installed on the rescue bit of the install DVD, boo!), and this is all so we can have grub2, which is supposed to be better or something.

I’m sure one day I will be thankful. But on my home machine, I didn’t know any of this, and just had anaconda tell me something about the boot image being too large and there was no space for it and my system may not boot. (I am not sure why I did not run into this problem on my laptop – presumably, looking at the disk layout now, because I kept the original install, which includes Windows, and just shrunk that and added linux – so it’s probably the windows thing doing the booting). And sure enough, the Fedora 16 install did not boot. It dropped me into my friend, the shell.

So here’s the thing. This new way of doing things needs more space than your average MBR, so you actually need to create a primary partition for this, and it needs to be in the first 2 TiB. So you know what time it is now. It’s resize-o-clock time – I get to learn the joys and mysteries of shrinking ext4-on-software-raid so I can make space for this new partition, which doesn’t need to be big, apparently 5 MB is more than enough. Aren’t I happy now that I stubbornly stuck to having a /boot partition as the primary one on my machines, so I can just shrink that a little?

So shrinking an ext partition I already had down pat. I learnt about shrinking software raid partitions, and again I got into the land of not understanding which of the many types of numbers (sectors ? blocks ? bytes ? cilinders ? Mebi vs Mega ?) are understood the same way by the tools, or not understanding how much of those numbers you need to count extra because of the layer of indirection being added (encryption on logical volume on LVM on software RAID anyone ?). So to be safe I end up shrinking 10% on each layer of the onion as I go deeper – then let the tools handle growing to the maximum space again, since that’s the one thing they’re usually decent at.

But you know, if I’ve done all this, I want to get it right. I don’t want a stinking BIOS boot partition sitting after my /boot partitions. That’s not how F16 sets it up by default. But I have never actually moved a partition. So, download gparted, look at it, figure out how it can let me do that, make sure I ask it to count by cylinders so it doesn’t leave gaps, be puzzled at why it doesn’t let me fractions for MiB sizes of partitions, and work around it in some other way. And so I finally have those two software raid /boot-wearing partitions where I want them – sitting right behind this new BIOS partition.

I create a new partition in fdisk (which is what I’m used to), but I can’t actually set the partition type to EF02, which has four characters where I expect two. But really that is what BIOS BOOT should be.

And now the internet tells me I need to set some flag on it using a tool called parted – some flag called bios_grub. Except when I type that magical command that sets the flag, it tells me it can’t exist:
[root@otto ~]# parted /dev/sda set 6 bios_grub
parted: invalid token: bios_grub
Flag to Invert?

Isn’t this tool nicely written for only the writer of the tool instead of for human beings? Of course I don’t know this when it barfs this at me, but at the end of this story I figured a bunch of things out that this tool could have told me.

You see, invalid token just means that it doesn’t accept the flag named bios_grub. I know this because I’m a programmer so I know the programmer used a token parser – a thing normal people shouldn’t have to know about. What’s that you’re asking? Flag to Invert? How about the Belgian flag, I would quite like to see the colors go in the opposite direction. No, that’s a prompt to choose a different flag to invert than bios_grub. Apparently bios_grub is a flag, not a setting, and I’m trying to invert it, instead of setting it. Can you tell me what flags you do know about, dear parted ?

(parted) help set
set NUMBER FLAG STATE change the FLAG on partition NUMBER

NUMBER is the partition number used by Linux. On MS-DOS disk labels,
the primary partitions number from 1 to 4, logical partitions from 5
FLAG is one of: boot, root, swap, hidden, raid, lvm, lba, hp-service,
palo, prep, msftres, bios_grub, atvrecv, diag, legacy_boot
STATE is one of: on, off

Wait, what ? You do know about bios_grub ? But you don’t let me set it ?

I seriously spent 30 minutes on trying to figure that one out.

In the end, it’s because a) I should run gdisk b) parted won’t let you set that flag on a normal MBR drive c) gdisk should convert to using GPT and d) the messages gdisk prints by default are SUPER scary and the docs say that this is intentional to keep away stupid Windows users (I am not making this shit up). Well, that’s why I use software RAID, isn’t it ? How about we take our chances, dive in deep, and let this gdisk thing do the conversion to GPT on the first disk. Gulp.

OK, I got lucky. That actually worked. I can now create this partition, with the proper flag set. While I’m at it, why don’t we try this ‘sort partitions’ option in gdisk so that this new partition, which is now at the start, but listed as number 4 out of 4, shows up as number 1. Sure, it will renumber all other partitions, but let’s just hope that most things use UUID’s and labels and what not by now, and if not I should be able to figure things out.

In what feels like Day 5 in a two-day weekend, the system now boots! I actually see a new grub (wait, why is that text-mode only again ? Fedora guys, you spent years to make everything look graphical, because that was some huge important feature that mostly got in my way when it took longer than it was supposed to and I had no way to see why except reboot and remove quiet and rhgb from the options) and now you suddenly let grub2 take that back from you? Show us some spine, please), and the system shows me plymouth again. Until it doesn’t anymore, and drops me into a terminal screen.

Hurdle number four. Can you guess what it is ? Go on, take a stab. If you’ve updated your system, I’m sure you know the answer. I’ll give you some whitespace to think about it…

SELinux. Riding in to relabel my file system to save it from the evil people out there. And sure, it warns me. This may take a long time. And then it proceeds to throw asterisks in my face. Lots of asterisks. It’s not the first time this happens. But every time it does, I cannot help but wonder one thing.

Who thought it was a great idea to throw asterisks at the user? How many asterisks am I supposed to expect? Never mind that you can’t actually count them unless you glue your eyeball at the screen, because there are so many they actually scroll off at the top. You know, if you squint hard enough, you can see the maniacally laughing face of the programmer who thought this was a nice way of showing progress. Never mind that tools like fsck can show a progress bar that actually means something (if you trick it into sending data to file descriptor 0) in a sensible way – one line on the console, and visible progress towards an end goal of 100%.

If only I could guess what a long time is going to end up being. Is it a ‘get a drink’ amount of time? Or ‘watch some dexter’. Or nookie time? Or, get the hell out of the house and do all the shopping for the next three hours because there’s no way you’ll be doing anything useful with this system for that long?

So I do all of those things, twice, and one even four times times (I won’t tell you which but I ended up having to pee a lot), and I come back, and the system has rebooted, and there’s actually a GUI asking me to log in.

You know, this Fedora 16 better be frigging spectacular after this six day weekend.

I log in, follow my standard upgrade checklist, try out some of my tools. Media keys don’t seem to work as before for my prototype music player (it flashes a nasty forbidden sign at me), and even though I set up to have nothing happen on inserting audio CD’s (because my LEGO robot is inserting CD’s into an external drive about fifty times a day), Rhythmbox craps on and FORCES me to select which of the many CD’s with exactly the same name that audio CD might be. So, par for the course so far.

Maybe a reboot will fix that, it may not know about those settings until I have everything installed and upgraded. And if I reboot, I’d better convert my second drive to GPT and fix my /boot and set that flag and all that. So I do. And for some reason I can’t figure out how to tell software raid that sda2 and sdb2 (which are both still perfectly mountable as ext file systems and were part of the previous RAID-1 /boot array before I resized them) really are a software raid. So there’s this point where I’ve wasted more time on trying that then it would have taken me to actually manually type every byte on that /boot partition, and I just give up and recreate a software raid on those two partitions and copy stuff over.

And then I reboot. And won’t you know it. Effing goddamn selinux relabel all over again. In fact, this way too long entry was typed completely in less than half the time selinux took to complete some work it had already done an hour ago.

I better have a working system after this last relabel finishes. Now excuse me while I go make some comfort food, potatoes and beans and runny eggs with butter sauce. I’m going to eat it while my good friend Dexter comes back from a long holiday. It’s the only thing that is going to get me out of this weekend funk. And you know who I will be thinking about every time my friend Dexter tells me of a problem he solved…

Overy 0.1

Filed under: Hacking,morituri,Music — Thomas @ 11:41 pm

11:41 pm

I’ m finally making some progress on one of my 2010 goals – making a Lego robot that can take CD’s and feed them to my computer to rip.

What am I trying to do ?

I’m making a computer-controlled robot out of LEGO that will allow me to rip multiple cd’s onto my computer, using morituri.

The goal is:

  • to use Lego Mindstorms for the robot
  • only use regular lego pieces, like Technics, for everything else
  • work with my computer, but preferably with any
  • rip 50 cd’s or more in batch

I’ve been asked a few times why I’m doing this. The main reason is because by now I own over a thousand CD’s. I have most of them ripped by hand to Ogg Vorbis, but disks are big enough these days that I really want to rerip all of them just once to FLAC. I’ve spent quite some time writing an accurate CD ripper for Linux, and I want to have all my audio CD’s in correct digital bytes on a computer, so I can use the files to transcode to whatever format is useful for whatever player I’ll have.

This probably sounds strange, but a while ago I got to wondering what I would not like getting stolen from my apartment, and my CD’s are pretty high on that list, if not number 1.

Some people ask ‘why not just do it by hand? You’ll probably get it done just as fast as it would take you to make the robot.’ I guess people who ask that question don’t understand the joy of making something. But there’s another reason to do a robot – I’m planning to offer my friends a remote digital backup of their music. Ideally, I could drop this robot off at a friend’s house with a Live CD and some instructions, and I would then transcode their music for their iPod or whatever they have. And keep an offline copy at my place purely for archival reasons, of course.

In any case, I am working on my first attempt at robot after building two of the sample ones from mindstorms.

The base mindstorms set is a bit limited piecewise, so I started by getting a really big Technics set that has sawtooth pieces (because that’s the mechanism I wanted to try to use for the CD loader)


After looking at a few other approaches out there, I decided I wanted to try one of my own before trying to reproduce someone else’s.

After lots of thinking and discussing with some friends, the following ideas fell into place:

  • If I want 50 cd’s at once, grabbing one is going to be a problem. After considering pneumatic pumps, arms, some fingers going through the middle and opening, or a wheel at the top of a stack, I went for a simple approach using the sawtooth pieces to space the cd’s, and a little axle going through the middle
  • Peter had a great idea to use a USB drive – this way the robot is self-contained and should work anywhere with any computer
  • I wanted to use the CD drive itself as much as possible, so I came up with the idea of rotating the CD drive, so that I can drop ripped CD’s by ejecting the CD when it’s 180 degrees rotated. I also want to insert the CD when the drive is either at 90 degrees (facing down) or some other angle, before loading it.
  • Mindstorms has 3 motors, so you can roughly (without weird tricks) create three kinds of movements. So I’m using one to pull in the CD rack, one to rotate the first CD 180 degrees into the drive, and one to rotate the drive after ripping.

Here’s the CD loader I made; it doesn’ t fit 100% but rubber bands finish the job for now. I’ll need more sawtooth pieces if I want to load 50 cd’s – anyone know where to get some ? The LEGO site doesn’t sell those pieces individually.


This was with 2 motors but without CD drive; it already has the mechanism to pull in the CD rack, and the axle (with wheel rim) to pick up the first CD in the rack. It’s mounted on a touch sensor so I can stop pulling in the rack when the rim hits a CD. The motor will then rotate the disc 180 degrees around the axle of the sensor, and drop it into the CD drive.


This is the first complete build that I finished tonight. The CD tray is mounted and opened so you can see where the CD is supposed to go. After loading, the CD drive would rotate back to horizontal, then eject the CD the other way around to get rid of it.

I thought I was ready to start trying it for real, but when I went through the process by hand, I noticed two pretty fundamental problems…


First of all, the external drive I used is one of those where you have to firmly press down on the CD so that it fits tight around the round bit in the center. My robot cannot press down. It would be very wobbly anyway because at the point where it hits the tray the CD reader is floating at an angle.

Second, it seems this external USB CD reader has no way of triggering a load electronically, something I had not thought of. It turns out most external drives don’t, and again, my robot cannot press on the tray to close it.

So, I guess tomorrow I’ll try to shop around for external USB CD readers that can eject and load electronically, and that have a normal tray in which I can drop the discs, like my desktop PC’s have.

Backup plans are:

  • Getting one of those hoover CD readers, that suck in and spit out CD’s. There again I don’t know if you can spit out electronically.
  • Getting one of those 3.5 inch carcasses and put in an internal CD drive. That will probably make it really heavy though, so that might give stability problems with the robot.

If any of you out there know about an external USB CD reader that has computer-driven eject and load, please let me know! For example, this LaCie Lightscribe drive looks like it might be one that would work – if you have it, let me know.

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