Author: jason

Of course, the problem with backing up stuff over the Internet is that the Internet is really slow.

So, last night I finally won an oscilloscope. I got a Tektronix TDS210 for $660.
Good news #1!

Then a few hours later my new backup software that I am writing successfully ran it’s first remote backup!
Good news #2!

Then this morning I got up and there was an email from Pollstar telling me The Pixies announced a Kansas City show (finally!) on the day before I leave for Florida, so I’ll be able to go! It was looking like I was going to completely miss out on this tour!
Good news #3!

That’s a hell of a 12 hours!

I had some other good news but it was gastrointestinal in nature, and you don’t really want to hear about that.

So, what’s new?

Well, the Orb is temporarily on hold while I wait to be able to find, or afford parts. I need a certain type of LED, which is generally called a SuperFlux LED and they are proving hard to find. The reason I want these LEDs specifically is because unlike normal LEDs they are square, so they fit together in arrays very nicely. Additionally you can get huge viewing angles and they will sink a lot more current (and therefore be more bright) than normal LEDs. So far I have only been able to find a supplier that will sell me tubes of 60 each. So, with three colors and at just over a dollar per part… well, I don’t really have the money to spend $400 on LEDs right now.

If you know of a place to buy SuperFlux LEDs in quantities less than 20, let me know!

In that same vein, I’m finally looking to buy an oscilloscope. I’ve been working on electronics most of my life and I’ve always wanted one, but they were always so damn expensive. Well, they are still damn expensive but I think it’s probably time to get one. I’m looking at a Tektronix Digital Storage Oscilloscope. Either a TDS 220 or TDS 210. Both are ultra cool, and can be had for around $800 on eBay. The only problem is I keep getting outbid 🙂 Soon, soon.

I almost had a TDS 210 yesterday, but at the last minute I discovered that the description of the item was false and the scope was kinda broken. I let that one go.

In the software realm, I’m currently writing what will be a free, open source network/remote backup suite. It will let you have a central (or distributed) backup storage area and will be able to back up from most platforms out there. Initial targets include Windows, Linux, Solaris, BSD and OS X. It supports the idea of community backups, so if you want to make a deal with a friend to back each other’s stuff up you can do that very easily. It has incremental, full and differential backups and all the communications and storage is encrypted. That way you can have your friend back up your sensitive or private files and he can’t read them.

I’m looking at probably a month or so before I do an initial realease for it. So check back here now and then for news. I’d also love to know if something like this already exists so I can stop wasting my time if so 🙂

In personal news, I started to study Japanese (nihongo) a few days ago, which has been really interesting. I’ve always wanted to learn another language, and the romance languages always seemed so boring, and similar. Japanese is a pretty strong departure from what I am used to, so it’s going to be a pretty tough experience, but I think it will be fun. I picked up “Pimsluer’s Japanese for English Speakers” on Audible, the Random House Japanese-English Dictionary and Living Language’s “Japanese Course Book” which I’ve been studying like crazy. So, if you’d like me to tell you that I understand Japanese a little (Nihongo ga sukoshi wakarimas) or tell you that the weather is nice (Ii otenki desu ne) I’m your man. For anything else, better give me a few years 🙂

And that’s it for now.

Every time I try to do something cool in Java I am reminded again how much it sucks. For instance, you can now query for root paths on the filesystem which is operating system independant. On Windows you will get a list of drive letters. On UNIX you’ll just get /. On MacOS you’ll get a list of volumes and so on.

That works great. What doesn’t work great is if you want to see if you can read the drive letters returned by Windows. On my machine I get A:, C:, D:, and E:. I think, “Hey, it would be useful to be able to tell if there is a disk in drive A:” Unfortunatly there doesn’t seem to be a way to do that. If you do any kind of IO query on that drive and there is no disk in the drive you get a big system modal error box that there is no way to programmatically close. Your program freezes never to return. If you are writing a client program that’s not too bad, the user can just dismiss the dialog but if you are trying to write a daemon type program such as the one I am trying to write you are totally screwed.

So, if anyone knows how to query the A: drive (a floppy drive in my case) without locking the program if there’s no disk in the drive, please let me know.

Man, that was some good sleeping. I took a Claritin D last night cause I was feeling the allergy burn and as usual it knocked me out. I had a long, slow dream all night (or at least seemed like all night, probably took 10 seconds) that ended just as some Air (the band) slowly woke me up before the alarm. I feel great!

I bought an Ambient Orb yesterday to play around with. It’s a pretty cool little thingy, but there are problems. If you just wanted to use it for keeping track of your stocks, I guess it would be okay but the problem is that the updates can happen up to 30 minutes apart. I had originally thought it would be cool to use the orb to monitor my web traffic, or status of the web server or something, but with updates that far apart, most likely I’ve already found the problem and fixed it before the Orb finds out.

Ambient is willing to sell you a serial kit, so you can send commands instantly, and quickly for $40, and they are even cool enough to supply a schematic so you can built it yourself if you like, but that removes the cool wireless aspect.

The ideal solution would be to find a way to reprogram the cap code in the pager inside, or even just find it out so you could send commands over the pager network. I’m still working on that facet. I can’t find a data sheet for the pager module that Ambient used in the Orb so as of now that’s a limiting factor. I know who makes it, but they are pretending they didn’t 🙂

This all came about because I decided to build an Orb. I got interested in the Orb the other day while browsing around and decided it would be a fun project. I’m using an Atmel AVR Mega 8 to control it and send PWM to discrete red, green and blue LEDs. Mine looks decent, but I was having trouble finding a good way to mix the colors. I was also just generally curious about how they did it, so I decided to buy the real thing and take it apart, which I did.

Hmm. More later. Tired now.

How many digits are in a number n bits expressed in base b?

digits = n / (n / log_b(2 ^ n))

In case your calculator doesn’t have a log_b(n) function on it (mine doesn’t), use the version below.

digits = n / (n / (log(2 ^ n) / log(b)))

I’ve needed to know that several times and never took the time to figure it out or find it, but today I did. Isn’t that handy?

Here’s a little JavaScript calculator you can use to try it out.

So I’m working on a little project that involves a bunch of LEDs and I ran into something I didn’t understand. I had always understood that LEDs effectivly had no resistance and had a maximum current they would pass before frying. For most that’s about 20-30ma. This is why whenever you hook up a LED you put a resistor in series. It all follows Ohms law very easily.

The trouble came yesterday when I noticed a circuit diagram that uses 6 LEDs in series, direct from the power supply to ground with no resistors. With what I knew, if that power supply could push more than 6x20ma = 120ma the LEDs should blow up. Obviously they weren’t so what is going on?

Here’s what I’ve come up with, and I’d appreciate it if you would tell me if I am wrong.
LEDs have a fairly unique (I think) property called forward voltage drop. An average LED always drops 2.0 volts no matter how much you put in or what else falls on the other side of the circuit. An LED has two important ratings. Voltage and max current. An average LED might be 2.0v and 20ma. The LED does not conduct until the forward voltage reaches the voltage rating and then at that voltage the LED will draw the current rating. So, if you feed an LED exactly 2.0v it will draw 20ma no matter how much the power supply is willing to provide. So, with those numbers we can calculate that the LED has an effective resistance of 100 Ohms. That’s the part I am not sure I am right on 🙂
With that in mind, if we give the LED 5.0v, assuming it’s internal resistance doesn’t change then the current is going to be higher. We get 50ma which is getting the point of the LED’s maximum current before it’s damaged.

The problem comes when you provide the LED with more voltage than it’s forward voltage drop. When the current gets to ground the voltage has to be 0, so if you provide more voltage than the LED is willing to drop it’s going to have to use more current to make up the difference. Also throw in the mix that an LED’s resistance goes down as current goes up, so the increase is exponential instead of linear. I haven’t been able to find much information on that yet, so I’ll just let it stand.

So, what I think is going on is that if the LED voltage drops all add up to the total voltage supplied then the voltage at ground is 0 (as it should be) and the LEDs don’t have to consume more current than they want to. If the voltage varies by a volt here or there it’s okay because the LEDs have a little headroom for how much current they can handle.

Does that make any sense? I hope it does, cause I feel like I *get* it now 🙂

Went and saw Kill Bill Vol. 2 last night with Scott, Adam and JoLynn. Wow. Pretty cool. It was completely unlike the first volume. The fighting was extremely minimal and I think you might have seen one or two drops of blood. Instead you got long dialogues and monologues, lots of background and in Tarentino style, seveal minutes of pitch black.

If you didn’t like the first one because of how violent it was, go see this one. The violence is mostly gone and what there is is pretty tame. If you did like the first one because of all the violence, go see this one to see why it all happened in the first place!

Oh God, I wanna see the Pixies so bad. Halllp!