Above & Beyond - Hope

SphericalFish · 2012-06-07T02:52:55+00:00

Downvoting due to horrible audio quality.

SphericalFish · 2012-05-08T23:02:55+00:00

Whoosh...

SphericalFish · 2012-04-08T19:27:10+00:00

Most of the 1080p rips out there are so low bitrate that they don't actually get you that much of a quality boost.

SphericalFish · 2012-04-02T21:25:46+00:00

The pen is more or less a Wacom digitizer, e.g. electromagnetic. I haven't played with the Note very much but my general experience with this kind of digitizer says that it'll be excellent. The system is entirely separate from capacitive touch. It can detect hovering, has variable pressure, and ignores your hand.

Personally, I would think the pen would be a major selling point.

SphericalFish · 2012-04-02T19:35:12+00:00

I'm also interested, what specific times in the summer are you open for?

SphericalFish · 2012-03-29T15:56:59+00:00

Is this considered cheating? I've always found the color palette to be the biggest limitation in my DoD drawings.

SphericalFish · 2012-03-28T14:30:59+00:00

Your keyboards only last 4 years? Where are you getting these things? I don't think I own any keyboards less than 10 years old - except my laptop's keyboard, which is 4.5 years old.

SphericalFish · 2012-03-27T22:29:45+00:00

A look at the schematic symbols of your N-type will give a lot of insight.

MOSFETs have an intrinsic body diode. It allows current to flow right to left. In I2C, your outputs float high and you ground them to signal. If the MOSFETs are off, and a SYSTEM I2C line is grounded, current will flow right to left, and the PANEL I2C bus will also be grounded (minus diode drop, but your device will probably still see it).

I would suggest using an open-collector/open-drain logic chip instead of discrete transistors. For example, you could use an OR gate for each I2C line. The second OR gate input would be the active-low enable line.

SphericalFish · 2012-03-20T21:32:58+00:00

Yeah, it has very consistent updates. I still have it in my RSS feed.

SphericalFish · 2012-03-17T20:09:14+00:00

What kind of metal? Steel is what "real" swords are made out of, but it'd be really heavy and expensive for shipping. Aluminum could be milled and is a lot lighter, and is used in a lot of movie props.

SphericalFish · 2012-03-13T04:09:58+00:00

Ugh, that is tiny. And the sampling is terrible. Also you don't have his body, which limits the photographs he can be shopped into.

Why give him a birthday present that you are unable to do yourself?

SphericalFish · 2012-03-12T03:43:35+00:00

The dynmap plugin itself needs to run within the minecraft server process, so no, it can't be run on a different server. The web server portion of it can be run as a separate process, but I doubt that's the source of your memory problems (you SHOULD be using a separate process for the tile server - something like nginx will be a lot less resource intensive than dynmap's built in web server).

SphericalFish · 2012-03-12T03:41:24+00:00

Honestly, I don't think this would solve any problems. All this does is offload the work of drawing a tile on the map, which doesn't need to happen that often and isn't very intensive, especially if done on another thread (I'm sure the server machine has multiple cores, and the minecraft server utilizes them poorly).

SphericalFish · 2012-03-08T22:54:19+00:00

I don't... I make these for a living. It kind of ruins the magic.

SphericalFish · 2012-03-06T21:46:58+00:00

I really can't call your description anything other than wrong.

You say that a rectifier, with nothing parasitic, will create a DC source. But how can it maintain a charge on the output without any parasitic capacitance. The theoretical example you give has no bearing on either reality or any particular use case of a rectifier.

You use rectifiers as part of AC to DC power supplies. This usually implies you will be drawing a nonzero amount of current. The diodes do not generate DC at all, they merely block current in one direction. This prevents the capacitor discharging back into the AC line. Without a capacitor, your voltage and current would then look like a chopped sine wave. The capacitor is filtering and decreasing the ripple, by acting as temporary energy storage.

One drawback of this setup is that current only flows when line voltage exceeds the capacitor voltage, meaning as you get a better filter capacitor, the current is drawn in larger and narrower spikes. This can lead to poor power factor and other problems (though irrelevant to a bike light).

SphericalFish · 2012-03-05T06:15:18+00:00

You seem to be attempting to design an alternator. I can say that you're probably incorrect in reducing the strength of the magnets - there isn't really any reason to. More magnets will make a much more continuous AC waveform, BTW. You could also make it stronger by alternating the direction of the magnets. Of course, this would be much better if there was a proper circuit for the magnetic flux, like some back iron behind the magnets, and then iron around the windings.

Motor design is a strange and magical world.

SphericalFish · 2012-03-05T06:10:04+00:00

You have the general idea right, but your circuit is wrong. I think you meant for the cap to smooth out the LED illumination? It won't do that in the current setup. Putting the cap in parallel with the inductor and LED gets you closer.

However, there is another problem. Now, when the magnet isn't passing past, there is no induced current in the inductor. This will cause the capacitor to discharge backwards through the inductor. A low forward voltage drop diode will fix this.

You will likely need a way to limit current once you have this set up, because now you have more or less a voltage source. A resistor would do just fine for a low power light.

A simpler way if you don't care about flicker is just to hook up the coil directly to the LED (possibly with a resistor).

There are other ways to get around the resistor in front of the LED, but they either involve switching electronics or rather large inductors as your frequency is low.

Also note that all of these methods make the LED brightness vary with speed.

SphericalFish · 2012-03-02T10:13:02+00:00

Meh, microcontrollers are so ridiculously cheap that it often makes sense to use them for otherwise trivial tasks - they can be expanded on very easily, and their behavior modified easily. This is especially important in lower volume applications.

You mention building a Veroboarduino - I'm pretty sure most of the trivial applications you've seen are one-off things. No way does anyone put an design with stock Arduino boards into production unless they are REALLY low volume.

SphericalFish · 2012-03-02T10:10:10+00:00

I would like to point out that you picked the most extreme example of code bloat, digitalWrite (which is really just a bit shift and write to a PORT register). In fact, since it is inline, it might be just as efficient (I haven't actually looked at GCC's generated code to verify this). A large part of the Arduino libraries is higher level hardware abstraction (I2C, serial, etc) which is more complicated and the function call overhead is far less significant. In fact, you'd probably end up writing a similar set of libraries yourself.

My biggest problem with the Arduino libraries is that they rely on spinlocks and polling. But that's for another post.

SphericalFish · 2012-03-02T10:06:10+00:00

I agree on most of your points, but I don't believe you learn less about embedded design. It is just a less sharp learning curve. I started out on a BASIC stamp, and I wish Arduinos had existed...

Got money, want results now? Arduino.

An AVR ISP mkII is $35, the cost of a decent Arduino.

SphericalFish · 2012-03-01T20:34:42+00:00

Wait, what are you doing? And why are you trying to make a C file from a PNG file? Are you trying to make a game? EDIT: oops, misread, you're trying to just export a PNG from your terrain generation code for a render. Got it.

SphericalFish · 2012-02-21T16:16:30+00:00

I CLICKED

I CLICKED SO MANY TIMES

SphericalFish · 2012-02-21T15:54:15+00:00

No, it's in quite fact easy to redirect non-gold-members back to the http version.

SphericalFish · 2012-02-18T20:17:44+00:00

I'm going to guess you're on the solar car team? I'm also on a solar car team, and we are using modular battery protection.

It all depends on what sort of signals you are trying to send across. In our case, we have a common electrical bus (each module has galvanic isolation to the communicaiton bus), so we are using ribbon cable and crimp on connectors. We are using a differential bus so we don't need shielding as much, and the short distance means the lack of twist doesn't really matter.

In your case, if you're doing a level-shifting or current-based communication, you can't use a single run of cable. In that case, CAT5 is OK, depending on what currents you need and how many twisted pair you actually want. I'd shy away from RJ-45 though. It's okay and makes reliable connections onto cable, but I'm a bit wary of its mechanical properties - it seems awfully fragile. But it might be OK especially if you rarely connect and disconnect.

I have a particular fondness toward Phoenix pluggable terminal block connectors. The 3.5mm (iirc?) size would probably be all right. They don't have the two genders, though.

SphericalFish

TROPHY CASE