Tag: tech

Ergonomic things.

Post author By mp.daniel
Post date 9 September 2013

I get wrist pain in … well, obviously, my wrists.

Man, that was a bit of a daft start to a post.

Especially when using a mouse, but also when I have to do a lot of typing. I do touch type, but not ‘formally’, with perfect full-hand position, and so on.

Anyway, to try and make things better, here are some of the things I’m using

Microsoft Natural 4000 Keyboard

One of the weird things about keyboards is that essentially, we still use the exact same design that was needed for swinging arm typewriters. Stuffing all the keys as close together as we can, in orderly rows, so that the arm can hit the paper in the same place every time.
Actually, though, our hands would be a lot happier somewhat spaced apart, and at an angle, rather than trying to line up next to each other.

I have been using one of these Microsoft Keyboards for over a year now at work, and although it’s not perfect, it is a lot nicer than regular cheap and nasty keyboards, and a lot cheaper than some other Ergonomic Keyboards.

I currently have it at home, as, since this is a bit of a quiet time at OMNIvision, I thought I should finally get around to learning a more sane keyboard layout than QWERTY. I’m learning Workman, which is a little obscure at the moment, but to me makes sense. We’ll see if it takes off at all in the future…

Kensington Trackball

The thing which makes my wrists hurt the most is using a mouse, so I’ve been playing for a while with using the popular alternative to mice: trackballs. This one is really cool, in that it has a built in scroll wheel. That’s normal on mice, but for no apparent reason, is kind of unusual on trackballs.

I’m not 100% sold on trackballs as the answer, I think probably as big a part of it as anything is having to reach way over to the side and grip at an angle. So I try to keep the trackball in the middle of the desk, and I have it also on an angle using an old empty CD spool.

Wowpen Joy

At home, I tried for a while using another trackball I got on ebay, as it was cheap, as it was second-hand. It also wasn’t very reliable, so it ended up being more frustrating than helpful. I then looked at Vertical Mice – mice which are designed to keep your hand in the ‘handshake position’ more naturally than the twisted flat position of normal mice.

A lot of vertical mice, like ergonomic keyboards, are pretty expensive. However, on ebay there were a lot of these incredibly named ‘WowPen Joy’ mice. The name itself is enough to put you off. Anyway, I thought I’d try and see how one was. It’s actually very nice. It is kind of small, but still works fine with my big hands, I just use my middle and ring fingers to click, not index and middle.

Yes, I think it’s helping. But still sometimes my wrists are painful, so much that I have to stop mousing or typing at all for a while. I need to work on my posture, I think. I’m considering trying a standing desk at work for a few months, as whenever I sit I do tend to slouch, no matter how many times I try to remember to sit up properly.

I also use “Time Out” computer break software on my work machine, which is really annoying, but almost certainly a good idea. Every so often it jumps up on my screen and tells me to stretch, and take a 10 second break from the keyboard, and then every 45 minutes or so, tells me to take a 5 minute break, which I use to do some cleaning, make coffee, go hang out with someone, or get one of the other non-computer jobs done that I need to. Sometimes, if I have nothing else really to do, then:

Contact juggling

I keep a contact juggling ball around, and play with that during the micro breaks, which is supposed to be good for muscles and stretching…

So why, you may ask, am I writing all this boring waffle about keyboards and so on. Well, partly, because it is kind of interesting to me. Partly it’s because I do find it easier to get started writing about factual/techy stuff – maybe that’s part of being an INFP, extroverting my TJ side, I dunno. I have some more philosophical thoughts which I can relate through all this geeky ergonomic clobber. I’ll post it soon.

Tags computers, ergonomics, photo, RSI, tech, work

Uncategorized

Ergonomic things.

Post author By mp.daniel
Post date 9 September 2013

I get wrist pain in … well, obviously, my wrists.

Man, that was a bit of a daft start to a post.

Especially when using a mouse, but also when I have to do a lot of typing. I do touch type, but not ‘formally’, with perfect full-hand position, and so on.

Anyway, to try and make things better, here are some of the things I’m using

Microsoft Natural 4000 Keyboard

Kensington Trackball

Wowpen Joy

Contact juggling

I keep a contact juggling ball around, and play with that during the micro breaks, which is supposed to be good for muscles and stretching…

Tags computers, ergonomics, photo, RSI, tech, work

Uncategorized

Documentation, and how balanced audio cables work.

Post author By mp.daniel
Post date 7 February 2013

I finally had a bit more time this morning to write a bit more in the A/V manual. There’s lots of bits and pieces of documentation on board, but no comprehensive single getting started manual. So I’m writing one, bring together bits and pieces from all over the place, sorting out what documentation there is, updating schematics, etc.

Anyway, here’s the rough version on the article I just wrote about how balanced sound cables work. It’s pretty much my standard explanation of Balanced Audio, and aimed at people coming to A/V from a non-techy musical background, rather than for Electronics Engineers.
You may find it interesting. Then again, you may not.

—–

Sound is basically vibrations in the air.

TODO: more details, pingpong ball analogy?

Inside an (SM57) Microphone head.
That is the bit of plastic and the coils!

This translates really easily into an analogue electrical signal: you simply turn the air vibrations into voltage vibrations. A Dynamic microphone does this by having a small bit of paper (or plastic) which vibrates with the air around it, and pushes against a very small copper coil which, moving inside a magnetic coil itself, generates a very-very-very small amount of electrical current.

TODO: more pictures.

This gets dumped down a wire, which gets amplified by (you guessed it) an amplifier into a very big amount of electrical current, which then drives a big electromagnet inside a speaker, which pushes another copper coil around, which is attached to another big bit of paper (the speaker cone), which causes the air around the speaker to vibrate – with the same vibrations that the microphone vibrated with, just bigger.

Simple, isn’t it? (well. Kind of.)

Balanced Audio Cabling

The trouble with simply dumping an audio signal down a cable, and picking it up at the other end is that your signal line, and return (usually ground) will pick up noise (say from A/C mains electricity, fluorescent lights, dimmers, mobile phones, etc) along the way.

Here’s an original signal:

And here’s some noise:

And the result:

This is a Bad Thing™.

So some clever engineers, back in the deep recesses of time figured out the following: You could take a signal, and before sending down the wire where it could pick up noise, invert it:

If we add the signal to the inverse, you get a grand result of nothing (e.g. -3 + 3 = 0).

Now, if we throw these two signals down a pair of very similar cables twisted round and round each other like crazy, then they’ll both pick up noise pretty much the same as each other:

Note that 3 (the original) + 1 noise = 4,
while -3 (the inverse) + 1 noise = -2. NOT -4!

This is really cool, because if we add these two signals together, we don’t get 0 anymore, we get no original signal, but you do get the noise (doubled).

So we’ll use our amazing maths skills again, and divide this doubled noise in half. (2/2 = 1).

And we can subtract this 1 noise from the noisy original signal (4-1=3)

Voila! The original clean signal is back again.

This is (roughly speaking) how balanced audio works. And since almost all professional audio equipment runs with balanced circuitry, all we need to do is make sure the cables are in good shape, and then everything works magically with hardly any noise.

This is why for balanced cables (XLR/Mic, or TRS jack) you have 3 pins: +, -, and ground. The ground is connected to a wire-mesh sheath around the other two, to try and keep as much noise away as possible.

(Technically, you don’t need to invert the signal, you could just use an empty zero, but for various impedance, op-amp, techy reasons, it works better if you do.)

Sometimes the ground wire will pick up noise itself, or due to being connected to different grounds at both ends of the circuit (say a piano on stage, and the A/V room sound desk) it will end up with a bit of random leaked current running down itself. This can show up as noise, so you often use a Ground-Lift switch to disconnect the ground at one end or the other, which can sometimes help.

A DI box takes an unbalanced signal, and turns it into a balanced one, which means you can send a signal a long way without noise.

Remember how the two wires have to be twisted together like crazy? This is so that if there is some noisy thing (like a flurescent light) nearby, both wires will be equally effected. This is so important, that for broadcast audio, sometimes cables with 4 or more wires are used. The + signal on 1 & 3, the – signal on 2 and 4, and then all of these are twisted together. There are brand names of these cables such as QuadStar, etc. Usually this is somewhat overkill for regular live sound though, as the cabling is much stiffer and harder to use day to day.

——–

So, what do you think?