Know How... 62

Looking for a Electronic Kit Project?

When shopping for an Electronic Kit project, look for the following: 

1. Clear and Detailed Instructions
2. Labeled PCBs (Printed Circuit Boards)

Quick Notes about soldering for beginners: 

1. Heat the PAD, not the solder. You don't want a lump of grey goop on the tip of your iron. You "DO" want a small coverage of solder that looks silver.
2. Tacking is your friend! For those hard-to-mount components, you can always put it into "best-guess" position and solder one pin. With the component held in place, you can now easily reheat the solder and move the component into position.
3. Proper heat in your friend! An iron that is too cool will take too long to heat the pad and will possibly damage the component. An iron that is too hot will burn things. And adjustable iron lets you dial-up exactly as much heat as you need for the project.

LED Notes 

1. The "Light Emitting Diode" is, first a foremost, a diode: meaning that it is a polarized component. It has a positive side and a negative side and will not work if you reverse them.
2. LEDs use the phenomenon of "Electroluminescence" to create visible and invisible light. EL is an optical/electrical phenomenon in which a material emits light when an electric current is passed through the material. EL differs from incandescent lights, which are heat-based, and chemiluminescense, which is chemical reaction based.
3. A LED consists of a Lens assembly (the plastic around the LED), the Cathode (which is always shorter) and the Anode (which is always longer) and then a junction of semiconducting material that has been doped to create a P-N Junction.
4. The material of the "P-side" of the junction has "electron holes" while the material of the N-side" has free electrons.
5. When a current is passed through the semiconductor, the negatively charged electrons and positively charged holes are forced into the P-N junction.
6. The Electrons will fall into the holes, but since the holes exists at a lower energy state than the electrons, the electrons must lose energy -- In the form of a photon: light.
7. The wavelength of the light, from Infrared to red, to green, to blue, to white, depends on the band gap energy of the materials that form that p-n junction. (How much energy the electron needs to lose to fit in the hole) In other words, different materials get you different colors.

Scott Wilkinson & Home Theater Calibration

We asked Scott about calibrating the Know How set. He said that open rooms make for terrible home theaters. The more reflective a room is, the more it's going to reinforce standing waves (a.k.a. room modes), which can create a very uneven sound.

You want to make the sound more even so that when you have people in your home theater, they are all having the same sonic experience.

To balance out, there are several ways. Scott says the best way is to build the room from scratch with special dimensions. You wouldn't want a cubicle room because it will reinforce sounds in three dimensions.

A high-cost method of calibrating your home theater audio is by hiring an acoustician. They can treat the rooms with materials that can either absorb frequencies or diffuse or reflect them. Where these treatments are placed is a science and a bit of an art.

Scott's low-cost solution is put some curtains up, put some rugs down, and put up some bookshelves. The rugs and curtains will help absorb sound. The bookshelves will act as diffusers as the different books with their different heights and depths. You'll want some reflection in your home theater. Creating an anechoic chamber (a room that absorbs all sounds) will make for a very unnatural experience.

Auto-calibration of AVRs 

Most AV receivers these days come with a microphone that you should place around the middle of your room. Then you tell your AV receiver to start calibration.

Place your speakers 

Your center speaker should be right in front of you, either above or below the screen. The front speakers are about 30-45 degrees to the left and right of where you are sitting. Your side surround speakers are about 110 degrees from center.

Placing a subwoofer in a corner will reinforce the bass and create standing waves in certain locations in the room (meaning an uneven bass experience). Scott likes putting the subwoofer at the quarter or half-way point against a wall between the front and side surround speakers. That placement can reduce the standing wave issue depending on the dimensions of the room.

What's going on when you do that calibration? 

The microphone and AVR are measuring the distance to each speaker, which sets the delays of the speakers. It's a very loud process with the reference level being around 85 decibels.

The next part of Scott's segment will be focused on what you can do to tweak the auto-calibration settings.

Quicktip: Unfreeze Finder or the Dock on OS X

If you've used OS X, you know how annoying it can be for Finder to die on you. Added to that, trying to restart it is a pain. You can try Force Quit, but sometimes that doesn't work. You can try Activity Monitor. But if that all fails, don't forget you've got a powerful ally on your side in Terminal. You can find it via Spotlight or go into your Applications > Utilities > Terminal

Then type the magic command:
killall Finder

killall is command
"Finder" is the process we're trying to impact

To kill the Dock, type this:
killall Dock

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Links

• Wayne and Layne
• Episode 7 of Know How: Soldering