YourITronics

I will present you here a 2.1 speaker project made from some leftover materials. Nothing fancy but i will try to get the most out of everything. In this first part i will give information about the overall design and the first work on the satellite speakers. Drivers i used were those i had laying around, a pair of 8″ woofers with nothing written on them, probably Chinese stuff (I will have to measure some of its parameters), a pair of 6.5″ mid-bass drivers i saved from some commercial speakers and a pair of horn-loaded soft dome tweeters from PAudio model PCT-300.

I plan on using the two 8 inchers for a subwoofer, i will have to measure some parameters to determine what box to build. The satellite speakers will have one mid-bass driver and one tweeter in a closed box. The box should not be bigger than 10l in volume.

Some of the Thielle – Small parameters of the 6.5 incher mid-bass are as follows:

Fs: 65.41Hz, Qts: 0.62, Qes: 0.76, Qms: 3.43, Vas: 18.9l, Sd: 150 cm^2, Xmax: 3mm, Re: 7.4 ohms, SPL: 90dB/w/m, RMS Power Handling: 50W

A closed 10l speaker models with a -3db band starting 85Hz with a Qtc little over 1. Below 85hz there is a 12db per octave attenuation so it will be pretty easy to match it with the subwoofer. I can lower the Qtc with heavy fill hopefully to a value below 1. Because of small dimensions of the cabinet the driver will never exceed maximum excursion.

Predicted low frequency response in WinISD

Now off to the wood work. Tools needed: Router, Jig Saw, Circular Saw, Electric Drill, Clamps, Screws, Glue, etc.

Lucky me i found a pair of old speakers measuring about 9l of internal volume. Almost perfect for my application. I only kept the top, bottom and the side panels. I make a new back panel and cut hole for the speaker terminals. I want the option of using separate amplifiers on highs and mids so i use bi-amp speaker connectors. I plan on painting the front baffle black and finish the rest in some dark colored carpet.

You can see here what i kept from the old speakers, the router getting ready, the back panel in position and the back panel with the connectors installed.

Now follows the routing of the front baffle. I use MDF for it’s easy to work with and has pretty good acoustical properties. First i prepare the router. I make the compass from a thinner board of MDF and i attach it to the bottom plate of the router. After this i measure the desired radius and make a hole in the board. This hole will be the center of the circle being routed.

Better measure 5 times and cut once…

The drivers are flush mounted and the front baffle’s edges will be rounded to minimize diffraction. The distance between the acoustical centers of the two drivers is 17cm. This distance corresponds with the wavelength of approximately 2kHz, which will be pretty much in the middle of our crossing point. This alignment avoids phase problems in this region. Also loading the tweeter with horn provides time alignment with our woofer.

Before talking about crossover lets look at the high frequency driver a bit:

As you can see it is pretty sensitive at 93dB, mine actually reaches flat region at 92 dB. Because of the waveguide there is a big boost on the higher mid-range. Also note the fs of 1.4Khz. This means we should cross this tweeter not lower than 2.8khz. I decided to cut it at about 4Khz with 12db/ octave slope and this way make it linear down to approximately 2kHz. Considering the gain provided by waveguide i will cross the woofer at about 1.4kHz 2nd order Butterworth again.

This is how crossover looks like… on paper for now:

In schemtic you will see the Zobel network in parallel with the woofer for impedance equalization and the L-pad on the tweeter to adjust for the increased sensitivity.

To be continued:

- Finishing cabinets, round-over the edges of baffles

- Building crossover, install and voicing

What could be 50% faster than iPhone 3G? The new iPhone 3G S! However this could be just a rumor and some good guys decided to have a look inside. On the outside seems pretty much identical to its older brother. To open the case you still need to get passed those two screws at the bottom and to use a suction cup for the front panel. You must be careful again to remove it nice and easy not to damage the connectors. There is one more connector in the lower right corner.

Detaching the LCD from the front panel is done like in the iPhone 3G, you must remove the screws and use a sharp tool to release it. On the other half the main board is shielded from EMI. First the board comes off with the shields, then you must remove the two shields to look at the chips. Once the iPhone shows its intimate parts we can see that the rumors are true. Instead of S3C6400 now there is a S5PC100 Samsung microprocessor running at 600Mhz instead of 412Mhz like the older 3G.

This PCB alone is some piece of layout engineering. The other big chip next to the microprocessor is a 16GB Toshiba flash memory. Under this PCB hides a 3.7V/ 1219 mAh battery just slightly higher than older one.

In the end, with the new microprocessor the 3G S is definitely an upgrade and it seems this new iPhone will be able to face bigger gfx challenges so that’s good news for gamers.

Under Surgery: iPhone 3G S: [Link]

The are a few ways to measure wind speed, some involving ultrasound transducers, some based on cooling effect of air flow but most common technique uses  spinning cups and measures their rotation speed. There are also a few ways to measure this rotation, some using a dynamo, some using Hall sensors but most use a photo-interrupter in a way much like it’s found in a computer mouse for example.

This kind of anemometer is presented in this project. Four hemispherical cups are attached to a rotating axis. At the other end of the axis there is a disc with  4 slits. Holes can also be used if they’re close enough to the edge. This disc’s slits or holes go in the photo-interrupter gap. Now when wind blows in the cups and spins the axis, the photo-interrupter will output a series of pulses whose period depends on the speed of rotation. Now you can either measure frequency, number of pulses within a time unit or the mean voltage of these pulses.

Note that the greater number the whole or slits are done in the disc the greater the resolution will be. The diameter of the disc is also an important factor in resolution.

The rotation speed is measured in this project by a PIC16F873 microcontroller. The photo-transistor has its collector connected to Port A0 from the PIC. The developer of the project is planning to display the measurement result on a screen but he also made an USB interface to send the data to PC. USBN9604 IC is used for this task. The article recommends that you ground the parallel input pins if not used so that it won’t cause interference.

The project right now is a work in progress but the principles of its operation have been stated. Also a schematic is provided and the circuit explanation. I for one, am waiting for complete article to check out the measurement algorithm.

Measuring Wind Speed: [Link]

Every so often you can find yourself unable to take a picture, because human reflexes can’t always handle the timing required in some circumstances. From wildlife photos of animals or lightning to various fast moving objects like bullets or even splashes or balloons popping, one can encounter many situations where hand-eye coordination or shooting skills just aren’t enough to get the job done. And here is where something like the Camera Axe comes into play.

This is an open source project, both hardware and software, that controls a camera or a flash, activating it at just the right time. The brain of the device is the ATmega328 microcontroller with Arduino Bootloader. The Camera Axe possesses a Flash Trigger to activate the flash with, a Camera Trigger for the camera itself, a Sound Sensor and a Light Sensor. The sound sensor is built using an electret microphone and its sensitivity can be adjusted with the potentiometer on the PCB. The light sensor is made with a photo transistor that detects both visible light and IR. The Camera Axe also has a RF receiver so it can be triggered remotely from about 200ft.

I have a lot of respect for open source stuff and this project makes no exception. You can find a detailed component list, schematics, pictures of the PCB, the enclosure and more pictures taken using the Camera Axe, as well as code and information about getting the board in the link below. The part list has detailed pricing for every component used, from voltage regulator and microcontroller to bolts and nuts and the whole thing costs about 120 dollars for a single Camera Axe, which is really cheap for what it can do.

A very interesting, fun, useful and detailed project, the Open Source Camera Axe is another tool for the photography enthusiast that is worth every penny. A demo video is also available in the link.

Open Source Camera Axe: [Link] – [via]

Central heating systems has been a good solution for many homes and even offices for quite some time now. If you own such a system I’m sure you would like to be able to control it remotely from your bed or even from a computer. This project presents such a controller. It has a 5/2 days programmer, that is 5 week days, 2 weekend days or for entire week.

The control panel allows you to turn on and off heat and hot water independently. It has 10 program entries that you can save and you have the possibility to manually override the program. Basically it is composed of two modules: the relay module that is placed at the boiler, which also has the 9 pin D connector for serial connection and the programmer panel which is connected to the relay module by a UTP cable.

The programmer panel has a 2×16 LCD display and five switches to select the desired program or manually control the central heating. PIC16F628A microcontroller was used in this project as the system’s brain. Dallas DS1307 was used for time management and for saving time settings in its memory. It is powered by a backup battery so it will not lose the memory data when mains power is taken. Max202 IC takes care of the serial communication.

Because of the UTP wire lenght the rellay output of the PIC can not drive the rellays directly, so a driver is used from Quasar Electronics. It is also a good idea to use protection diodes on those outputs to take care of spikes.

LCD will show the current operation mode for central heating and hot water, the on/ off state and the time. Switch 1 and 2 turns the system on/off , switches 3 and 4 are used for manual control and switch 5 is used for programmer setup. A detailed explanation of the programmer’s operation is presented in the link with all schematics and construction procedures as well as the software for the microcontroller.

PIC-based Central Heating Controller: [Link]