Hiện nay, màn hình LCD gần như đã hoàn toàn thay thế được công nghệ màn hình CRT cũ, bởi những ưu điểm vượt trội mà nó mang lại, như kích thước lớn hơn trong khi lại gọn nhẹ hơn, màu sắc tươi sáng và đặc biệt là ít tốn điện hơn nhiều lần.
Mới đây Dell đã công bố kết quả hoạt động kinh doanh Quý 3/2012 của mình. Theo đó, lợi nhuận trong 3 tháng vừa qua của hãng đạt 475 triệu USD, giảm 47%
Nokia và Microsoft vừa tổ chức một sự kiện dành cho các lập trình viên tại Singapore vào ngày 17/11 vừa qua, trong đó nhất mạnh đến việc phát triển phần mềm cho Windows Phone 8.
Sunday, 20 January 2008
First, the different components involved are
1.) DC motor
2.) Output drive circuitry
3.) Arduino (of course)
In it's most simple form (forgetting back EMF) the motor would look like this circuit:
The Arduino would be driving this motor with an external transistor configuration shown below using a fixed frequency and variable PWM (pulse width modulation) to control motor speed,
Now, lets put them together and we have our basic motor drive circuit,
Now lets look at how the current flows when the transistor is on,
Notice the clamping diode installed around the motor. This will help clamp any energy coming from the coil in the reverse direction when the transistor switches off.
Now that we understand the basic setup. Lets see if we can shed some light as to why resets are happening.
Lets start off with making sure we still have a clean 5v supply running the Arduino when we're running the motor...
DC motors can suck a lot of juice from the 500mA limited USB supply. Lets look at the high side of the motor's supply to make sure we're doing anything nasty to the poor USB.
The below image shows how a capacitor is used to bucket the energy.
So maybe, we should limit the capacitor's ability to draw too much current from the supply by adding a series resistor. Using a passive component like a resistor has some efficiency implications. There are much better ways to limit current through the use of active components.
For our purposes of trying to clean up the 5v supply, we can entertain the idea. See the image below.
Say for instance, the bucket capacitor is 10uF. On power up, it will take 25ohms * 10uF = 250 microseconds to charge up to 62% or 1 time constant. After that, the voltage ripple on your 5V supply should be much less than before because the current is safely limited to motor.
Wednesday, 16 January 2008
These days, it takes a lot for mass produced electronics to get noticed. Usually when I look at something electronic these days, I tend to notice the outer packaging. Shopping for cell phones, mp3 players, etc. I usually go with the one that looks best.
Playing with electronics hardware has kept me busy and awake all hours of the night because there's something inherently self-satisfying about using electronics to create something. Wiring, connecting, and sometimes soldering to create projects has enabled me to learn a lot about electronics.
From the pictures, they've spent lots of time making the packaging of the modules, but it seems like they've missed the idea. How do premade and pre-packaged device allow people to make electronics creations?
Since I like to tinker, what if I don't like their screen or camera module? What do i do if it can't fit into my application? I'm just not sure I'll have enough ability to customize the modules to my liking. Where is the hardware tinkering? Everything is already done for you.
They have done a decent job at selecting some of the modules that people might like to play with, but I hope they leave something for me to do with them!
Monday, 14 January 2008
Without further ado, here's a picture of the GPS shield sitting on my Arduino:
I'd go into further detail about the circuit or the schematic, but there's really nothing to talk about. You just pull the board out of its wrapper, snap on the antenna, plug in +5V (red wire) to the pin tower labels "+5" and ground (black) to the pin tower labeled "GND". Set the board starting at the Arduino's pin number 8, and you're set to go.
As usual, I've posted the source code for the project over at liquidware - enjoy!
Here's a picture of the contents of the kit, poured out onto my desk (which is actually a small piece of cloth-covered corkboard from my old office):
I then clamped the PCB onto the "3rd hands" and began soldering away:
After only 15 minutes with the gun, and only 1 redo, I sat back and appreciated my work of art:
But it got me thinking... why not make an extender board, that allows someone to attach two modules onto the Arduino base? That way, you could put two breadboards on one Arduino, or possibly a breadboard and a GPS kit?
The possibilities would be endless... and I shall call it the "Pin Replicator Shield". I've started a project entry over at liquidware to hold my thoughts and progress on the new shield.
Friday, 11 January 2008
- A screen
- An input device (buttons, switches)
- A power supply
- A functional component (GPS, MP3 decoder, Wifi, Cell phone, etc.)
Sunday, 6 January 2008
The first thing I did was rush over to the Arduino website and start browsing around. In search of ways to play with it, it didn't take me long to stumble on this section,
Wow! I could not believe how many hardware devices there are here. Tons of contribution to this area has really expanded the capability of my $30 Arduino. Definitively well spent cash.
It's so unbelievably easy to use one of these things. Take for example, you want to print out a number to PC via the serial port, you don't even need to do any processing at all on the bytes to get it into ASCII form -it's all done for you.
unsigned char num;
This may seem silly to write about, but I'm used to writing tons of support code to make this soft of thing work. It really is plug-in and "play"!