Loading ...
Işıklandırma ve özel efekt sistmelerinde kullanılan DMX protokolüle ilgli uyguluma örneği Pic18f2550 ile yapılmış. Devrenin videosu aşağıda http://www.youtube.com/v/P-BeQWD1lSU
Bu proje www.micropic.es sitesinde yer almakta. Ãœye olunduktan sonra yazıları anlamak için google traslate veya babel fish transtlation yardımcı olabilir. Programları indirmek için “Descargar(Download)” kısmını takip ederek dosyalara ulaÅŸabiliyoruz.
The DMX protocol is widely used in lighting systems and special effects for events, clubs, venues, …
The Receptor DMX you present has a target purely experimental, and only this, to try to interpret the DMX512 protocol in its display and demonstrate the value of the selected channel at any given moment.
DMX protocol
It consists of a system very easy to install, since it allows many devices slaves chained to a cable only 3 threads:
– DMX +
– DMX -
– GND
The information is divided into 512 channels. Each channel contains one byte. Devices that are connected to the bus, are identified with one or more channels, and only met with the instructions they arrive in these channels. It is usual that a device used several of them, and physically identifying with the code channel beginning. Thus, if a head projector used, for example, 16 channels, and is identified with the code 128, automatically set aside channels 128 to 143 for himself.
The information is passed along this diagram times:
As noted, the entire fabric has several parts:
– BREAK signal: it is a low level with a minimum of 88us
– Mark after BREAK: high level with a minimum of 8us
– Byte Start: Start always worth the byte 0
– Time between bytes: is a high level that can reach up to 1 s
– Plot of 512 bytes: Here are the data of 512 channels
Each byte is transmitted:
– A bit low to start
– 8 data bits
– Two stop bits to high level
Thus, while some considerations regarding the protocol are as follows:
– Minimum duration for a full plot: 22.7 ms
– Maximum speed refresh information: 44 times per second
The circuit is composed of a PIC as heart, a ULN2003 for displays and a MAX485 for the bus DMX. I have chosen a 18F2550 because it was handy, but the software could be modified to enter a micro much smaller because it requires very little.
The CIP stored in its RAM the values of all 512 DMX channels, allowing it to “absorb” the complete information of the plot.
The channel DMX is selected by the keypad matrix.
There is another output device: the led. That led PWM and is managed by its Duty cycle is dictated by the fact DMX channel selected. In this case, there is no waiting for: the information is displayed in real time while you are writing the selected channel.
The connector DMX only needs three signals: + DMX, DMX-and GND. I have added Vdd also because it allows me to feed some auxiliary circuit that can connect to the bus, but is not essential.
USE
Using the device is easy. When you turn the device is already internally to capture the entire fabric that you arrive by the connector DMX. The display contains the word “OFF” while the user does not select any channel with the keyboard matrix.
As is pressing the keyboard, the display will show the selected channel.
While playing the keyboard, flash points of decimals displays to warn that we are seeing the channel selector, instead of DMX data. After a few seconds the information appears on the displays.
The value of the selected channel also is represented in the led, whose intensity is regulated by PWM.
Since the device memorizes the entire fabric (512 bytes) can be disconnected from the bus and examined retrospectively as if it were physically connected.
