Input Signal: Northlight
Serv8 board accepts DMX512(1990) as specified by USITT. The Serv8 can receive data at the full rate and is responsive to all 512 channels.
Output: Output is 8 PWM servo channels. Update at 50Hz. There are 255 discrete
servo positions.
Address: Set the starting address to the first in a group of 8. Start with address 0 up to 511 for DMX and 254 for PC serial port.
Power requirements:
8 to 12 volts AC or DC @ 100 mA.
Board connections: All
connections to the board are made via micro screw terminal blocks. Acceptable
wire size is 20 - 30 AWG. See drawing for connector locations.
All IC chips are in sockets
for easy replacement.
Red Power LED: The Red LED indicates the board is getting power.
Green Signal LED: If the green LED is blinking, there is no valid signal present.
If the LED is on, but dim, try to reverse the DMX signal wires. A valid signal will produce a steady bright LED.
PC Serial port protocol
To communicate with the Serv8 through
the serial port, you can use just about any computer that has a serial
port on it.
Some computers, like the Apple, come with serial ports which are directly
compatible with the RS-422 / RS-485 signal levels the Serv8 want to see. RS232 levels are close enough to be used with the decoders without adapters.
The protocol used is compatible with a number of servo controllers including Scott Edwards’s mini SSC servo controller.
There are several commercial animatronics software packages and freeware available for a servo controllers using this protocol.
A freeware Visual Basic example is available on the Northlight web site. Includes source and compiled code.
Mini SSC protocol
To send a new output level command, 3 bytes
are needed.
The first is a “sync” byte with a value
of 255.
The second byte is the servo address. It is a number from 0 to 254.
The third byte is the actual position data, between 0 and 254.
This sequence is followed for each servo.
For example, as shipped the Serv8 board address is 1. The output channels are addressed 1-8. Simple enough, For servos 9 - 15 the decoder board address would be set to 9. Channel 3(on the board) would be 11 to the controller, the board address plus the channel # - 1.
To change the level of a channel 3 to 50%, three bytes must be sent.
Sync , Address , Posn .
255 , 3 , 128
Connections:
Only 2 wires are needed from the PC serial port.
PC ground is connected to DMX input 1.
The RS232 signal is connected to DMX input 2.
On a standard DB-9 connector use these pins:
Pin 3 = Serial data
Pin 5 = Signal ground
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