North Light SRV08 User manual

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64
128
255
Start
Address
DIP
switch
decimal
equivalent
Northlight Systems SRV08 hobby servo motor controller Quick Start quide
Connecting for the first time
Make connections one at a time.
First connect the power.
Is anything hot? Does the green LED blink? Did you measure the power with a voltmeter?
Second connect the DMX source.
Does the LED glow or flash very fast?
Last thing.
Connect your servos last.
Features
 Quality low power DMX receiver chip equal to 1/8 unit load on DMX line
 ESD protection and “fail safe” features on DMX receiver chip
 Allows DMX512 digital protocol to control 8 – RC type servos.
 256 or 4096 positions across the output range.
 All outputs on standard 3 terminal, .10” , “Futaba” style connectors.
 Mini DIP address switch, address 512 channels.
 On board, low dropout voltage regulator for controller power.
 Separate connectors for board power and servo power.
 8 - Selectable output pulse widths.
Input Signal
Northlight SRV08 board accepts DMX512 .
The Serv8 board can receive data at the full rate. The SRV08 is responsive to all 512 channels.
Output
Output is 8 servo’s @ 1 to 2 milliseconds. Update rate @ 50Hz. Output pulse has 255 or 4096 discrete
positions.
Output Pulse Width
The default output is from 1 to 2 milliseconds @ 50 Hz. By using the configuration jumpers, J1-J3, the output pulse width can be
increased or decreased. See the section on setting the pulse width for a chart of the settings.
There are 256 or 4096 discrete servo positions for all pulse widths.
Address switch
9 position mini DIP switch on the circuit board for infrequent address changes or OLED address switch on a
ribbon cable for applications requiring an address switch on the front panel of an enclosure.
Setting the Start Address
Set the starting address to the first in a group of 8.
The address is entered on the DIP switches in standard binary code starting with 1.
See the chart of all 512 address switch positions at the back of the manual.
Each switch on the DIP switch, numbered 1-9, has a decimal equivalent.
To calculate the address on the DIP switch, just add up the decimal equivalents of the
switches.
For example, to set the DMX output address to 9, set switch 1 and 4 to on. Switch 4 is
equal to 8 plus 1 equals 9.
Power requirements
5 to 12 volts DC @ 80 mA. for controller board. Servo power is separate.
LED Indicators:
Green DMX activity LED. Flashing when no DMX or steady on good DMX

Board connections
All outputs use standard 3 pin, 0.10”, “Futaba” connectors. See drawing for connector locations.
Power and DMX512 signals use screw terminals.
Physical Dimensions
2.50”L X 1.50”W +/- .10”
The DMX input pin numbers correspond to the
XLR pin numbers.
DMX512 ,Pin 1 is signal ground – not earth
ground.
Using the configuration jumpers
There are 2 configuration jumpers on the
SRV08.
A1 – Determines the output in the event of
DMX signal loss.
This function is not affected by the A2 setting.
Open(no jumper) – When the DMX signal is lost, the servo’s will go to DMX zero position. This is the default setting.
Closed(jumper in place) – When the DMX signal is lost the Serv8 will hold and continue to output the last valid data.
A2 – Determines the control signal protocol.
Open(no jumper) – the Serv8 is configured to receive DMX512. 1 DMX cannel per servo, 8 bit.
This is the default setting.
Closed(jumper in place) – The serv8 is configured to receive 12 bit DMX. 2 DMX channels per servo with the first channel
representing “coarse” and the second channel representing “fine” control. Thie mode the servo pulse has 4096 steps from 0- 4095.
Servo1 = DMX channel 1(coarse) DMX channel 2(fine).
Servo2 = DMX channel 3(coarse) DMX channel 4(fine).
Servo3 = DMX channel 5(coarse) DMX channel 6(fine).
Servo4 = DMX channel 7(coarse) DMX channel 8(fine).
Servo5 = DMX channel 9(coarse) DMX channel 10(fine).
Servo6 = DMX channel 11(coarse) DMX channel 12(fine).
Servo7 = DMX channel 13(coarse) DMX channel 14(fine).
Servo8 = DMX channel 15(coarse) DMX channel 16(fine).
Termination
A common problem with DMX systems is improper termination.
A simple terminator consists of a 120 Ohm resistor connected across pins 2-3 of the
DMX signal
The servo board provides an on board terminator using standard square pin
connectors on .10” centers.
A toggle switch can be placed across the terminals for convenient front panel
terminator selection.
The termination resistor should only be in when the servo board is the last device on
the DMX link.
Servo connections
Standard “futaba” connections. Typically Black is ground , Red is V+ and
yellow is signal.

Setting the Pulse width
The Serv8 board is capable of 8 pulse widths. The most common is a pulse of 1-2 milliseconds @ 50Hz with
1.5 ms as center or rotation. On most servos this produces 90 degrees of movement. This is the default
setting when shipped.
The maximum pulse width produces about 180 degrees of movement. Some servos don’t have this much
travel and may be damaged.
Be careful when using the longer pulse widths. If the servo “chatters” the pulse width is too wide.
When the pulse is shorter than normal or stretched, the center of the pulse will be maintained at 1.5 Msec to
keep the servo centered.
The table below shows the jumper settings for 8 pulse widths.
Jumpers Min pulse width Max pulse width Pulse range
J1
J2 1.25 mS 1.75 mS 0.50 mS
J3
J1
J2 1.18 mS 1.83 mS 0.65 mS
J3
J1
J2 1.10 mS 1.90 mS 0.80 mS
J3
J1
J2 1.00 mS 2.00 mS 1.00 mS
J3
J1
J2 0.90 mS 2.10 mS 1.20 mS
J3
J1
J2 0.85 mS 2.153 mS 1.30 mS
J3
J1
J2 0.775 mS 2.25 mS 1.45 mS
J3
J1
J2 0.65 mS 2.325 mS 1.60 mS
J3

8 BIT DMX vs 16(12) BIT DMX
8 bit DMX is a single channel that will produce 256 (0-255) discrete pulse widths.
In 16 bit DMX , 2 channels are used, they are linked together to form a 16 bit “word”.
The first channel is the “coarse” adjustment and the second channel is the “fine” adjustment.
This is not the same as two adjacent channels where they are acting independently.
For example, assume that you are moving the servo from zero to 90°.
At the beginning, both the coarse and fine channels are at 0. As you start the move, the fine
channel increments from 0-255. When the fine channel reaches 255, it resets to zero and the
coarse channel increments from 0 to 1. The process then repeats, incrementing the coarse channel
until the first 4 bits of the coarse channel are set.
The SRV08 uses 12 bits This gives the servo a total of 4096 possible pulse widths, resulting in
much more precise control. The advantage of 12-bit resolution is the smoothness of the movement
and precise placement.
To get full resolution with 4096 steps requires a quality servo and tight linkage. If you are trying to
sweep 90°, that would be .021° per step. That is not that easy to even measure. Any slop/backlash
in the internal gears of the servo or external linkage might appear to be a missed step or
inconsistent movement.
A cheapo analog servo might not resolve such fine steps.
Analog servos have what is called a 'deadband'. This is the amount of variation in the pulse width
that has to occur before a change in position. If the deadband is too narrow, the servo could
oscillate due to noise and consume more power than required. If the deadband is too wide the
servo will not be as sensitive to changes in the pulse width.
According ti HiTec , standard (Analog) servos have a deadband of around 8us and high
performance servos have a deadband of 1~3us.
The point is that 'analog' servos have a finite resolution.
A 'digital' servo will also have a deadband that will limit its ultimate resolution. however many can be
set to very low or 0 deadband.
Warranty
Northlight Systems warrants this product against defects in materials and workmanship for a period of 1 year.
Returns Policy
If there is a defect, we will repair or replace the product at out discretion.
We offer a full refund on the purchase price if returned in original, unused and “like new”, condition in less than 30 days.
Return the product with a description of the problem. Free repairs are for defective parts or workmanship only.
Repairs due to improper hookup, over voltage, short circuits, physical damage etc., will be charged to the customer.
Northlight will repair any circuit board for a flat fee of $20.00 plus return shipping.