Synchronisation of several LMS5xx

There are two scenarios where it makes sense to synchronize the LMS5xx scanners in an application. 
# Optical interference between two or more LMS5xx can occur, if they have to be installed within the same scanning plane. Several LMS5xx can be synchronized to avoid this type of interference. 
# The synchronisation feature can also be used to increase the scanning frequency of an area by placing several units over the same area and adjusting the phases to alternate scanning.

 

As an example for the synchronisation, the parametrization is here described for synchronising two scanners.
Through the SOPAS software an LMS5xx PRO must be set to be Master only via Output 6 (master synchronisation) and connected to a second LMS5xx through Input 4 (slave synchronisation). On the LMS5xx Lite Output 3 is used for master synchronisation and SyncIN for slave synchronisation. Using the Synchronisation Phase value (range: -180° ... 180°) in the SOPAS software each Master-Slave link can be differentiated.

 

 

 

Master (I/O cable):

• brown (24V OUT3-6): to 24V
• black (GND OUT3-6): to GND
• red-blue (OUT6): to IN4 of the Slave

Slave (I/O cable):

• green (GND IN3/4) : to GND
• grey (IN4): to OUT6 of the Master

 

 

 

Master:

 

• terminal14 (24V EXT.): to 24V
• terminal 15 (GND EXT.): to GND
• terminal 26 (OUT6): to IN4 of the Slave

Slave:

• terminal 9 (GND IN3/4) : to GND
• terminal 11(IN4): to OUT6 of the Master

 

 

 

Master (I/O cable):

 

• red (24V OUT1-3): to 24V
• blue (GND OUT1-3): to GND
• pink (OUT3): to SyncIN of the Slave

Slave (Data cable):

• red (GND SyncIN) : to GND
• blue (SyncIN): to OUT3 of the Master

 

 

 

Master:

 

• Terminal 9 (24V EXT.): to 24V
• terminal 10 (GND EXT.): to GND
• terminal 5 (OUT3): to SyncIN of the Slave

Slave:

• terminal 8 (GND IN) : to GND
• terminal 7(SyncIN): to OUT3 of the Master

 

On the connection platine of the LMS500 there ware two yellow switches. Their position has to be as follows:
Switch Position
IN-GND V_Out(S1)
V_OUT Sys

 

 

Make sure that both devices are running at the same scan frequency.
OUT6 of the Master has to be parametrized as Master Synchronisation: Parameter / Network / Interfaces / IOs / Digital Outputs:

IN4 of the Slave has to be parametrized as Slave Synchronisation: Parameter / Network / Interfaces / IOs / Digital Inputs:

The phase of the slave can be freely parametrized between -180° ... 180°:
 

 

 

 

 

Make shure that both devices are running at the same scan frequency.
OUT3 of the master has to be parametrized as Master Synchronisation: Parameter / Network / Interfaces / IOs / Digital Outputs:

SyncIN of the slave has to be parametrized as Slave Synchronisation: Parameter / Network / Interfaces / IOs / Digital Inputs:
The Phase is to be done same as in the PRO, also the Master signal must look like in the example for the PRO above.

 

The master delivers via OUT6 a rectangular signal, which starts with a rising edge at angle 0� and its periode equals the actual used scan frequency.
The Master-Signal of the LMS200 for the synchronisation is:
* high (+24V) from 0° - 180°
* low (0V)  from 180° - 360°
For the LMS5xx it is the same.
The output signal of the OUT6 of the Master must look like this if it is measured with an oscilloscope: (e.g. 100Hz Scanfreq.)
Using the Master scanner without any slaves is possible. 
It could be used for a hardware signal to determine when the mirror is betwenn 0°-180° or 180°-360°.
 

 

Feature available from V1.20 firmware on.
In V1.10 the monitoring of the external synchronization signal checked, whether the connected signal was roughly in the right range. If this was not the case synchronization was disabled and a "0" displayed on the front panel of the device.
The actual allowable input frequency was only a fraction of this range and was set around +/-0.1 Hz around the nominal frequency. This allowed two LMS5xx to synchronized, but made it difficult to sync to an externally generated signal. What is more, it was possible that the LMS5xx could not sync but did not indicate this on the display.

In the V1.20 version the monitoring and the actual ability of the device match, i.e. the device is capable to lock over the full range of +/-2% of the nominal frequency.
The current state of the external synchronization signal is displayed on the "Digital Inputs" page once "Slave synchronisation" is selected:

none:          no external signal detected
too slow:    external signal detected, but below permitted input range
good:         external signal within tolerance (refer to table above)
too fast:     external signal detected, but above permitted input range

 

Only SICK internal function, not to use by the customer.

 

The Slave signals a "0" on the display, sets a warning and deactivates synchronization on Slave, when:
- the period of the scan frequency of the Master is less than (period of scan frequency minus 1ms)
- the period of the scan frequency of the Master is greater than (period of scan frequency plus 1ms)
- no synchronization signal on the Slave is available
This could happen, when:
- different scan frequency between Master and Slave
- heavy shaking of the device
- synchronization wire not connected
Once a correct scan frequency of the Master is detected the Slave resumes synchronization, clears the display and removes the warning.
If Slave Synchronisation is chosen and no cable is connected, no warning message is displayed .
A problem could also be, that the power supply for the output is not connected (Pin "24V EXT": to 24V; Pin "GND EXT": to GND)
Synchronization Signals for different synchronization phase values:

Possible wiring issues if it is:

- the GND In3/4 pin is not connected to GND (by the Slave), add. double freqency by the Slave is shown

- no 24V on the Pin 24V Ext of the Master
- GND out 3-6 is not connected to GND by the Master
- Out 6 of the Master is not linked to the IN4 of the Slave

 

Max. length of the cable between two scanners is 15m.

 

The signal goes by 0° from low to high. One Periode of the signals equates exactly to one rotation, means e.g. 20ms by 50Hz.

 

A Slave can also be a Master and by this way is able to give the signal he received from his Master to the next slave. So it is possible to build up a line of several scanners where every Slave is Master for the next one.
Always pay attention, that the Signal of the first Master in the line may not be exactly the signal that is received by the last slave because of the internal processing time of every Slave/Master.

 

The synchronisation frequency from the master LMS5xx has a tolerance of  +/- 2%
The max. and min. tolerance which the slave LMS5xx can accept is +/- 2%

 

Check the length of the cable, it should not exceed 15m from one scanner to the other.
The cable should be a shielded one (our standard cables are shilded ones). The shield of the cable must be connected zentral starlike. The shield of the cable has connection to the housing or the device.
Take care about the correct connection of all GND's of the device, that may cause mose of the noise. All GND's should be connected starlike.

 

Sync by outputs: One master is able to synchronize up to 6 slaves.
Sync by CAN: there is no limit for the number of slaves.

 

Sync by outputs: It is possible to build up a star wired network of the scanners or a line where every Slave is the master for the next slave (see chapter above)
Sync by CAN: As the scanner has only one CAN bus output, a star topology is not possible, because all Slaves have to participant of one single CAN bus. 

 

if an external synchronisation is done via IN4, a delay in the timing can only come from the external signal device, because the internal timer fo IN4 is very accurate.