complete laser room access solution
laser interlock system mounting
advanced non-defeatable laser room
A Tutorial Explaining Laser Safety Systems' Unique Design Approach to Laser Room Interlock Systems
While these systems perform adequately for small laser rooms, they may be over-sized for some situations and under-sized for others.  In other words,"one size" does not "fit all".   They have a finite number of inputs and control outputs, and they generally lack the ability to handle special control situations.
First we take a look at the space that is going to become a laser area.
In the example below there are two doors and two laser tables...
Step 1
typical laser room
Step 2
Next we need to determine what is needed at the various locations throughout the room.  In the image below we have documented the desired module controls...
Notice what we have done with the doors. Our client wants Defeatable access because they have long-term experiments where qualified laser workers must transit in and out of the room while the laser remains in operation. To accomplish this, a Defeatable Access Module will be placed at the main entry door.  Laser curtains at this entry point protect personnel in the hallway during access. On the second door we will install a Non-Defeatable Access Monitor Module to prevent any unintended laser exposure.  Both doors will have laser warning modules outside to warn of laser operation.
Step 3
In this step we have drawn a single
line around the room using the shortest logical route to connect
all required control elements.  This line, shown in orange, represents the cable run and is numbered at the locations where modules will be placed.

Key:
1  Laser Warning Module
2  Defeatable Access Control Module
3  Laser/Shutter Relay Module
4  Non-Defeatable Monitor Module
5  Laser Warning Module
6  Laser Interlock Control Module
7 Laser/Shutter Relay Module
laser room safety system
Step 4
Now we have taken the orange line and straightened it out to linearly show all control elements from start to end.  The orange line represents the 8-conductor interlock cable that will be routed around the room and pass through every control module.
What you now have is a rough electrical wiring schematic.  If you're familiar with our systems, you need little more than this to complete 90% of the electrical installation of our system in this example.
building a laser interlock system
Step 5
The diagram below is the final wiring schematic for the laser room interlock we designed in this example.  As shown, the color-coded 8-conductor cable passes through all main modules.  The Keypad and Push-to-Exit modules are pre-terminated and connect to the LSS2388 Defeatable Access Control Module by push-in phone-type jacks. 

By design, each module "knows" its function and will coordinate with all other modules to maintain a safe and effective interlocked control system.  Additional modules can be added at any point simply by placing them in between other modules, or by extending the "start" or "end" termination nodes to the end of any new cables and modules added.
An advanced laser interlock system
Power Connection
We are frequently asked about the number of modules that can be added to our system.  The number is actually quite surprising.

Our power supply provides 1 amp to the system.  Most of our modules consume anywhere from 11mA (0.011 Amps) for the simple modules, up to 110mA (0.11 Amps) for our most complicated module, the LSS2388.  With this in mind, we can easily have systems with 20 or 30 simple modules and still have power for 4 or 5 of our most complicated modules.  When quoting a system, we ensure it falls well within the allowable power budget.       
Step 6
Our system is powered by 24VDC applied through a LSS2384 Laser/Shutter Relay module.  We chose to have power supplied through the LSS2384 module for the following reasons:
Total Module Count
1.  the LSS2384 module will likely be installed at a laser table;
2.  the laser table will have a power outlet nearby;
3.  our power supply simply plugs into an outlet; there is no concern about the need to wire to   
     the 115V AC mains;
4.  the output cable to interlock the laser or shutter is designed to come through the LSS2384 module,
    making it the logical point of entry for system power.
Final Step
The remaining item in the planning of the room interlock system is the method of installation on the wall.  The modules can be placed inside a wall if the project is planned before room construction, or, in existing rooms, they can be placed on the surface of the wall using surface track and surface- mounted boxes.

Laser Safety Systems carries a large variety of Hellermann-Tyton components for surface mounting for clients with classroom or cleanroom types of environments. Clients with industrial environments should use standard metal conduit and surface boxes for the added protection of wiring.

To select the length of cable, we add up all linear runs between all modules and multiply this length by two to ensure adequate cable length.
laser room door control
Back
Next
Laser Safety Systems takes an entirely different practical and common-sense approach to laser room interlock design.

Our system is based on portable and strategically-placed control modules.

advanced laser interlock
Referring to the diagram to the right, each main module has an X1 and X2 screw terminal connector that accepts our 8-conductor color-coded interlock cable.  The wires connect to the module using simple and reliable screw-down wire cage clamps.

Figure 1.  An example of a typical Non-Defeatable laser room interlock system.
Figure 2.  An example of a typical Defeatable laser room interlock system.
Figure 3.  An example of typical laser table controls.  Not shown above, our clients also often place our LSS2383 Emergency Stop Module at stations operating high-power laser.
In this link you will find a full size copy of the Laser Interlock Schematic shown in step 5 of the example exercise above.   Note:  The pdf page is sized to 36" by 24", so it may open in a blank area of the display depending on your browser settings.
To understand the unique advantages of our approach, one must review the "one size fits all" traditional approach to laser interlock hardware.
Main
Interlock
Cable
in/out
Main
Interlock
Cable
in/out
As you flip through the example below, you will see a start to finish room plan for a typical laser area.  The beauty and simplicity of our design will quickly be evident.
Now that you understand how our systems are designed, planned and installed, you may wish to see a few examples below of typical installations of both the Defeatable and Non-Defeatable access systems.
The traditional laser room interlock controller is built in a single box. This box is mounted somewhere in the laser room and the wiring is carried out in multiple conduits to different areas of the room, as shown in the diagram to the right.
Each time a new laser is added to the room, a new wire run (and possibly a new conduit) must be routed between the laser and centralized controller. 
Placement of the controller within the room must be carefully considered, because laser workers must walk over to the controller in order to operate the system.
We have designed modules to perform every known control function.  Each module "knows its job" and can control the state of the interlock or be controlled by the state of the interlock.  If any module within the system calls for a safety trip function, it will instantly be processed by all modules.  All trip functions use dual redundancy for added safety.

Every module is built to function within a network of modules installed along a single common control cable routed around the room.  This allows the client to purchase only those modules necessary to perform the desired interlock function.  Being modular, the controls can be split-up and placed exactly where needed. New modules can be added at any time or existing modules can even be moved between different labs that utilize our control system.