Workstation Activity Sensor Solutions
Real-Time Signals From Each Workstation
The Ecogate solution focuses on providing exhaust ventilation only to machines that are currently active while closing the gates at inactive machines. In woodworking applications, this means that only the machines actively producing sawdust have their gates open, while other gates remain closed.
To achieve this, Ecogate needs to read the signal from each workstation, indicating that the workstation requires ventilation or dust collection. The signal is connected to the Ecogate gate sensor input. In this blog post, we explore the different options for obtaining dry contact at various workstations.
Technical Note: The sensor input at the gate uses two wires with 24 V DC. When an external contact connects these wires (with a current of around 10 mA), the gate opens. Avoid connecting any external voltage to this sensor input! Workstations should provide a dry contact (relay output), or, if not available, use one of the sensors recommended by Ecogate for proper functionality.Optimal Solution: Machine Manufacturer Provides Dry Contact
The ideal approach is for the manufacturer of the machine to provide a dry contact to trigger an Ecogate gate. This is exemplified when Andersen Windows purchased machines for expanding their facilities in Minnesota and Wisconsin. They specified when ordering the new machinery that they should be equipped with a dry contact for Ecogate. This is perfect, as the manufacturer fully understands the functions of the machine and can close the dry contact a few seconds before the machine needs ventilation. This allows the gate enough time to be fully open when dust collection is necessary. This approach requires minimal time during installation, making it very cost-effective.
A similar approach was used during our installation at Ikea. Ikea contacted manufacturers of the equipment, requesting a software update that would include the dry contact output (of the PLC) for Ecogate. A disadvantage of this approach is the relatively slow response time from manufacturers (compared to specifying output for an Ecogate system at the time of ordering).
A notable example of this solution is when Rubbermaid in Missouri installed a new Schelling CNC saw. We requested engineers from the manufacturer commissioning the new saw to create a dry contact for Ecogate. This request was easily fulfilled: the dry contact was wired, and proper timing was programmed in the control PLC of the saw.
Second Best Solution: Custom PLC Programming
Many machines use a PLC to control their functionality. Some PLC programming for custom machines is programmed directly by factory maintenance engineers. This is ideal because they can add the functionality of the dry contact output for Ecogate to their program. A similar situation is when a manufacturer programs the machine PLC, but factory engineers have the PLC source code and can modify it, providing the best possible signal. This approach requires some time to modify the PLC software. This option has been used at Andersen Windows, Rubbermaid, and other factories.
Third Option: VOLT or CURRENT Sensor, or DRY CONTACT
If neither of the above options is available, Ecogate will set up workstation activity sensors during system installation. This is a very common approach in many typical system installations.
To correctly understand the machine function, the Ecogate Chief electrician will need help from local maintenance. They will walk through the factory, machine by machine, determining to which circuit the sensors can be connected. Ideally, it will be a circuit that is active before ventilation is required. For example, on a CNC saw, it will be the circuit that activates an arm holding material to be cut, as this circuit is active before the saw starts cutting.
What sensor is necessary? If the dry contact is available or can be added as an option to the contactor (most contactors allow attaching optional dry contact), then a sensor is not necessary, and the contact can be wired to the gate sensor input. If the dry contact is not available, we can use either Ecogate AC-DC VOLT or AC VOLT sensor or current sensor. You can read more about sensors offered by Ecogate here.
Configuring Options in greenBOX Software
The greenBOX software provides several options for configuring workstation activity sensors:
Normally Open/Normally Closed Logic: The Input logic can be set from Normally Open (NO) to Normally Closed (NC).
Input Timer: If a signal is active for a very short period (for example, 0.1 sec), but we need to keep the gate open for a longer time, we can use the Input Timer function.
Off Delay: For each gate separately, we can program OFF DELAY time. The gate will not close immediately after the signal from the workstation is no longer active but will close after the set delay.
Keep Gate Open: This is typically used if the sensor is not yet installed or if the sensor is not working. This option will keep the gate open until the sensor is repaired or installed.
Open Gate only if Sensor is Active: This option means that the gate will not be used for minimal airflow. This is typically used for all sanders, as it is not acceptable to open the gate and start ventilation if the operator is changing the sanding belt (a vacuum will make it difficult or impossible to remove and reinstall the belt).
Author: Ales Litomisky
