Controllers for Laser Shutters Tutorial
The controller product line provides the source of electrical power to open and close the laser shutter. We offer a choice of AC line connection or DC supplied voltage to operate the controller. Controllers are calibrated and labeled for a particular model of shutter.
The shutter cable plugs into the controller receptacle. A signal source, such as a pulse generator or microprocessor output, is plugged into the BNC connector or screw terminal. Internally, DC power waveforms are generated and sent to the shutter whenever the input signal is high.
Controllers also provide a manual toggle switch or terminals for such connection, to allow the shutter to be controlled manually. Safety Interlock models offer additional output connections for shutter position sensor electronics.
The controller and shutter are very similar to a common amplifier and speaker system. The controller, as an amplifier, sends waveforms of inductive load power, and the shutter, as a speaker, is the inductive load receiving the electrical power. When the two are closely matched for the application, the performance of the design is maximized.
Simple DC circuits can be used to drive most electro-mechanical devices, including laser shutters. But when performance becomes demanding, the design features of the controller are tailored for the intended applications.
Models have design emphasis on one or more of the following features: rapid switching speeds, high repetition rates, exposure repeatability and jitter control, low shutter heat dissipation, shock/vibration/acoustic noise control, safety interlocking, and special OEM considerations.
The internal circuits vary greatly as performance features are combined. It is very important to choose the proper controller to assure maximum performance from the laser shutter.
The controllers are simple to use. After plug or wiring connections are made, simply apply the control signal. Whenever the signal is high (3-12 VDC), the shutter is opened. When the signal goes low, the shutter closes. The input is resistive, at about 3 K Ohms. Your signal source must be able to source the required current, typically 1 mA at TTL voltages.
Safety interlock models offer additional circuitry to read the Position Sensors built into the laser shutter. Either TTL totem pole outputs or mechanical microswitch contacts are accessed at the rear panel of the safety interlock controller models. These outputs toggle between hi/low (open/close) as the shutters cycle. The signals are useful for driving computer safety systems, amplified door lighting systems, LED displays, and processing software.
Other safety interlock features include a reset button, requiring acknowledgement of an interlock breach, and an interlock continuity connection, typically used with switches on laboratory doors or curtains.
When selecting a controller, first choose between a modulation type or safety interlock type, then review the features that match your application.
Below is an example of a simple Capacitor Discharge Circuit. It is very simple, but robust and low cost. All of our safety interlock shutters can be driven with this circuit as well as with our controller models. Modulation shutters typically cannot use this circuit due to recharging limitations.