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Telescope protection
ETH-2 has 3 inputs for special sensors which are used by high priority telescope protection functions which are designed to prevent telescope malfunction due to its incorrect operation - one might think of them as the last line of defense against expensive hardware damage. These are:
Since activation of any of the three protection sensors presents the last hope of saving the valuable equipment from permanent damage, one needs to be sure that they will be able to alarm ETH-2 in case of emergency. That is the reason that we designed all of them to conduct when inactive and to stop conducting when activated - otherwise breaks in their cables could render them silent without warning. But because of this decision, breaks in protection sensor cables are guaranteed to activate ETH-2 protection functions and disrupt scientific work. In order to enable telescope operators to continue its use even when one or several protection functions are permanently activated, a simple software procedure for disabling any of the three of them is provided. This can be done both locally by pressing the keyboard keys and remotely, using the dedicated PC application.
ETH-2 protection output is low power type (100mA / 27VDCmax) that is optically insulated from the device itself. In order to enable it to control the telescope motion system, it is necessary to design the interface hardware appropriate for each particular telescope type and model. In the simplest case, that can be an electromagnetic relay with a few additional components that disrupt telescope motion system power supply when ETH-2 protection output activates. But more able designers should feel free to implement any sophisticated protection algorithm that suits their needs better - for example, ASCOM compatible PC application software provided can be used to initiate automatic telescope recovery routine.
If telescope stopping is implemented by restricting its motion system power supply, then in order to start the telescope and move it into a safe position, it is necessary to temporarily override the protection. In order to avoid complicating interface hardware with this further, ETH-2 has a dedicated momentary push button on its housing, the exclusive purpose of which is resetting the telescope protection output. While this button is depressed, blinking message "Restart" is displayed and alarm tone is generated by ETH-2. Reset function can as well be issued remotely either from the PC application software or via the remote console.
designed by LP 2013