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User’s manual for the Telescope Emergency Stop System (TESS)

User’s manual for the Telescope Emergency Stop System (TESS) on the Magellan telescopes.

1. Description. 

The system was designed to allow any person to stop the telescope on an emergency. It has 14 red ‘Emergency Stop’ pushbuttons located throughout the telescope (see tables 1 and 2 at the end of this document), which interrupt the direct power of the telescope (also know as ‘Dirty power’) when activated.

Direct power is used to feed the most powerful and critical equipment and systems of the telescope, so interrupting it makes all of them to stop. These equipment and systems are: 

  • Main Drive PWM motor amplifiers and motors.
  • HPU (hydraulic power unit).
  • Dome motor amplifiers (AKA Baldors) and motors.
  • Tunnel fan motor amplifier (AKA Toshiba).
  • OSS equipment: Counterweights, mirror covers, coolant pump.
  • Instrument rotator PWM motor amplifiers and motors.
  • 110V outlets inside the dome.

 
All these equipment and systems are fed through two 3-phase power contactors located in the equipment room.

Picture A. The 3-Phase contactors (doors open) in the equipment room (Baade).

 

2. How it works. 

The red ‘Emergency Stop’ pushbuttons have two contacts each (one normally open and one normally closed). The normally closed contacts of the 14 pushbuttons are connected in series, and wired to interrupt the direct power when any of them is activated (the normally closed contact opens). The normally open contacts of the pushbuttons are wired to individual inputs of the PLC, in a way that they take their related PLC inputs to electrical ground (GND of the 24Vdc) when the pushbutton is activated (the normally open contact closes). This means that the system has two independent parts: The 110Vac (power) circuit, and the GND (of 24Vdc) signals.

 

The PLC is located behind a metal plate in the control room. On the plate you find a message display (part of the PLC system), one of the 14 red pushbuttons and a yellow pushbutton also known as ‘Reset switch’ or ‘Reset Pushbutton’ (see pictures B and C).

 

The PLC program deals only with the signals from the 14 red (E-Stop) pushbuttons, and it also monitors the Relay which turns OFF/ON the mentioned 3-phase contactors. By monitoring this relay (RL2), the PLC is able to determine when there has been an external power interruption (outage), unless the relay itself has failed.

The PLC has no connection to the 110Vac (power) circuit which interrupts power to the equipment and systems listed above. 
 
 
 

Picture B. TESS plate (Baade telescope).

 

Picture C. TESS plate (Clay telescope). 

3. How to use it.

3.1. On an emergency (triggered by a user). 

 

When you detect that one of the mentioned equipment or systems is out of control, interrupt the direct power by pressing (pushing) any of the 14 red pushbuttons. The yellow lamp of the Reset switch will then turn ON, indicating the absence of direct power to the telescope systems, and the PLC display will show a message indicating the number of the zone where the activated pushbutton is located (see the table on the paper sheet below the display) and the time when it was activated (picture D). If you press the ‘Ack alarm’ button of the display, it will show you a message saying ‘Reset red PBs first’ for a few seconds (picture E), then returning to the previous message.

 

Once the emergency has been controlled/solved, you have to reset the pushbutton used to trigger the TESS by pulling it (picture F). After the PLC detects none of the pushbuttons is active, it shows a message saying ‘You still need to press RESET switch’ (picture G).

 

The direct power is only restored when you press the yellow Reset switch (you can actually hear the 3-phase contactors going active). Once the PLC has detected that relay RL2 is active again, it will display a message saying ‘OK, now please press “Ack alarm” button’ (picture H). The display returns to its default ‘No alarms’ message after you press the ‘Akc alarm’ button (picture I).

Picture D. Control room E-Stop PB activated by user,

alarm message displayed, and yellow lamp on.

 

Picture E. Message if user tries to acknowledge alarm

before restoring active E-Stop pushbutton.

Picture F. Pressed E-Stop pushbutton being reset by user.

Picture G. Reminding message when E-Stop pushbutton has been reset.

You still need to press the Reset switch (left) to restore direct power.


Picture H. Direct power has been restored by user, message reminding user to acknowledge the alarm (by pressing the ‘Ack alarm’ button).

Picture I. Default ‘No alarms’ message after pressing ‘Ack alarm’ button.

 

3.2. After an external power interruption (outage). 

It is very important to be aware of that you will always need to restore direct power to the telescope after an external power interruption (after the external power has been restored, to be precise).

 

In this case, the yellow lamp of the Reset switch will turn on, and the PLC display will show you a message saying ‘No power/RL2 damaged’ and the time it happened (picture J). If you just press the ‘Ack alarm’ button, it will show you for 5 seconds a message saying ‘Check Power -> Then press RESET switch’ (picture K).

 

If external power is present, pressing the Reset switch (picture L) will restore the direct power to the telescope.(again, you can hear the 3-phase contactors going active).

Once the PLC detects the relay RL2 is active again, it will display a message saying ‘OK, now please press ‘Ack Alarm' button’ (picture H). Press it to take the display back to standard message (picture I, ‘No alarms’ and the current local time).

 

Picture J. Message for an external power interruption, and yellow lamp on.

Picture K. Message reminding the user to restore power before pressing ‘Ack alarm’.

 

Picture L. User ready to restore direct power to telescope by pressing the Reset switch.

 

4. E-Stop pushbuttons distribution. 

The tables indicating the location of each red E-Stop pushbutton on the telescopes are below. 
 

Table 1. Zones identification and red pushbuttons’ locations for TESS at Baade. 

Zone   Description  

Location of red pushbutton

         
Zone 1   HPU room   To left when going into the room
Zone 2   Ventilation tunnel power distribution   Right of oil chillers and power cabinets
Zone 3   Foundation west   Left of the door of tunnel to Magellan 2
Zone 4   Foundation east   Entering to ventilation tunnel – right
Zone 5   Azimuth supporting ring   To the left of stair when going up
Zone 6   Equipment room A   Near the access door – left when going in
Zone 7   Equipment room B   Above and to the right of the UPS
Zone 8   Control room   To the right of Telescope ESS display
Zone 9   Observing floor door 1   Next to control room’s door
Zone 10   Observing floor door 2   Next to door to auxiliary building
Zone 11   Azimuth platform 1   White chassis under NASW stair
Zone 12   Azimuth platform 2   White chassis under NASE, not stair
Zone 13   NASE platform   To the right when getting to platform
Zone 14   NASW platform   To the left when getting to platform
         
 
 
 

Table 2. Zones identification and red pushbuttons’ locations for TESS at Clay. 

Zone   Description  

Location of red pushbutton

         
Zone 1   HPU room   Next to HPU
Zone 2   Ventilation tunnel power distribution   Next to oil chillers
Zone 3   Foundation west   Right side of door of tunnel to Mag 1
Zone 4   Foundation east   Entering to ventilation tunnel
Zone 5   Azimuth supporting ring   To the right of stair when going up
Zone 6   Equipment room A   Near the access door
Zone 7   Equipment room B   Above of UPS
Zone 8   Control room   To the left of Telescope ESS display
Zone 9   Observing floor door 1   Next to control room’s door
Zone 10   Observing floor door 2   Next to door to auxiliary building
Zone 11   Azimuth platform 1   White chassis under NASW stair
Zone 12   Azimuth platform 2   White chassis under NASE, not stair
Zone 13   NASE platform   To the right when getting to platform
Zone 14   NASW platform   To the left when getting to platform
         
 
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