Emergency Procedures - Carleton-SRCL/SPOT GitHub Wiki

E-Stop

As taken from Kirk Hovell's MASc. thesis:

In an emergency, it is important to have a system that is completely separate from the system that is failing protect the failing system from itself. In this case, a separate wireless link is made from an emergency stop transmitter circuit on the ground station desk to the on board Arduino Mini. The Arduino Mini is responsible for controlling the emergency stop circuitry. All the components on the 12 V power line pass through a power MOSFET before returning to Ground, except the air bearings solenoid. The Arduino Mini is powered by the 5 V voltage regulator, and uses one of its digital output pins to send a High or Low signal to the gate of the MOSFET depending on the desired status of the emergency stop. Since the Arduino Mini is powered by the 5 V regulator, its Ground is the same as the 5 V and 12 V Ground. Therefore, since the source pin of the MOSFET is connected to 12 V Ground, applying a +5 V signal to the gate of the MOSFET will exceed the gate-source threshold voltage and allow current to flow.

Communication between the emergency stop button on the ground station table and the Arduino Mini is accomplished through 315 MHz RF transmitters and receivers. The main wireless link between the ground station computer and the Raspberry Pi 3 is through Wi fi.

The RF transmitter is connected to an Arduino Mini and is embedded in the Emergency Stop Button located on the ground station table. The RF transmitter is wired to the Arduino Mini exactly as outlined in the documentation. A 12 V supply line is used, to increase the outgoing signal of the transmitter. An antenna is also used, to increase the range of the signal. The transmitter electronics are plugged into a power source and is continuously operating. The RF receiver electronics are attached to the Arduino Mini on the control panel of the spacecraft platforms exactly as outlined in the RF receiver documentation. An antenna is also used on the receiver to increase reception. When the Emergency Stop button is raised, the RF transmitter repeatedly transmits a "good" signal (the number 20). When the receiver electronics receive the "good" signal, a High signal is applied to the gate of the emergency stop MOSFET. When the Emergency Stop button is pressed, the RF transmitter repeatedly sends a "bad" signal (the number 13). When the "bad" signal is received, a Low signal is sent to the gate of the MOSFET by the Arduino Mini. If no signal is received for 5 seconds, the receiving Arduino Mini automatically triggers the Emergency stop, as there is a fault in the system rendering the system unsafe.

LEDs are used to alert the operator to the current status of the Emergency Stop circuitry. The E-Stop LED is solid blue when the "good" E-Stop signal is being received. When the LED is solid red, this indicates that the "bad" signal was received. When the LED flashes red, this indicates that no E-Stop signal is received, that the E-Stop has been triggered, and that there is a fault in the Emergency Stop circuitry. The same "good" and "bad" signals are transmitted blindly to all receivers. Therefore, when the E-Stop is triggered, all active spacecraft platforms will simultaneously trigger their Emergency Stop circuitry.

Puck damage

Avoiding Damage to the Pucks

The pucks are extremely expensive and extremely sensitive.

  • Do not touch the surface of the pucks without wearing gloves.
  • Do not place the platforms down on the table without floating.
  • Ensure the pucks have been cleaned properly before putting them on the table.
  • Do not allow the pucks to slide off the table in an experiment.

Consider the following picture of a puck following an incident in 2017, which resulted in all 8 pucks being replaced. Don't be that person!

Puck damage

Compressor Failure

Hearing and eye protection must be worn while operating the compressor. In the event of a failure, such as a rupture of the compressor line, air will escape and create significant noise, which can result in permanent hearing damage. Assess the situation. If safe to do so, power off the compressor. Otherwise, leave the area and contact Carleton Campus Safety Services at (613) 520-3612.

Platform Leaks

Platform leaks happen OFTEN. If you hear a leak, start by evaluating the severity of the leak. If the leak is small and is having a negligible impact on the experiment, it may be safe to continue. However, if the leak is significant enough to cause the spacecraft to move unprompted, then it is best to stop all experiments until the leak can be resolved.