PROMPT - Project for Recording, Observing, and Measuring Parachute Tube

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• The pressure of the parachute bay 
• The temperature inside the parachute bay
• The temperature in the booster
• Whether or not the payload has been deployed

Temperature Sensing:

Since this board needs to monitor 2 remote temperature sensors, choosing a relatively low-cost and compact temperature sensing solution is important. Thermistors are immediately out of the running since the motor's temperature can reach up to 212C, far beyond the range of most NTCs. So, a choice is left between RTDs and Thermocouples. While RTDs would be more accurate/precise, they are more expensive and available in fewer packages than a thermocouple would be. Based on this, thermocouples seem to be the direction the team will go in. To compensate for the lower precision, a J-type or similar thermocouple can be utilized instead of the much more common K-type thermocouple.

Pressure Sensing:

The pressure inside a standard parachute bay should be . between 8 and 15 PSI when the parachutes deploy. In case that value is incorrect, a significantly overrated sensor was chosen. The selected sensor also has considerations for the attachment of a measuring tube, to allow the sensor to be situated away from the bulkhead, therefore reducing wiring complexity.

Remote Connection:

PROMPT will be connected to the backplane through the standard RS485 interface provided on the sensor board. This interface also provides a 5-volt supply for PROMPT. In the event that an RS485 connection cannot be established, PROMPT will log its data locally.

Power Systems:

PROMPT is primarily intended to operate off of the regulated 5v provided from the backplane through the sensor board's connection. To allow for PROMPT to be utilized independently, the power system should be rated to allow for the direct connection of a 2S LiPo battery. This will include all the requisite battery protection circuits, such as reverse-polarity protection and over-current protection.

Component Selection:

0-60PSI pressure: ABP2LANT060PG2A3XX

• Used by Sparkfun
• i2C interface
• Not on JLCPCB

Thermocouple Amplifier: MAX31855 

• Used by Adafruit
• 3-Wire SPI interface
• Cannot be used with grounded thermocouples
• JLCPCB: C52028

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• Unknown, probably STM32

Memory: W25Q128JVSIQ

• Same as most other devices on the backplane
• JLCPCB: C97521

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