Voltage Regulator Board User Guide

Transcription

1 Embedded Systems for Space Applications Voltage Regulator Board User Guide David Hoskins Josh Chapman University of Tennessee at Chattanooga 4/23/17

2 Overview The objective of this project is to provide the correct voltages for each experiment within the CubeSat project. A PCB was created that regulates a voltage of 5v to each experiment using a 6v battery. There is a dedicated voltage regulator for three experiments, the flight computer, and an on board microcontroller. Each voltage regulator circuit includes a voltage divider, which controls the output of the regulator. A potentiometer has been designed into each regulator s voltage divider in order to give flexibility to each regulation channel. An on board microcontroller can measure the voltage output of each regulator, and can communicate to the flight computer via SPI communication protocol. Interfacing between the voltage regulator board and all other peripherals within the CubeSat project are made using a 13 pin JST connector, a two pin connector for the 6V battery, as well as six pin ICSP connector. Operation In order to set the voltage board up for operation, three main features must be checked. 1. Battery a. The battery must be fully charged to 6V, and be connected to the board via the two pin JST plug. 2. Voltage output for each voltage regulator a. Before flight, each voltage regulator channel output must be measured to ensure the proper voltage is being supplied. i. Use a voltmeter to measure the voltage on pins 2, 4, 6, and 8. Connect the ground terminal of the voltmeter to pins 1, 3, 5, or 7. ii. To change the voltage of each channel individually, change the value of the potentiometer to get the desired voltage output. Make sure not to exceed the ratings for any of the components on the board. 3. Connections a. There are three connection points on the board for interfacing to peripherals. The list below shows the connectors on the board, and their pinout. i. Two pin JST battery connector 1. Pin 1 is VCC and pin 2 is ground. ii. 13 pin JST output connector 1. Pins 1-8 consist of connections to from the voltage board to the experiments and flight computer. 2. Pin 9 is 3.3V from the flight computer to the voltage regulator board for use in the logic converter. 3. Pins are for ISP communication.

3 Table 1 - Output Connector Pinout Pins Value 1 GND 2 5V 3 GND 4 5V 5 GND 6 5V 7 GND 8 5V 9 3.3V 10 SS 11 SCK 12 MOSI 13 MISO iii. 6 pin ICSP (In Circuit Serial Programming) connector. 1. The pinout for the ICSP can be seen below. Figure 1 - ICSP Pinout The on board microcontroller should contain the Arduino bootloader. This can be uploaded to the chip via the ICSP connector using a FTDI programmer. The code on the Arduino utilizes the ADC pins in order to monitor the voltage output of each channel. The microcontroller polls and records these values for viewing after recovery of the satellite.

4 Developer s Amendment Due to the ordering of incorrect parts, several features of the voltage board had to be scrapped. These features included, A current sensor for each channel A power MOSFET to shut each channel off if it exceeded ratings An inverter to keep the gate voltage of the power MOSFET high (Closed), until a high value was applied from the microcontroller which would open the power MOSFET connection. For future iterations of this voltage regulator board, the proper implementation of the aforementioned parts should be featured. There should be, Voltage and current protection for each regulation channel. An ability to measure voltage and current for each channel. An ability to open each channel if the voltage or current exceeds the rating for any component within the circuit. A consideration within the design to allow power to be supplied even if the microcontroller is off.

5 Appendix The schematic, PCB file, and microcontroller code can be found attached to the electronic form of this user s guide. Double click the icon of the file to open. DipTrace ( must be installed onto your computer in order to view or edit the files. If the reader s only copy of this user s guide is a hard copy, the authors can be reached at david.d.hosk@gmail.com. Voltage Regulator Board 2.4.dch Voltage Regulator Board PCB 2.4.dip The full parts list for this project can be found at here. If the reader only has access to a hard copy of this user guide, please contact Dr. Daniel Loveless at daniel-loveless@utc.edu.