Order a Pcb

Custom Printed Circuit Boards (PCBs)

Please refer this PCB checklist : PCB Checklist FA25.pdf

How to check your gerber file : PCBway_gerber_file_check_FA25.pdf

How to use the PCB oven (2070 ECEB) : Using the PCB Oven

In this course, you will be creating and ordering a PCB to use in your project. The primary method for ordering PCBs is to order them through PCBWay. With the help of your TA, you can order a simple, 2-layer, 100mm x 100mm PCB through PCBWay at no cost to you. This PCB will simply be fabricated, as opposed to assembled, so a major portion of this class will be soldering and assembling the PCB you order. This means that you will need to source your components either through the course or other means. See the getting parts page for more details.

Alternatively, you can order a PCB from any outside vendor (including PCBWay) and pay for the cost of the board out of pocket. By paying for a PCB yourself, you are not required to meet the deadlines imposed by the course and can sometimes get your board more quickly.

In rare cases, some teams will be allowed to order PCBs through the Electronics Services Shop in ECEB. If you have need of special board layouts or require a PCB very early in the semester, please discuss this option with your TA as early as possible.

PCBway Orders Through the Course

Orders through PCBway can be submitted and paid for by the ECE department with the help of your TA. Orders will be uploaded to PCBway by your TA and paid for on the dates listed on the course calendar. Please note that the PCBway orders will not be manufactured or shipped until they are paid for so please be aware of the lag time between order submission and payment. In addition, your order must pass PCBway's audit before the payment date for your order to be processed. In order to help students pass audit more quickly, we have provided a DRC file that can be imported in to EagleCAD to verify that your board meets PCBway's capabilities. Passing the DRC does not guarantee that your board will pass audit but it does greatly increase the probability of that event.

Electronic Services Shop

Orders placed through the Electronic Services Shop will require TA approval so please discuss with your TA before contacting the Services Shop. The software most commonly used is EagleCAD. Contact a technician in the Electronic Services Shop with questions.

Please be aware of the PCB deadlines posted on the course calendar. If you are unable to meet these deadlines, you will not be able to order a PCB through the the Electronic Services Shop. You will still be able to order PCBs through third party vendors, just be aware that rushed orders can become expensive.

Commercial quality boards

The most commonly used programs for board layout are Eagle and Orcad Layout. The two software packages below allow a schematic to be drawn and translated into a board layout.

Once the board has been laid out, some companies will manufacture small quantities for a very reasonable price.

ATTITUDE DETERMINATION AND CONTROL MODULE FOR UIUC NANOSATELLITES

Shamith Achanta, Rick Eason, Srikar Nalamalapu

Featured Project

Team Members:

- Rick Eason (reason2)

- Srikar Nalamalapu (svn3)

- Shamith Achanta (shamith2)

# Problem

The Aerospace Engineering department's Laboratory for Advanced Space Systems at Illinois (LASSI) develops nanosatellites for the University of Illinois. Their next-generation satellite architecture is currently in development, however the core bus does not contain an Attitude Determination and Control (ADCS) system.

In order for an ADCS system to be useful to LASSI, the system must be compliant with their modular spacecraft bus architecture.

# Solution

Design, build, and test an IlliniSat-0 spec compliant ADCS module. This requires being able to:

- Sense and process the Earth's weak magnetic field as it passes through the module.

- Sense and process the spacecraft body's <30 dps rotation rate.

- Execute control algorithms to command magnetorquer coil current drivers.

- Drive current through magnetorquer coils.

As well as being compliant to LASSI specification for:

- Mechanical design.

- Electrical power interfaces.

- Serial data interfaces.

- Material properties.

- Serial communications protocol.

# Solution Components

## Sensing

Using the Rohm BM1422AGMV 3-axis magnetometer we can accurately sense 0.042 microTesla per LSB, which gives very good overhead for sensing Earth's field. Furthermore, this sensor is designed for use in wearable electronics as a compass, so it also contains programable low-pass filters. This will reduce MCU processing load.

Using the Bosch BMI270 3-axis gyroscope we can accurately sense rotation rate at between ~16 and ~260 LSB per dps, which gives very good overhead to sense low-rate rotation of the spacecraft body. This sensor also contains a programable low-pass filter, which will help reduce MCU processing load.

Both sensors will communicate over I2C to the MCU.

## Serial Communications

The LASSI spec for this module requires the inclusion of the following serial communications processes:

- CAN-FD

- RS422

- Differential I2C

The CAN-FD interface is provided from the STM-32 MCU through a SN65HVD234-Q1 transceiver. It supports all CAN speeds and is used on all other devices on the CAN bus, providing increased reliability.

The RS422 interface is provided through GPIO from the STM-32 MCU and uses the TI THVD1451 transceiver. RS422 is a twisted-pair differential serial interface that provides high noise rejection and high data rates.

The Differential I2C is provided by a specialized transceiver from NXP, which allows I2C to be used reliably in high-noise and board-to-board situations. The device is the PCA9615.

I2C between the sensors and the MCU is provided by the GPIO on the MCU and does not require a transceiver.

## MCU

The MCU will be an STM32L552, exact variant and package is TBD due to parts availability. This MCU provides significant processing power, good GPIO, and excellent build and development tools. Firmware will be written in either C or Rust, depending on some initial testing.

We have access to debugging and flashing tools that are compatible with this MCU.

## Magnetics Coils and Constant Current Drivers

We are going to wind our own copper wire around coil mandrels to produce magnetorquers that are useful geometries for the device. A 3d printed mandrel will be designed and produced for each of the three coils. We do not believe this to be a significant risk of project failure because the geometries involved are extremely simple and the coil does not need to be extremely precise. Mounting of the coils to the board will be handled by 3d printed clips that we will design. The coils will be soldered into the board through plated through-holes.

Driving the inductors will be the MAX8560 500mA buck converter. This converter allows the MCU to toggle the activity of the individual coils separately through GPIO pins, as well as good soft-start characteristics for the large current draw of the coils.

## Board Design

This project requires significant work in the board layout phase. A 4-layer PCB is anticipated and due to LASSI compliance requirements the board outline, mounting hole placement, part keep-out zones, and a large stack-through connector (Samtec ERM/F-8) are already defined.

Unless constrained by part availability or required for other reasons, all parts will be SMD and will be selected for minimum footprint area.

# Criterion For Success

Success for our project will be broken into several parts:

- Electronics

- Firmware

- Compatibility

Compatibility success is the easiest to test. The device must be compatible with LASSI specifications for IlliniSat-0 modules. This is verifiable through mechanical measurement, board design review, and integration with other test articles.

Firmware success will be determined by meeting the following criteria:

- The capability to initialize, configure, and read accurate data from the IMU sensors. This is a test of I2C interfacing and will be tested using external test equipment in the LASSI lab. (We have approval to use and access to this equipment)

- The capability to control the output states of the magnetorquer coils. This is a test of GPIO interfacing in firmware.

- The capability to move through different control modes, including: IDLE, FAULT, DETUMBLE, SLEW, and TEST. This will be validated through debugger interfacing, as there is no visual indication system on this device to reduce power waste.

- The capability to self-test and to identify faults. This will be validated through debugger interfacing, as there is no visual indication system on this device to reduce power waste.

- The capability to communicate to other modules on the bus over CAN or RS422 using LASSI-compatible serial protocols. This will be validated through the use of external test equipment designed for IlliniSat-0 module testing.

**Note:** the development of the actual detumble and pointing algorithms that will be used in orbital flight fall outside the reasonable scope of electrical engineering as a field. We are explicitly designing this system such that an aerospace engineering team can develop control algorithms and drop them into our firmware stack for use.

Electronics success will be determined through the successful operation of the other criteria, if the board layout is faulty or a part was poorly selected, the system will not work as intended and will fail other tests. Electronics success will also be validated by measuring the current consumption of the device when operating. The device is required not to exceed 2 amps of total current draw from its dedicated power rail at 3.3 volts. This can be verified by observing the benchtop power supply used to run the device in the lab.