UCL students competing in EUROBOT – Eurocircuits PCBs inside the BOTs.

THEIR STORY

We are a group of 28 students from the Université Catholique de Louvain, and we are currently following a Master’s in mechatronics.

Our study program includes an important project, which is to participate to an international robotic contest named Eurobot. In this contest, teams have to design and construct a small autonomous robot that can perform several actions, such as manipulating blocks and sorting them by color, or shooting ping-pong balls in a basket.

Although there are several specifications to fulfil (e.g., regarding the size of the robot or restrictions regarding its components), we also have a lot of freedom regarding the mechanisms embedded in the robot. Therefore, Eurobot is a nice opportunity to train our engineering skills in design and programming.

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This year, the choice was made to go for an off-the-shelf BMS because there was already a lot to design. This off-the-shelf BMS is there to:

• Measure the temperature of every battery cell
• Measure the voltage of every battery cell
• Measure the output current of the battery pack
• Control the high- and low to chassis contactors
• Control the pre-charge circuit

The BMS consists of a BMS-master and BMS-slaves. The master talks to the slaves over CAN to get the voltage and temperature of every cell. The PCB that holds the slave modules is produced by Eurocircuits. This PCB made the battery modules look organized and kept the measurement wires towards the battery cell tabs short. Below you can see some photographs of the boards.

After a lot of work, the 20 best teams from all over the world were selected to the competition week from the 15th till the 22nd of July.

With that last week, all the work came together in one final run, and we ended 2nd in the SpaceX Hyperloop Pod competition of 2018!

Sjors Verkamman

PS. Also read our previous BLOG (Dutch)

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We would like to thank Eurocircuits for supporting our team with PCBs which sit in the heart of the MARCH III electrical system.

Robert de Lange, Acquisition Manager & PR, Project MARCH from the Delft University of Technology

Project MARCH, Stevinweg 1 | 2628 CN Delft | The Netherlands

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A deep dive into the exoskeleton electronics

At Project MARCH we are building an exoskeleton to give back full mobility to paraplegics. In this blogpost I want to take you through our electrical system and the Printed Circuit Boards (PCB) we designed for our newest exoskeleton: the MARCH III. First a short introduction to the electrical parts and then a more detailed explanation of all the PCBs.

I would like to start with the ‘backpack’ of the exoskeleton. On its bottom, a big battery pack to supply the exoskeleton its power. It connects to a large Printed Circuit Board above it, that implements certain protection measurements, like over-current and over-voltage, and allows monitoring of the energy flows: the Power Distribution Board. It also supplies power to all the other electronics: ‘low voltage’ for most and ‘high voltage’ for our motors. Those motors, (brushless) drone engines, are what make the joints of the exoskeleton rotate. They do need, however, a special module to get it spinning. This module is called a servo driver and sends the right signals to the coils inside the motor. We created a custom PCB for our servo driver, which you can read more about below.

Power, power distribution, servo drivers and the motors are the main electrical components of the exoskeleton. One big part, however, is still missing: the sensors in the exoskeleton. Important are the ones that can measure the rotational angle of the motors. They supply the timing information, which the servo drivers need to send out the right signals to the motors at exactly the right time. We designed our own angle sensor and you read more about in the section ‘The rotational angle sensor PCB’, below. There are more sensors in the exoskeleton, but those are relatively ‘simple’. Exemplary are the temperature sensors which we use to be absolutely sure the motors of the joints don’t overheat.

A board computer, or master, is connected (through EtherCAT) with the servo drivers and controls the joints, such that the exoskeleton actually walks. At strategic points in the exoskeleton small ‘EtherCAT compatible’ microcontroller boards (called General EtherCAT Slaves) are placed which allow connecting all sorts of peripherals, such as the temperature sensors above, but also a crutch (with buttons and a screen) which allows full control over the exoskeleton by its pilot.

Power Distribution Board

In figure 1 the Power Distribution Board can be found. On it are visible six, bright yellow, connector pairs which allow easily hooking up the six joints of the exoskeleton (technically speaking, their servo drivers). Each connection is protected by an active over-current circuit which also allows us to sequentially turn on the servo drivers, limiting the switch-on current surge they draw. In the middle two blocks: DC-DC converters which provide the ‘low voltage’ for things like the board computer and the EtherCAT slaves and ‘logic voltage’ for the PDB itself. On the top right a place to mount a microcontroller (an mbed) which implements the communication with the master and allows control of the over-current ciruits, like resetting them.

The General EtherCAT Slave

The General EtherCAT Slave in figure 2 is a little PCB which in essence is a little microcontroller with EtherCAT compatibility. It allows us to easily hookup a sensors anywhere on the exoskeleton, because the microntroller supports many protocols and implementing it in the exoskeleton is pretty much just a few ethernet cables. Last year we designed our own, but this year we had to admit there was a much smaller General EtherCAT Slave available online. The opensource project [1] allowed us make ‘our own’ at Eurocircuits relatively easily.

The servo driver PCB

In figure 3 one may find the servo driver PCB. Functionally seen, it is not so complex, as its main goal is to route the right connectors to the right pins of our stock-bought servo driver, which does all the heavy lifting regarding low-level motor control. More challenging was to make the design as small as reasonably possible to allow the ‘bones’ of the exoskeleton, were they are mounted onto, to be small too.

The rotational angle sensor PCB

The last PCB we made for the MARCH III is the one seen in fugre 4. We are still in the process of testing it, but it should allow higher resolution (i.e. more ‘detailed’) angle sensing on the joints. Which in turn allows better (e.g. more accurate or smoother) control of the joints.

We would like to thank Eurocircuits for supporting our team with PCBs which sit in the heart of the MARCH III electrical system.

Robert de Lange, Acquisition Manager & PR, Project MARCH from the Delft University of Technology

Project MARCH, Stevinweg 1 | 2628 CN Delft | The Netherlands

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Welcome to the first Engineers of Innovation BLOG.

Who are we?

Engineers of Innovation is an alumni society of the Amsterdam university of applied sciences. The society aims to teach her members about multiple disciplines of mechanical and electrical engineering by building and competing in solar boat races. The main goal for our solar boat is that it sails as efficient as possible, this is not solely done by optimizing the drive train. There are other factors that consume power as well, like the friction with the water, peripheral electronics and the race strategy.

In this BLOG.

We will elaborate on our latest circuit board, from concept to fully assembled board, and our cooperation with Eurocircuits.

Data Logging system requirements.

Our first design is a data logging system which logs the data generated by the electronics in the boat like: the battery, MPPT’s and even the throttle. The data generated by the electronics is transmitted over the CAN bus lines so it makes sense that the datalogging system can read from the CAN bus. But there were a lot of other requirements for this design as well.

At the start of the project we had a meeting where the requirements were drafted as follows:

1. Supply voltage 12 volts – 32 volts
2. Can communicate over at least two separate CAN busses
3. Writes to at least two SD cards for redundancy
4. Communicates over internet (3G / 4G)
5. GPS signal reception
6. Ethernet functionality
7. Wi-Fi capabilities
8. Backup power supply used for safe shutdown
9. Possibility to connect an LCD display
10. On board IMU

Linux and communication on board.

We wanted to run Linux on the system to shorten development time when writing the software, the disadvantage here is that a lot of microprocessors that run Linux have come in a BGA package which makes them pretty hard to solder by hand. We searched online for a system on module that can run Linux, has enough I/O pins and peripherals that support CAN, MMC, UART, Ethernet, SPI, I2C, USB and an LCD. In the end we chose the Acme Acqua D36 board for use in our application.

For GPS and 3G / 4G communication we chose to use a modem in mini-PCIE form factor so we can update the modem when new functionalities like 5G are rolled out.

Schematics and Layout.

The next step in the design is drawing the schematics and selection of the components surrounding the Acqua board such as the voltage regulators, CAN transceivers and ESD protection. This part of the design takes up the most time and manpower because all parts have to be compared against each other to make sure the most efficient and best fitted part are used.

After the schematic design is complete the design has to be checked and approved by other members of the society before the process continues in the PCB design environment. The design of the PCB took a couple of nights.

First job in the layout phase is placing the components, to see where they fit best and the minimum amount of via’s is necessary in the signal traces. When the rough layout is known, the connecting traces are drawn, usually starting from the highest frequency or sensitive signal and working down to DC.

Posted below are a couple of screengrabs from the datalogging system design process. When the electrical part of the design is finished, we start with the design of the solder mask to make sure the sponsors that are helping us creating the board are on it, as well as some jokes made in those late nights of designing the board.

Check and double check.

Once the design is finished, the design is checked with a design rule check program before another member of the society checks the layout to make sure it all looks alright. When the design is approved, the Gerber files are generated and uploaded in our Eurocircuits customer account.

In our online account we have a lot of options to choose from to make sure our circuit board looks and behaves the way we had in mind while designing . These options can help with the electrical characteristics of the board, like fine tuning the copper thickness of the traces to ensure the calculated impedance of our signals is exactly as we need it to be. Other options like determining the surface finish or the thickness of the solder paste stencil help us during the production process. Selecting the soldermask colour ensures that our circuit boards always look cool.

Populating the boards.

After the circuit boards have been received by mail we started with the component placement. For the datalogging system we only use a stencil for the top side since most IC’s on the bottom side are SOIC packages which are easy to do by hand. For the top side of the board, a stencil was used to apply solder paste. This method is faster, easier and ensures that the right amount of paste is applied to the pads. After placing the components on the board by hand the boards are placed in a reflow oven which heats up and transforms the paste into solder. When the boards are done the through hole components can be placed and the board can be tested.

When the board is completely tested the CAD files can be requested free of charge upon agreement that the files will not be used for commercial purposes in any way. More information on this can be found here.

We would like to thank Eurocircuits for making it possible for us to create systems which will help us to improve and reach our goal to sail as efficient as possible!

Didier Chaigneau
Voorzitter Alumnivereniging Engineers of Innovation
Weesperzijde 190, 1097 DZ, Amsterdam – website

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Introduction

In an electric Formula Student car, like the one of our team (Formula Electric Belgium), the power supply is a large lithium-ion battery made from 144 battery cells in series and 2 in parallel. This battery runs at a voltage between 500V and 600V, weighs about 50kg and contains 6.9 kWh of electric energy.

To make sure this battery can work in a safe manner, a system is needed that can control the voltages, current and temperatures of the battery. Because for the battery to be safe, the voltages, temperatures and current must stay within a safe operating window.

Figure 1: Battery Management System functions

This is where the battery management system (BMS) comes in. This system measures every cell temperature, cell voltage and the total current and then decides whether the battery can stay active or not. When the battery reaches one of its limits, the BMS shuts down the battery, causing the car to come to a stop.

The battery management system also uses its data to inform the user of the status of the battery. And it sends data to the Electronic Control Unit (ECU) of the car, so that it can act upon potential problems inside the battery, e.g. reducing the power of the car when the battery is almost empty.

Battery Management System

The battery management system of Umicore Pulse (latest electric race car), uses a master-slave topology. The slaves measure the voltages, temperatures and total current and send the results to the master. The master then decides upon this data whether the battery can be active.

Figure 2: BMS architecture of Umicore Pulse

In the battery of Umicore pulse there are 9 slaves, each measuring one module. A module is a separate battery segment of 67V that can be disconnected so that it is safe to work on the battery. The electronics of the slaves are built on a printed circuit board that also connect the separate battery cells together, resulting in module that only needs a connection for communication.

Figure 3: Battery module of Umicore Pulse

All the modules (and their slaves) are daisy chained together and connected to the master PCB. Apart from deciding whether the battery can be active or not, the master also communicates the status of the battery to the rest of the car through CAN messages. And the master can also send the data to a pc through USB.

Battery Master

The battery master not only contains part of the battery management system, but also handles a large part of the other safety features of the car. These safety features are placed in what we call the safety loop. The safety loop is a chain of all the emergency buttons in the car, some other safety devices and the battery management system itself. The safety loop directly supplies the insulation relays of the battery, so that if an emergency button gets pressed, the battery immediately turns off.

The whole safety loop is pure hardware, so that no software errors can influence the safety of the car. Even part of the battery management system is pure hardware, since it is connected to a hardware latch, that can only be reset by a button on the side of the car.

Figure 4: Battery Master overview

Another very important safety device that is directly connected to the master is the insulation monitoring device (IMD). This device monitors the isolation resistance between the high voltage battery and the low voltage part of the car (which is connected to the chassis). When the resistance becomes to small the IMD immediately opens the safety loop, so that the battery is turned off. In this way, it is made sure that no electric chocks are possible when touching the car.

Figure 5: Bender Insulation Monitoring Device

The printed circuit board of the master is made in the same dimensions of the IMD, so that they can be stacked on top of each other, to keep everything as compact as possible. This made for a big challenge to get all electronics parts of the master placed. The master PCB is also one of the few PCBs where high voltage and low voltage are present on the same board. This requires a separation according to the rules, and a galvanic separation one the communication lines from the high voltage side to the low voltage side.

Figure 6: Battery Master PCB

On the master there is also an extra stripped-down slave circuit installed, like those of the actual slave systems on the modules. This stripped-down slave system delivers some advantages regarding the communication between the master and the slave modules. But it is also used to measure the total current of the battery, and the total voltage. A connection is made to a small separate pcb where a resistor divider and a current clamp can be found. In this way the power of the car can be monitored, and with this information the ECU can drive the car in such a way that the regulated power limit of 80kW never gets passed.

Figure 7: Battery power meter

Fire extinguisher

The battery management system, together with all the other safety features in the car, makes sure everything keeps running safe and smooth. But nevertheless lithium-ion batteries will always be a safety risk, because they’re highly flammable. For that reason, a special fire extinguisher is installed inside the battery, this fire extinguisher generates aerosol that can suppress the fire. This fire extinguisher is specially made to put out lithium battery fires, because they are hard to stop with conventional extinguishing methods.

Figure 8: Battery Fire extinguisher

Conclusion

In an electric Formula Student car, safety is a big concern. Not only the lithium battery has to be managed, but also the high voltages need to be controlled so that the car can be operated safely. Thanks to the support of Euroxircuits we have all the resources we need to build these safety systems, and make sure that the user of the car can operate it without risk. Thanks to the great quality of PCBs, the technical inspection of the car went smoothly, and we were able to build a very reliable car.

Yentl Frickx, Head of Electronics 2018 – 2019

Formula Electric Belgium | www.formulaelectric.be

Diestsesteenweg 692 | 3010 Kessel-lo | tel. +32 (0) 492.80.24.02 | yentl.frickx@formulaelectric.be

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Introduction

In an electric race car, it is very important to have some systems to indicate to track marshals whether the car is safe to handle or not. Usually this system is a light which can be found on a high point on the chassis. If the light is green, the car is safe to handle, if it is red/orange the car might be still on a high voltage potential.

Figure 1: Indicator light on an F1 car

In Formula Student this is no different. According to the rules you must install a TSAL (tractive system active light) in the top of the roll hoop. This light will be green when the car is turned on, but the high voltage system is turned off. And will blink red when a voltage higher then 60 V is present on the high voltage bus, or when one of the accumulator insulation relays is switched on.

Figure 2: TSAL light on a Formula Student Car

TSAL system

The TSAL system exist out of two parts, with one PCB for each part. There is the TSAL light itself, and there is the board that drives the light.

The Light itself is a double-sided PCB that holds three RGB high power leds on each side. In total the leds can consume up to 5.5 Watts, and unfortunately not all this energy goes into light energy. The compact design made it challenging to cool the leds enough, to keep them at reasonable temperatures.

Figure 3: TSAL-light PCB

To keep the PCB from overheating, two heat pads where added so that a thermal connection can be made to the roll hoop. Thermal via’s where then required to make sure that the PCB heated up uniformly. So that as much heat as possible could be transferred to the roll hoop. In this way we where able to keep the temperatures of the leds below 100 ˚C.

To drive the TSAL light, a separate driver board was designed. This board is a pure hardware logic, because the use of a microcontroller would introduce the possibility of software errors. This is also one of the few PCBs in the car that has both high voltage and low voltage present at the same board. Due to safety reasons, and required by the rules of Formula Student, high voltage and low voltage must be isolated from each other. And when the two are present on the same board, a minimum spacing is required.

Figure 4: TSAL-Driver PCB

The TSAL driver board compares two signals, to decide which color the TSAL must have. There is a signal coming from the battery, which indicates whether all insulation relays are open or not. On the other hand, the driver board measures the voltage on the DC bus, to indicate any voltage higher then 60V. These two signals are compared with each other and drive activate the correct light. The power stage of the lights are two led drivers that can supply a continuous current to the leds, to provide an as efficient possible system.

Figure 5: TSAL-Driver overview

Another extra feature available on the TSAL driver board is a system to discharge the high voltage system of the car. This is needed because the high voltage bus has a very large capacity, needed to provide the motors with a very stable supply. When the relays of the battery are opened, it can take up to one hour for the voltage to drop below 60V. While it is a requirement that the voltage drops under 60V within 5 seconds. The discharge system makes sure this requirement is met. The system is also driven with a signal coming from the battery that indicated the position of the relays. When the relays are all open, the discharge system is activated. Which dissipates the remaining energy from the high voltage capacitors in a power resistor.

Figure 6: Discharge system

Battery voltage indicator

In the Formula Student competition, there is an extra voltage indicator on the battery. This is required because the battery is charged outside the car. This voltage indicator is activated when the voltage on the output of the battery is larger then 60V. But an important extra requirement of this indicator is that it needs to be supplied by the high voltage system itself. In other words, the led should go on when 60V is applied to the circuit, without it having an external supply. But it should also survive 600V. Which results in some demanding circuitry.

Figure 7: Battery HV-indicator light

Because the light must be supplied with the high voltage circuit, there are two solutions for this system. One is to use a resistor divider with a Zener diode, but this would result in a very large heat dissipation at 600V. The other is to build a small power supply.

For our solution we opted for a fly back DCDC converter to provide the system with the required voltage to operate, without too much heat losses. The largest challenge in designing this fly back circuit is that the system must be working between 60V and 600V. Which in it’s turn requires a rather special control chip, and a very specific transformer. On top of that, the board needs to be compact, and routing should be executed with care, to make sure that the supply doesn’t get disrupted by its own switching noise.

Figure 8: Voltage indicator PCB

Conclusion

The safety systems in Formula Student are very important and make sure that students can work safely on this project. Thanks to Eurocircuits, our team (Formula Electric Belgium) had the needed resources to build this safety critical systems, and drive the car (Umicore Pulse) safely on events, while passing the technical inspection without any problems.

Yentl Frickx, Head of Electronics 2018 – 2019

Formula Electric Belgium | www.formulaelectric.be

Diestsesteenweg 692 | 3010 Kessel-lo | tel. +32 (0) 492.80.24.02 | yentl.frickx@formulaelectric.be

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This years pod, Mujinga, contains three different Eurocircuits PCBs

First of all, we designed a circuit needed for our network communication. It processed the input data of the microcontroller and directed it further to the wireless radio.

Next we had Eurocircuits produce a PCB for our brakes. We had two independent braking systems, including two solenoid valves each. To be able to brake properly, we designed a switching circuit based on a logical input for each valve and printed it on a board in a compact format, which was able to withstand the peak currents of the valves and also very robust. Our hydraulic braking system was able to decelerate our pod with more than 5g.

For reaching high speeds, we needed a high power energy source, which in our case was a self made 10 kWh battery consisting of a 180S3P configuration of LiCoO2 chemistry cells. This pack was able to deliver us a peak power of 500 kW.

To ensure a safe operation we use a BMS measuring all the cell voltages and temperatures. To route the voltage and temperature sensing lines to the slave modules of our Battery Management System, we used custom PCBs produced and partly assembled by Eurocircuits, which were screwed onto the busbar connections between to cells.

Since the cells could not operate inside a low pressure environment, we had to build a pressurized containing the packs and the monitoring electronics. To be able to nicely route the data lines from the BMS to our microcontroller, we made a PCB which got mounted on the feedthrough of the enclosure.

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Gabriela Fernandes, Business Lead

swissloop | ETH Zürich, LEO B 9.1 | Leonhardstrasse 27 | 8092 Zürich | Switzerland
+41 79 958 41 85 | gabriela.fernandes@swissloop.ch | www.swissloop.ch

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THE HYPERLOOP CONCEPT

In 2013, Elon Musk introduced the concept of Hyperloop – a novel, high-speed ground transport system. This mode of transportation projects to levitate passenger and cargo in so-called “pods” in near-vacuum tubes at speeds of up to 1,200 km/h. The realization of Hyperloop redefines the barriers of time and distance. The vision is to revolutionize the ground transportation system towards a faster, more energy-efficient and environmentally sustainable solution. In order to accelerate the development of functional prototypes, SpaceX announced the third Hyperloop Pod Competition 2018. Swissloop is participating for the second time and aims to build the world’s fastest Pod.

SWISSLOOP – THE FUTURE OF TRANSPORTATION

Swissloop was founded in October 2016 and is trying to in- novate Europe’s transportation landscape by developing the Hyperloop concept into a real-world application. The team consists of 20 students from ETH Zurich and other Swiss Universities, with backgrounds in mechanical and electrical engineering, physics, computer science and industrial design. We are also supported by a network of alumni, advisors and partners from the industry. At the Elon Musk’s SpaceX Hyperloop Pod Competition in LA, Swissloop placed third in 2017 and reached top 10 in 2018 out of over 1000 competitors worldwide.

SWISSLOOP TEAM 2018

PROTOTYPE MUJINGA 2018

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Gabriela Fernandes, Business Lead

swissloop | ETH Zürich, LEO B 9.1 | Leonhardstrasse 27 | 8092 Zürich | Switzerland
+41 79 958 41 85 | gabriela.fernandes@swissloop.ch | www.swissloop.ch

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The Team

Electric Superbike Twente designs, builds and races a fully electric racing motorcycle. The goal is to show how awesome and fast electric transportation can be. 2017-2018 was the very first year for the team, so everything is built from scratch. Most components are designed by in-house by the team. For example: frame, swingarm, battery manager, electric motor, battery pack and ECU. The last one is a great example of efficient PCB design with Eurocircuits PCBs.

Functionality

The ECU (electronic control unit) is the central computer of the Lion-GP. It handles a lot of sensor data, for example coolant and motor temperatures, brake and suspension data, Bluetooth tire pressure or 12V battery status. On top of that, it handles the different driving modes. This makes it possible to turn on and off regenerative braking, or adjust the mapping from throttle to torque output. Also, it communicates with all the other electronic equipment, such as the BMS, charger, datalogger and inverter. Finally, it handles all data and registers for the inverter as well.

The PCB

This is a lot of functionality, but in racing it has to be packed as light and small as possible. Therefore, a six-layer PCB layout is made. Fun fact: it has the Bluetooth antenna integrated in the PCB. The outline of the PCB is made exactly to the dimensions of the box it will ride in. This includes the PCB mounted connector and mechanical holes for mounting. To keep the PCB as small as possible, components are placed at both top and bottom.

The result

The box with the ECU is mounted in the nose of the superbike. All the data is processed to the display and datalogger. This year, the design has contributed to multiple wins in the MotoE-competition.

We would like to thank Eurocircuits for supporting our team with PCBs which sit in the heart of our Electric Superbike.

Jeroen Goudswaard, Powertrain manager, Electric Superbike from the University of Twente

Electric Superbike Twente, Auke Vleerstraat 3b, 7521 PE Enschede, The Netherlands

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