Lights Lab Live – conducting a remote/interactive LED lab

This blog post comes from Dr Gavin Williams, Senior University Teacher with both MEE and EEE departments at the University of Sheffield - g.williams@sheffield.ac.uk

The Electronic and Electrical Engineering (EEE) department conducts extensive optoelectronics research [1]. This research focus influences our undergraduate and post-graduate teaching, where we make extensive use of The Diamond’s teaching cleanroom.

This facility was forced off-limits to students during the Covid 19 pandemic. Instead, we have been running live online laboratory (lab) sessions. This article describes one such lab, in which we investigate the electrical and optical properties of light emitting diodes (LEDs). Even though the laboratory has now fully reopened in-person, a similar activity has been used for Recruitment/Outreach and has been delivered to over 100 sixth-form students during lunchtime ‘Taster’ sessions. The remote access lab technology enables participation by more students than ever before, increasing our geographical reach in encouraging access to higher education.

The system (Fig.1) has two light sources: a red/green/blue (RGB) LED and a white LED. The RGB LED is powered via an Arduino Uno running code that allows the pseudo-brightness of the three channels to be independent controlled by adjustment of the pulse width modulation (PWM) signals [2]. The signal to the red channel is displayed on an oscilloscope. The white LED is powered via a source-measure unit (SMU). A fibre-coupled CCD optical spectrometer is positioned to capture the emission from both LEDs. A webcam is positioned to show the two LEDs, the fibre and, in the background, the oscilloscope display. The instruments are all under software control [3,4,5] running on a local PC. The PC can be accessed remotely, enabling the student to configure and control the various components.

Figure 1: Schematic system diagram

There are a number of experiments that the student can perform with the system (Fig. 2). The typical current-voltage (IV) characteristics of an LED can be measured by configuring the SMU to perform a voltage sweep (Fig.2f). PWM brightness control can be investigated using the red channel of the RGB LED. The emission spectra of the RGB and white LEDs can be recorded (Fig.2e). With the prior collection of a ‘null’ background spectrum, it is possible to display the position of the lights in CIE colour space [6]. This enable the student to explore the generation of white light by two methods: by combining RGB or by realising that the ‘white’ LED is, in fact a blue LED plus a yellow phosphor [7]. One deficiency of the system is the fact that the camera is easily saturated, hence the colour is often bleached. However, once this fact is explained to the students, it provides an opportunity to discuss the operation of charge-coupled devices (CCD).


Figure 2: Screengrab of remote desktop showing the multiple applications
a) Camera view, showing LEDs, optical fibre and oscilloscope, b) Circuit simulator (Tinkercad), c) Arduino IDE code, d) Arduino serial monitor, e) Optical spectrometer interface, f) SMU control

The lab enhances some of the formal aspects of our courses. It help to demystify the physics of p-n junctions (diodes) by enabling them to equate photon energy to the band gap of the semiconductor. At a system level, it provides a simple example of PWM control. The students collect their own unique data sets, which they analyse and plot within a lab report – this is a much better than giving all students the same data set to analyse! Even more broadly, the lab gives the students an appreciation of the complexity of colour vision and of the world of detail behind components that can be purchased for just a few pence. 

References
[1] The University of Sheffield, https://www.sheffield.ac.uk/eee/research/semiconductor-materials-devices (Date accessed: 7 July 2022).
[2] Williams GL and Funnell A, Tinkercad RGB LED control,
https://www.tinkercad.com/things/gLLlv7trV8e (Date accessed: 7 July 2021).
[3] Arduino IDE, https://www.arduino.cc/ (Date accessed: 7 July 2021).
[4] Keysight Quick IV SMU control software, https://www.keysight.com (Date accessed: 7 July 2022).
[5] Thorlabs OSA software, https://www.thorlabs.de (Date accessed: 7 July 2022).
[6] CIE 1931 Colour Space, Wikipedia https://en.wikipedia.org/wiki/CIE_1931_color_space
(Date accessed: 7 July 2022).
[7] Nobel Prize in Physics (2014), https://www.nobelprize.org/prizes/physics/2014/press-release/ (Date accessed: 18 June 2021).

One Kit to Rule Them All - Designing Inclusive Lab Kits Across a Whole Programme

Adam Funnell, Senior University Teacher in MEE, discusses how take home lab kits can be enhanced through programme level design of activities and equipment.

The growth in using Take Home Kits to deliver practical engineering teaching is one of our biggest successes and innovations that we have kept from the covid-19 pandemic. When the labs were closed to on-site teaching, we found kits to be a great method for delivering practical learning outcomes across a whole range of courses, but especially in electronics and mechatronics. In activities with intended learning outcomes around practical integration of subsystems and open-ended investigations, kits provide an ideal delivery method. There are further benefits to meeting a range of student learning styles, increasing opportunities for practical learning, and inclusive teaching practice. 

It is common to use kits to illustrate individual experiments or even for modules, but it is rare to work across modules to create a single curated set of parts for use in multiple circumstances. The figure below shows how practical activities (or "labs") are traditionally designed within engineering programmes. Each activity sits within a related module, or perhaps a cluster of labs is created to sit alongside basic knowledge transfer content modules. But in either approach, there is no developmental thread of practical skills, and no co-ordination between the different activities across all of the supporting content to make a coherent practical programme aligned in time with course content.


By giving responsibility for practical engineering education to a dedicated team, learning outcomes can be analysed for overlap and complementary activities. This in turn means that a single set of equipment can be specified and certified safe for take home operations, providing both time and cost efficiencies for staff. We selected a range of passive components, along with an Arduino Uno microcontroller. On top of the basic resistors, capacitors and diodes, we also chose solar panels and small DC motors to enable more exciting small projects to be delivered.

We can develop pathways between each of the practical activities in the kit, to ensure that skills that are carefully shown at basic levels can be applied in future lab activities and reinforce learning.

The figure above shows how practical exercises are structured from basic tasks, and how the activities interrelate with a structure of pre-requisites. Importantly, the practical activities spread across the content modules, shown in red at the bottom right of each activity. While the practical exercises form a coherent pathway on their own, they also line up exactly with the content delivery from each core content module.

For example, a basic activity common to all exercises is basic microcontroller programming, including input and output connected to electronic circuits. This activity can be followed by an exercise in analogue voltage reading, which in turn can be extended to creating and characterising a simple voltmeter. All of the exercises to this point support a "general skills" module and a "programming" module, by providing hands-on experience of working with real equipment. 

However, the next activity can use the voltmeter that students designed, to measure the voltage drop across different coloured LEDs. The fundamental device physics governing the colour of semiconductor devices can be explored with an engaging practical activity. Students can use the voltmeter that they built themselves to explore how the different semiconductor bandgap voltages correspond to different coloured light emitters. This activity supports a more fundamental device physics module within the programme, yet can be served by just the same practical take home kit, and within a coherent pathway of practical exercises.

Similarly other pathways can be created on transistor exercises to link in with both circuit simulation tutorials and fundamental device behaviour; and with solar cell characterisation to explore basic properties before integrating into a full system. By designing the practical exercises across a whole programme at once, practical learning becomes integrated, effective and efficient.

Inclusivity is arguably the most important aspect to design into our lab programmes. We want all students to be able to participate in practical work, with no barriers to gaining important experience. In our analysis, Take Home Kits offer students flexibility to work around caring responsibilities, and enable students to work at their own pace in an environment that is comfortable to them.

However, we discovered important suggestions for improving accessible lab practice while delivering our teaching, including:

  • Many of our students have visual impairments, including colourblindness. This presents an issue when working with small components, which may have tiny labels or colour codes to identify them. When working in the lab, this would be mitigated by using multimeters with large screen displays to measure resistors and capacitors, and confirm their value. Portable multimeters can be distributed to students that require them, at the university's cost to ensure access for all.
  • Every take home kit must be distributed with a resealable box to hold all of the parts. Some of our students may have young children and/or pets, who should not be left with small parts due to the choking and sharp pointed hazards they present. A strong cardboard box is sufficient and cost-effective for this in our experience, so long as it is resealable.
  • The primary enhancement to accessibility of practical work is allowing fully flexible working hours, in addition to or instead of fixed timetable slots. However, the students concerned must also have access to staff support. It is most effective to provide support in real time, using video calls or similar, to help troubleshoot with building circuits and systems. This means staff need to show some degree of flexibility with their time, which in turn needs understanding from leadership teams regarding their workload and time allocation.

Overall, we see Take Home Kits as just one part of a whole package of practical training for engineering education. We are never going to stop delivering in-person practical classes in our laboratories, but along with remote access practicals, simulations and interactive video simulacrums, Take Home Kits help us embed practical education right at the heart of engineering programmes.

You can read our full paper presented at IEEE EDUCON here:
One kit to rule them all: designing take home lab kits at programme level | IEEE Conference Publication | IEEE Xplore


Adding depth to engineering education

Teaching engineering often involves using pictures. These pictures could depict the mechanics of some physical phenomena with a sketch, describe the relationship between different parameters with a graph or illustrate the interactions between components of a complex system with a diagram. If you imagine how you would explain any of the classic concepts of engineering science, things like bending moments in a beam, the development of a fluid boundary layer or the voltage and current in an electrical circuit, you will most likely include sketching schematic pictures to represent these systems as part of the process.

 


Two dimensional representations are ubiquitous in the communications between engineers. Yet the world in which engineers apply their craft is, more often than not, three dimensional. So why is it that 2D drawings are so much more widely used to convey engineering concepts than 3D ones? 

For a long time the tools available to the engineering educator, such as notebooks, printouts, drawing boards and whiteboards, have been limited to flat surfaces. Common devices used for digital methods of communication, such as monitors, mobile phones and projectors are also mostly flat surfaces. But that isn’t necessarily going to remain the case and there are indications that 3D could become the new standard in how ideas are communicated.  Engineering educators need to pay attention to this. 

Firstly, although most digital devices have a flat surface to display their content, they have the advantage of being able to represent 3D objects by dynamically orienting the projection of the 3D object onto the 2D screen.  It is only recently that computing hardware has become powerful enough and software has been efficient enough to make the creation and manipulation of 3D content widely accessible. TinkerCAD offers the creation of 3D objects with nothing more than access to a web browser and passing 3D content between different systems is now almost a turnkey process.

Secondly, students are much more likely to consume their content through a digital device rather than anything paper based, giving wider access to the potential to display 3D objects. This has been a clear trend for a number of years now, but the Covid-19 pandemic has cemented the superiority of the digital display of teaching material compared to the printed page. 

Finally, the potential future utilisation of virtual and augmented reality for all manner of common tasks cannot be ignored. While in its infancy, especially for teaching, the plummeting cost of VR hardware coupled with the noticeable investment being made by the large tech giants is an indication that this technology could become a mainstream component of how people interact. 

The limitations of traditional tools to articulate visual concepts have influenced our methods for communicating, such that the use of 2D visualisation is completely ingrained in our professional lives. I was taught engineering using 2D, so my mind thinks about explaining things using 2D and so the cycle continues. But as we are now all acutely aware, disruptive technologies can change traditional industries rapidly, and those that don’t pay attention get left behind. 

As with implementing any new technology, there is a cost in developing the skills required utilise the tools. To justify that investment of resources, there has to be a clear benefit. In many cases, the presentation of information in 2D will be preferable to 3D visualisation, as 2D schematics can be used to make complex systems straightforward to understand without the burden of having to manipulate the image to look around it. There are plenty of examples of the arguably unnecessary use of 3D to convey information where 2D would have worked equally well. 

In the Fluids Engineering lab, we were very excited to create and share with students, in advance of their experiments, a digital 3D version of our teaching wind tunnels. This allowed them to rotate around and zoom in and out of the equipment. The idea was to provide an introduction to the apparatus so students could prepare for the lab class. The tool is very impressive. However, the ability to rotate around the equipment and zoom into and out of the 3D object isn’t enormously helpful, as students using the real equipment will typically stand in front of the fixed equipment and do not experience the other viewpoints.  Manipulating the 3D object on the screen is quite fun, and there is an advantage in making an activity more engaging even if the extent of the communication of content isn’t enhanced. But if that is the justification, we should be conscious of this rather than kidding ourselves that we are adding any substantial value to the learning.


As I am particularly interested in practical engineering education, I’m aware of the increased use of 3D photography and videos to provide virtual lab tours.  Just type “360 lab tour” into google and you will find a plethora of examples. But is there any educational value in providing students a tour of the lab in advance of their arrival? There is definitely a marketing opportunity to show off impressive facilities and the possibility of students being less anxious about entering an unfamiliar environment. But I question if there is much learning from knowing the relative positions of the furniture or pieces of equipment in 3D that couldn’t be achieved through simpler means, like a map. Or signs. When students come into my Fluids Engineering lab, they can usually find the piece of equipment they are looking for after a quick scan around the room, because they are aware of what it looks like from a 2D photograph they have been provided with in advance. 

I’m constantly on the lookout for examples of where using 3D has a distinct advantage over other approaches. So far I have two, which I will offer here, but I’m keen to hear if people have others. 

To convey a sense of scale 

Engineers can work on some pretty big stuff. I can remember being taken to Drax power station as part of my undergraduate studies and being awed by the size of the various fans and pipes and other massive engineering things. When I led the programme for Energy Engineering I would always take my students to a wind farm. While you can explain that large turbines have 100 meter blades spinning at 150 miles an hour, to really sense what it feels like you need to stand underneath one. If you have never done it, I’d highly recommend it. 


Obtaining a similar experience of scale and awe can be achieved using VR headsets. The sensation of being physically present isn’t quite the same, but the accessibility is unrivalled. Taking large groups of students on field trips is expensive and an organisational nightmare. Even relatively local sites will be a challenge to find the time to accommodate. But with a £300 headset students could travel to a range of different engineering facilities across the planet and once the content is created, the scalability is virtually unlimited. 

When 2D schematics do not represent 3D objects

One of the more enthusiastically received experiments we do in the Fluids Engineering lab is the generation of smoke rigs. We can make small ones with custom built smoke ring generators, or giant ones with a plastic dustbin into which I cut hole in the bottom.  There is something mesmerising about watching the smoke gently precess down the length of the lab, holding together with stability afforded by the vortex. 

I ask students if they had ever seen anything like it before during their studies of fluid mechanics and I am surprised with how frequently the answer is that they have not. I am surprised because they definitely have, as similar structures appear as “recirculation zones” in the step where pipes expand from a smaller to larger diameter - a reasonably classic piece of fluid mechanics that all students do learn about. But after some further questioning, it occurred to me that the lack of recognition is caused by the overwhelmingly common presentation of this structure in 2D. It had compromised their understanding of the actual physical manifestation of the system. 

Shown above is a slice through a circular pipe. The recirculation zones are the ovals and this is pretty much universally how they are depicted in all explanatory teaching material. But it is just a slice to allow it to be shown in 2D. In the real, 3D pipe this 2D cross section is rotated around the axis and the recirculation zones take on the shape of a doughnut, which an Engineering would call a "torus" because we are cool, and is almost identical to the structure seen in a smoke ring. 

I created the 2D water flowing form a smaller to larger diameter pipe schematic shown above in 2010 using open source vector graphics tool Inkscape. I chose 2D because this is the way I had been taught about recirculation zones and because building 3D content was prohibitively out of my expertise. However, if I were to prepare this teaching material in 2022, I would consider doing it in 3D using easily accessible, simply to use and free tools. In about 60 seconds and with nothing more than a web browser, I can create a torus in TinkerCAD, download the .STL and upload it to Sketchfab to embed within a webpage.  

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