Planet Sakai

June 20, 2017

Michael Feldstein

Setting a Standard for Explanations in Learning Science and Ed Tech

Via John Gruber, I was struck by this quote from David L. Goodstein in his book Feynman’s Lost Lecture:

Feynman was a truly great teacher. He prided himself on being able to devise ways to explain even the most profound ideas to beginning students. Once, I said to him, “Dick, explain to me, so that I can understand it, why spin one-half particles obey Fermi-Dirac statistics.” Sizing up his audience perfectly, Feynman said, “I’ll prepare a freshman lecture on it.” But he came back a few days later to say, “I couldn’t do it. I couldn’t reduce it to the freshman level. That means we don’t really understand it.”

First of all, I love what this says in general about the relationship between teaching and academic work. My high school English teacher Mrs. Galighani used to say, “If you’re not writing clearly, then you’re not thinking clearly.” Feynman takes this to the next level. If you can’t explain your research clearly to a smart novice in a manageable amount of time—say, the amount of time you have in a single lecture period—then maybe you don’t fully understand what you’re talking about. And not just you, but maybe even your entire field.

I’ve certainly found that to be true in both educational technology and educational research. I’ve read a lot of academic papers that sling a lot of statistical lingo to obscure the fact that they haven’t actually proven anything. Actually, that’s not entirely fair. I think some authors get so buried in the lingo and the details that they don’t actually realize that they haven’t proven anything. The same is true, by the way, with many of the theoretical papers in the constructivist camps that get all wrapped up in French literary theory and add the suffix “-atized” to every third word. Clarity is hard. Even Feynman didn’t know that he didn’t fully understand why spin one-half particles obey Fermi-Dirac statistics—indeed, that nobody did—until he tried and failed to boil it down to a freshman-level lecture.

On the other hand, we get marketing copy or press summaries of summaries of summaries that completely lose the original thread, never mind the nuance. Again, I suspect in most cases the authors don’t know that they are dumbing down the research. They are working on deadline, with a word count limit, and a finite knowledge base.

The end result in both cases is the antithesis of enlightenment. If we are to move education forward, then there has to be a social contract between those who do the research and those who could use it in the classroom. Authors must commit to communicating clearly to laypeople—to reducing their research to the level of a freshman lecture. In return, people consuming that information must be willing to commit the time and effort that they would hope and expect from freshmen sitting in on one of their own lectures.

There is a role here for “media,” writ large. At e-Literate, we make an effort to make complex research accessible to laypeople who are willing to invest in reading an 8,000-word article. We also attempt to recover information that is lost in translation when academic studies get boiled down so far that there’s nothing left in the pot. But we’re not going to solve the larger problem with a blog. Academia needs to embrace the notion of education as an applied science, which means we need to generate both supply and demand for Feynman-style explanations of what we are learning about learning.

The post Setting a Standard for Explanations in Learning Science and Ed Tech appeared first on e-Literate.

by Michael Feldstein at June 20, 2017 10:39 PM

First Board Meeting For Kaplan / Purdue University: Tuition Levels Set

Last week was the first meeting for the board of trustees for NewU, the working name for Kaplan University now that it has been “acquired” by Purdue University. And yes, the scare quotes are intentional given the $1 purchase price. I’ll give the group high marks for transparency by the press release.

In its inaugural regular meeting, the Board of Trustees for Purdue’s new affiliated institution, currently referred to as NewU, approved plans to offer a dramatic tuition discount for Indiana resident students and free tuition for Purdue employees.  The new Indiana resident rate, also approved by Kaplan University’s trustees, will take effect at the beginning of KU’s next academic term. [snip]

An Indiana resident student pursuing an associate or bachelor’s degree will pay the equivalent of $220, including technology fees, per quarterly credit hour, which is a discount of approximately 45 percent. The total cost to graduation for a bachelor’s degree would be $39,600, compared to a total cost to degree of $80,088 (including room and board) for Indiana residents at Purdue’s West Lafayette campus.

The reason there are two boards of trustees involved – for NewU and for Kaplan U – is that the deal still must be approved by state and federal regulators and by NewU’s accreditor HLC.

To confirm the basic math:

  • Kaplan University operates on a quarter system, with ~180 credits needed for a bachelor’s degree. Their current tuition is $371 per credit for an online undergraduate degree, plus $295 technology fee per term. Assuming full-time student taking 15 credits per term, tuition and technology fee totals $70,320 for cost of a degree.
  • In-state NewU students will pay $220 per credit (with technology fee bundled in) leading to $39,600 for cost of a degree.
  • None of this includes textbooks or course materials.
  • The “approximately 45%” discount indicates the out-of-state total cost of $72,000. I assume the difference with $70,320 is from some other fee or perhaps a slight increase in tuition levels not made public yet. Close enough.

Some other notes:

  • Graduate students pay between $385 – $485 per credit depending on the specific program. In-state students will receive a 10% discount.
  • Most online students do not take their program full-time, so treat the above as a starting point to understand tuition at NewU.
  • While there are no direct subsidies, with Indiana taxpayer money used to fund NewU, there will be indirect subsidies as a result of the in-state and employee discounts.
  • For a comparison, consider the University of Florida Online, which is on a semester system. Their out-of-state tuition and fees are $552.52 per credit and in-state tuition and fees are $129.18 per credit. Translating in rough numbers to a quarter system for comparison purposes, this is approximately $368 per credit for out-of-state and $86 per credit for in-state.
  • Arizona State University Online (ASU Online) “undergraduate tuition ranges from $490 to $633 per credit hour, which includes program fees and all residency types”.
  • In other words, Kaplan / NewU tuition for out-of-state is in-line with other public research university tuition levels. Their in-state discount is better than ASU Online (no discount) but not as deep as UF Online.

The real issue to watch over time, assuming approval of the deal, will be whether NewU remains primarily an out-of-state school, essentially providing revenue to Purdue University and discounted education to a small minority of in-state students[1] , or whether the transition to a public university ownership and brand will lead to much higher percentages of in-state students. Mitch Daniels seems to want to have his cake and eat it, too, using the current mix of enrollment to justify the financial potential of the deal yet also promising benefits to Indiana residents.

Remember that UF Online’s biggest mistake was assuming that they could get 43% of the student body as out-of-state students lured just by the University of Florida brand rather than by subsidized in-state tuition. What they have found in reality is that 90+% of students are in-state students, looking both for brand and tuition. NewU is not starting from scratch, having roughly 32,000 students already, but this deal is unique. We do not know what the impact of changing from the Kaplan University / for-profit brand to some form of the Purdue University / public brand will be.

If NewU sees similar trends as UF Online, then we might see a much greater mix of in-state students paying $220 per credit instead of $371 per credit. That will change the revenue and operating income / loss assumptions of NewU. I’d love to see the business plan or internal working assumptions around enrollment totals and in-state/out-of-state mix going forward.

  1. There is no indication that Indiana students are over-represented at Kaplan University, and the state has ~2% of the total US population.

The post First Board Meeting For Kaplan / Purdue University: Tuition Levels Set appeared first on e-Literate.

by Phil Hill at June 20, 2017 08:57 PM

Adam Marshall

System Improvements: WebLearn v11-ox6

WebLearn was upgraded on 20th June 2017 to version 11-ox6. We apologise for any inconvenience caused by the disruption.

Here is a list of some of the improvements:

  • Single file upload limit is now 250MB (Resources, Assignments etc.)
  • A link to one’s personal Calendar has been added in the top right Top Right “personal” drop down

  • Anonymous Submission sites
    • Site Info tool cannot now be removed in error
    • It is now not possible to change the Admin Site – all ‘submission’ sites are forced to be managed by Exams and Assessment
  • Favourite sites are now clickable

  • One can how hide / or un-hide one’s self in a site via Home > Preferences > Sites
  • Replay (Recorded Lectures)
    • All instances now have the same ‘play button’ icon
    • Individual recordings can now be inserted into Lessons (using IMS LTI Content Item Message)
  • Citations List improvements
  • Site Members will display the photos which have been set in a user’s Profile by default (as there are currently no available ‘official photos’)
  • Interactive videos (and other content types) from can now be used within Lessons (and Resources): “H5P makes it easy to create, share and reuse HTML5 content and applications. H5P empowers everyone to create rich and interactive web experiences more efficiently“. H5p includes
    • Interactive YouTube videos (annotate, ask questions etc.)
    • Image juxtaposition
    • Drag and drop / Drag the words
    • Hotspots
    • Many many more content types

  • Resources:
    • The superfluous recycle bin link has been removed
    • Folders can be expanded on a mobile phone
    • Emoticon images inserted pre-WebLearn 11 will now appear correctly
  • Forums and Topics are correctly copied during ‘Duplicate site’ and ‘Import from site’ both seem to lose
  • Researcher Training Tool
    • Search Results page is now fully responsive
    • Improved rendering in Internet Explorer 11
  • Lessons tool: ‘Add section break above’ no longer results two blocks appearing below



by Adam Marshall at June 20, 2017 02:01 PM

June 16, 2017

Apereo OAE

OAE at Open Apereo 2017

The Open Apereo 2017 conference took place last week in Philadelphia and it provided a great opportunity for the OAE Project team to meet and network for three whole days. The conference days were chock full of interesting presentations and workshops, with the major topic being the next generation digital learning environment (NGDLE). Malcolm Brown's keynote was a particularly interesting take on this topic, although at that point the OAE team was still reeling from having a picture from our Tsugi meeting come up during the welcome speech - that was a surprising start for the conference! We made note about how the words 'app store' kept popping up in presentations and in talks among the attendees again and again - perhaps this is something we can work towards offering within the OAE soon? Watch this space...

The team also met with people from many other Apereo projects and talked about current and future integration work with several project members, including Charles Severance from Tsugi, Opencast's Stephen Marquard and Jesus and Fred from Big Blue Button. There's some exciting work to be done in the next few weeks... While Quetzal was released only a few days before the conference, we are now teeming with new ideas for OAE 14!

After the conference events were over on Wednesday, we gathered together to have a stakeholders meeting where we discussed strategy, priorities and next steps. We hope to be delivering some great news very soon.

During the conference, the OAE team also provided assistance to attendees in using the Open Apereo 2017 group hosted on *Unity that supported the online discussion of presentation topics. A lot of content was created during the conference days so be sure to check it out if you're looking for slides and/or links to recorded videos. The group is public and can be accessed from here.

OAE team members who attended the conference were Miguel and Salla from *Unity and Mathilde, Frédéric and Alain from ESUP-Portail.

June 16, 2017 12:00 PM

June 15, 2017

Michael Feldstein

Whither Moodle?

On e-Literate and even more so with our LMS market analysis service, we have called out many times the broad dominance of Moodle in terms of active installations worldwide. In every region outside of North America (US and Canada), Moodle has largest market share by far, and it is second place in North America.

But the trajectory of Moodle new implementations (higher education degree-granting institutions moving from another LMS to Moodle as the primary LMS) is striking, especially in the US and Canada as seen below, with Moodle highlighted (all data is from our partner LISTedTECH). (Update: Image link fixed – wasn’t showing in some areas)

Remembering that 2017 is partial-year data, this view still shows that Moodle’s selection as a new LMS has virtually ceased in the US and Canada after peaking in 2010. In that year 41% of new implementations were movements towards Moodle, yet by 2016 the number was down to just 2%. And for the first quarter of 2017, 0%.

If we look at a combination of Europe, Latin America, and Oceania (Australia, New Zealand, surrounding island countries), we get a somewhat different story, however.

Moodle implementations Europe & Latin America & Oceania

In this view, the data is not so clear, and the peak years are later. In 2012 and 2014 an astounding 76% of new implementations were movements towards Moodle. But we might be seeing a change. In 2016 the number was down to a still-healthy 49%, but for the first quarter of 2017 it is only 3%.

While we should avoid over interpreting 2017 partial-year data, the data seem to indicate a collapse of Moodle selections in the US and Canada, and potentially a significant slow-down in other regions.

While not shown in the data above, a large number of the non-North American Moodle selections are coming from movements from standalone Moodle instances to Moodle Partner offerings, especially to Blackboard’s Moodlerooms group outside the North America and to eThink in North America.


  • The Moodle community needs to wrestle with the question of whether having a large installed base but few new implementations is healthy for an open source project. After the US Moodle Moot last August in Los Angeles, I noted:

There was an interesting response from Martin during the Q&A after his keynote, when someone (from a long-time Moodle-using university) asked for his view on the competitive nature of Canvas. Martin replied (and I paraphrase; someone correct me if I’m wrong) that Moodle is not profit-driven and it doesn’t matter that much when schools move to Canvas. What? The community, at least in the US, cares quite a bit. Moodle Partners care about their business, Moodle advocates care about the adoption and health of the open source community, and the level of Moodle development staff depends on how many schools choose Moodle over Canvas or any other solution. I get the point that Moodle HQ may not care for the same reasons as a VC-backed profit-driven company, but they should care.

  • Instructure has signaled very strongly to investors that it plans to target the installed Moodle base for growth of its LMS, Canvas. Just last week the University of Minnesota, a long-time Moodle customer, announced that its 80k students and 6 campuses would be moving to Canvas. Ask Blackboard what happens when you take this company too lightly.
  • We are seeing markets outside of North America (Europe, Latin America, and Oceania) becoming more like the local market in terms of LMS vendors under consideration for institutional adoption. Four providers – Canvas, D2L Brightspace, Blackboard Learn, and Moodle – get the lion’s share of new selections across the four regions. If Moodle ceases to be a factor in higher education new implementations other than migrations to Moodlerooms and eThink, that is not healthy for the market. Four primary providers is already a small number – we need more, not fewer to keep all vendors honest and motivated to innovate.
  • Looking further at our data, over the past two years the vast majority of Moodle departing institutions in North America have moved to Canvas; outside North America most Moodle departing institutions have moved to Canvas and Blackboard Learn and secondarily to D2L Brightspace; outside North America most new Moodle adoptions have come from Blackboard Learn and Claroline.
  • When you combine the precipitous drop in new implementations with the observed movement from standalone or mom-and-pop Moodle installations to larger Moodle Partners like Moodlerooms, you see a broader movement towards cloud hosting and enterprise solutions. This is interesting in that Moodle is not feature-poor, but the support and hosting models of the big three proprietary vendors and the larger Moodle Partners seems to be a key driver for change.
  • Note that all of the above is focused on higher education markets and not for K-12 or corporate learning.

We don’t want to cause too much alarm for open source advocates and for the Moodle community, as there is no risk in the near term for the installed base to reduce to unhealthy levels. But these data seem to show a big change to the world’s largest LMS market position by a dramatic slowdown in new implementations. The question is where Moodle is going for higher education LMS usage.

This should be a trend to watch, and one that I believe the Moodle community should discuss more openly.

The post Whither Moodle? appeared first on e-Literate.

by Phil Hill at June 15, 2017 06:19 PM

June 12, 2017

Apereo Foundation

June 10, 2017

Dr. Chuck

Tsugi DB Upgrade Required Upgrade in Master (start of 0.4.x)

Attention Tsugi Production folks.

If you have been following along and doing database upgrades when I told you – my Tsugi commits this morning:

Will not even be noticed. These commits are the first that *depend* on the recent database upgrades being in place.

If you have been ignoring my messages and upgrade from a master a month ago to current master with a git pull, your LTI launches will break because there is now SQL in LTIX in master that depends on:


As well as “deleted” columns in all of the core tables.

If you upgrade and “brick” your Tsugi (which I highly doubt will happen), there are two ways to unbrick a Tsugi:

(1) Go straight to the admin UI

This code specifically tries to limit how much of Tsugi is working (i.e. there are no LTI launches involved in this page) for the admin interface to work. So go to admin, enter the password and do the database upgrade and things should pop back to normal. This is the preferred unbrick trick and works almost all the time.

(2) Log in and drop back to a tag if you are checking out my Tsugi – I made a tag/release with the code that adds all the needed fields, but does not depend on those fields. It can work before or after a database upgrade:

A simple

git checkout 0.3.2

Should do this trick. Launches should work even with a pretty old non-upgraded DB. Log in, upgrade the database, and then re-checkout master and all should be well. You might need a tiny DB upgrade after going back to master – but it does not affect the LTIX runtime.

All my servers,, and my Coursera auto grader are all running master solidly as of an hour ago.

If you get stuck, let me know – I will be watching my email.

by Charles Severance at June 10, 2017 05:08 PM

June 05, 2017

Adam Marshall

Copyright support site in WebLearn – updated June 2017

The Copyright support site in WebLearn has been updated with a new ‘look’ and links to the latest information about copyright requirements, with specific reference to the use of learning materials in a virtual learning environment. The site is publicly available.

The support site in WebLearn is being developed in conjunction with the Bodleian Libraries; it provides links to copyright guidance currently being updated and expanded by Bodleian librarians and staff in the University’s Gardens, Libraries and Museums (GLAM) division, in line with the provisions of the University’s CLA (Copyright Licensing Agency) licence.

The message is:

  • Provision of resources (images, text, articles etc.) for students in WebLearn falls largely under the terms of the CLA licence. For queries contact your college or departmental contact person.
  • Be aware that even if a journal article is your own work, you may have signed away the copyright to a publisher.
  • Always check the terms and conditions of the item, or failing that, request permission from the rights holder.
  • Consider releasing your own material under a Creative Commons licence to make the usage conditions clear to others.

More information:

by Jill Fresen at June 05, 2017 09:43 AM

June 03, 2017

Dr. Chuck

Sakai 11.4 released!

This message is from Neal Caidin, Sakai Community Coordinator.

Dear Community,

I’m pleased to announce on behalf of the worldwide community of participants that Sakai 11.4 is released and available for use [1] !

Sakai 11.4 has 144 improvements, mostly bug fixes, [2] including:

18 fixes to the interface (aka Morpheus)
15 fixes for the Lessons tool
14 fixes for Samigo Test and Quiz tool
8 fixes for Assignments tool
7 fixes for the Gradebook tool
6 fixes for Accessibility issues (a11y)

Improvements (features or enhancements) added in this maintenance release include:
Support for Melete Import (LSNBLDR-311)
New property to override the system default and reset tools during navigation (off by default) (SAK-31389)
Improved display option for subset menus (SAK-31824)
Email sent by Messages tool links directly to the specific message sent in Sakai, making it easier to respond to the message (SAK-32240)
Drag and Drop upload enhanced to allow overwriting of existing files (SAK-30924)
Searching on scores improved in Samigo Tests and Quizzes (SAM-3130)

Other areas improved include (in alphabetical order):

Citations Helper
Delegated Access
External Tools (LTI)
PA System
Resources (Content)
Site Archive
Site Info
Sites Admin

Three security issues were fixed in 11.4 (details will be sent shortly to the Sakai Security Announcements list)

[1] Downloading information available at –

2a. Improvements in 11.4

2b. or look directly in the Jira filter –

2c. Github issues (for GradebookNG only)

by Charles Severance at June 03, 2017 12:57 AM

The path to Tsugi 0.4.x (Roadmap for the next month or so)

I just wanted to let you know about the roadmap for the next month or so that will finish the 0.3.x release and move master to 0.4.0. There will be non-upwards compatible changes in 0.4.0 as the first step will be to do some cleanup after the Tsugi-Koseu split. At this point certain things can be used the old Tsugi way or the new Koseu way – once we go to 0.4.x we will remove the backwards compatibility stuff. More below.

Tasks to finish 0.3.x:

– Add code to the LTIX runtime that handles new data model items (url fields for memberships and outcomes, an user image field, and others). The data fields are mostly there already (please upgrade your database).

This will wrap up and make the file 0.3.x release. Some people will want to switch from master to the 0.3.x branch to avoid or delay the 0.4.x changes.

Major 0.4.x changes:

(1) Remove the vendor folder from

This means that to upgrade Tsugi, you will need to do both a

git pull
composer update

And when tsugi-php or koseu-php are upgraded – you will need to do a

composer update

I know folks think that having vendor in github violates the separation of church and state

I think that after the switch, you will realize it was kind of nice to *only* need to do a git pull and leave the “composer updates” to me.

(2) Make it so that the Koseu tools that organically grew in Tsugi will only exist in Koseu. As an example in my web site, the following URLs all work

Post 0.4.x, only the first (Koseu-style) url will work – the old code will be removed from /tsugi – so the best way to smooth the transition is to switch to the Koseu-style urls. See these files for examples of how to switch:

Comments / questions welcome.

by Charles Severance at June 03, 2017 12:54 AM

June 02, 2017

Adam Marshall

Local WebLearn coordinators

Are you a local WebLearn coordinator (or administrator) and are you aware of your responsibilities regarding your unit’s WebLearn presence? Register to attend the lunch time session offered free of charge by IT Services (Mon 12 June 2017, 12:30 – 13:30): WebLearn: Overview for local WebLearn coordinators.

At Oxford University, management of a unit’s WebLearn presence is devolved to one or more ‘local WebLearn coordinators’ in the unit who act as a contact between the unit and the central WebLearn service team.

  • The local WebLearn coordinator(s) should be the first point of contact for the unit’s WebLearn users and also act as local administrator(s).
  • They can allocate rights to other members of the unit to create and manage WebLearn sites.
  • We recommend that units develop a clear policy regarding who can do what within their WebLearn areas, and also assign responsibilities for keeping content and site membership up to date.
  • Local WebLearn coordinators need to monitor important announcements made by the central  WebLearn service team and relay them to their users as appropriate.

More information:

by Jill Fresen at June 02, 2017 04:05 PM

June 01, 2017

Apereo OAE

Apereo OAE Quetzal is now available!

The Apereo Open Academic Environment (OAE) project is delighted to announce a new major release of the Apereo Open Academic Environment; OAE Quetzal or OAE 13.

OAE Quetzal is an important release for the Open Academic Environment software and includes many new features and integration options that are moving OAE towards the next generation academic ecosystem for teaching and research.


LTI integration

LTI, or Learning Tools Interoperability, is a specification that allows developers of learning applications to establish a standard way of integrating with different platforms. With Quetzal, Apereo OAE becomes an LTI consumer. In other words, users (currently only those with admin rights) can now add LTI standards compatible tools to their groups for other group members to use.

These could be tools for tests, a course chat, a grade book - or perhaps a virtual chemistry lab! The only limit is what tools are available, and the number of LTI-compatible tools is growing all the time.

Video conferencing with Jitsi

Another important feature introduced to OAE in Quetzal is the ability to have face-to-face meetings using the embedded video conferencing tool, Jitsi. Jitsi is an open source project that allows users to talk to each other either one on one or in groups.

In OAE, it could have a number of uses - maybe a brainstorming session among members of a globally distributed research team, or holding office hours for students on a MOOC. Jitsi can be set up for all the tenancies under an OAE instance, or on a tenancy by tenancy basis.


Password recovery

This feature that has been widely requested by users: the ability to reset their password if they have forgotten it. Now a user in such a predicament can enter in their username, and they will receive an email with a one-time link to reset their password. Many thanks to Steven Zhou for his work on this feature!

Dockerisation of the development environment

Many new developers have been intimidated by the setup required to get Open Academic Environment up and running locally. For their benefit, we have now created a development environment using Docker containers that allows newcomers to get up and running much quicker.

We hope that this will attract new contributions and let more people to get involved with OAE.

Try it out

OAE Quetzal can be experienced on the project's QA server at It is worth noting that this server is actively used for testing and will be wiped and redeployed every night.

The source code has been tagged with version number 13.0.0 and can be downloaded from the following repositories:


Documentation on how to install the system can be found at

Instruction on how to upgrade an OAE installation from version 12 to version 13 can be found at

The repository containing all deployment scripts can be found at

Get in touch

The project website can be found at The project blog will be updated with the latest project news from time to time, and can be found at

The mailing list used for Apereo OAE is You can subscribe to the mailing list at

Bugs and other issues can be reported in our issue tracker at

June 01, 2017 05:00 PM

May 26, 2017


Interested in Transitioning a Sakai Course Site to Canvas?

There have been several inquiries by faculty wishing to move their current Sakai course to the Canvas Learning Management System. The following guide has been prepared to help those interested in making this transition. At any time, if you have questions or need additional assistance, please contact ATS, 116 Pearson Hall,, 302-831-0640. Sakai to… Continue reading

by Nancy O'Laughlin at May 26, 2017 05:57 PM

May 23, 2017

Ian Boston

Ultrasonic Antifouling

The board design went off to PCBWay via web browser and 5 days later 5 boards arrived by DHL from China. The whole process was unbelievably smooth. This was the first time I had ordered boards using the output of KiCad so I was impressed with both KiCad and PCBWay. The boards were simple, being 2 layer, but complex being large with some areas needing to carry high amps. So how did I do ?


I made 1 mistake on the footprints. The 2 terminal connectors for the 600v ultrasound output didn’t have pads on both sides. This didn’t matter as being through hole the connectors soldered ok. Other than that PCBWay did exactly what I had instructed them to. Even the Arduino Mega footprint fitted perfectly.

How did it perform ?


Once populated the board initially appeared to perform well. Random frequency from 20KHz to 150KHz worked. The drive waveform from the Mostfet drivers into the Mosfet was near perfect with no high frequency ringing on the edges with levels going from 0-12v and back in much less than 1us. However I noticed some problems with the PWM control. There was none. With PWM pulses at 10% the MOSFETS would turn on for 90% of the time and drive a wildly resonant waverform through the coil. Rather like a little hammer hitting a bit pendulum and having it feedback into resonance. On further investigation the scope showed that when the Mosfet tried to switch off the inductor carried on producing a flyback voltage causing the MostFet to continue conducting till the opposing mosfet turned on. Initially I thought this was ringing, but it turned out a simple pair of 1A high frequency Schottky diodes across each winding of the primary coil returned the energy to the the 12V line eliminating the fly back. Now I had ringing, at 10MHz, but control over the power output via a digital pot. I could leave it at that, but this 10MHz would probably transmit and cause problems with other equipment on the boat.

Screen Shot 2017-05-20 at 08.06.52

I think the difference between the red and blue signals is due to slightly different track lengths on each Mosfet. The shorter track not ringing nearly as much shown in the blue signal. The longer track with more capacitance ringing more and inducing a parasitic ring in the blue track. To eliminate this 2 things were done. Traditional Snubber RC networks had little or no impact. So a 100nF cap as close as possible to the Drain and Source on each Mosfet (RPF50N6) eliminated some of the high frequency, and a 100uF cap on the center tap to store the energy returned to the 12V line by flyback. This reduced the peak current.

Screen Shot 2017-05-20 at 09.41.32

There is still some ringing, but now the frequency is less and it is less violent. The ripple on the 12V line is now less than 0.2v and filtered out by decoupling caps on the supply pins to the Ardiono Mega. All of these modifications have been accommodated on the underside of the board.

Screen Shot 2017-05-23 at 07.40.29

The board now produces 60W per transducer between 20 and 150 KHz at 50% PWM drawing 5A from the supply. This is very loud on my desk and far louder than the Ultrasound Antifouling installed in Isador, which seems to work. I will need to implement a control program that balances power consumption against noise levels against effectiveness, but that is all software. There are sensors on board for temperature, current and voltage so it should be possible to have the code adapt to its environment.

Board Layout mistakes

Apart from the circuit errors, I made some mistakes in the MoSFET power connections. Rev2 of the board will have the MosFETS placed as close to the primary of the transformer with identical track lengths. Hopefully this will eliminate the ringing seen on the red trace and made both line the blue trace.

I have 4 spare unpopulated PCBs. If I do a rev2 board, I will use PCBWay again. Their boards were perfect, all the mistakes were mine.



by Ian at May 23, 2017 07:02 AM

May 18, 2017

Sakai Project

Global Accessibility Awareness Day

(posted on behalf of Matt Clare, Brock University, Chair of Sakai Accessibility Working Group)


Thursday, May 18 2017 is Global Accessibility Awareness Day.


Sakai should have a positive impact on all who encounter it, a key part of this goal is how accessible Sakai is.


Today is Global Accessibility Awareness Day (GAAD) and part of GAAD is building awareness of what we all can do to promote access for, and inclusion of, people with different abilities.


Sakai has a good history of accessibility but recent versions of Sakai have not been released with a thorough review of the accessibility and to what degree it meets recognized international standard like the WCAG 2.  I’m pleased to share that thanks to community efforts in fundraising over $61,000 and 60 hours of development work Sakai’s accessibility has been reviewed by a recognized accessibility reviewer, SSB Bart, and our plans are to deliver Sakai 12 with an accessibility compliance statement.


by NealC at May 18, 2017 11:51 AM

May 10, 2017


Sakai Status – 10 May 2017 UPDATE

An earlier reported issue of the Sites button and related Favorites list has been resolved as of 1:25pm EST.


Remember – there are several ways to get to your course sites:

  • Use of the Sites button (waffle icon) in the top right
  • Use of the Favorites (starred) sites in the Sites Favorites tab
  • Use Overview>Membership to see all course sites
  • Use Overview>My Worksite Setup to navigate to course sites

If you continue to experience issues, be sure to log out and/or restart your device and then contact the HelpDesk if you continue to experience problems.

by Dave E. at May 10, 2017 05:26 PM

Sakai Status – 10 May 2017

Some faculty and students have reported an issue with Sakai’s Sites button and Favorites list.  The issue has been identified and is being worked on presently.  Faculty and students can still access their courses by using Overview>Membership after logging in:


A status with new information will be posted as soon as it’s available.

by Dave E. at May 10, 2017 04:55 PM

Take away to Help Students in Course Sites

Just as it’s important at the end of the term or session to turn in grades to the Registrar’s Office via – it’s important to close out course sites in Sakai, specifically to unpublish them.


The immediate question I typically get from faculty is, “Why?” Well here’s a few reasons:

  • Keeps you and students organized.  Sakai provides all users with the ability to favorite sites (place a star next to them using the Sites button) per user. Favorite sites appear in the top blue banner of Sakai. Leaving sites in a published state, crowds out and creates confusion for students.
  • Helps protect against plagiarism and cheating. By unpublishing course sites you protect your own courses and similar or identical courses taught by other instructors from students being tempted to or fully deciding to share their papers or assessments with other students who may be taking the course in the future.
  • Sakai doesn’t automatically surface or show the most current term courses (though this has been discussed as a feature to implement), so it’s important to unpublish courses so students are less confused about where to look for their current courses.

Unpublishing a course takes about 7 seconds:

  1. In the course site go to Site Info
  2. In Site Info select “Manage Access”
  3. Change the selection from “Publish site – accessible to all site participants” to “Leave as Draft – accessible only to site maintainers”
  4. Select Update

Unpublishing a course doesn’t remove your (instructor) access to a course site, it only does so for students who were officially enrolled in the course. Student’s data (grades, forum posts, assignments) will all remain in the course site. By design, Sakai does not delete data – several protections are put in place to prevent or wholly disallow data removal.

There’s obvious room for leaving some course sites published – esp. at the graduate or PhD level, but by and large, most sites should be unpublished at the end of each term or session – a few days or weeks following the official end date of the course.

by Dave E. at May 10, 2017 01:30 PM