Dinghy Sailing Assistant – Part 2 – Prototype Assembly

In this post I will go over the assembly and look of my first prototype for the sailing assistant. I still have not designed the case, but hope to do so soon and get it 3D printed somewhere. I first tried out all the electrical connections and modules on a protoboard. However I forgot to take any pictures… After everything was successfully connected I moved all the modules to a perfboard to make it more compact and eliminate all the wires.


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OpenROV – 1 – Welcome to the family!

I’m very happy to present you the new member of the family! His official name is OpenROV #1634, but he likes to be called… hmm, I think we don’t have a name for him yet.


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Dinghy sailing assistant – Part 1

LaserOne of my passions is to sail. I frequently sail on smaller boats, like the 470 and Laser 4000. These small boats don’t have any electronics build in, and I really wanted to log some data like position, speed etc. Until now I have been using a Garmin Foretrex 201 GPS, but I wanted to be able to save the tracks, visualize them on top of a map… I really liked the design of some of the available options on the market, but the price scared me off. So I decided to try build one myself.


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Waterproofing Marine Equipment – 06 – A deeper look into the EVM

For this week I have prepared a post focusing a little bit on how all these wireless power devices work. It’s not my intention to explain the theory, it’s more like taking a closer look at some of the signals, try to reproduce some figures from the datasheets etc.

When we power up the transmitter (at first without a receiver), it starts emitting a digital ping every 500 ms. This ping is what we can see in figure 1.


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Waterproofing marine equipment – 04 – Efficiency Tests

This  post belongs to of a series of posts that I wrote for the Element14 Beyond the Phone Wireless Design Competition. I’m not going to modify the content in any way, they will be copies of what was posted there. 

This last week I have been busy doing some tests to the wireless power kit.

The first thing I wanted to measure was the efficiency. I decided to measure efficiency from 0 to 1.2 Amps of output current in steps o 100mA.  Obviously efficiency is going to change with the distance between the coils, so I measured it with the following coil separations: 1, 3.5, 9.5 and 11mm. These strange numbers result from the combination of the following:

  • 1mm: It’s the thickness of the plastic mount to which the receiver coil is attached. I wasn’t able to accurately measuring it, so I took Hendrik Lipkas word for it.
  • 3.5mm: The receiver plastic mount + the acrylic base of 2.5mm
  • 9.5mm: I 3d printed two small 5mm stand-offs for testing.  Add 1 on top of the prior 3.5 mm and you get 9.5mm
  • 11: Removed the transparent plate and used both stand-offs. 5+5+1 = 11 J

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A CSV exporter for ROS bag files

The other day I was working with some bag files I had recorded on the Sparus II AUV (the one on the right in the website banner) and needed to process the recorded data. In order to do so, I wanted to export the different topics content into .csv files.

A moment later I had found this ROS-answers thread, suggesting a simple, one line bash implementation of what I needed:

 for topic in `rostopic list -b bagfile.bag` ; do rostopic echo -p -b bagfile.bag $topic >bagfile-${topic//\//_}.csv ; done

This worked perfectly for what I needed, but I quickly wanted to be able to specify to extract not all but only a list of topics and change the output file name

With those requirements in mind, my first bash script was born! I  could have   done it with python, but I had a good excuse to try something new.

It accepts a list of topics, as well as a string to prefix to the name of al output .csv generated files. In order to use it you have to place it in the same directory as the bag file you want to extract from and pass the bagfile name as an argument. Optional arguments are a list of topics to extract (it defaults to all) and a prefix to append to the name of every .csv (by default it appends the bag filename)A help command is also included.

You can find the code on Github.

Waterproofing marine equipment – 03 – Unboxing the kit

This  post belongs to of a series of posts that I wrote for the Element14 Beyond the Phone Wireless Design Competition. I’m not going to modify the content in any way, they will be copies of what was posted there. 

Yesterday morning I finally received my Demo Kit! Hurray!  Here are a few pictures of the kit and my first impressions:

When I started opening the packet it felt like a Matryoshka doll: a box inside a box inside a box! It certainly was well packed, maybe even too well.

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The final plastic case really got my attention. It is a nice transparent case. Once opened, we find the following content protected by foam:


  • Transmitter Module
  • Receiver Module
  • Load
  • 1.2A 5V power adapter
  • 3 Jumpers
  • A pair of tweezers!
  • Usb Cable
  • User Guide

In general, it feels like a quality kit where effort has been put into. Great!


And I really like the detail that the case is also a part of the kit, allowing us to power the transmitter while inside. Therefore they have made a small cutoff on the front panel where the usb-cable can go through. On the top we find a drawing indicating where to place the receiver. Plug the adapter in and voila: the leds light up. It’s a nice detail that really increased the wow-effect when I showed it to my family.

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A funny thing I noticed is that, while transmitting power, the kit makes noises. They are very soft and probably, if the whole thing was in a PCB not loud enough to be noticed. Nevertheless I would like to know the source of it and if it’s normal.  I have attached a small audio file to this post.  You might need to turn up your volume to hear it.


I already started taking some measurements and did some tests, but still without a clearly defined plan and it’s too early to draw any conclusions. More on testing next week!

Waterproofing marine equipment – 02 – Dummy Load

This  post belongs to of a series of posts that I wrote for the Element14 Beyond the Phone Wireless Design Competition. I’m not going to modify the content in any way, they will be copies of what was posted there. 

Still waiting for my kit to arrive, which has given me time to read through the datasheets and other documentation of the bq500212A and bq51013B, as well as the evaluation modules. It really is amazing how much info, documentation and other support material TI has available at their website.  If you are interested, you should really check it out!

One thing I have noticed is that, in order to check the performance of the transceiver, I will need to test it under different load conditions. I could just connect and disconnect resistors to the output, but there are better ways to do this… an electronic controllable dummy load! While looking through the web I found the great video at the EEVblog where Dave designs and builds a constant current dummy load ( http://www.youtube.com/watch?v=8xX2SVcItOA ) . So I quickly decided to go his way and try to build it myself.

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Waterproofing marine equipment – Initial Thoughts

This is the first of a series of post that I wrote for the Element14 Beyond the Phone Wireless Design Competition. I’m not going to modify the content in any way, they will be copies of what was posted there. 

First, I want to thank Element14, Würth and TI for giving me the opportunity to test their devices. I’m really excited and look forward to get my evaluation kit and start experimenting!

As a sailor, I have always been interested in the application on new technologies to the marine boating industry and it has repeatedly surprised me how long it takes until a new feature gets implemented in a boating product. In my opinion, a main reason therefore is how aggressive the marine environment is. Salt, water and electronics have never been a good mix.

Therefore, Wireless Power offers a perfect solution in order to completely seal our products, reducing the risk of water damage.

My plan is to divide the work for the future months into several sub-projects or parts

1. General Testing:

I would like to start with testing a little bit the development kit and playing around with it. At first, I am thinking of testing efficiency while varying the distance between the coils, the materials between coils and maybe even taking a look at different coils. But it really all depends and I may come up with other parameters to measure. All this has probably been already done and I see it more as a nice way of getting started.

2.   PCB Design

I would like to design a PCB with a small footprint with all necessary power management included. This means the wireless power and li-po charging solution, as well as a buck-boost converter to give a nice and stable 3.3V output regardless of battery state. Maybe I could also add even another version with a 5V output.

3.   Assembly, Testing and Integration into existing “Product”

Once the board is designed I will get them produced by one of the common PCB fabrication services.  After they are home again, I expect to solder them with my latest acquisition/hack, a reflow oven. And then, I will have to test the boards to check that they work as they should. If I still have time I will try to incorporate this design as an add-on to a marine safety product project that I’m currently working on.

So, a lot of work coming in our direction.  I’m sure, whatever the result, it will prove as a very interesting experience.

More to come next week!

New Blog!

Ok, first post on the new site… Wuhu! I finally found the time to set everything up and start blogging! The main motivation for this has been, as for a lot of blogs out there, to serve as some kind of notebook for the different projects I have been working on in the last time. In this way I hope to be able to come back any time and check why the hell I decided to do something the way I did…

I probably think that in the next weeks I’m going to upload files and project logs for older stuff, starting with my blog posts for the Beyond the Phone: Wireless Power Competition, held by Element 14 this year where I participated.

Although my mother language is Spanish I’m documenting everything in English, as it is the de-facto language for the maker community. So please be patient if you find any errors :) .

Let’s see where this goes…