Archive for July, 2017

Here is a blog post that expands on my mini tweet storm about measles becoming endemic again in the US due to a drop in children’s vaccination rates. I put the graphics and links all in one place so you don’t have to keep clicking through to other websites to see them.

This story comes from Arstechnica where they quote the researchers who point at that a drop of 5% in the MMR vaccination rate drop will triple the number of cases and be very costly in terms of public healthcare costs. The personal costs are pretty high, too. Quoting:

Measles, in particular, requires vigilant vaccination. The highly infectious virus can linger in the air for hours after a cough or sneeze. Those sickened develop high fevers, rashes, inflamed eyes, and cold-like stuffy nose and cough. But people can spread the infection days before those symptoms appear. About 30 percent develop complications, such as pneumonia, brain swelling, and blindness.

So there’s that.

Since I am originally from California I was curious about how prevalent unvaccinated kids are these days in my home state. A while ago I did an analysis of data from the California Department of Public Health on the percentage of kindergarten children who had been granted “Personal Belief Exemptions” in 2015. Here is a map of California with counties colored according to percentage of unvaccinated kids.


Note that it looks like most of the northern half of the state suffers from this risk. The county names are not listed in the graphic but the 20 with the lowest vaccination rates are shown on my Rpubs page at Nevada county leads with 21.4% unvaccinated, followed by Mariposa county at around 15%. Amazing in this day and age, like a third world country in this respect.

Something odd I noticed when I was writing this post is that the data that I used in this analysis has been moved or removed from the CDPH website. So the link to the source on my Rpubs page is now broken. The CDPH website does have some summary data that shows vaccination rates overall are climbing back up. Here, for example they say that overall vaccination rates went from 93% in school year 2015-2016 to 96% in 2016-2017. So that’s good news, although still a little low. I haven’t spent the time to search for the raw data; perhaps it is there somewhere.

The developing country of Thailand, where I live, hasn’t lost its mind. The vaccination rate for measles has risen rapidly since 1984 and was reported at 99% in 2015. Here is a chart from World Bank based on the data they have collected.

Thailand Measles Vaccination Rates

Vaccination Rates of Children Age 12 – 23 Months in Thailand

From on 27 July 2017.

Maybe it is because so many people in Thailand can still remember the horrible days before nearly everyone received vaccinations.

I previously posted about a robot arm built with cardstock and Arduino. The idea comes from a project on called Cardware. The motivation for Cardware is that there are lots of hobbyist robotics components available like servo motors, controllers, sensors, etc, but to put together a complete robot of any kind you have to either buy an expensive kit (which may not even be available depending on where you live, e.g. Amazon does not ship to Thailand) or have the tools and expertise to fabricate something like 3D printed plastic or laser cut MDF body components. The talented project owner of Cardware developed plans for folded card stock as the body components that can be assembled into a complete robot.

There are multiple advantages of this approach:

  • Availability – card stock, or something similar, and general purpose glue are available nearly everywhere in the world, although there may still be some challenges as I discuss below in the video.
  • Tooling – an internet connection and printer are the tools needed to be able to download and print the patterns on the card stock. Even in less developed areas there is usually a school or internet shop where this can be accomplished. After that all that is needed is a pen and a cutter to score and cut the pieces.
  • Cost – high quality card stock is inexpensive by Western standards. It isn’t cheap by local standards in Thailand (and probably many other developing countries), but one can substitute lightweight cardboard such as cereal boxes, although there are some issues (mentioned in the video below).

The are some disadvantages to this approach. Dimensional accuracy and stability are not tightly controlled and depend highly on the quality of your cuts and folds. As a result, one can easily end up with a robot that is not well aligned and does not move smoothly. Another disadvantage is the fact that cardstock is not nearly as durable as 3D printed plastic or laser cut MDF. Due to the clever design and folding the strength is pretty good, but pivot points wear rapidly. Durability can be improved a bit by using lots of glue such as PVA to strengthen seams. And pivot points can be strengthened by gluing in plastic bearings made from something like short pieces of tubing cut from ball point pen cartridges.

In the video below I demonstrate the early stages of a build of version 2 of Cardware. At this stage I am driving two servos with the Arduino Uno.

In the video below I discuss some issues with the materials used in Cardware. My focus is on how this robotics learning platform can be globalized so that learners in developing countries can easily make use of it. In Western countries it is easy to take for granted something like cardstock. But it could be a real obstacle in a developing country.

These issues aside, I went ahead with the next version of Cardware using cardstock rather than reclaimed cereal boxes. The designer did some very nice work on it and I encourage you to visit to see more details about Cardware. I finished the papercraft part of the project and started installing the servos. At that point I did not have enough servos to complete the project so it was put on hold. Events have intervened since then so it is still incomplete and looks like this at the moment

Robotic quadrapod make from cardstock, hobby servos and Arduino MEGA

Cardware Quadrapod

I anticipate a new blog post once it is fully assembled with all servos and an Arduino MEGA as controller.

An Arduino Uno combined with a multi-function shield makes a great inexpensive starting point for projects. I had an extra Arduino-compatible laying around so picked up a multi-function shield with the idea to use it as a teaching tool. It has a 4-digit 7-segment display, a buzzer, three pushbuttons, a trimming pot, and a number of headers for attaching additional things like up to three servos. That provides lots of opportunities to dabble and learn how to control physical hardware with Arduino code.


Arduino Multifunction Shield

I originally had just a vague idea of how I would use the Arduino + multifunction shield for teaching purposes. But then I decided to combine it with a project I was contributing to on The project started out as something called Cardware (which has since evolved quite a bit). The concept is that there are lots of hobbyist robotics components available like servo motors, controllers, sensors, etc. But to put together a complete robot of any kind you have to either buy an expensive kit (which may not even be available depending on where you live, e.g. Amazon does not ship to Thailand) or have the tools and expertise to fabricate something like 3D printed or laser cut body components. The talented project owner of Cardware developed plans for folded card stock as the body components in which servos could be mounted and then the components assembled into a complete robot.

More details on the development of Cardware will be in another blog post. Now I will just jump to the finished result of combining Cardware with an Arduino Uno + multifunction shield.

I introduced this to the teacher who runs the coding club at my kid’s school. They are already using to teach primary school kids coding. The kids in the club make art and games using Blockly. Adding a real world physical component like this gets kids excited and is what makes robotics such a great way to inspire young learners. There are many kits available targeted at that space. But I like this approach because it is much more DIY. It is more challenging than snapping together pieces of a kit so more adult help is needed. The Arduino can be programmed using a Blockly-like tool within the Arduino IDE. So kids can actually program the robot arm to move the way they want it to.

It’s probably old news to experienced makers and crafters, but I only recently discovered this adhesive called B-7000 that works well on a number of plastics. Several projects I built utilize plastic bottle caps to fashion wheels, often requiring gluing a couple of caps together. Those are typically made of LDPE or HDPE. Empty yogurt containers, made of polypropylene, were used in another project. I had poor results using the cements I had on hand (hot glue, cyanoacrylate, “all purpose” plastic cement). After a little research I learned of B-7000 and, happily, it is available on Aliexpress at attractive prices.

A few test pieces showed it forms a very strong bond on the two materials I previously had trouble with.


The test items were subjected to stress testing by a very strong six year old. Those two bottle caps are inseperable. The yogurt containers bonded pretty well but did come apart with only a moderate amount of force. Good enough for most projects but if a super strong bond on polypropylene is desired then a different adhesive is needed.

Of course, like so many items on Aliexpress that come from China, you get the silly English labelling.


“Surprise adhesive force” and “Stimulate the taste-free”, chuckle. But the adhesive works very well and at about US$1 for a 25ml tube it is a good deal.

In the US you can probably find it at a local craft store and there are many sellers of it on Amazon. Being in Thailand means there are few local sources for specialty craft materials such as this adhesive and Amazon does not ship here. But Aliexpress has nearly everything, and much better prices (that 25ml tube cost me US$1.00). You just need the patience to wait three weeks or so for it to arrive. There are plenty of sellers. Another option in Thailand is Lazada which delivers in under one week, but at several times the price.