Shipping the OPEnSampler


The late-summer OPEnSampler is shipping! We’ve come a long way from the foam puck concept with several iterations throughout the process. The team at Zurich will provide us with much needed field and user testing as we add more members to the team working on the firmware and companion software. Packed into the 80QT Pelican Rolling Cooler is the OPEnSampler, batteries and power supplies, spare tubing and bags, and lots of foam and bubblewrap. The sampler we are sending uses silicone tubing and the June 22 board, but samples effectively and reliably. The serial command interface allows the operator to plug in a laptop and tell the sampler when and how to sample, and the operator interface makes initiating the sampling process quite simple.

There is still much more development to be done! The next batch of samplers include many more features described in previous posts, such as GSM communication capabilities, power decoupling and filtering, and additional sensors to control the sampling process. The hard Teflon tubing will increase the quality of the sampled water and the new pumps, once integrated, will allow large-particle suspended sediments to be sampled with ease.

The next step is to update documentation. This has been a weak point in the design process and the changes and timing of one iteration to the next were not always transparent. Considering the purpose of the device is to be shared with the community of water sampling, you can expect more frequent and detailed updates on the designs following this milestone. I will be updating the GitHub page shortly with the latest and greatest .STL part files for our printed parts, documentation, and the new PCB board files. Later on I will be adding assembly instructions and new code will be posted. In the coming weeks there will be two of the new samplers on our lab tables: the bottle sampler and the bag sampler.Stay tuned!

Capstone Team Intro: Hunter Lien

My name is Hunter Lien and I am one of the new additions to the OPEnSampler team! I’m currently a senior here at Oregon State University getting my degree in computer science focusing on computer security. I first got into computer science back in freshman year of highschool when my school started a computer science program. Every level of the class was taught by a single teacher, Mr. Bartlo and I consider him the biggest contributing factor to my interest in this field. He always encouraged us to move outside our comfort zone and even helped us get funding for projects that might have required additional hardware.

Travis, Chase, and I make up the senior capstone group responsible for developing an Android application capable of interfacing with the OPEnSampler hardware. We will be working on this for the next 6 months at which point we aim to have a functioning product. All three of us will be posting weekly blog posts on the OPEnSampler website to let you all know how progress is going in whatever area of the application we happen to be working on. I’m really excited to get started with this project and can’t wait to be part of it’s success.

Capstone Team Intro: Travis Whitehead

A Bit About Capstone:

Earlier this year, OPEnS Lab submitted several project proposals to Oregon State University’s capstone course for computer science (CS) students. Capstone (or Senior Design) is a three-term course in which students work in small teams on projects that solve real-world problems. One of OPEnS Lab’s proposals was to enhance the OPEnSampler with GSM support enabling long-distance status updates, and to ease the sampler’s configuration with a mobile app that will communicate with the Sampler over Bluetooth. That’s where we come in!

I won’t go into too much detail in this post, but you’re welcome to read the problem statement we prepared for capstone, available in our fork of the OPEnSampler GitHub repository.

(If seeing PDFs in git hurts you, rest assured we’ll be doing some cleanup and reorganization in the near future.)

Right now, we’re mostly getting started by preparing written documents that will guide our future work. The week before last we finalized our problem statement, and this week we’ve been working on drafting a requirements specification. Although we don’t have an exact time-line laid out, our end game is to have completed this project by OSU’s Undergrad Engineering Expo during the Spring (where we will be presenting our contributions).

A Bit About Me:

I’m Travis Whitehead, a Computer Science student at OSU with the exciting opportunity to work on the OPEnSampler for my capstone project (along with my teammates Hunter and Chase– who will also be introducing themselves in separate posts). As I don’t have a lot of background experience with mobile development, microcontrollers, GSM, or Bluetooth specifically– I’m expecting to learn a lot this year!

As a free software enthusiast, I’m delighted about the “Openly Published” aspect to OPEnS Lab. In my spare time, I work as a Student Systems Engineer at OSU’s Open Source Lab a (similar sounding) organization that provides various forms of hosting for open-source projects. Luckily, there’s room in my heart for more than one open lab.

This is the first of many updates I’ll be writing as we continue to work on this project– So stay tuned!

Capstone Team Intro: Chase Coltman

Hello, my name is Chase Coltman, I one of the three capstone students working on the new companion app for the OPEns Lab Water Sampler, OpenSampler. I am excited to bring some of my previous mobile development experience to this project and make a great addition to this team. Currently, I am in my Senior year at Oregon State University, and I am studying Applied Computer Science, with a focus in Simulation and Game Programming. I am thrilled to be a part of this team and can’t wait to see what’s in store.

Previously here at Oregon State, I have taken several classes that will be very beneficial to our assignment. Two of the most beneficial classes I feel will contribute the most to this project are Mobile Software and Cloud Development, and Intro to Usability Engineering. My Mobile Software and Cloud Development class will likely be the most useful as we focused on app development, however we did not cover certain things like GSM or BLE, which is going to play a very large role in the companion app. My other class, Intro to Usability Engineering, was more about general UI design, good user/design focused elements such as Affordance, Consistency and of course Usability. 

Evaporometer 2.0 First Prototype

Abstract: Here is an update on the progress of the second versions of the Evaporimeter. We have now printed the pieces and mounted the electronics onto the 3D printed pieces. 

Objective: To inform the reader of the features and changes to the Evaporimeter design. 

Methods: I did all the CAD on Fusion360.  Here is the Assembly.


This is the CAD for the new design. 

This is the first prototype of the second version. We have to yet test the whole system, but we are getting there. There are some minor things to fix first before this design of finalized. 

This version has a barrel jack that will be used for solar power charging; this was intended for an external solar panel attachment. We are planning to integrate the solar panel into the project’s electronics, so we will be8 making a new base cap that has the solar panel in it and the electronics on the underside.

This design also gives the user access to uSD and USB by just sliding a cap off. This will be very nice when you have to get the data from the uSD card or you have to reprogram the microcontroller. 

The solar shield on this design is outdated. I want to make an octagonal version of the shied that will cover all the sides of the strain gauge. This will make it so that the heat is more evenly distributed.

Evaporometer 2.0

Abstract: Here is an update on the new evaporimeter design. This design will include the ETA sensor on it. It has not yet been designed, but the electronics base has the port for it.

Objective: This post is intended to update the reader on the new design for evaporimeter.

Methods:  I did the CAD in Fusion360. Here is the link

Results: The following CAD are the main pieces that make the new evaporimeter design. 

This is the main body that holds the battery and the electronics. The battery sits at the bottom of the case and the electronics sit on top of the battery supported by a 3D printed base.

This piece is the on that holds the electronics in place. The bottom PCB is bolted onto this piece; this one is specifically designed to bolt the Feather RTC and uSD card wing. 

This is the cap that will close the case. This is designed to be modular in height for 3D printing. Our electronics are made so that more capabilities can be added after production; this is done by stacking other shields onto the existing boards. 

This is the assembly of the case without the cover. The aluminum piece extruding from the side is the strain gauge and the black piece is a cordgrip used to pass a cable with four conductors that will be used to communicate with the light and humidity/temperature sensors.

OPEnSampler October 17 Update


Much has happened with the samplers in the past two weeks! There are two categories of updates: those relevant to the Zurich Sampler and those relevant to the new versions of samplers. In short, the frames have been assembled for the new samplers and the PCBs are being soldered up; the new pumps arrived; the final pieces of the Zurich Sampler are coming together and it will be ready to ship very soon.


New Sampler Updates:


The sample-bag OPEnSampler frame was assembled by Adnan and I the other week and it fits snug in the Pelican 80QT rolling cooler. It fills up quite a bit of the space as intended, and there is extra room on the sides (the thickness of the wheel wells) for ice packs. Before more are assembled I think I will reduce the width of the sampler by about 5mm to account for the wells being slightly convex.


The Main Control Boards arrived the other week along with all the components of the two samplers. They look great! Azad and Adnan are soldering the components to them and will likely finish in a couple weeks.

New Pumps:

The new pumps arrived and we will be testing them soon. It looks proming but we will need to change either the tubing or the tube fittings to work with the rest of the sampler tubing. These will be added to the new samplers Azad and Adnan are assembling.

Android App:

In other news, three students will be working on adding an Android app to receive updates from and control the sampler remotely as their senior capstone project for their majors in computer science. In the coming weeks they will be contributing to the blog by introducing themselves and eventually posting updates on their work on the app.

Zurich Sampler Updates:

Quick Disconnect Fittings:

I finished the design of the endcap on which the two quick disconnect fittings are mounted and it is currently printing. Designing the endcap was more of a challenge than I initially predicted due to the awkward nature of the barbed fittings and the Pelican’s small outlet port. Because the threaded outlet on the Pelican cooler is too small to fit two fittings side-by-side, the endcap was designed in two pieces that would clamp together with an o-ring and three M2 screws. The male fittings can be threaded through the front panel with an o-ring to mitigate airflow. The sampler tubing can be pushed through the main body of the endcap while it is disconnected from the front panel, and then attached to the barbed ends of the fittings. The main body is then screwed onto the Pelican’s outlet port and the front panel is attached to the main body via M3 screws and nuts, completing the assembly. Intake tubing is attached to the intake fitting via the female quick disconnect fitting.


The optional filters were quite easy to integrate into the design. The filter mesh is 470 micron stainless steel from Grainger with open ends. The front of the intake is blocked with a simple 3D-printed plate and the other end is blocked with another plate with a compression fitting screwed into it. All components of this assembly are glued with “ABS paste”, a solution of dissolved ABS plastic filament in acetone. The paste acts to weld the plastic components together.

Operator Interface:

The new Operator Interface turned out quite well. It consists of a 12V barrel jack port for powering the device with either a battery or a voltage regulator, a power On/Off switch, an enable switch for changing sampler modes (field use vs lab testing), an interrupt override button for initiating sampling in the field and also for lab testing, and a USB type B socket for communicating to the Arduino with a laptop. The panel is 3D printed and slides into the 15mm extrusion.


There’s a ton of development happening on the OPEnSampler and I’m excited to showcase the new design once the two new samplers are completely assembled. In the coming weeks we will ship out the OPEnSampler for the first time, I will update the gitHub page with the latest designs and bill of materials, the capstone students will introduce themselves on this blog, the new pump will be tested, and the new samplers will be fully assembled.

Shield Sandwich for Dogbone Tags

By Brett Stoddard


One problem that I’ve been having with burying the Smartrac Dogbone tags is that soil is that they break after some use. After taking a close look at some of the broken tags it appears that this is caused by the abrasive soil eventually cutting through the outer lamination of the Dogbone tags and then damaging the IC that controls the tag, causing them to become unresponsive. To counter this, I designed a two part protective enclosure for the tag that will hopefully protect them from damage. The design is outlined below:



This “Dogbone Sandwich Shield” is made up of two identical 3-D printed parts. The sandwich ends were designed to be slightly larger than the Dogbone’s footprint with two tabs on the long ends. The tabs were placed like this to minimize interference with the moisture sensitive area of the tag which sits at its center. 

Assembling the product was a fairly simple process. First, the Dogbone tag was stickered onto one of the sandwich ends. Then a small amount of acetone was brushed onto all of the sandwich end’s tabs. They were then pressed together to create a sandwich with the Dogbone in the middle. The sandwich was then treated in an acetone air bath to seal the edges. After 20 seconds in the air bath, the part was removed and put in a vice under a small amount of even pressure to make it even until it hardened. It takes around a day to fully harden, but it is tough enough after an hour. Below is a picture of the final shield. 



Two built RFID sandwiches. One made of ABS plastic, the other made from HIPS


The presence of the shield surrounding the Dogbone tag made it slightly less sensitive to moisture, however, the variance from readings with the shield was no greater than it was without them. Therefore, using the shield will not influence the accuracy of the sensor once, but it will require some re-calibration.

Thinking Ahead

Thinking ahead, creating shields like this one with varying thickness could allow for changing the sensitivity of the tags. Currently, without a shield, the tags read their lowest value before the soil has gotten completely saturated and are able to read soil that is more than completely dry. Adding a shield that is a certain depth should shift the reading range to be centered and allow the tags to read over a larger range of soil conditions than they currently do.


STL file shield tag

Waterproof Evaporometer

Abstract: It was recently discovered that our transmitter is no longer sending data and that the last reading on the humidity sensor was 100%. I wonder what happened? We are now moving ahead in the design process to create a waterproof system. 

Objective: I intend to describe design considerations and current ideas that have come up to design the new enclosure for the evaporimeter base. 

Materials and Methods: 

This the new concept for the evaporimeter:

Screen Shot 2017-10-04 at 10.33.40 AM.pngScreen Shot 2017-10-04 at 10.33.40 AM.png

The idea of the new base is to have a case that consists of a main body and cap. I think it is a good idea to use a rubber gasket to seal the junction between the two. In terms of materials, I plan to keep on using ABS for the time, but using T-Glase, Bridge, or Nylon is also recommended to keep water from entering into the 3d printed case.

We also need to run some wire into the casing from the sensors on the outside. Using a coupling mechanism would be our best solution. The only problem is that our system is very small and the coupling mechanisms for that scale are very expensive, about $40 per set. Another solution that was brought up was to use rubber sheet and perforate a small hole to run the wire through. This rubber sheet will seal up against the wire and keep moisture out. We are also leaning towards using a cordgrip and using a 4 wire cable. Another solution was to find some type of waterproof ethernet cable.


For now, we will be testing the cordgrip and ethernet options. These seem to be the most inexpensive options. I will also be ordering the rubber gasket to get a good seal for the base case. 


Coupling Mechanism

Example Cordgrip

Rubber Seal

First Look at The Data


Over the last two months, our OPEnS Data logging hub in the HJ Andrews forest has relayed over 100,000 data points to our Google Spreadsheet through the transmission protocol below. This post will provide a brief look at some interesting trends found within our dataset.

Data Transmission DiagramData Transmission Diagram


The Objective of this post is to look at some POI within our data set including some interesting plots of data during the Great North American Eclipse.


After collecting data points every 5 minutes for a little over two months we were fortunate to begin looking at the wealth of valuable data we had collected. As I began to analyze specific areas of the data that I found interesting, I was able to see some pretty fascinating trends that one would expect to see such as the Inverse relationship between relative humidity and temperature. I then began exploring other trends within the data and found that although some trends were expected some were not.

Graph showing the inverse relationship of relative humidity and temperature Graph showing the inverse relationship of relative humidity and temperature 

It became clear after looking at the load cell data (well after all water we added to the system would have evaporated) that there was a periodic fluctuation much greater than any residual noise would account for. When plotted alongside daily temperature, it was clear that fluctuations were temperature dependant and we deducted that the exposed aluminum force gauge was expanding with high afternoon temperatures and contracting with colder overnight lows. This behavior visible in the graph below.

Our data is not without its issues, We found our load cell (evaporation mass) data was greatly compromised by the thermal expansion properties of the aluminum rod throughout daily temperature fluctuations.Our data is not without its issues, We found our load cell (evaporation mass) data was greatly compromised by the thermal expansion properties of the aluminum rod throughout daily temperature fluctuations.

All issues aside, we were able to capture some pretty remarkable data during the Great North American Eclipse on August 21st, the below plot focuses on the point of totality, and how this event altered the standard linear trend of light intensity increase throughout a morning with a very steep fallout in both the Infared and Full spectrum light intensity. This anomely can be viewed below.

Light Intensity Data during the Total Eclipse 8/21Light Intensity Data during the Total Eclipse 8/21


After briefly looking at the data from this spreadsheet it clear that a more in-depth analysis will be required to really gain an understanding of the relationships and trends within the data set. However, even at a glancing look, it is clear from the strain gauge and temperature relationship will be a major consideration in the redesign and further models of our sensor suites.

-Tom DeBell