I've bee working on the ETA attachment and here is an update on what it looks like and where the design will go next.
I've bee working on the ETA attachment and here is an update on what it looks like and where the design will go next.
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.
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.Here is a summary of the design
t 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.
After months of prototyping, experimenting and redesigning we have successfully deployed our first, "fully open source" transmitter and receiver with near real time updates to a google spreadsheet. This post will give a step by step procedure on how to set up all the software and web interfaces for this project.
On Thursday July 27th, members of the OPEnS Lab finally deployed a working prototype of the Evaporometer at the HJ Andrew's Experimental Forest. They were accompanied by Professor Bo Zhao, a member of his data visualization team, and coordinators at the HJ Andrews Forest as the receiver hub was set up at a station near the Discovery Trail and the Evaporometer-transmitter was drilled into a log overlooking a stream.
The system has been completed and we are now testing the components' response to semi-realistic conditions. I say semi because it is only being tested right outside the lab. Here is what our setup looks like.
With these tests that we are running, we aim to verify the functionality of the whole system. We need to make sure that the receiver and transmitter are communicating. On the receiver side, we want to see that it can run on the power supply and no connection to a computer. On the transmitter side, we want it to run on battery and be able to transmit all the data coming in from the sensors. We also intend to verify the data coming in from the sensors.
Materials and Methods:
We are going to implement an evaporimeter system right outside the lab and test the components' response to the local enviroment.
To simulate a rainfall we will use the OPEnS Lab rain catcher calibrator with the 20 min setting. Here is the setup:
The image above displays the evaporimeter in action.
We set the calibrator setup above the evaporimeter and allowed it to drip 500ml of water in 20min.
We have been testing the system and fixing anything to have it ready for deployment; this was all done during July 17th-21st. We will be doing more testing on the 24th to finalize the data collection and begin the analysis.
One final thing to do is to print the electronics casing in white to prevent the humidity and temperature sensor from reporting incorrect data from the heat absorption of the black plastic.
This post is dedicated to our testing results and a few comments about why the Evaporimeter's first test took so long to complete!
It has been some time since any updates were posted on development of the Evaporimeter device designed to remotely transmit evaporation data via LoRa transmission to a central receiver and then to an internet hub. There have been A LOT of changes - so many additions and revisions to the overall design that perhaps now it is best to introduce the Evaporimeter as an entirely new model with an expanded focus on reporting data for a multitude of environmental factors.
The Evaporometer wireless star network system is weeks away from being prepared for the Andrew's Cyber Forest! This post details the features and improvements leading up to the current state of the system.
Bo Zhao (OSU GeoVisualization) and Chet Udell (Director, OPEnS) have teamed up to deploy a number of wireless environmental sensors in the Andrews Cyber Forest. The Evaporometer wireless star network currently consists of one receiver hub connected to the web and a group of sensor transmitter devices. Devices communicate through LoRa long-range low-power radios up to 20km line of sight. Data will be publicly accessible and visualized in realtime by Bo Zhao's group.
Transmitter nodes consist of the following:
Hub consists of:
Multiple Transmitter nodes will be distributed in a star network arrangement around the central hub. They will each transmit data from their sensors in 15min intervals. Receiver Hub will log each transmission onto a local micro SD card. It also uploads transmissions in near real-time onto a secure Google spreadsheet. Bo Zhao's bots will dynamically pull data from this sheet for visualization.
Deployment will take place July 27.
We're releasing details about our project after ten weeks of development including support for portable limply batteries, project code/resources, and why some additional functionality is necessary before deployment.
Having the electronics secured and accessible on the evaporimeter is essential. The solution that we came up with is having a transparent jar that would screw on the evaporimeter's pole attachment. Here is the updated design:
When turned to the underside, one can see the extruded base to accommodate the threads and the breadboard and battery compartments. The breadboard slot might be edited to have a slide in feature instead of having a little slot to hold it in. The battery slot is just fine. Here are some pictures of the assembled pole attachement with the jar:
The inside is not a smooth print because it prints on the support material, but we are more concerned about function of the inside piece and not the aesthetics.
A humidity/temperature sensor and a uSD card adapter are being added to the electronics. I prototyped these new electronics and wrote code for them. An intern here at the lab is integrating the code and new electronics into the current design.
As progress on the LoRa radios leads to integration into the Evaporometer Project, we take a closer look at some of the aspects of data transmission and providing portable power.
Cutting up the wick has been the last part of getting the evaporimeter completed. The method used to cut the wick is quite unique. We placed densely-packed wick inside an acrylic tube and then froze it. This is done so that the wick is easier to cut because when it is dry it is difficult. Freezing it allows us to cut it with a bandsaw really quick.The wick is as long as the tube itself and then cut to size. Here is a picture of what the setup should look like:
After cutting them we just insert them into the evaporimeter and let the water melt. We then fluff the wick and the system is ready to go. The only problem with this method is that the wick gets dirty while cutting. The bandsaw cleans itself on the wick and since the wick is white it is really noticeable.
The main body of the pole attachment has been done for some time, but getting the wires of the strain gauge through the tube was the lasting thing remaining. The main trouble was that the wires would only go through a section of the guiding tube and then get stuck. They now go through all the way very smoothly.
The first iteration had a right angle that impeded the passage of the wires. It would only get through the hole but not through the corner. The logical next step was to reduce the amount of curvature that the wires had to go through. To work around this problem, I inserted a piece of wire through the top hole and soldered all the tips of the wires from the strain gauge together. I then pull the wire, and since all the wires were soldered to it, they all came through. This worked well but is not ideal. This is why further development was needed.
The final design was different than what I was initially thinking about. There is no curve to the side instead there is loft coming from the side of the block in the form of a rectangle to a circle. This design makes it so that the wires don't have to go through corners.
This is the iteration that will be used for testing in Kenya. Here is an interactive model of the piece:
The rain catchment check valve was essentially shelved mid summer to move on to projects that showed more promise after poor performance of the design. Recently a researcher requested I send a couple check valves to her to set up in Kenya later in March, and so I decided to spend some time seeing if I could redesign the checkvalve in a more purposeful manner rather than trial and error, this time with more knowledge and resources (the Fusion3 F400 3D printer is so fast!). The purpose of the rain catchment check valve is to allow water through flow, while limiting the size of (ideally sealing) the drain to significantly reduce evaporation of collected water samples. The water flows from the TAHMO station to the checkvalve and drains into a collection bag.
This design would be based on a similar function as the last one: water flows into a chamber and raises a buoy, opening a drain that allows the water in the chamber to flow down and into the collection bag. I decided to incorporate an O-ring to assist in blocking the drain when little to no water is left in the chamber. While the original design allowed the buoy to be printed inside the chamber during the same print, using an o-ring meant the chamber and buoy should be printed as separate parts. This actually turned out to work better, anyways. In order to seal the top of the chamber a third part, the cap, would need to be made. I designed it to be twisted on the outside of the chamber's top, pressing a large O-ring against the top edge of the chamber with enough force to form a watertight seal.
To connect to the TAHMO station, the side opening slides over the TAHMO's spout and a long ziptie is looped around the TAHMO station and the valve's outer wall, pressing the two together. This means the water enters the chamber at a low velocity and angle, which is significant because the momentum of the water is directed nearly horizontally and initially at the top of the buoy. This means the force on the buoy from the flowrate of the water acts to tilt it off of its seal rather than add force to the seal of the O-ring.
One of the largest issues in the original design was the buoy's lack of a correcting method after being tilted. There were two ways I could fix this: place the center of mass of the buoy as low as possible, and to find a way to limit its movement to the vertical axis. While I kept the first option in mind, such a small mass (<3g) can easily be overcome by small pressures such as a water droplet or a defect in the print. The fins on the side of the buoy act to prevent more than a couple degrees tilting.
The main problems to overcome are friction and catching on the sides of the chamber walls. Some dimensions require adjusting to properly fit onto the TAHMO station. Overall, this design works significantly better than the previous version.
The system has been printed. There are so minor flaws with will be addressed, but we have our first prototype.
In the image above we can see both of pieces that are 3D printed. The pole attachment is locked to a piece of aluminum extrusion just for demonstration purposes; it also has a battery sitting on it to keep it from falling. Our validator has a 6mm hole diameter siphon and will drain all the container in about 50-55 seconds. An ADC will be amplifying the signal coming from the strain gauge and outputting data to an Arduino UNO. All the electronics will be located on top of the pole attachment.
The flaws that were previously mentioned were about the attachment. The holes for the u-bolt are a little bit too close so I had to drill them out to get the u-bolt to fit. Another thing that will be changed is the little tube on the side that guides the wires coming from the strain gauge. It has a 90-degree corner that makes it difficult to pass wires through it, so I will modify the design to make it smoother. Other than that, our desing is complete.
After many tests to figure out what would work out the best, we have chosen our best design. We will be using a 6mm diameter hole for the siphon, this will be sufficient for what we need it to do. I have been able to put together a model of the whole system to be able to visualize the prototype. Here is a rendering of the Super Validator configuration:
This model only has the parts that will be 3D printed, the electronics will be sitting on the part that is attached to the pole. The electronics consist of a strain gauge connected to an ADC that will be sending data to an arduino.
The electronics have been calibrated and tested. We are currently printing both the validator and the pole attachement, and will soon have the first working prototype.
After running the test we were able to conclude that the 8mm diameter hole is too big to create the siphon at the slowest rate on the OPEnS Calibrator. 6mm diameter hole works just fine but takes a little more time than what we want it to. We are going to try a 7mm diameter hole and see how it performs. If this does not work, we will move to other designs. Here are links to the other designs we will try:
We have created three working prototypes of the validator. The main difference between each of these is the diameter of the hole that siphons the water out. We are currently working with 4mm, 6mm, and 8mm diameter holes.
We wanted to drain the validator in about 30 secs, if possible. We started by printing a 4mm diameter hole for the siphon but that turned out to be insufficient. We went on to make a 6mm diameter hole and it performed better but not quite as we wanted it to. After that iteration, we made an 8mm diameter and it worked great, with such wide orifice came a drawback.
To test the performance of each of the validators we used the OPEnS Calibrator; it was set to the lowest setting which is the 30 min setting. I initially filled the each validator with 500ml of water and then added more water to reach a height of about 1cm below the siphon's top. The calibrator was then placed on an o-ring stand above the validator and left to filled the validator the rest of way.
The rest of this post will discuss each of the validators performance and show the videos of the trials.
The 4mm diameter has troubles creating the siphon but after it is established it works just fine. For some reason, the siphon is not created and we need to push the water into the hole to get it started. This validator takes about 2mins and 20 secs to drain itself.
The 6mm diameter validator works just fine. The only thing that restricts the flow of water is the mesh that it has at the inlet and outlet of water, created to keep bugs away. With both meshes, it drains in 1min 35sec. With only the inside mesh, it drains in 1min 18sec. Having no mesh at all lets it drain in about 50sec. This version can create the siphon effect at the rate the water is coming down from the OPEnS Calibrator.
The 8mm diameter validator drains the fastest; it will drain in about 20-25 sec. The only problem with this is that the water flow coming into the validator has to be really high otherwise, the siphon can not be established. The flow of water coming down from the OPEnS calibrator is not enough to commence the siphon effect, so the water only really trickles out of the validator.