Open Hardware for groundwater monitoring in rural Africa - application for the riffle?
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toby...@gmail.com
Sep 26, 2016, 5:13:36 AM9/26/16
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Hello all,
First time poster here - apologies if this is in the wrong place, or not following protocol.
I am totally inspired by the activity in this community! I have a project that needs an open-source solution, and am hoping to lean on you all for advice.
I’m working with community leaders on small-scale water development projects in rural Zambia, helping households access clean water by drilling boreholes. Part of the plan is to develop and deploy affordable open-source water monitoring hardware, sending groundwater level data to an open-access database. This will help track and maintain the water resource, in addition to providing clean water access. The vision is to build a distributed water monitoring network including as many actively used boreholes as possible, to track groundwater quantity over time and space. Such monitoring capacity is currently nonexistent.
My question is this: do you think that the riffle could be a good fit for this application, either using the capacitive measurement approach, or by using an i2c pressure sensor? I think battery life will likely be an issue as we want to minimize labor for maintenance and data collection as much as possible. With the capacitance approach, I wonder if biofilms and the depth of the borehole (~60m) would be problematic.
Ideally we would link the datalogger to ICT to transmit once daily over SMS, and possibly include a solar cell or hydrogenerator.
Anyway - I'm sure it will take time and trial and error to come to a functional solution, but I appreciate any and all input!
With many thanks and best wishes,
Tobias
First time poster here - apologies if this is in the wrong place, or not following protocol.
I am totally inspired by the activity in this community! I have a project that needs an open-source solution, and am hoping to lean on you all for advice.
I’m working with community leaders on small-scale water development projects in rural Zambia, helping households access clean water by drilling boreholes. Part of the plan is to develop and deploy affordable open-source water monitoring hardware, sending groundwater level data to an open-access database. This will help track and maintain the water resource, in addition to providing clean water access. The vision is to build a distributed water monitoring network including as many actively used boreholes as possible, to track groundwater quantity over time and space. Such monitoring capacity is currently nonexistent.
My question is this: do you think that the riffle could be a good fit for this application, either using the capacitive measurement approach, or by using an i2c pressure sensor? I think battery life will likely be an issue as we want to minimize labor for maintenance and data collection as much as possible. With the capacitance approach, I wonder if biofilms and the depth of the borehole (~60m) would be problematic.
Ideally we would link the datalogger to ICT to transmit once daily over SMS, and possibly include a solar cell or hydrogenerator.
Anyway - I'm sure it will take time and trial and error to come to a functional solution, but I appreciate any and all input!
With many thanks and best wishes,
Tobias
Don Blair
Sep 26, 2016, 6:55:10 PM9/26/16
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Hi Tobias,
Your project sounds amazing -- thanks for sharing! I'm very interested to figure out exactly these sorts of questions, for similar applications (mostly farming right now). Here are some off-the-cuff thoughts ....
Networking topology. I'd started to fiddle around with some relevant networking diagrams to sort through the various data flow options. Sounds from your description that you're already settled on the top two rows of that diagram -- sending data via SMS. One option is to have each well monitor sending data directly to the cloud via SMS (top row of diagram); or, if the bore holes are within a kilometer or two of one another and you're not on rough terrain, you might save SMS fees by using low power radio modules (RFM69, LoRa) to first send data from each well via low-power radio to an SMS gateway, and then to the cloud.
Power. I worked on a project that used an Adafruit Fona (cell phone module) and a Riffle to transmit data to the cloud every 10 minutes (and sleep in-between), which lasted for about two weeks on a 2200 mAh battery -- it lasted about two weeks. The sensor used in that setup was essentially the same circuit as the capacitive depth circuit I've described here, and so the overall power requirements for a capacitive depth sensor would likely be similar (things might change for the i2c sensor, but I don't think it would use more power). We can do the numbers in detail, but transmitting only once per day could extend the lifetime on that battery to over a month, I'd think. Then, of course, you could choose a larger battery -- e.g. a car battery could last you for years :) Or, you could use one of the available circuits out there (Adafruit sells them) for solar recharging. One advantage of using a large battery and servicing it infrequently is that you could obscure the monitoring tech from passersby, if that'd be useful (I've been surprised at what's been stolen / destroyed in rural New Hampshire :)).
Sensors. Using the capacitive approach would be the least expensive option, but it's as yet unproven, and might (not sure) have trouble with such long depths (and with other factors, like changes in water conductivity, temperature, and, as you mention, bio-fouling). One (as yet half-baked idea) I thought of a few weeks ago was to use *two* capactive cables, one of them shifted vertically a fixed distance above the other (4 centimeters, say). The idea would be that if fouling occurred relatively uniformly across the wire, the difference in capacitance between the two wires could still be used as a unit of capacitance/length to assess the height of the liquid.
Blue Robotics has developed a nice enclosure for a Measurement Specialties i2c pressure sensor (intended to be used in diving watches -- $20 on Digikey) -- the same sensor that has been used in several ROV projects, and by Edward Mallon. Compared with other pressure sensors out there, these are very inexpensive; Ed has deployed his PVC+epoxy enclosure design for several months at a time. Depending on your budget / resources, and how important it is to leave these unattended for signficant periods, you might consider interfacing with more robust, pre-made, proprietary metal-enclosed pressure sensors, and use open hardware for the rest of the data chain. A quick search reveals an apparent range from $80 to $600; glancing at the specs, it looks like you'd need to boost the 3/5V microcontroller voltage to 10 or 12 Volts (not difficult) and maybe code up an interface with an SD-12 protocol (I think this has been done by folks at Stroud and elsewhere, and code for this could be hunted down).
If you have the patience and time, it would be really neat to work on seeing how robust and accurate the capacitive meausurement can be. I've been playing around with using Ethernet cable + a jack as a shield for this approach. It would require some iterative testing and development. One neat way to begin could be to co-deploy the capactive sensor along with the i2c pressure sensor, and then periodically measure (with a physical plumb line) to get a sense for sources of error. Errors due to temperature, for example, could likely be compensated for with an inexpensive temperature probe and a little extra code.
If you're content to simply know whether the water level is above or below a few points -- e.g., you only want to know whether the water level is below a certain critical "low" value, or whether it's "low", "medium", or "high", rather than a continuous water level measurement -- then I think this is pretty straightforward to accomplish in a robust way, with a few pairs of wires. Then there's no calibration issue. Combining this approach with the continuous-capacitive approach might also be an inexpensive way of calibrating / registering the capacitive sensor without requiring additional hardware / measurements.
A caveat with the i2c pressure sensor (and the reason I drew a box labeled "S" for the pressure column in my diagram) -- i2c signals might not transmit reliably over long distances, so you might want to have a microcontroller right next to the i2c pressure sensor, and then have the microcontroller send the data (via serial, or some other, more robust protocol) to another microcontroller at the surface. This will mean a significantly more elaborate enclosure sitting in the water.
Aside: there are also ultrasonic sensors that are sometimes used to measure water depth. Depending on the range of water depths (measured from the surface) you're anticipating, they could also be worth trying out -- I don't think (though I'm not sure) that they're effecting for depths-below-surface much greater than 10-20 feet. The cheapest standalone options I've seen (Matbotix) are about $80 ea; so far as I know, they haven't yet been demonstrated to work in a field-deployed water level measurement.
Microcontrollers. If you're interested in using SMS or SMS+low power radio, I'd suggest using Adafruit Feathers; there are several varieties, including boards that have a cell phone module or a low-power radio module directly on board. A simple shield (or handmade protoboard setup) could be arranged to connect modules if you need more than one functionality at once (e.g. you might have a gateway node that requires both SMS and low power radio).
Very happy to chat more / answer any questions on this ramble / brainstorm!
Cheers!
Don
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Dan Beavers
Sep 27, 2016, 11:03:34 AM9/27/16
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I have a couple of additional thoughts on this.
1) Depth Sensor Proposal https://publiclab.org/n/13126 This may work
also. Experiments have not been performed yet to my knowledge so it may
not be a straight forward measurement. Of course either power for the
air pump or a regulated air source will be required. I would suspect
there would be no fowling issues with a continual air flow.
2) How will the wells be pumped? If a vacuum system is used, with a
one-way valve at the top of the well, then a vacuum sensor would
theoretically provide a depth indication whenever the well is pumped.
There would be a lot of noise during the pumping but soon after a pump
event ends a good reading might be obtained.
Dan
On 2016-09-26 17:54, Don Blair wrote:
> Hi Tobias,
>
> Your project sounds amazing -- thanks for sharing! I'm very interested
> to figure out exactly these sorts of questions, for similar applications
> (mostly farming right now). Here are some off-the-cuff thoughts ....
>
> *Networking topology. * I'd started to fiddle around with some relevant
> networking diagrams
> <https://github.com/dwblair/groundwater-monitoring-notes/blob/master/topologies.svg> to
> and by Edward Mallon
> <https://edwardmallon.wordpress.com/2014/03/27/adding-a-ms5803-02-high-resolution-pressure-sensor/>.
> *Microcontrollers.* If you're interested in using SMS or SMS+low power
> Post to this group at plots-wat...@googlegroups.com
> <mailto:plots-wat...@googlegroups.com>
> <mailto:plots-waterquality%2Bunsu...@googlegroups.com>.
>
>
> --
> Post to this group at plots-wat...@googlegroups.com
> <mailto:plots-waterqual...@googlegroups.com>.
1) Depth Sensor Proposal https://publiclab.org/n/13126 This may work
also. Experiments have not been performed yet to my knowledge so it may
not be a straight forward measurement. Of course either power for the
air pump or a regulated air source will be required. I would suspect
there would be no fowling issues with a continual air flow.
2) How will the wells be pumped? If a vacuum system is used, with a
one-way valve at the top of the well, then a vacuum sensor would
theoretically provide a depth indication whenever the well is pumped.
There would be a lot of noise during the pumping but soon after a pump
event ends a good reading might be obtained.
Dan
On 2016-09-26 17:54, Don Blair wrote:
> Hi Tobias,
>
> Your project sounds amazing -- thanks for sharing! I'm very interested
> to figure out exactly these sorts of questions, for similar applications
> (mostly farming right now). Here are some off-the-cuff thoughts ....
>
> networking diagrams
> <https://github.com/dwblair/groundwater-monitoring-notes/blob/master/topologies.svg> to
> sort through the various data flow options. Sounds from your
> description that you're already settled on the top two rows of that
> diagram -- sending data via SMS. One option is to have each well monitor
> sending data directly to the cloud via SMS (top row of diagram); or, if
> the bore holes are within a kilometer or two of one another and you're
> not on rough terrain, you might save SMS fees by using low power radio
> modules (RFM69, LoRa) to first send data from each well via low-power
> radio to an SMS gateway, and then to the cloud.
>
> *Power. *I worked on a project that used an Adafruit Fona (cell phone
> description that you're already settled on the top two rows of that
> diagram -- sending data via SMS. One option is to have each well monitor
> sending data directly to the cloud via SMS (top row of diagram); or, if
> the bore holes are within a kilometer or two of one another and you're
> not on rough terrain, you might save SMS fees by using low power radio
> modules (RFM69, LoRa) to first send data from each well via low-power
> radio to an SMS gateway, and then to the cloud.
>
> module) and a Riffle to transmit data to the cloud every 10 minutes (and
> sleep in-between), which lasted for about two weeks on a 2200 mAh
> battery
> <https://www.adafruit.com/products/1781?gclid=CjwKEAjwjqO_BRDribyJpc_mzHgSJABdnsFW87cGR9DbAB3tr4ZLwbmeEyCPJBJ2H3ZjOXXUvKzSihoCMtTw_wcB> --
> sleep in-between), which lasted for about two weeks on a 2200 mAh
> battery
> it lasted about two weeks. The sensor used in that setup was
> essentially the same circuit as the capacitive depth circuit I've
> described here <https://github.com/OpenWaterProject/riffle_328-depth>,
> essentially the same circuit as the capacitive depth circuit I've
> and so the overall power requirements for a capacitive depth sensor
> would likely be similar (things might change for the i2c sensor, but I
> don't think it would use more power). We can do the numbers in detail,
> but transmitting only once per day could extend the lifetime on that
> battery to over a month, I'd think. Then, of course, you could choose a
> larger battery -- e.g. a car battery could last you for years :) Or,
> you could use one of the available circuits out there (Adafruit sells
> them) for solar recharging. One advantage of using a large battery and
> servicing it infrequently is that you could obscure the monitoring tech
> from passersby, if that'd be useful (I've been surprised at what's been
> stolen / destroyed in rural New Hampshire :)).
>
> *Sensors. *Using the capacitive approach would be the least expensive
> would likely be similar (things might change for the i2c sensor, but I
> don't think it would use more power). We can do the numbers in detail,
> but transmitting only once per day could extend the lifetime on that
> battery to over a month, I'd think. Then, of course, you could choose a
> larger battery -- e.g. a car battery could last you for years :) Or,
> you could use one of the available circuits out there (Adafruit sells
> them) for solar recharging. One advantage of using a large battery and
> servicing it infrequently is that you could obscure the monitoring tech
> from passersby, if that'd be useful (I've been surprised at what's been
> stolen / destroyed in rural New Hampshire :)).
>
> option, but it's as yet unproven, and might (not sure) have trouble with
> such long depths (and with other factors, like changes in water
> conductivity, temperature, and, as you mention, bio-fouling). One (as
> yet half-baked idea) I thought of a few weeks ago was to use *two*
> capactive cables, one of them shifted vertically a fixed distance above
> the other (4 centimeters, say). The idea would be that if fouling
> occurred relatively uniformly across the wire, the difference in
> capacitance between the two wires could still be used as a unit of
> capacitance/length to assess the height of the liquid.
>
> Blue Robotics has developed a nice enclosure for a Measurement
> Specialties i2c pressure sensor (intended to be used in diving watches
> -- $20 on Digikey) -- the same sensor that has been used in several ROV
> projects <http://store.openrov.com/products/openrov-imu-depth-module>,
> such long depths (and with other factors, like changes in water
> conductivity, temperature, and, as you mention, bio-fouling). One (as
> yet half-baked idea) I thought of a few weeks ago was to use *two*
> capactive cables, one of them shifted vertically a fixed distance above
> the other (4 centimeters, say). The idea would be that if fouling
> occurred relatively uniformly across the wire, the difference in
> capacitance between the two wires could still be used as a unit of
> capacitance/length to assess the height of the liquid.
>
> Blue Robotics has developed a nice enclosure for a Measurement
> Specialties i2c pressure sensor (intended to be used in diving watches
> -- $20 on Digikey) -- the same sensor that has been used in several ROV
> and by Edward Mallon
> <https://edwardmallon.wordpress.com/2014/03/27/adding-a-ms5803-02-high-resolution-pressure-sensor/>.
> <mailto:plots-wat...@googlegroups.com>
>
> Public Lab mailing lists (http://publiclab.org/lists) are great for
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Kina Smith
Sep 27, 2016, 6:19:07 PM9/27/16
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You might also look into the Particle Electron for a way of connecting to the internet. https://www.particle.io/products/platform/cellular-iot-sim
It has a pretty well developed backend for sending data online. They typically use the data networks to transfer data, not SMS, so that may or may not work depending on cell signal and 3g availability. I havn't done this yet, but you should also be able to send SMS from them because you can interact with the cell module via AT commands.
Their backend is very easy to use to get data online though and they say their cellular service is 'worldwide'. Not sure what that means for Africa, but it could be worth asking. It'd might ease the development process a little, as dealing with Cellular modules can be frustrating at times.
I feel like there are better options if you require a network connection. The riffle is good at logging data locally, but it doesn't talk to the internet out of the box.
-kina
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Tobias Lunt
Sep 28, 2016, 2:37:29 AM9/28/16
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Hi all,
Wow, thanks for your terrific responses! Don, Dan, and Kina - you are the best. Any additional input from the list is also hugely appreciated. I’m going to reply to the list one more time here in case this thread is useful to others, but afterwards I’ll communicate directly with those who reply so as to avoid spamming everyone else.
A little more information about the project. The wells will use a low-tech hand pump, likely the India Mk 2 model, or more ideally, the afridev pump, but that’s less likely because it’s more expensive. With these pumps I’m not sure that a vacuum sensor would be a feasible approach but I’m open to being corrected on that!
Our priority is to make this solution as affordable and scalable as possible with near-zero maintenance - so consequently minimizing component costs and power draw are essential. I’m also sensitive to what Don mentioned about destruction or theft, which is pushing me away from solar (which also would need cleaning periodically). I wonder about including a simple hydrogenerator to take advantage of the water flow within the standpipe. If this could be done at low cost without disrupting flow too much, it would be a pretty elegant solution and might lower battery costs.
In an ideal world, we’d make a sensor that could be replicated at under $100 by anyone with access to a 3d printer and a little electronics know-how, in a way where the sensor didn’t need to be serviced for two years or so at a time…or more. There’s a partnership between google and charity: water that is doing this for flow measurement on these kinds of boreholes (with a $5 million investment from google.org). So we’re aiming high, but it seems like it’s possible.
I would definitely be open to testing the capacitance approach and/or manometer approach. At the end of the day, however, we need something that’s reliable and doesn’t need too much (if any) calibration at installation so that it’s super easy to deploy. It seems that using an off the shelf pressure sensor with open hardware for the rest of it may be an “easier" solution, but pricier. As always there appears to be a trade-off between plug-and-play and expense. But i’m definitely open to testing out new ideas!
Given the parameters and aims of this project, do you collectively feel like including a riffle in the module would be a good idea, or is it better to use other controllers and components (adafruit feather 32u4 fona, arduino uno + SMS shield, etc), especially when cost and power draw are concerns? What other components and considerations am I missing?
Anyway, thanks to all for your input. There is a lot of information to consider and build upon (open ROV, openCTD, Ed Mallon’s blog, MoMo, etc etc). And lots of upside potential if we can make this work. I very much appreciate your thoughts and help, and tolerance for beginner questions!
All the best,
Toby
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Patrick Hixenbaugh
Sep 28, 2016, 8:26:34 AM9/28/16
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I definitely appreciate seeing this discussion on the list - keep it going!
From my limited experience, I think the RTC on the riffle makes it a good choice for long deployment and battery life compared to something without one. It lets the riffle sleep in extremely low power mode between measurements. Curious to see other answers!
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Tobias Lunt
Sep 28, 2016, 8:55:20 AM9/28/16
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This is a great point, thank you Patrick. Something I hadn’t thought about. Other things I’m missing? Also, thoughts on advantages/disadvantages of adding an RTC to an arduino arrangement (e.g. DS3231, also here at adafruit, pretty cheap), vs sticking with a riffle? Also, any thoughts on Li-ion vs LiPo for the battery would be welcomed...
Thanks all for your input.
Toby
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Kina Smith
Sep 28, 2016, 3:44:43 PM9/28/16
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The RTC on the riffle does make it excellent for micro power applications. I feel like I read somewhere that the 32u4 tends to consume more current in its sleep modes (the MCU on the Feather). It's going to be a challenge to keep the costs below 100$ using off the shelf parts and including battery/Cellular modem. Is there enough money to have a custom board designed? As far as battery chemistry, if you're looking to save money and weight/size isn't a design constraint, why not go with a sealed lead acid? They're cheap and readily available everywhere.
Toby
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Tobias Lunt
Sep 30, 2016, 4:00:59 AM9/30/16
to plots-wat...@googlegroups.com
Thanks again to all for the input. I’m going to starting thinking more seriously about my approach over the next couple of months and then hopefully start building a prototype over the winter…I’m sure I’ll back in touch with this list between now and then.
My best,
Toby
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