Arduino stepper motor controlled slurry pinch valve

Some ideas for a motorized pinch valve using a geared stepper motor controlled by an arduino. Need to design and print mounting brackets, gearing mechanism, linear actuator, etc. Design parts in (e.g.) Autodesk fusion 360, print on 3D printer.

One idea…

Another idea

Example of an existing (air driven) pinch clamp

Requires flexible tubing — silicone?

Silcon® Silicone Tubing

3/4″ ID x 1″ OD Silcon® Tubing- US Plastics Item #: 54042

Like this pinch valve but turned by high-torque stepper motor driving linear actuator instead of manual knob.

Another example linear actuator mechanism…


3d printed rack and pinion
NEMA 17 High Torque Stepper Motor 78 oz-in  $12.49
Stepper Motor Easy Driver


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Protected: Biorealis/KRAAFT Digester Project

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Serenity Gardens Eco-village Plot Plan

Here is a link to a plot plan (1 MB pdf) of Serenity Gardens Eco-Village. It was current as of November 2013.

sgev for fb


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SGEV Sinkhole – Water reservoir

Idea:  Explore feasibility of damming the gully below this sinkhole, and using the resulting lake or pond as a water reservoir. Potential advantages include:

  • Positive way to control seasonal flows, site drainage and prevent further erosion damage. Working with the land, turning a liability into an asset.
  • Better use of land. Far more volume/capacity than using a bulldozer to build a pond on flatter (and thus more valuable for other purposes) land.
  • Depending on flows: Build a slow sand filter (details here) and pump station adjacent to it or just below. Or an “artificial aquifer” (details here).
  • Filtered water can either be pumped from this reservoir to lots above, or gravity fed to lots below.

Sinkhole at NE corner of Lot 35 / NW corner of Lot 31

Location on Plano

Location on Plano


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SGEV Gray water treatment

A good greywater recycling page — general info and links to other systems:

Another good graywater resource:

Artificial aquifer Tube Well: A way to filter pond or surface water:


Engineers without borders: A good page full of links to resources:

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SGEV Utility Guidelines Updated

Clause 3 – Utilities and Energy Plan

UPDATE: Jan 30, 2014:

ICE power is now available at the lower end of the property and will be extended up along the main road to the community center. As time goes on and more lots are sold, it will be extended to all lots.  This will be a somewhat less expensive capital cost than the originally proposed hydroelectric system — which also turned out to have a bunch of unexpected bureaucratic and permitting barriers to overcome. I will be rewriting the guidelines to reflect the changes as time permits…



  1. The community will be connected to the electric utility grid.
  2. The property includes multiple potential sources of renewable energy including a river with significant hydroelectric potential, solar, biomass and wind. We are currently in the process of assessing each of these resources – both the amount of energy available from each, and the cost to develop it.
  3. The current estimate, as of January 2013, is that the combined capacity of micro-hydro and solar PV alone will be able to supply 100% of the demand, at an average per household consumption of 6-7 KWH/day or 200 KWH/month. This is based on an assumed average of 2 KW of solar PV panels per household, plus 50 KW from the river. Hydro will dominate in the rainy season, solar in the dry season.
  4. 6-7 kWh/day is generally considered adequate to supply the basic needs of a well-designed, small, efficient home in the tropics. (To understand what this actually means, an online calculator is available at Users can plug in their own estimates of expected or desired daily use, and see how many panels would be required to supply the demand. The tool can also be used to estimate the percentage of the total demand supplied by each resource.
  5. Various interconnection schemes are being evaluated, each with its pros & cons. The simplest and most straightforward off-grid system – but also the most costly and least efficient – would be for everyone to have their own stand-alone system with solar panels and batteries, and then be hooked up to the centralized system for supplementary battery charging. Estimated cost for this type of system is about $4-5 per watt, or $8-$10,000 for a nominal 2 KW system. (Estimate assumes quality components, professional installation and quantity purchase discounts. Market prices continue to change rapidly.)
  6. A much better interconnection method would be an AC-coupled mini-grid, (as described in video at In this scheme, fewer panels and batteries would need to be purchased, and they would be installed in fewer, larger arrays, rather than on each house. This system can provide the same amount of power at lower cost because it has fewer parts, the panel arrays can be more optimally placed, and it allows more efficient use of the energy available. It can also be easily added onto as demand increases.
  7. The primary gain in efficiency derives from being able to move electricity around the grid from where it is produced to where it is needed, as both supply and demand fluctuate. In the first scheme above, this isn’t possible. For example, on a house that the sun is shining on but where no one is home (maybe even for weeks or months?), any excess energy (after the batteries are fully charged) cannot be fed back into the grid. It will just be wasted.
  8. Usage charges will be applied to cover operating and maintenance costs. As the system will be owned and operated by, and solely for the benefit of the community, usage charges will be set by actual cost of production. With solar and micro-hydro alone, these costs will be nominal, consisting primarily of labor cost to cover maintenance and repairs. If or when a diesel generator is added to the mix, there will also be fuel costs. Fuel crops have been planted on the property to offset these costs. (See for details.)
  9. It would be prohibitively expensive to build a system that could supply as much electricity as anyone ever wanted to use, so the supply to each home will be limited – both the instantaneous power draw (kW) and the total daily energy usage (kWh). A sophisticated metering system will be needed to regulate that usage. Appropriate products are being researched and evaluated (e.g.
  10. Members will be required to provide their own power (e.g. onsite solar panels, wind turbine, small, low-decibel generator, etc.) to meet the demand for any usage above and beyond the capacity of the centralized system.
  11. Efficiency is primary! Low wattage lighting (LED or CFL) and fans, low energy use refrigerators and gas stoves are mandatory. ”Tico” washing machines are encouraged, with clothes lines for drying clothes. Air conditioners will not be allowed to be connected to the mini-grid (nor are they considered necessary for a well-designed house at this altitude.) House plans are available that incorporate natural ventilation by way of cupola, roof monitor, or clerestory, interacting with well-placed operable windows and doors.

Clause 4 – Water Supply and Wastewater Collection

  1. A potable water line will be plumbed to each home site.
  2. Members are also encouraged to install onsite rainwater catchment systems – rain gutters, storage tank and filtration system. The goal is to not only supplement the centralized water system, but to provide redundancy and a measure of local self-reliance in keeping with the mission statement.
  3. A centralized sewer system will not be provided. Each house will have either a standard Costa Rican ‘biodigestor’ (septic tank) or a composting toilet (recommended). It is also recommended that graywater be treated onsite to a quality suitable for reuse for secondary uses (e.g. irrigation). To learn more about the benefits of urine separation and dry composting toilets, see They conserve both water and valuable nutrients, in keeping with the mission statement.
  4. Food Waste – All organic food waste will be composted or digested as part of the integrated food production system.
  5. All Members must participate in the Recycling and Reclamation Program. Residents should have a composting bin for food waste and any other compostable materials, along with recycling bins for crushed metal cans, glass and plastic bottles and/or containers. Members must take recyclable materials to the designated recycled waste collection site located at the main reception/parking area.

SEGV guidelines_3b.pdf (download file as pdf document)

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Battery technologies Li-ion vs Lead-Acid

A good article from HomePower:

Lithium-Ion Batteries for Off-Grid Systems

Are They a Good Match?
Issue Date Dec 16, 2012

For decades, lead-acid battery technology has been the mainstay of battery-based renewable energy systems, providing reliable storage and ample energy capacity. The most common battery used—flooded lead-acid (FLA)—requires regular watering to maintain electrolyte levels and venting to avoid the buildup of hydrogen and sulfuric gases. Additionally, FLAs are large and heavy, making battery replacement a challenging task for some systems.

With all of the recent action in the electric vehicle and personal electronics industries, lithium-ion (Li-ion) batteries have gained much attention. Here, we examine Li-ion battery pros and cons, and discover why most system owners won’t be swapping out their FLA batteries anytime soon.

Link to a BMS (battery management system) addresses issues described in article…

Link to Solar Liberator Indiegogo R&D effort. Invest $799 for a 500 watt plug & play appliance with 80 AH of Li-ion battery, available April 2014. Estimated retail price $1,000 or 2/watt

Solar Liberator dramatically reduces the complexity and cost of solar power. With an inverter, smart battery and control electronics packaged into an easy to use appliance, it requires no further setup. Solar Liberator comes in 500W, 100W and 25W variants.

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SGEV Solar PV notes and suppliers

Energy matters article comparing Solaredge Power optimizers and inverters with micro-inverters. Micro-Inverters Vs. Power Optimizers

“Micro-inverters had their share of the limelight, but the victor of the battle between solar panel level add-on electronics may be the power optimizers.”

Case Study from Photon magazine.

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Energy Storage, Load Balancing

Problem # 1:

Let’s say we have a river able to generate 100 kW.  In a 24 hour period, it produces 100 * 24 = 2,400 kWh.  Let’s also say that we have a total daily demand of 2,400 KWH, but it is not evenly spread out: for 16 of the 24 hours, it averages 50 KWh, and for the remaining 8 hours it averages 200 KWh.

If we just throttle the turbine back (typical control method) to 50% of its capacity during the off-peak 16 hour period, we will have just dumped 800 KWh, and will then have to have some other source of energy (solar? wind? diesel?) to make up the extra 100 KWh during the 8 hour peak period.  If the river is the ‘fuel’, we will have wasted a full third of it.  My first obvious thought was to add enough battery capacity to store the excess during off-peak.  But then the questions of cost, comparison between different storage technologies, balance between storage and generation, etc. arise.

Problem # 2

The sun shines and the wind blows unevenly throughout the day and throughout the year.  (See distribution pattern).  The peaks and valleys do not coincide with the usage peaks and valleys.  The challenge is to find the most cost effective, environmentally benign, sustainable and efficient way to store the energy when the supply exceeds the demand, for use when the demand exceeds the supply.  This storage can take many forms, and addresses both problems.

General how-to information:




A Costa Rican cooperative effort between Cummins Diesel, AASEA and Earth University:


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Holon design notes

Each cluster of 8-10 homes will be grouped around a centrally located “Waste to Energy Center”, or ‘holon‘.  Each holon will include electric generation capacity sized to supply 8-10 homes designed to use an average of 7 kWh/day, or 200 kWh/month.

The center consisting of a simple pole building with a sheet metal roof covered with solar panels and housing batteries, switch gear and a diesel generator.

  • Solar PV on roof
  • Central composter (a place to empty humanure and kitchen scraps from household toilets)
  • Walk-in cooler and freezer with lockers

Initially — until the hydroelectric system is brought online — energy sources will include only solar PV and diesel generators.

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