Photos

My first solar powered pumping experiments (circa 2007) made use of ordinary electronic tap timers to impose some discipline on the pump.  However, these did not allow sufficient control and so, I embarked on a course to develop my own electronic device that could control the pump via a relay. My first breadboard prototype (November, 2011) is on the right with the first custom manufactured printed circuit assembly to its left.  This design used timer/counter ICs to implement the control functions.

The printed circuit assembly was mounted beneath the PV panel in a plastic box with the relay adjacent.

The next version (January 2012) still used a relay but it was mounted on the printed circuit assembly (leftmost) with the electronic circuitry which was completely redesigned to use a quad comparator IC for improved capability although using analogue circuitry.

When the Raspberry Pi computer was created in February 2012, I became aware that significant improvements could be made if control was implemented via programmable micro-controllers and power MOSFET switching devices.  The above printed circuit assembly was arrived at after several design iterations and allowed a pair of MOSFETs to operate in parallel to allow switching of high currents without use of a heat sink.  Recent improvements in power MOSFET technology have given rise to devices with very low on-resistance (eg IRL40B209) such that sufficient current (~20A at 12V) can easily be carried by a single device without needing a heat sink.  The IRL40B209 is also specified for switching up to 40V so it should be capable of controlling a 24V pump with a generous margin.  However, no testing has been conducted at 24V yet.

The above photo shows a rather overgrown installation adjacent to and slightly above a dam.  The 12V pressure pump being used here is typical in that it can self prime up to 2 or 3 meters lift.  The installation is located above the dam to put the pump out of harm's way when the dam gets flushed by heavy rain as it does from time to time.  For water inlet to the pump, a length of 1" rural poly pipe is anchored by a short trench and extends out into the dam.  At the end of this pipe there is a filter made from a 60cm length of 90mm PVC storm water pipe with many small holes (1mm) drilled in it, both ends capped and one end fitted with a check valve (foot valve). This solar panel is larger (90W) than I would normally recommend but the extra expense is justified by the fact that there is an electric fence energiser (not visible) sharing the solar system with the pump.  The stepping stone that can be seen in the foreground amongst the grass is the lid of the pump enclosure that is detailed below.

With the (heavy) enclosure lid slid open, it can be seen that the walls are concrete blocks sitting on a a concrete stepping stone (floor) and fixed in place by Liquid Nails adhesive.  There are 4 additional paving stones glued in place at the top of the walls to act as stand-offs to provide gaps that allow for ventilation, cable and hose entry.  The 28Ah battery is larger than I would normally recommend, the extra capacity being provided for an electric fence energiser that shares this installation.  The SmartSPR simply sits atop the battery, held in place by its connecting cables.  The pump is a 19 l/m 12V unit by Seaflo, a fairly recent Chinese entry to the market at around the $100 price point on Ebay.  I'm very satisfied with the performance of this pump so far.  Short lengths of 18mm garden hose are used to provide flexible connections to the fixed 1" rural poly pipes on both inlet and outlet sides.  The inlet side is fitted with a filter to prevent ingestion of grit.  The outlet side is fitted with a check valve to prevent back flow when/if the pump is disconnected for maintenance.