This is our new 2016 REUK Solar Water Heating Pump Controller with LCD Display and Datalogger. Functionally very similar to our best selling 2014 Controller, this new controller retains the 16×2 backlit LCD to display the temperatures measured of the solar panel and of the water being heated, as well as displaying system status and set up information, but offers the added benefit of a datalogger to accurately keep track of the minimum, maximum, and average temperatures recorded by the two temperature sensors at no extra cost.
This controller can be used to control a circulation pump which pushes water through a solar collector (solar water heating panel) to heat the contents of a domestic hot water tank, swimming pool, hot tub, etc. The connection diagram is provided below.
Powering the Controller
This is a 12VDC powered device (10V to 15V), and so should be powered either by a solar charged or otherwise 12V battery or with one of our mains plug-in 12VDC power supplies. You cannot power this controller directly from a 12V charging solar panel as the controller needs a reliable constant supply, and a ’12V’ solar panel can easily output up to 21V.
The Temperature Sensors
For the 2016 Solar Water Heating Pump Controller we have chosen to continue to use digital DS18B20 temperature sensors. These give excellent accuracy and reliability, and are also readily available in a good quality fully waterproof version with 1 metre long leads attached.
This controller is supplied with non-waterproof temperature sensors. Please email firstname.lastname@example.org if you require one or both of your sensors to be waterproof as there is a small supplement (£1 per sensor) to pay for waterproof sensors.
The instructions for setting up and using the 2016 controller are as per the 2014 controller and are available here: Solar Water Heating Pump Controller Instructions. Below are the instructions for making use of the new datalogging functionality.
In order to access the datalogger display, press the Override Button for half a second. (As with the 2014 controller, pressing it for a few seconds engages the manual override.) The display will then show the minimum, maximum, and average temperatures of each sensor as recorded by the datalogger since it was last cleared by the user. The datalogger data will remain on display for around 30 seconds, or until the Override Button is pressed again for half a second.
To permanently erase all data from the datalogger, press the Programming Button for half a second while the datalogger is on the display. PRESS AGAIN TO CLEAR DATALOG will be displayed. Press the Programming Button once more within three seconds and the display will show DATALOG EMPTY. Do nothing, and the display will return to the datalogger without any data being deleted.
Note that once the datalog has been cleared, the previously stored data is permanently deleted and cannot be recovered.
While in manual override mode, the datalogger can still be accessed following the same instructions as above and it continues to be updated.
The temperature of the sensors is measured multiple times per second and stored in short term memory over the course of an hour. At the end of the hour, the collected data is written to long term memory where it remains even if the power to the controller is cut. Therefore, if you must disconnect the power from this controller, you will lose only up to one hour of the most recently collected data.
Technical Notes ds18b20 temperature sensors output a reading of -127 degrees C when the sensor is disconnected (unpowered), and 85 degrees C when the sensor is powered but is either out of range or there is problem with the 1-wire connection such as disconnection. On the standard screen, these readings will be displayed so that the user knows that there is a problem, but those values will NOT be saved as the minimum, maximum, or included in the average temperature calculations. This does however mean that if the temperature of a sensor is actually at exactly 85.0 degrees C, those readings will be ignored by the datalogger.
The reason the data is not written directly to long term memory after every temperature measurement is that this EEPROM (Electrically Erasable Programmable Read-Only Memory) built into the microcontroller has a specified minimum life of 100,000 write/erase cycles. Write to the same location in memory once per second and it could be worn out and unable to retain data properly within just a few days! By writing the data only once per hour, the usable lifetime of the memory for the datalogger will be measurable in decades.
Bespoke Solar Water Heating Pump Controllers
If you require a solar water heating pump (or other) controller which operates differently from this 2016 Controller with changed or additional features, please contact email@example.com with details of your exact requirements; for example, if you need a maximum temperature override, or more comprehensive/permanent temperature datalogging.
Pictured above is the 2016 Controller fitted with a 10 Amp relay for switching higher power (and/or higher voltage) pumps for example.