For sale we have our new 2016 12VDC REUK Solar Water Heating Pump Controller with LCD Display and Datalogger which retails at £38.95 on the REUK.co.uk website, but on SPECIAL OFFER here at a special low price of £25.95. The pump controller comes supplied with a temperature sensor for the hot water storage tank, a temperature sensor for the solar water heating panel. (If you require one or both of the sensors to be waterproof, send me a message).

This device is designed to monitor and control a solar water heating system used to heat domestic water, swimming pools, hot tubs, and similar, automatically turning on your circulation pump only when required. The backlit 16x2 LCD display constantly shows the measured temperatures as well as supplying system status information.

The new datalogging function added for this 2016 model keeps track of historical temperature sensor readings and stores the minimum, maximum, and average temperatures recorded by each of the temperature sensors since the datalog was last reset by the user. These values can be viewed at any time on the LCD display.

There is a 1 Amp maximum 12VDC output from the controller when the pump is to be ON. This output can then be connected across the coil of a relay of your choosing to actually do the switching of the pump. This can be a PCB type relay, a relay board, an automotive relay, or a solid state relay (SSR) according to the voltage and current specifications of your chosen pump.

The pump controller requires a constant 12VDC power supply - i.e. it cannot be directly connected to a PV solar panel - it must be connected to a 12V battery or a 12VDC plug in mains power supply (100mA-1A rated). 

Full details of this controller, its many user features, operation, and set up instructions are available here:  Solar Water Heating Pump Controller with LCD Display. Please read this information carefully and understand everything before making a purchase - feel free to ask any questions you may have.
The additional instructions for the new datalogger functionality are provided below:

Datalogger Instructions
  • In order to access the datalogger display, press the Override Button for half a second - pressing it for a few seconds engages the manual override. The display will then show the minimum, maximum, and average temperatures of the sensors (S for solar panel, T for hot water tank) 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 delete 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.
  • 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. 
Datalogger 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.
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