New REUK Differential Thermostat PCB

Posted on November 3, 2014 by neil

Pictured below is the latest (November 2014) version of our Differential Thermostat designed to be used in simple solar water heating systems, fan controllers moving warm air to cooler areas, and many other applications.

This device is based around this solar water heating pump controller design which we have been selling now for over 8 years. When the left hand side temperature sensor is measured to be hotter than the right hand side sensor, the up to 2 Amps output is turned on, and remains on until the temperature difference between the two sensors has fallen to zero.

This output can be used to directly power small pumps or fans etc, or can be used to switch a relay which can in turn switch high current or higher voltage devices.

Click here for more details and/or to purchase this new Differential Thermostat from the REUK Shop.

Raspberry Pi-Mote Mains Control

Posted on October 3, 2014 by neil

We are currently reviewing the Pi-Mote from Energenie. This is a small Raspberry Pi compatible radio transmitter board which can control up to four 13A mains sockets. We are reviewing the starter kit which includes two radio controlled sockets and the Raspberry Pi transmitter board (pictured below).

The Pi-Mote simply plugs onto the GPIO pins of the Raspberry Pi (compatible with both Raspberry Pi B and B+ but for the B it takes up all of the GPIO pins) and then a simple provided Python script is run on the Pi to supply an identifying control code to each of your sockets so you can subsequently toggle them on or off individually (or all at the same time) as and when you desire.

We sell a lot of low voltage controllers designed to be used to control mains powered devices – e.g. pumps in solar water heating pump controllers and in rainwater toilet flushing systems, immersion elements, motors, lighting, heaters, coolers, etc. The benefit of the Pi-Mote is that it is completely unnecessary to mess around with any mains wiring – you just plug the mains powered device(s) to be controlled into energenie radio-controlled sockets, and then use software on the Raspberry Pi to control the devices remotely.

We will be conducting a thorough review of the Pi-Mote and writing some Python scripts to provide some real world examples of its potential uses for a detailed article coming soon on the REUK.co.uk website. In the meantime, click here for more information or to buy the Pi-Mote Starter Kit now.

Automatic Pump Timeout Circuit

Posted on October 2, 2014 by neil

Picture below is an automatic timeout circuit we recently made for a rainwater collection system.

This is for use within a rainwater toilet flushing system with 3000 litres of rainwater storage capacity and a standard header tank in the loft with a ballcock. The pump is a 12V pressure activated pump of the type common in motorhomes and boats. As the toilets are flushed, the ballcock drops in the loft tank and the pump automatically switches on to refill the tank with water from storage butts in the garden.

If the rainwater supply runs out then the pump will run dry okay, but if it is left running dry for too long it will burn out. Therefore a device was required which would automatically cut the power to the pump if it was detected as having run for too long – more than five minutes. (It was not possible to use float switches to detect low water levels in the water storage vessels due to their location).

Handily the chosen pump outputs a 12V signal while it is running, so this can be used to monitor the status of the pump without the need to detect the increased current draw through the cables when the pump is running or the sudden dip in battery voltage when the pump switches on etc.

The device we made is fitted with a 10A rated relay with NC and COM connections – therefore when the relay is not energised, NC and COM are shorted out inside the relay and the pump receives power. When the relay is energised, NC and COM are open and so the pump receives no power.

When the pump is detected to have started running, a timer starts. If this timer gets to five minutes then the relay is energised cutting the power to the pump to save it from burning out. An LED is used to let the user know that this has happened and they system has to be powered off and then on again to reset it after the pump has been checked and the water stores replenished.

As the rainwater storage is also sometimes used to water gardens from a connected tap, the device also has a manual override. Pressing and holding the button for one second triggers the override and then the pump can be run for as long as the user wants until the override is cancelled with the button.

If you require any kind of rainwater pump and/or monitoring system, email neil@reuk.co.uk with details of your requirements.

Poultry Lighting Controller with Low Voltage Warning

Posted on October 2, 2014 by neil

We have been selling poultry lighting controllers for the last eight years designed to increase egg production during the long nights of winter. See here for details: Poultry Lighting Controllers.

Pictured below is a modified version of our standard Mark 3 lighting controller (sold here: REUK Super Poultry Lighting Controller) to which we have added a low battery voltage warning LED.

This modified version is designed primarily for use in lighting set ups where a solar panel is not used, and so the battery has to be charged by the user. When the battery voltage powering the controller and connected lighting falls below 12.0V, the red LED turns on to show the user that they need to recharge the battery as soon as possible to ensure reliable operation and battery longevity.

Contact neil@reuk.co.uk if you need any kind of poultry lighting controller with details of your exact requirements.

Low Voltage Disconnect with Dual Regulated Outputs

Posted on October 1, 2014 by neil

Pictured below is a low voltage disconnect circuit with two individually switchable 12V regulated outputs ideally suited for use with voltage sensitive LED spotlights and similar in battery powered systems.

This device is effectively a dual output version of the 12V Regulator with Low Voltage Disconnect which we sell in the REUK Shop. Each output has its own low dropout 12 Volt regulator (LM2940) and can supply up to 1 Amp.

This particular dual unit is most suited to LED lighting scenarios in which there are two strings of bulbs which you need to be able to switch on or off individually – i.e. String 1 on, String 2 on, or both String 1&2 on.

Should the battery voltage fall below 11.9 Volts then the low voltage disconnect will cut the power supply to the outputs until the battery voltage has gone back above 12.5 Volts.

We sell a huge range of low voltage disconnects, 12V regulators, and mixtures of the two, so please contact neil@reuk.co.uk with details of your exact requirements if you cannot find what you need in the REUK Shop.

East West Solar Water Heating Pump Controller

Posted on September 25, 2014 by neil

We have recently finished work on a new solar water heating pump controller to be used where the array of solar water heating panels is split between an East and a West facing roof instead of the more typical single South-facing (in the Northern Hemisphere) solar array. This controller has been based around our 2014 Solar Water Heating Pump Controller with Display with some additions and changes.

This controller has connections for three waterproof digital temperature sensors – one for the East array, one for the West array, and one for the hot water tank (or pool).

The customer for this controller did not want to have the water flowing through both solar arrays at the same time to prevent heat collected on the hotter sunny side of the roof from being immediately radiated away from the cooler side. Therefore his system features two solenoid water valves which, when the pump is turned on, will ensure that water only flows through the hotter of the two solar heating arrays.

The display (LCD) for this controller shows the three measured temperatures on the top line, the temperature difference between each solar array and the hot water tank (or pool), which if either of the valves is open (therefore also indicating that the pump is running), and the temperature difference (diffON or diffOFF) required for the system to change state (i.e. for the pump to turn on or off).

In the above photograph, the valve on the West side is open, and the west solar array is +5.8 degrees Celcius hotter than the hot water tank. When this temperature difference falls below 4 degrees (diffOFF), as the East array is relatively cool (just +1.2 degees hotter than the tank) the West valve will close, the pump will turn off, and the display will now show diffON – the temperature difference required before the pump can be turned on again. (If the East array had been hotter than the tank by more than diffON at this time then the pump would keep going, the East valve would open and the West valve would close).

This controller also has a manual override facility which lets the user force the pump to run with the East valve open, the West valve open, or even both valves open at the same time – for example while testing. The values of diffON and diffOFF can be set by the user as per the standard 2014 solar water heating pump controller.

If you need a controller like this (or any other solar water heating pump controller), please email neil@reuk.co.uk with details of your exact requirements.

Vineyard Frost Detection Warning Indicators

Posted on September 18, 2014 by neil

Pictured below is a frost detection warning light system we have been putting together to be used in vineyards (though it could of course be used for any other temperature sensitive crops).

This device takes a 12VDC power input, and connects to a waterproof DS18B20 digital temperature sensor. On the output side are three 12V outputs which will be connected to three 2.4W LED lighting units (one red, one yellow, and one green) and mounted on towers attached to the vineyard posts so that they can be seen from up to 100 metres away. (In the photo above we are just using three individual LED bulbs of the relevant colours during testing and calibration.)

When the temperature is measured to be >+1 degree Celcius, the green light is on. When the temperature is from 0 to +1, the yellow light is on. When the temperature is between -1 and 0 the red light is on. When the temperature falls below -1 degree Celcius, the red light flashes.

Above you can see testing in progress. The bowl on the left contain water, salt, and ice (measured to be -5 degrees Celcius after half an hour in the freezer) and the bowl on the right just ice and water (measured to be just above 0 degrees Celcius). The red LED is in the middle of flashing to indicate that the measured temperature is below -1 degree Celcius.

We have made multiple identical units for this particular vineyard which will be distributed around the area making it possible for the vintner to know immediately where any pockets of frost are located.

If you need any kind of thermostat, low/high temperature warning system, or temperature datalogger, email neil@reuk.co.uk with details of your exact requirements.

Thermostat with Datalogger and LCD Display

Posted on September 6, 2014 by neil

Pictured below is a thermostat we have just completed which includes an LCD display and temperature datalogging to a micro-SD card.

This will be used to control and monitor a small (4′ x 4′ x 6′) shed cooling system. The cooling parts of a second hand fridge have been mounted to an inside wall of the shed, and this thermostat with its digital temperature sensor and relay is used to turn the cooler on and off as and when required to keep the shed cool.

The display shows the current temperature of the shed and the system status. The user can set the high temperature and low temperature thresholds at which the cooler will be turned on and off respectively; and their chosen thresholds are displayed on the bottom line of the display.

Every 30 seconds the temperature of the sensor and the cooler status (on=1, off=0) are logged (written to a csv text file on a micro-SD card) for later analysis on a computer using Excel or similar.

If you need something similar to this, or anything else utilising temperature datalogging, monitoring, and control, email neil@reuk.co.uk with details of your requirements.

Dawn Dusk Lighting Controller with Regulated Output

Posted on September 4, 2014 by neil

Pictured below is a modification of our standard Mini REUK Dawn/Dusk Lighting Controller which has the addition of a regulator on the output so that it can be connected directly to LED lighting, and connections to enable a PV solar panel to be connected to the battery via the board.

We used an LM2940CT-12 regulator on the output side which will supply up to 10 Watts of 12.0V output to protect sensitive LED lighting from excessive voltage from the solar charged battery. (If the battery voltage falls below around 12.3V, the output voltage will fall to around 0.3-0.5V below the battery voltage).

We added a Schottky Diode to solar panel input so that the battery will not drain charge through the solar panel at night. A Schottky type diode was chosen as only around 0.3V of solar voltage is dropped through it compared to the 0.6V+ typically dropped through a standard silicon type diode.

Header Tank Filling Pump Controller

Posted on September 3, 2014 by neil

Pictured below is a controller we have just finished for a customer. We make a lot of rainwater toilet flush pump controllers, but this one is a little different from the norm.

This controller is for a pump with its own integrated run-dry float switch protection. A second float switch is located in the header tank. When the header tank float switch goes low (as the water level drops), a user programmable (1 to 99 minutes) timer starts a countdown. When the timer has elapsed, the pump is switched on with the on board relay, and is run until the float switch goes high on the increasing water level.

This version will work well for situations in which water is taken regularly from the header tank, and in particular in situations in which water will be taken from the header tank a few times typically during the timer countdown after the water level first used – e.g. multiple people coming home at the same time and all using the toilet.

The advantage of this system is that only one float switch is needed in the header tank (and there is no need to estimate the time taken to fill the tank by the pump etc).

The disadvantage of this system is that sometimes when the header tank is not being used, the water level will drop because of evaporative losses or leaks in the pipework etc. To mitigate against this, we set up the controller to run the pump for a minimum of 30 seconds each time it is turned on, and also to require one continuous second of changed float switch condition before any action is taken so that turbulence is ignored and to avoid multi-switching (which could rapidly damage the pump).

If you need a pump controller for your well, sump, rainwater toilet flushing, etc, then please email neil@reuk.co.uk with details of your exact requirements.

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