Conservatory Cooling Fan Controller

We sell a wide range of types of differential temperature controllers which are primarily used in solar hot water systems. However, with slight modifications, they can also be put to good use in other scenarios.

thermostat for conservatory coolingPictured above is an Arduino Pro Mini based fan controller we made for use in conservatories and other sunny rooms to help to keep the temperature from getting too hot.

This device can be used to turn on an extractor fan when the temperature in the room gets above a user set value, and keep it on until the room temperature has fallen below a second user set value. By dumping excess hot air from the room, the room’s temperature can be kept in a comfortable range.

display for conservatory cooling fan controller

In the photograph of the device’s display above, the air temperature is showbn to be measured as 18.2C. The fan (which is currently off) will turn on when the air temperature goes over 25C, and then turn off again when the air temperature falls below 20C.

We have also previously made these types of thermostatic controllers to automatically drive hot air from a sunny conservatory into cooler regions of the house. An insulated conservatory can still get very hot even in the winter months, so sending the hot air to the cooler side of the house is an easy and cheap way to reduce heating bills.

Solar Water Heating Pump Controller – East West Aspect Collectors

Pictured below is a solar water heating pump controller which we recently made for use within a system which has two solar collectors – one on an East-facing roof and one on a West-facing roof.

solar water heating pump controller for use within a system with east and west facing solar collectors

We have previously made an East West Solar Water Heating Pump Controller for use in a more complex system which controlled valves which were used to select whether to take solar heated water from the East or from the West-facing collector. The above pictured controller however is just based around our 2014 Solar Water Heating Pump Controller, with the additional of a third sensor and a modified display output.

display for east west solar water heating pump controller

The standard 2014 controller will turn on the pump when the solar collector is a user programmed number of degrees hotter than the tank or pool to be heated. Our modified East/West version instead runs the pump whenever either the East or West-facing collector is that user programmed number of degrees hotter than the tank or pool.

The water in the system is pumped from the tank or pool, up through both solar collectors in turn, and back again in a loop. Therefore, this simpler version has the disadvantage that water from the hotter collector (or from the tank/pool) may cool a little in the colder collector as heated water flows through it. However, overall the system is pretty efficient considering the disadvantage of having to face collectors to the East and West instead of to the more optimal South (in the Northern Hemisphere) due to the orientation of the building.

If you need any kind of solar water heating pump controller, please email with details of your requirements.

12V Low Voltage Disconnect with Display and SD Card Datalogger

12V low voltage disconnect with display and sd card dataloggerPictured above is a low voltage disconnect device which we recently made for a client. It offers all of the battery monitoring, protecting, and datalogging functions and features of our REUK Programmable Low Voltage Disconnect with Display and Datalogger, but with the added benefit of an on board microSD card to store the measured battery voltage once per minute.

low voltage disconnect sd card datalogger

The voltage data is written to a simple text file on the SD card. When the battery is connected to the low voltage disconnect and powers it, POWER CONNECTED is written to the log file. Then each subsequent minute, the battery voltage is written to the file preceded by the number of minutes since the power was last connected. For example the line 6,13.98 indicates that 6 minutes after the power was connected, the battery voltage was measured to be 13.98V.

While the pre-existing basic datalogging of the LVD is useful for constantly displaying the minimum, maximum, and average measured voltages, every now and then it is good to have the option to copy the data from the SD card to a PC for more detailed analysis and plotting etc.

If you need any kind of datalogger, please email with details of your requirements.

Solar Water Heating Pump Controller for Distant Pool

Pictured below is our standard 2016 Solar Water Heating Pump Controller with Datalogger. We recently made a modified version of this controller for use in a particular situation where the standard unit would not be very efficient.

2016 SOLAR PUMP CONTROLLER WITH LCD DISPLAY AND DATALOGGER. Solar water heating pump controller with backlit display to show temperatures and system status information and a dataloggerIn this case, the controller was to be used to heat a swimming pool. The problem was that this pool was located 30 metres away from a garage where the controller would be fitted, with 50mm water pipes already installed running underground to and from the pool from the garage (on the roof of which were installed solar water heating panels). There was therefore no easy way to retro fit a temperature sensor at the pool – that would necessitate digging a new 30 metre long trench, fitting sensor cable into an armoured tube, and burying it.

It was however possible to fit a temperature sensor to the return water pipe where it emerged in the garage, but the contents of that pipe would cool down much faster than the large volume of water in the pool, and this would result in the pump being turned on frequently unnecessarily, often cooling the pool instead of heating it.

To get around this problem, the controller was modified to provide additional features. The key feature was that the pump would not be turned on until the temperature of the solar panel exceeded a user programmable value. When this threshold is reached, the pump is run for a user programmable number of seconds (TD) which circulates the water through the system sufficiently to get an accurate measurement of the temperature of the pool water. When TD seconds have elapsed, if the temperature differential between the solar panel and pool exceeds the user programmed differential (diffOFF), the pump will continue to run until the differential falls below diffOFF – standard operation for the 2016 controller.

If however after the test run of the pump, the differential is not high enough, the pump will be turned off, and the temperature of the pool sensor will be saved. For up to the next four hours this saved value of the pool temperature will be used rather than the sensor temperature (which will rapidly fall when the pump is turned off). The pool temperature over the course of 4 hours will not fall by more than a degree or two, so using this saved value is acceptable for efficiency. During the 4 hours, if the temperature differential exceeds the second user programmed differential (diffON), the pump will be run as per standard operation and after TD seconds the controller will start to use the current pool temperature sensor measurement instead of the previously saved value as the pipe in the garage will now be at pool temperature. The pump will continue to run until the differential falls below diffOFF.

If during the 4 hours, diffON is not achieved, the controller will wait until the solar panel temperature exceeds the user programmed temperature before running the pump for TD seconds again and repeating the above processes.

Overall these modifications (together with a few additional features not described above) will result in a far more efficient system than our standard controller would have given and less wear on the pump.

If you have any special requirements which are not met by our standard controllers, please email with details.

Replacing 30 Year Old Solar Hot Water Controller

Pictured below is the differential temperature controller fitted to a 1980’s solar hot water system. After many years of successful operation, this controller finally failed (pump stays on all the time) and needed to be replaced.

Old solar water heating pump controllerSomething functionally identical was required, at least externally for the benefit of the user, so we were tasked to build a differential controller with relay to switch a mains powered pump, and to include a power on LED indicator, a pump on LED indicator, and a physical switch to select between standard automatic operation and ‘override’ which forces the pump to run.

Circuitry found in 1980's differential temperature pump controller

The internals of the old controller are pictured above. It shows a simple system with mains power going in and coming out again on its way to the pump switched by a relay, a transformer to get low voltage DC from the incoming mains AC, a potentiometer which is probably there for the installer to set the temperature differential required between solar panel and hot water tank for the pump to be turned on or to zero the measured difference when the sensors are at the same temperature, and the connections (two core) for two temperature sensors which are almost certainly going to be thermistor type sensors. There is also an IC visible which will most likely is a microcontroller, a 555 timer, or a comparator.

The sensor leads (and all other leads) were soldered in place upon installation, and the sensor cables were run through walls and are therefore inaccessible. Since the existing cables were 2-core, we had to build the new controller using sensors with two connections – LM335 – rather than the 3 connection digital sensors we use in most of our controllers – DS18B20 temperature sensors.

Our 2013 Solar Water Heating Pump Controller is the most similar unit we sell to this existing controller, so used that as the foundation of the controller we built.

modified 2013 solar water heating pump controllerAll LEDs, buttons, and switches have to be external to the controller board, so these have extended leads which connect via screw in terminals. We supplied a plug in 12VDC power supply rather than fitting a transformer directly to the circuit board, and we added an LED which turns on when the unit is powered, and the override switch which can be used to force the pump to run. We fitted the programming button (used to set the temperature differentials at which the pump turns on and turns off) to the circuit board, but connected terminals in parallel with it so that an external button can be panel mounted now or at a later date.

If you need a modified version of one of our differential temperature controllers, please email with details of your requirements.

Low Voltage Disconnect for Glacial Movement Research GPS in Greenland

Pictured below is a special low voltage disconnect (LVD) device which we have been supplying for a few years for use by academic researchers in glaciology.

low voltage disconnect for glacial movement monitoring with GPS in Greenland

Solar charged batteries are being used to power GPS dataloggers on glaciers in Greenland. These GPS devices accurately record the movement of glaciers, and this (velocity) data can be used in a wide range of polar and climate change research.

The specific set up for which these LVD devices were designed has a 48 Watt PV solar panel charging a 60-100Ah 12V battery via a Sunguard solar charge controller.

In high polar regions, in the summer, the sun is in the sky 24 hours day, but in the winter is is below the horizon 24 hours per day. Therefore, during the winter months the battery cannot be charged. For the battery to still be usable in the spring it must retain some charge, so the GPS has to be disconnected before it overly discharges the battery.

The GPS modules have their own built in low voltage disconnect circuitry, but a step-up voltage regulator is fitted between the 12V battery and the GPS modules (which need 15+V to operate), so the GPS sees a steady consistent good voltage right up until the 12V battery is virtually dead.Glacier in Greenland - monitoring glacial moevement

In our standard low voltage disconnects, the output is turned off when the battery voltage falls and remains below a user set low voltage for 10 seconds. The output turns back on when the battery voltage reaches and remains above a user set cancellation voltage for 10 seconds.

For a solar powered system and often very limited daylight hours, this can see the output being turned on and off multiple times per day. This is not a problem for an LVD used with lighting for example, but the GPS modules used for this project create a new datalog file each time the power to the module is connected, and there is a 512 file limit. If over the course of the many months that the GPS module remains on the glacier unattended, the power to it is cut and restored more than 512 times, data will be lost which is not acceptable.

In order to prevent this problem, our low voltage disconnect engages as usual after 10 seconds of low voltage being measured ensuring that power to the GPS is rapidly cut if the voltage is low, but then the voltage has to remain consistently over the cancellation voltage for one hour before the power to the GPS module is restored. Doing this ensures that the GPS is only powered up when the battery is known to hold enough charge to make it worthwhile taking up one of the 512 available file spaces.

If you need any kind of special low voltage disconnect or voltage monitoring device, email with details of your requirements.

Dawn Dusk Henhouse Door Controller Instructions

Pictured below is the connection diagram for the Arduino based standard REUK Dawn/Dusk Henhouse Door Controller. This device is sold as shown including the light detector (non-waterproof), but NOT including the rollers switches and motor which you must source yourself. We recommend the following:

Connection Diagram

connection diagram for Arduino based dawn dusk hen house door opener

Choosing a Motor

The choice of motor is particularly important. We favour the high torque low RPM type of motors linked to above because they are very strong, slow moving, and they do not draw a lot of current. Most importantly, if they are prevented from turning, they still draw well under 1 Amp. Other motors may draw only a couple of Amps in normal operation, but if the door becomes jammed (debris, snow, ice, motor or mechanism seizing, etc) then they can draw very high currents which exceed the 10 Amp rating of the components used on this controller. We suggest that a 5 Amp fuse is fitted in the positive line between the 12V battery (or power supply) and the positive Power Input of the controller.
You will have to double check which way the motor turns to open/close the door, and reverse the connections to it from the controller if the motor is turning the wrong way – i.e. trying to open the door at night, or close the door in the morning.

Roller Switches

For the roller switches, pretty much any will do the job electrically, so you just need to ensure that the ones you choose are sturdy enough to operate reliably with the door mechanism you have put together. The switches need to be wired to the controller such that the terminals are shorted out (closed) when the switch is closed, and are open when the switch is open. Most roller switches have three terminals – a COM (common), an NO (normally open), and an NC (normally closed). You need to use the COM (usually found in the centre), and the NO.

Setting the Light Level Threshold

You have one thing to set up – that is the light level threshold at which you consider it to be the point between day and dusk (and therefore the point between night and dawn). This calibration option is only available between connecting the power to the controller and it detecting dusk – i.e. during what it considers to be day time.
To calibrate the light level threshold, press and hold the Light Level Calibration Button. The red and green LEDs will both turn on. When they turn on (after around one second), release the button. Whatever is the measured light level by the light detector at this time will be stored in memory as the light level ‘threshold’. The red and green LEDs will rapidly flash for 10 seconds to let you know that calibration has been successfully completed. From now on, whenever the light level is brighter than this threshold it is ‘day’, and whenever the light level is darker than this threshold it is ‘night’. Obviously you need to go through this process at dusk when the ambient light level is the same as you want it to be when the door is to close. You need to have the light detector in the actual location and orientation it will have in operation.
The light detector is not waterproof and must therefore be protected from rain and also condensation. Ideally face it in a Southerly direction – if it is facing East or West then then ‘dawn’ will be detected late or early respectively.

Using the Door Controller

The controller starts off assuming that it is day time, so you want to start off with the door open. If the light level falls below the threshold you have set, the red LED will turn on. If the light level remains below the threshold continuously for 10 seconds, then the controller will assume that it is now dusk and will run the motor to close the door until the lower roller switch closes. The controller will then sleep for 2 hours to avoid a false dawn detection if the sun brightens up as it gets close to the horizon (as it often seems to do). During this time the red and green LEDs will blink so you know what is happening.
When the controller finishes sleeping, the ambient light level will be much lower (since it will be 2 hours further into the evening). The light detector will then wait until dawn. When the measured light level exceeds the threshold, the green LED will turn on. If the measured light level remains higher than the threshold continuously for 10 seconds, the controller will assume it is now dawn and run the motor to open the door until the upper roller switch closes. Again the controller will sleep for 2 hours to avoid false dusk detections.
This process will repeat every day.

Further Information

If you have any questions about the connection, setup, and use of this controller, email

Animal Feeder Motor Controller with Timer

Pictured below is a motor controller we made recently for an automatic animal feeder system.

Animal feeder motor controller with timerThe feeder itself has two buckets on a belt which is connected to a 12VDC motor. When the motor is run, the buckets scoop up feed from a container and drop it into a trough for the animals. If the motor is left running, more and more feed will be scooped up and added to the trough, so a controller was required to ensure that each time the motor was run, the correct amount of feed was deposited in the trough reliably.

The motor needs to run for less than one minute each time, therefore a 12V programmable digital timer was chosen. The user can programme the timer to turn ON for one minute at the exact times of day that the animals are to be fed.
A switch was added to the mechanical setup which closes each time the buckets have completed one full revolution – i.e. picked up and deposited feed.

The central controller waits for the timer to turn ON. Then it turns on the motor, and keeps it running until it detects the mechanical switch closing indicating that the feed buckets have been through one rotation.
When the timer next turns ON, the switch status is ignored for the first couple of seconds (since it remains closed until the motor has moved the buckets around a bit), and then the controller keeps the motor running until the switch closes again…another feed complete. This automatic feeder will keep the animals fed the right amount at the right times of day for as long as there is feed left to be scooped up.

If you need any kind of timer or motor controller, email with details of your requirements.

Multi Level Low Voltage Disconnect with Display

Pictured below is a special multi level low voltage disconnect controller which we recently made. As with our other low voltage disconnect products, this device is designed to automatically disconnect loads from a battery when the battery voltage drops below a user set threshold. The loads are then reconnected when the battery voltage has risen above a second higher threshold.

Three level low voltage disconnect (LVD) controller with relays and display

What makes this low voltage disconnect special is that it can be programmed with three independent pairs of voltage thresholds, and control three sets of loads. If you have a selection of devices powered from your 12V battery, some will be more important than others, and some will use more power than others. Having multiple LVD voltage thresholds allows you to choose which devices should have their power cut first as the battery charge level goes down. Cutting the power to high consumption low importance devices leaves more charge available to keep the more critical devices going for as long as possible.

If the battery was powering a large amount of lights for example, one light could be connected to the lowest voltage threshold output to stay on as an emergency light, while the rest of the lights could be turned off at a higher threshold. On a boat, the fridge and navigation system would be connected to the lowest threshold output, while the television and most lighting could be connected to a higher threshold.

display for three level low voltage disconnectThe standard display shows the voltage measured on the battery, as well as the status of the three outputs corresponding to the Bot (Bottom), Mid (Middle), and Top ranges. In the image above, at a battery voltage of 12.32V, the Top range is off while the other two remain on.

all outputs off low voltage disconnect

At a lower voltage (10.55V shown above), all three outputs are off.

all outputs on low voltage disconnect

…and then with the battery voltage fully restored (13.53V while being charged), all three outputs are on.

By pressing the View Thresholds button, the user set voltage ranges are shown on the display.

Showing the voltage ranges for the multi threshold low voltage diisconnectAbove for example the bottom range has the low voltage disconnect at 11.0V and the cancellation voltage (at which the output will be turned on again) at 12.2V.

programming the multi threshold low voltage disconnectProgramming the six voltage thresholds is done using the two on board buttons. These thresholds are stored in non-volatile (long term) memory and are therefore not lost when/if it is disconnected from the battery.

When the battery voltage is measured to have moved above or below a threshold which will result in an output status changing, the back light of the display flashes on and off. The voltage has to remain constantly on the new side of the threshold for 10 seconds before the output status will actually change so that any spikes and dips in measured voltage do not result in devices being turned on or off unnecessarily.

If you need any kind of low voltage disconnect, battery monitor, and/or datalogging device, email with details of your requirements.

Intel Curie tinyTILE – Mini Arduino 101

intel curie tinyTILEPictured above is the new tinyTILE development and production platform featuring the Intel Curie module. This board is a miniature version of the Arduino 101 and measures in at just 35 x 26mm (1.38 x 1.02 inches), and has been designed to fit on prototyping breadboards.

The tinyTILE board can be programmed using either the Arduino IDE or Intel’s own software – the Intel Curie Open Developer Kit (ODK), and the I/O connections are functionally identical to those on the Arduino 101.

With its small size, low-power consumption, array of motion sensors (6-axis sensor with accelerometer and gyroscope), and Bluetooth Low Energy (BLE), tinyTILE should be ideal for battery powered wearable devices and any other IoT projects involving motion monitoring.

tinyTILE has a 32-bit 32 MHz Intel Quark SoC, 384 kB flash memory, and 80 kB SRAM. It also includes a digital signal processor (DSP) offering quick pattern matching identification of actions and motions.

tinyTile can be USB powered via its micro-USB connector. The board has its own internal 3.3V regulator and 3.3V (but 5V tolerant)  I/0 connections.

tinyTILE is available now from (US+) and (UK) amongst others.