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 neil@reuk.co.uk with details of your requirements.

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 neil@reuk.co.uk with details of your requirements.

Poultry Egg Incubator with Humidity Sensor

Pictured below is a controller we recently made for use in a poultry egg incubator, designed to keep eggs within a very narrow specific temperature and humidity range for a few weeks. This is achieved using a heater, a fan, and a humidifier.egg incubator with humidity sensor, fan, heater, and humidifierThe eggs need to be turned at least three times per day every day except for the last few days before hatching. Previously we made a Controller for Poultry Incubator which had a motor which was turned on and off at different times of the day to turn the eggs. For this new incubator, the motor used is a very slow turning 12 VAC device makes 6 full rotations every 24 hours. That motor therefore did not need to be controlled with a timer – it is just left running at all times.

egg incubator controller status summary displayThe display for this controller shows the current measured temperature from the waterproof DS18B20 digital temperature sensor (read at 12 bit resolution = 0.0625°C resolution), and the humidity from a DHT11 sensor (within 5% accuracy). The DHT11 actually has a built in thermistor, but its temperature measurements are nowhere nearly accurate enough for this type of project.

The bottom line of the display shows the three devices being controlled – heater, fan, and humidifier respectively. In the image above, the heater is marked as being on. If the humidity level gets too low, the humidifier will be switched on. If the temperature gets too hot, the fan will turn on (and of course the heater will already be turned off by then).

Setting humidity range for poultry egg incubator

The user has full control over the thresholds at which the heater, fan, and humidifier will turn on and turn off. The temperature thresholds for the heater and fan can be set in steps of 0.2°C, and the humidity thresholds in steps of 2%.

For example, the heater could be set to turn on at or below 36.4°C and off again at or above 38.4°C. Then the fan could be set to turn on at or above 38.6°C and off again at or below 37.4°C. Humidity should ideally be around 60% (raising to 65% just before hatching), so the humidifier could be set to turn on at or below 56% and off again at or above 64% relative humidity.

display for egg incubatorWith all the thresholds programmed in by the user according to the requirements of the particular type of eggs to be incubated, a button can be pressed to show in turn the values programmed in – for example, above the humidifier is shown to be set to turn on at or below 43% RH and turn off at or above 70% RH.

If you need any kind of egg incubator controller (or the electronics for a temperature and humidity controlled humidor – functionally pretty much identical to an incubator!) – please email neil@reuk.co.uk with details of your specific requirements.

User Programmable Target Shooting Controller with Display

Pictured below is a target shooting controller which we recently made for a shooting club in Australia.

programmable shooting target controllerWe had previously made them a controller with fixed time series – for example, Standard Pistol 150s, 30s, and 10s, Centre Fire face target 3s then away for 7s repeating 5 times, and Rapid Fire 8s, 6s, and 4s. Other clubs in the area required something similar, but with flexibility in the timings.

shooting target controller display - start seriesWe therefore enhanced the software written for the original controller so that all of the different time series could be modified, reducing or increasing the time that the target faced the shooter by the operator at the range to meet specific and potentially changing needs.

shooting target controller display modify series timingWhen the start button is pressed, the target turns away from the shooter. After 7 seconds the on board buzzer sounds for half a second and the target faces the shooter. (An external 12V buzzer or siren can be connected to the terminals on the controller board if a louder sounds is required). After the user programmed time, the target turns away from the shooter (again accompanied by the sound of the buzzer), and then a further 7 seconds later, the target is turned back to face ready for the next shooter.

If you need any kind of shooting target timer controller, please email neil@reuk.co.uk with your specific requirements. (Search for shooting on the REUK.co.uk website for information on some of the other turning target timers we have made in the past.)

Hen House Door Controller for Dawn/Dusk or Timer Operation

Pictured below is a controller we recently made to open and close the door of a hen house automatically.

hen house door controller with light detector for dawn/dusk operation and a programmable digital timerWe make a lot of door controllers for a range of different needs, and in general they either open and close the door depending on times programmed into a timer, or automatically detect dawn and dusk with a light detector and open or close the door accordingly.

With this particular controller, the user can select between two modes – dawn/dusk mode or timer mode. If timer mode is selected, the door will open when the timer turns ON and close when the timer turns OFF. In this way the door can be made to open and close at times convenient to the owner – for example opening the door later on weekend mornings so that the poultry do not disturb neighbours.

If instead the dawn/dusk mode is selected, the door will open at dawn and close at dusk, with the ambient light level for the day-dusk and night-dawn thresholds calibrated by the user when setting up the controller and light detector in its location.

If you need any kind of automatic door controller, email neil@reuk.co.uk with details of your specific requirements.

Turning Shooting Target Controller

Pictured below is a controller we recently made to control a shooting target for competitive shooting.target-turning-timer-crowleBased around an Arduino Pro Mini, this device is used to edge or face a shooting target according to preset and user-set timings.

Display for a shooting target controller

By default, the target is edge on to the shooter. When the start button is pressed, a relay closes which turns the target face on to the shooter. An accurate timer then starts and counts down the number of seconds the shooter has until the target is turned edge on again.

There are five preset modes – 165 seconds, 35s, 8s, 4s, and 2s. There is also a sixth mode which the user can programme to be any duration from 1 to 999 seconds.

Buttons are fitted to the circuit board, but there are also connectors to which external buttons can be connected so that the device can be fitted in a box with just the two external buttons and display visible.

If you need any kind of shooting target controller, please email neil@reuk.co.uk with details of your requirements.

Apple Store Fan Thermostat

Pictured below is a device we recently made to act as a fan controller for an apple storage room.apple store fan controlling thermostatThis device has two waterproof DS18B20 temperature sensors connected to it and a relay to switch the power to a fan which drives air from outside the apple store to the inside.

Whenever the outside temperature is measured to be a couple of degrees cooler than the inside temperature, the fan is turned on to drive the cooler air into the store. When the temperature differential falls to zero – i.e. the inside and outside temperatures are equal or the inside is cooler, the fan is turned off again.

This device also has built in frost protection to prevent freezing air from being blown into the apple store. If the outside temperature falls below 2 degrees C, the fan is turned off if it is on, and remains off until the outside temperature has increased by a couple of degrees.

If you need any kind of thermostat, email neil@reuk.co.uk with details of your requirements.

Programmable Automatic Plant Propagator Thermostat

In our March 2015 blog post Automatic Plant Propagator Thermostat, we showed a device we had made to automatically turn on/off 12V heat pads under young plants to prevent them from getting too cold (or hot).

This device connected the power to the heat pads when the measured temperature was below 17 degrees and off again when it had got back up to 23 degrees.

Different plants require different temperature ranges, so in order to meet those demands, we created the device pictured below.

programmable automatic plant propagator thermostatThis device has been enhanced with a user programming button enabling the user to set the low temperature threshold at or below which heating pads should be turned on, and also the number of degrees of temperature increase which must occur before the heating pads are turned off again. This gives a far more flexible thermostat for a wide range of plant propagation.

If you need a thermostat like this or similar for plant propagation thermostat, email neil@reuk.co.uk with details of your specific requirements.

Automatic Dawn Dusk Gate Opener

24v dawn dusk gate controller openerPictured above is a controller we made recently for a gate which is to be opened at dawn and closed at dusk automatically.

The controller is based around our standard REUK Dawn Dusk Relay Controller which uses a light detector and user calibration to detect the arrivals of dawn and dusk depending on measured ambient lighting levels.

This particular unit is designed to control a large gate motor which requires two contacts on its electronics to be shorted out (connected together) for one second to toggle the state of the gate – i.e. open the gate if it is closed, or close it if it is open.

When dawn is detected, the on board relay closes for one second which opens the gate. Then, when dusk is detected, the relay closes again for one second which closes the gate. The controller has a selection of timers and automation logic built in which prevent false dawns and false dusks being detected when there are clouds moving across the sun early and late in the day.

If you need any kind of dawn/dusk detecting controller, email neil@reuk.co.uk with details of your requirements.

Battery mAh Capactity Tester

low voltage disconnect with stopwatch for battery testingPictured above is a device we made recently to help estimate the capacity of 12V and 24V batteries. It is based loosely around our 12V Low Voltage Disconnect with Display, but with some major changes and functionality additions.

The customer for this device has a Farnell Electronic load which is capable of discharging batteries at up to 1.5kW (e.g. 12V @ 125A). He wanted to be able to use this to discharge batteries under test, to time accurately the discharge duration, and to automatically turn off the electronic load when the battery voltage falls below a user set level (for example 9.5V for a 12V battery).

This electronic load can be controlled externally by terminals on the back of the unit (Load Enable/Disable). If 5 VDC is connected across those terminals, the electronic load is enabled (turned on), otherwise it is disabled (turned off).

We therefore designed a device which the user can set with their choice of low voltage threshold. Then, when they press the Start Button, a regulated 5V is put across the terminals on the back of the electronic load which starts discharging the battery under test. At the same time, a stopwatch (created in software on the Arduino Pro Mini around which this controller is built) starts to display the number of days, hours, minutes, and seconds that have elapsed since the battery discharge began.

When the battery voltage is measured to have fallen below the low voltage threshold, the stopwatch stops, and the 5V signal to the electronic load is disconnected preventing the battery being discharged any further and potentially being permanently damaged.

The time on the stopwatch is saved in memory on our device and is displayed on the LCD until the user presses the reset button. It is saved in this way just in case after a multi-hour/day test has been completed, someone accidentally disconnects the battery from the timing device before noting the displayed timing results.

If you need any kind of voltage measuring device, low voltage disconnect, and/or timer, please email neil@reuk.co.uk with details of your exact requirements.