Apple Store Fan Thermostat

Posted on November 30, 2016 by neil

Pictured below is a device we recently made to act as a fan controller for an apple storage room.This 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

Posted on October 11, 2016 by neil

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.

This 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.

Irrigation Pump Timer with Low Voltage Disconnect

Posted on October 2, 2016 by neil

Pictured below is a device we made to control the pump of an automatic and often unattended irrigation system which is solar powered.

A programmable digital timer is set with the times that the pump is to be run – typically very early in the morning and in the evening. The pump for this particular irrigation system is relatively high powered, so could not be switched directly by the timer. Therefore a 10A rated relay is built into the controller.

As this system is solar powered and also often left unattended, it was essential to include a low voltage disconnect which will automatically prevent the pump from running whenever the measured battery voltage is found to be <11.9V. It then waits until the battery has been charged back up to over 12.5V before allowing the pump to run again.

LED indicators are included to show when the programmable timer is ON, the status of the low voltage disconnect, and also the status of the pump switching relay.

If you need any kind of irrigation pump timer or controller please email neil@reuk.co.uk with details of your requirements.

Testing Arduino Low Power Library with Pro Mini

Posted on August 2, 2016 by neil

In general when using an Arduino Pro Mini in one of our projects or products, we use an external LP2940CZ-5.0 voltage regulator instead of the on board regulator. This is because most things we make are for 12V battery systems, and the voltage from a 12V battery can get to well over 12V which is the specified upper input voltage for a Pro Mini. We have measured that one of these regulators with a 10uF capacitor across its 5.0V output, draws a quiescent current of only 0.079mA.

We have found that an Arduino Pro Mini, whether powered as described above, or with the on board regulator draws around 20mA @ 12.0V. This is very high for an always on battery powered device – it will use 500mAh (0.5Ah) of battery charge per day. Therefore, we are always interested in testing ways to minimise power consumption.

We set up the above test circuit with a 12V input, and our usual LM2940CT-5.0 regulator connected to an Arduino Pro Mini (16MHz / 5V). With a sketch containing just delay(8000); in the loop() function – i.e. the Arduino will wait 8 seconds, then wait another 8 seconds, then wait another 8 seconds, etc – we measured a current draw of 19.793mA @ 12.0V input voltage.

We downloaded and installed the following Lightweight low power library for Arduino – LowPower.h, and modified our test sketch as shown below to power down the microcontroller for 8 seconds within the loop.

This time we measured the current draw to be just 6.265mA @ 12.0V input voltage – a huge reduction of around 70% power consumption obtainable just by replacing the delay function with the powerDown function from the LowPower library.

We make a lot of dataloggers and monitoring devices which spend most of their time doing nothing – just waiting to take the next measurement. Therefore this low power library is a quick and easy way to reduce power consumption.

(Note that 8 seconds is the maximum power down duration that can be set with this library, but by using loops of multiple 8 second intervals in your sketches, you can create a low power consumption delay of as long as you want.)

If you use a Standalone Arduino on a breadboard directly powered by a battery pack of the correct voltage (i.e. no voltage regulation required), it is possible to run your Arduino off less than 50uA @5V (<1000th the power consumption of our tests above) and therefore power something for years with a AA cells or smaller. See here for an excellent article How to Run An Arduino For Years on a Battery from the Open Home Automation website where they use the JeeLib low power library with a standalone Arduino.

Solar Water Heating Pump Controller with SD Card Datalogger

Posted on July 28, 2016 by neil

Pictured below is a controller we recently made for a solar water heating system including a full datalogger.

This controller is based closely around our 2016 Solar Water Heating Pump Controller which already has basic datalogging functionality – minimum, maximum, and average temperature sensor readings displayed on the LCD.

To this we have added a micro SD card reader and a high accuracy DS3231 Real Time Clock (RTC). Every 15 seconds, the temperature of each of the sensors, the status of the controller, and the date and time are appended to a logging text file on the micro SD card.

The collected data can then be copied over from the SD card to a computer for detailed analysis, graph plotting, and so on.

This controller is based around an Arduino Pro Mini coupled with an LCD module, DS3231 RTC module, micro SD card module, and DS18B20 temperature sensors – all of which are readily available and economically priced. The only difficulties with this project came from the limitations of having only 32KB of flash memory (program space) on the Arduino Pro Mini – not a lot when including so many code libraries for the various modules and sensors as well as 750 lines of of project specific code for this complex datalogging controller.

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

Hen House Door Controller with Voltage Indication

Posted on July 19, 2016 by neil

Pictured below is another of our hen house door controllers – this time using a light detector to automatically detect dawn and dusk (user light level calibration), but with the addition of three battery voltage indicator LEDs.

This device will open and close a hen house door at dawn and dusk respectively when the measured ambient light level dictates. As this device is to be used with a small 12V battery, there is a chance that the battery will go low on charge preventing reliable operation.

Therefore we have added three LEDs (LED-1, LED-2 and LED-3) connected to flying leads so that they can be located somewhere easily visible while the controller itself is in an enclosure to keep it clean and dry.

When the battery voltage is measured to be greater than 12V, all three LEDs are turned on. When the voltage is between 11.8V and 12V, two are on. When the voltage is between 11.5 and 11.8V, 1 LED is on, and when the voltage is below 11.5V, no LEDs are on.

Each day when the user goes into the hen house to collect eggs, they have a quick visual indication of the state of the battery voltage so that they know when they need to think about recharging it.

If you need a hen house door controller, please email neil@reuk.co.uk with details of any specific requirements you may have.

Battery mAh Capactity Tester

Posted on July 16, 2016 by neil

Pictured 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.

Pictured below is an alternative version of the same thing, designed for use with 12V batteries, and provided with an OLED display on board.

This device works the same as the unit detailed above, but it has a smaller footprint, draws slightly less current from the battery itself, and it has a 1 Amp rated output to the electronic load @ 12VDC.

Pictured above is the display in standard operation showing the battery voltage at present, the low voltage threshold level (below which the electronic load will be switched off), and the running time so far.

Below shows the display when the device is in programming mode when the low voltage threshold can be set to a suitable value by the user.

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.

Automatic Irrigation System Timer Controller

Posted on July 16, 2016 by neil

Pictured below is a timer controller we recently made for a commercial irrigation system. This set up currently has four solenoid valves which when opened, water different regions in a large greenhouse. The number of solenoid valves will soon be increased to eight, so we had to make this controller work now with four valves, but be ready to control eight in the future. The controller is based around an Arduino Pro Mini.

The main controller board above drives four or eight of the 10 Amp rated relays on the relay board pictured below.

The small button at the top left of the main controller board can be used to toggle between four valve or eight valve operation as per the user’s requirements.

The valves are to be opened on a four hour cycle. With four valves, each valve is opened for 15 minutes in turn with a 15 minute delay between. Then after a two hour delay, the cycle repeats. With eight valves, each valve is opened in turn for 15 minutes with a 15 minute delay between each. The cycle then immediately repeats.

If you need an automatic timer controller for an irrigation system, please email neil@reuk.co.uk with details of your exact requirements.

Motion Sensing MP3 Player for Bird Hide

Posted on June 9, 2016 by neil

Pictured below is a device we recently made for use within a bird hide. When motion is detected inside the hide (via a small KC7783R PIR sensor module), a small MP3 player is turned on to play an educational soundtrack.

Because the length of the track may be changed, the device is fitted with a button which enables the number of minutes that the MP3 player is powered after motion detection to be adjusted so that the whole track is played, but no power is wasted by not leaving the MP3 powered when the track has played (since this is a solar PV powered set up).

If you need any type of motion sensing device or timer, please email neil@reuk.co.uk with details of your requirements.

Archery Timing Circuit

Posted on June 1, 2016 by neil

Pictured above is a timing circuit for archery competitions. Outdoor archers shoot six arrows in one go and are allowed 4 minutes. Indoor archers shoot three arrows in one go and are allowed 2 minutes.

The user can select one of two options – option 1 (outdoor) and option 2 (indoor) for either a two minute or four minute competition. The controller board itself has a red, yellow, and green LED on it and a small buzzer. There are also four relays which can control larger lights – e.g. when the red LED is illuminates, a relay will be closed which can control multiple large red lights. The same is repeated for each LED and also for the buzzer relay which can control multiple buzzers or sirens.

The Mode button is used to select the desired timing option. The red LED will be on while the controller is sleeping. When the Start/Stop button is pressed, the timer starts and the green LED turns on. With the outdoor timing option, the green LED stays on for 3 minutes and 30 seconds. With the indoor timing option, the green LED stays on for 1 minute and 30 seconds. Then the yellow LED turns on to give the archer notice that their time is running out. After 30 seconds the red LED turns back on again and the buzzer sounds briefly to indicate that time is up, and the device is reset ready for the next archer.

While the timer is running, you can press the Start/Stop button to cancel the timer and reset the controller. Alternatively, you can press the Pause button to pause the competition. The buzzer sounds 3 times quickly to indicate that the competition has been paused and then when the Pause button is pressed again, the buzzer sounds 3 times. The timer continues from where it left off exactly after the buzzer sounds for the third time.

If you need any kind of bespoke timer device, email neil@reuk.co.uk with details of your exact requirements.

REUK.co.uk

The Renewable Energy Website

Category Archives: arduino