New Raspberry Pi Model B+

Posted on July 16, 2014 by neil

We have just received our new Raspberry Pi Model B+. This is not the Raspberry Pi 2 or C (which is likely to be released in 2017), but is instead a Model B with a few very useful changes and additions.

The biggest addition is a further two USB ports bringing the total up to four USB 2.0 ports. This is particularly useful since a mouse and keyboard would use all the ports on the Model B leaving no ports free for thumb drives, and other peripherals without the use of a secondary powered USB hub.

Raspberry Pi B+ can now be configured to output a total of 1.2 Amps in total (0.6A by default) from its USB ports (assuming a good quality 2A power supply is used). Therefore external hard drives can be used without the need for a powered hub.

The original SD card slot has been replaced by a micro-SD card which means no more SD card sticking out of the Raspberry Pi, and it is easier and cheaper to buy micro-SD cards.

A further 14 GPIO pins have been added to the 26 pins found on the Raspberry Pi Model B for a total of 40 GPIO pins for hardware projects. The layout of the first 26 pins has been kept the same for backwards compatibility.

Finally, power consumption has been reduced a little, sound quality has been improved with the audio connector changed to integrate composite video, and the overall layout of the board has been changed and mounting holes added to the corners of the board.

The processor and RAM (512MB) remain unchanged.

We will be doing some interesting projects with our new Raspberry Pi B+ over the next few weeks and months to make use of the additional functionality offered by this new model.

Pyboard Python for Microcontrollers

Posted on July 10, 2014 by neil

Pictured above is the Pyboard – an open source prototyping platform designed and manufactured in the UK. This board with its ARM microcontroller (STM32F405 clocked at 168MHz) is programmed using micropython a low memory usage version of the Python 3 scripting language.

The board has LEDs, microswitches, a built in accelerometer, and 30 general purpose IO connections (including 4 PWM, 14 ADC, I2C, and SPI pins) for connection to external components and analogue/digital sensors for your projects.

The board has 1MB of on board flash memory, 192KB of RAM, and also a micro SD card slot which can be used to store scripts and hold project generated data. It has a built in USB interface.

Pyboard fits in the marketplace somewhere between Raspberry Pi and Arduino. A Raspberry Pi is a full computer which means that it can be complicated to use, power hungry, and large in size. An Arduino is simple to use, has lots of useful GPIO and shields, and they are available in small versions, but they are not very fast and scripts need to be compiled on a PC before loading them to the Arduino. Pyboard is perfect for processor intensive stand alone projects – particularly for anyone who already has experience programming with Python.

Pyboard is just 33 x 40mm in size and weighs just 6g.

The official Micro Python website is here, and the tutorial which shows how to get strarted with Pyboard and Micro Python is here: Micro Python Tutorial.

New REUK Low Voltage Disconnect with Display

Posted on June 6, 2014 by neil

Pictured below is the new REUK Programmable 12V Low Voltage Disconnect with LCD Display. This device allows batteries and battery banks to be protected from being too deeply discharged, and also enables battery monitoring.

For full details, instructions for use, and to purchase, click here: REUK 12V LVD with LCD). It has been added to the existing low voltage disconnect circuits in the REUK Shop.

Valiant PremiAIR 4 Stove Fan

Posted on June 3, 2014 by neil

In our article Valiant Heat Powered Stove Fan published back in 2012 we reviewed the FIR300 Self-Powered Stove Fan from Valiant and showed how this device can help increase the temperature in the room being heated by a logburner or multifuel stove.

The reviewed FIR300 stove fan is pictured above on the left next to the new PremiAIR 4″ Stove Fan (FIR361) also from Valiant which we will soon be reviewing in detail.

The immediately obvious differences are the four blades instead of two which should increase the air flow, a new motor, and a more compact design with the motor housed within the heatsink rather than protruding out from it.

The heatsink on the new PremiAIR 4″ has a larger surface area with a new design for faster heat dissipation. Therefore more power should be available to the motor by the seebeck effect increasing the effectiveness of the stove fan.

When reviewing the FIR300 stove fan, we used an accurate digital thermometer and manually logged the temperature in the room minute by minute. For our FIR361 review we will put together a multi-sensor datalogger using a Raspberry Pi and/or Arduino to collect much more data for analysis so that the effectiveness of the fan can be judged – one sensor at sofa height, one at ceiling height, one close to the stove, etc.

UPDATE JAN 2014 – We have now published our detailed article: Valiant PremiAIR 4 Heat Powered Stove Fan Testing on the REUK website. In the end, rather than building another SD Card Datalogger for this project, we used a Raspberry Pi Model A+. We will be publishing a detailed article in the coming months on how we programmed and set up this datalogger (including the source code), and also how viewed the data in real time through a mobile phone browser.

Low Voltage Disconnect with LCD Display

Posted on May 20, 2014 by neil

Pictured below is our latest low voltage disconnect circuit with LCD display.

As with our standard programmable low voltage disconnect (LVD), this device is designed to protect batteries from being discharged too deeply and permanently damaged. The user can set the low voltage at which the output loads will automatically be switched off, and also the higher cancellation voltage above which the output loads will be switched back on again.

This particular LVD has a backlit LCD on which system information is constantly displayed. It is also used when setting the low and high voltage thresholds which makes things a lot clearer and simpler than using LEDs or a rotary switch to programme those in.

As shown above the display shows the measured battery voltage updated multiple times per second and given to 2 decimal places of resolution (and calibrated to be accurate to within +/- 0.02 Volts across the range 10-16V).

The system status is usually ON or OFF, but can also be LOW or HIGH when the battery voltage is transitioning one of the thresholds about to change the state of the system. The high and low threshold voltages are also permanently displayed.

In order to avoid the output cycling on and off too often (particuarly as the battery voltages can spike or dip depending on the loads they are powering) there is a time delay during which the voltage must remain under/over the voltage threshold before the system will change from ON to OFF or OFF to ON respectively. During that time delay the backlight of the display flashes as a visual indicator that the threshold has been breached. We chose to flash the display itself rather than flashing an LED either on the board or on leads, since it is much easier to panel mount just the LCD than to mount both that and an LED indicator.

This particular client-tailored LVD has a MOSFET directly switching the output loads which can have a maximum total rating of 3 Amps. We can also make this with a relay fitted on board for direct switching, or a lower rated output which can be used to energise a high current (or high voltage) rated relay external to the board – e.g. an automotive relay or a solid state relay (SSR).

This low voltage voltage disconnect with LCD is now available direct from the REUK Shop. Click here to find out more or to purchase now: buy REUK Low Voltage Disconnect with LCD.

We will shortly be adding a very similar unit with the addition of datalogging functionality. Over the last couple of years we have sold many LVDs with built in dataloggers (see here for an example: Low Voltage Disconnect with Display and Datalogger), and we now have refined things to the point that the product is ready for general sale. In the meantime, if you have any requirement for a low voltage disconnect with or without a display and with or without datalogging, please email neil@reuk.co.uk with details of your requirements.

Solar Water Heating Swimming Pool Controller with Display

Posted on May 7, 2014 by neil

Pictured below is another of our solar water heating pump controllers – this time with digital waterproof temperature sensors (DS18B20), and an LCD to show the measured temperatures of the solar heating panel and swimming pool as well as system status and for the user to programme in the settings.

As this controller is to be used in sunny Australia it includes a pre-programmed maximum temperature override to prevent the swimming pool from getting too hot. When the pool is measured to 31 degrees Celcius or hotter, the pump will not to be turned on again until the pool temperature has fallen to 28 degrees.

Pictured above is the LCD showing the solar panel temperature of 26 degrees C, and the pool at 32 degrees C. Therefore the pool is too hot and even when the solar panel temperature increases, the pump will not turn on.

At the bottom of the circuit board is a pair of screw in terminals which will be connected to the output from a 12V programmable digital timer. In the winter, the customer for this controller wants to be able to automatically run the pump at the same time each day for a certain time just to circulate water around the system.

If you need a solar water heating controller for any application, with or without a display, email neil@reuk.co.uk with details of your exact requirements.

12V Programmable PIR Timer with Override

Posted on February 6, 2014 by neil

Pictured below is a modified version of our standard 12V Programmable PIR Timer with 3A Output.

The standard version turns on an output after motion has been detected, and keeps the output on until a user programmed time has elapsed.

This new version retains all the same functionality as the original, but has the addition of a pair of screw in terminals into which the contacts for an external push to make button can be connected.

The software on the microcontroller has been modified for this version to provide manual override functionality. If the output is off (because no motion has been detected), pressing the override button (for more than half a second) turns on the output and the red LED flickers constantly.

To cancel the manual override, the override button is again pressed for more than half a second which turns off the output.

If the override button is pressed while the output is already on (from a recent motion detection event), then the output will be turn off.

If you need any type of PIR sensor linked timer/controller, email neil@reuk.co.uk with details of your exact requirements.

Solar Water Heating Pump Controller for Hot Tub with Maximum Temperature

Posted on January 7, 2014 by neil

Pictured below is another of our solar water heating pump controller variations. Again based on our 2013 solar water heating pump controller with relay, this controller is modified to use digital waterproof temperature sensors (ds18b20), and also to have a user programmable temperature limit.

This controller is designed to be used with solar heated hot tubs and jacuzzis. As the volume of water in a hot tub is relatively small (compared to swimming pools for example) it is possible for the water in the tub to become unpleasantly or even dangerously hot after an extended period of sunshine.

This controller has been modified to have a user programmable maximum temperature. When the temperature of the water in the hot tub reaches this maximum, the pump will turn off and stay off until the hot tub temperature has dropped by at least 2 degrees Celcius.

Programming the maximum temperature is simply the matter of holding the button to enter programming mode at start up, then pressing it X times where 20 + 2*X is the desired maximum. For example, 8 presses for a 36 degree Celcius maximum.

If you need a solar water heating pump controller for a domestic system, swimming pool, or hot tub, with or without an LCD display, email neil@reuk.co.uk with details of your exact requirements.

Playhouse Lighting Controller with LVD

Posted on January 6, 2014 by neil

Pictured below is the connection diagram for a controller we have built to be used in a child’s playhouse. The playhouse will have a solar charged battery which will be used to supply power to three LED spotlights with a light switch, a small fan to circulate air and prevent the playhouse getting damp or too hot, and a dual cigar lighter socket with USB sockets which will be used to charge battery powered gadgets.

As the playhouse will be used by children, safeguards have been fitted to prevent the battery from becoming excessively depleted and permanently damaged.

In order to prevent the lights being left on and forgotten, when the light switch is turned on, a timer starts and if after one hour the light switch has not been turned off, the lights turn off automatically and will not turn back on until the light switch is toggled.

The output from the controller to the LED lighting is regulated to 12.0V so that excessive voltage (particularly when the batteries are being charged) does not damage the voltage sensitive bulbs.

To reduce power consumption, the fan which is used to ventilate the playhouse is turned on for just one hour every six hours automatically by the controller. The output to the fan is not regulated as the fan is rated for use with up to 18V, and if the battery voltage is high it is because there is or has been a lot of sunshine. Therefore the faster fan speed will prevent the playhouse getting too hot and stuffy.

In order to prevent the battery from running too low on charge, an automatic low voltage disconnect is incorporated. When the battery voltage falls below 11.9V, the outputs to the fan and lighting turn off, and only turn back on again when the measured battery voltage exceeds 12.4V.

The cigar lighter / USB socket is connected directly to the battery as the gadgets being charged by it will not draw much current for long if left connected since their batteries will get full and charging will stop automatically.

If you need a controller such as this, or with any of the features it has, email neil@reuk.co.uk with details of your exact requirements.

Simple Low Voltage Disconnect with Two Outputs

Posted on January 6, 2014 by neil

Pictured below is a low voltage disconnect circuit with two outputs.

We make a basic low voltage disconnect (LVD) designed specifically for use with low voltage LED lighting which incorporates a low-dropout 12V regulator. This device ensures that:

the battery does not get damaged by running too low on charge. If the measured voltage falls below 11.9V the output loads are switched off and not switched on again until the voltage is measured to be 12.5V or above.
the LED lighting is not damaged by excessive voltage (>13V) – particularly important with solar powered lighting systems where battery voltage can get up to 15V.

The pictured LVD/regulator is different in that it has dual outputs. The LM2940CT-12 voltage regulator is limited to around 1 Amp of output load, so our standard unit is not suitable in cases where the total LED lighting load exceeds around 8-10 Watts. Where the total load is more than around 2 Amps, we use an LT1084CP-12 regulator on the output side, but these are very expensive. Therefore where the LED lighting load is around 10-18 Watts, and can be split into a pair of separate lighting circuits, we simply make a double output regulator and split the load.

If you need something along these lines, email neil@reuk.co.uk with details of your requirements.

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