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.

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 neil@reuk.co.uk 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 element14.com (US+) and cpc.farnell.com (UK) amongst others.

Hen House Door Controller with Voltage Indication

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.

Hen house door controller with low voltage indicationThis 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.

Introduction to TM1638 Display Module for Arduino

Pictured below is an electronic display module we have been testing out recently.

TM1638 Arduino Display Module

Available at under £2 including delivery (see here: buy TM1638 module), the pictured device offers 8 LEDs, 8 input buttons, and 8 7-segment LED display digits which can be fully controlled with just 3 pins from your Arduino (or other microcontroller unit).

We are looking at these to offer alternatives to the LCDs (liquid crystal displays) we currently use in our solar water heating pump controllers and low voltage disconnects in particular, since the two sets of 4 digits on these modules’ displays can show a voltage to two decimal places plus other information, or two temperature sensors readings also to two decimal places simultaneously. Seven segment displays are much more readable from a distance, and the availability of 8 LEDs and 8 user input buttons opens up many new possibilities.

Initial results of testing have been very positive. If you are interested in getting started with these modules and Arduino, an excellent starting off point is this excellent article: Arduino and TM1638 LED Display Modules from the Australian site tronixstuff.com. All you need is an Arduino board, the Arduino IDE (the software required to programme your Arduino), and the TM1638 library available here.

Programmable Target Shooting Timer Relay Board

Target shooting relay timer controller with display

Pictured above is a target shooting timer relay controller with programmable options for different shooting programmes. With this device the user can set the number of seconds that the target is to remain edge-on to the shooter and how many second that it is to remain face-on to the shooter, and also how many cycles of edge and face the shoot will comprise.

Target shooting timer display

The backlit display with this device shows the user programmed number of seconds that the target will edge (E) then face (F), and the number of cycles (C) for which it will be repeated. It also shows the current status of the target.

There are two buttons on the controller. The MANUAL button is used to enter the programming mode to set the timings for the programme and also to toggle the target manually between facing and edging. The AUTO button is used to start the programme. The programme starts by edging the target, and finishes also with the target edged.

target shooting timer relay display in action

While the shooting programme is running, the display continues to show the user set programme values and the status of the target. It also shows a running countdown of the time remaining during this part of the cycle, and also which cycle the shooter is currently on.

If you need any kind of automated user-programmable timer for target shooting, please email neil@reuk.co.uk with details of your requirements.

24V Low Voltage Disconnect with SD Card Datalogger

Pictured below is a low voltage disconnect device we recently made for use with a 24V battery system. In addition to the user-programmable low voltage disconnect functionality and LCD display of our standard Programmable 12V LVD with Display, this modified 24V device also includes a full datalogger, storing measured battery voltages at regular intervals to a micro-SD card for later analysis.

24V Low Voltage Disconnect with SD Card DataloggerThis particular unit is destined to be used by a company specialising in the maintenance of the UK’s transport infrastructure; with the low voltage disconnect used to protect batteries from being overly depleted, and the datalogger used to track the rise and fall of battery voltage over time.

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

Solderless Power Supply Module for Breadboard

We recently came across this handy little power supply module designed and built for use with prototyping breadboard (MB102 size) by YwRobot in China.

breadboard power supply moduleThis is a very useful device for anyone getting started with electronics thanks to its low cost (approximately £1 delivered) and ease of set up and use.

The module simply plugs into a breadboard and gives two pairs of rails which can be configured to give you 2x5V rails, one each of 5V and 3.3V, and you can also set one or both pairs of rails to 0V.

mb102 breadboard power supply modulePictured above we have used the small yellow jumpers to set one pair of rails to 3.3V/0V, and the second pair of rails to 5V/0V. The board is then ready to supply a few hundred mA at 3.3V and 5V to any project you may want to prototype/build on the breadboard.

The module is powered via USB. Virtually everone now has a micro-USB charger at home for mobile phone and table charging etc, so it is surprising that they chose to use a full size USB-A connector. It would have been much better to go for a micro-USB connector.

The module has two low drop linear voltage regulators to supply the 3.3V and 5V outputs. When we tested this with a USB power supply outputting 5.46V, we measured 5.123V on the 5V rail, and 3.286V on the 3.3V rail.

If your USB power supply provides less than 5V (or more likely, you have less than 5V after losses in a long/cheap cable) the 5V rail will always be a few tenths of a Volt lower than the incoming voltage – therefore you cannot guarantee a reliable 5.0V output from this module when powered via USB. Similarly, it is best not to use this connected to a USB port on a PC as the voltage of PC USB ports can jump around a lot depending on what the PC is doing at any particular instant.

There is however a standard DC barrel jack for DC input power. Using a standard 6V DC power supply should give you a full stable 5V output from the module.

There is an on/off switch on the module, with a green LED to show the current status. This is useful not just because it saves you from having to unplug or switch off your USB power supply at the power point, but also because the capacitors in a power supply retain charge after you unplug the power supply and this charge will feed through the module into your electronics project until those capacitors have discharged. That could have unforeseen consequences as the voltage input to your circuit drops.

The quality of the components used and the build quality are as you would expect from a product offered at such a low price, but these modules are still an excellent first purchase for anyone interested in circuit prototyping.

These modules are available on their own, or together with a suitable breadboard and jumper links as a complete starter package. Click here for more information or to make a puchase of one of these power supply modules.

Dawn Dusk Hen House Door Controller with Timer Override

Pictured below is a hen house door controller we recently made for a customer which is a modified version of our standard Dawn Dusk Hen House Door Controller.

hen house door controller with light detector and timer overrideThis controller will automatically open a hen house door at dawn and close it again at dusk. Dawn and dusk are detected via a light detector, and the user can calibrate the light level at which they consider it to be the transition between day and dusk and between night and dawn to meet their needs.

The modified version pictured above has the additional benefit of a programmable digital timer. We make hen house door controllers with light detectors which automatically detect dawn and dusk, and we also make them with programmable digital timers so that the user can instead set the exact time that the door is to open and close. This particular controller is our first which has both a light detector AND a programmable digital timer for maximum flexibility.

The purchaser of this controller expressed a wish to be able to have the hen house door close at dusk automatically, but also to be able (sometimes) to open the door later (or even earlier) than dawn. Therefore, in the summer when dawn could be at 4am, the timer can be used to keep the door closed until 6am or later to keep the noise down and avoid disturbing neighbours. The programmable digital timer we used can be set with different timings for weekdays and weekends, so for example, the door can be kept closed until much later in the morning on the weekend to keep the noise down.

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

New Raspberry Pi 2 Model B – Six Times More Power

The new Raspberry Pi 2 Model B has just been released, and promises to be six times more powerful than the previous Raspberry Pi models.

Raspberry Pi 2 Model BThe original Raspberry Pi was released around 3 years ago, and since then technology has moved on and competitors have joined the marketplace. The single core 700MHz processor and 512MB of RAM of the recently released Raspberry Pi A+ and B+ make them feel quite sluggish and out-dated, and there are many applications which cannot be used as they run so slowly.

The new Raspberry Pi 2 Model B though has a quad-core 900MHz processor (ARM Cortex-A7) with a full 1GB or RAM,  effectively turned the Raspberry Pi into a low spec PC capable of running the new Windows 10 (which will be offered free of charge for Raspberry Pi to makers!) and the full range of ARM Linux distributions.

The new model is fully backwards compatible with previous models, it will just run everything much faster. You just need the new ARMv7 kernel version of Raspian, and all existing projects will work.

Amazingly, despite the huge lift in specs, the new Raspberry Pi 2 Model B will still be sold for just $35 (around £25-30 in the UK).

Get yours now (in the UK) at cpc.farnell.com.