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.

Picaxe Based Dual One Shot Timer Relay with Code

Posted on July 18, 2016 by neil

Pictured below is a simple timer relay circuit we recently made which we will detail here together with the source code for the microcontroller since we have had many requests for example code for timers of this type.

We received a request for a timer with two buttons. Pressing the first button was to cause a relay to close for 10 minutes, and pressing the second button was to cause the relay to close for 30 minutes. The relay was to be used to switch a mains powered appliance.

In our article Make a PICAXE Repeating Timer, we show how to make a repeating on/off timer using a PICAXE microcontroller. The timer pictured above differs in that it has button inputs to deal with and also a one-shot instead of repeating timer.

The red LED is used to show which timer is running – off, but flickering on briefly once per second is the 10 minute timer; on, but flickering off briefly once per second is the 30 minute timer. The green LED is connected across the coil of the relay (with a current limiting resistor) to show when the relay is closed.

The PICAXE code below could be greatly reduced in length but to keep it simple to read through, understand, and adapt, we have left it with separate functions for the 10 minute and the 30 minute timers (instead of making one general function which could run for any duration in response to any button press).

symbol button1 = pinC.1
symbol button2 = pinC.2
symbol led = C.0
symbol relay = C.4

' Start with the relay open and the red LED turned off.
low relay
low led

main:
   if button1 = 1 then goto run10minutes
   if button2 = 1 then goto run30minutes
   pause 100
   goto main

run10minutes:
   'make sure button is held a little before closing the relay,
   high led
   for b0 = 1 to 5
      delay 50
      if button1 = 0 then 
         low led
         goto main
      endif
   next b0

   'Close the the relay
   high relay 

   'wait for the button to be released.
   do
      pause 50
   loop while button1 = 1

   low led

   for b0 = 1 to 10 'minutes
      for b1 = 1 to 60 'seconds
         high led
         pause 100
         low led
         pause 900
      next b1
   next b0

   'Open the relay.
   low relay

   goto main

run30minutes:
   'make sure button is held a little before closing the relay,
   high led
   for b0 = 1 to 5
      delay 50
      if button2 = 0 then 
         low led
         goto main
      endif
   next b0

   'Close the the relay
   high relay 

   'wait for the button to be released.
   do
      pause 50
   loop while button2 = 1

   low led

   for b0 = 1 to 30 'minutes
      for b1 = 1 to 60 'seconds
         high led
         pause 900
         low led
         pause 100
      next b1
   next b0

   'Open the relay.
   low relay

   goto main

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.

Window Blind Motor Timer Controller

Posted on July 15, 2016 by neil

Pictured below is a device we made recently to control window blinds so that they automatically close in the evening and open in the morning to give the impression that someone is at home when they are away on holiday.The motor set up with these particular blinds is a small 3 Volt DC unit, but the controller is powered by 12 Volt DC. The motor needs to be turned forwards to open the blinds and turn in reverse to close the blinds. Therefore a pair of relays are used (as explained here: Reversing the Polarity of a Motor with Two Relays) to give the reversing polarity output for the motor.

A programming button is fitted to the device which is used to set the number of seconds that the motor is to run to fully open or fully close the blinds. In addition, there are a pair of microswitches which act as limit switches ensuring that if blinds reach the end of their motion before the expected time, the motor will be turned off so that it does not burn out under the heavy load of fighting resistance. Therefore, the motor runs until either the user programmed run time has elapsed or the limit switch is hit. If there was not a time limit, then if the blinds became jammed, the limit switch would never be reached, and again there would be the risk of the motor burning out.

If you need any type of motor controller or timer, please email neil@reuk.co.uk with details of your exact requirements.

REUK.co.uk

The Renewable Energy Website

Monthly Archives: July 2016