Valiant PremiAIR 4 Stove Fan

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.

Comparison of Fir300 and Fir361 stove fans from ValiantThe 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.

Rear view of Fir361 PremiAIR 4 inch stove fan from ValiantWhen 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 Early Warning Alarm

Pictured below is another of our low voltage disconnect (LVD) circuits designed to protect batteries from being overly discharged.

12v low voltage disconnect for latching relays with early warning buzzer and LEDThis particular LVD has a few added features. First of all, to reduce power consumption by the LVD itself, it has been designed to work with a latching relay. The chosen relay (click here to download the latching relay datasheet) has two coils – one coil to latch the relay closed (set coil), and the other to release the relay (reset coil).

latching relay connections for low voltage disconnectThis controller can be programmed as per our standard REUK Programmble Low Voltage Disconnect with the disconnect voltage and cancellation voltage. While the voltage is good, the relay will be left latched closed, and then when the voltage falls below the disconnect voltage, it will be latched open.

As an added feature, when the measured battery voltage is 0.2V or less more than the disconnect voltage, the external LED (which can be panel mounted somewhere easily visible) turns on, and an on board piezo buzzer sounds briefly every half a minute until either the user starts to charge the battery, or the disconnect engages due to even lower measured voltage.

If you need any kind of low voltage disconnect circuit, email with details of your exact requirements.

Project of the Day – Automatic Toilet Flush Counter

This week we have been working on a project for a toilet manufacturer making a device which will count and log the number of times a toilet is flushed or partially flushed.

Although flow meters are already in place to measure the exact volume of water consumed by the toilets being tested, the key metric to calculate accurately is the amount of water used per flush, and to obtain that information it is essential to also count the number of times the toilet has been flushed.

There is no easy direct way to detect whether a full or partial flush has occurred, so two float switches have to be inserted into the toilet cistern – one just below the full cistern depth and the other just above the cistern depth immediately after a full flush.

automatic counter to log and display the number of times a toilet is flushed

When the level of water in the cistern drops below full (indicated by the upper float switch going low), we know that a flush has begun. Typically a full flush will take around 5-10 seconds at most to empty the cistern into the bowl (at which point the lower float switch will go low). Our system waits for up to 15 seconds to see if a flush is a full flush. If during that time the lower of the two float switches does not go low, it knows that a partial flush occurred.

This flush is then added to the relevant counter – full or partial – and displayed. The system then waits for the cistern to fill up again, and when upper float switch goes high it re-arms the flush detector ready to detect the next flush.

UK Home Energy Smart Meter Project Delayed

The installation of smart meters into all 30 million UK homes have been delayed by more than a year with the first meters unlikely to be installed until Autumn 2015, and all 30 million meters until 2020.

smart meters installation in the UK

The delays to the £11-12 billion project has been caused by industry needing more time for designing, building, and testing the systems which will enable the energy companies to communicate with the gas and electricity meters – for example to get daily accurate meter readings for all of their customers.

The huge costs of the project should be more than offset in the savings from not needing to employ people to read meters, and deal with customer complaints relating to estimated bills. Smart meters should help consumers understand their power usage and therefore take steps to reduce it.

9V from 12V Regulator Module – Alternative to L7809

About six months ago a Chinese company on eBay had a special offer selling the item pictured below for US$2 each. We bought five and put them somewhere safe and then forgot what they were for.

L7809 alternative - high current 4 Amps 9V output regulatorA quick test today showed them to be efficient 9V from 12V regulators working much the same as the common L7809 regulator.

With a bit of searching around we finally found the details for this product. It is an high current voltage regulator which takes an input voltage of from 12-23 VDC and outputs 9 VDC. No heat sinking is required up to a constant 2.5 Amps of output current, and they are rated to supply brief peaks of up to 4 Amps.

9V from 12V regulator module - 4 Amps

The pin connections (the three legs) have 2.54 mm (0.1 inch) pitch exactly the same as for the L7809 regulator, and the device is also of similar overall dimensions. Therefore, this little PCB can be used to substitute an L7809 (pictured below) where more current than the 1-1.5 Amps (with heat sink) maximum of the L7809 is required.

L7809 voltage regulator


It could for example also be used instead of the LM317T we use in our standard 9V from 12V regulator (though we have designed that with R1 = 330, R2 = 2K8 so that we get an output of around 8.8V compared to the 9.3V this regulator module outputs – a lower voltage to reduce power consumption for renewable energy powered applications). With thicker cables for the connections this would give a 2.5 Amp constant current 9V from 12V regulator with no need for heat sinking.

This module has a small integrated circuit labelled MP2307DN which a quick search on Google shows up as a 3A constant load current DC-DC step-down power supply module and a monolithic synchronous buck regulatorwhich has been used in this case to provide a 9V output.

At the time of writing we can only find this device here: L7809 Alternative Module priced at US$4.99 plus US$1.99 for air mail delivery. (The same vendor also has similar L7812 and L7833 alternative modules for 12V and 3.3V outputs respectively.)

12V High Torque Motors

We have been selling hen house door controllers now for a few years: hen house door controller. Nothing too complicated, just a programmable timer or light detector based controller to turn a motor in one direction in the morning to open the door, and then turn the motor in the opposite direction in the evening to close the door.

We have always recommended using motor car windscreen wiper motors for this application as they are cheaply available, robust, strong, and reversible. But, they are also large, heavy, different motors have different power/current requirements, and they all use far more power than is ideal for this project necessitating big relays and thick cables.

30 RPM 12VDC high torque motor

30 RPM 12VDC high torque motor

After much searching and testing we have finally found an alternative motor which we are happy to recommend for this application. It is a good quality motor fitted to a sturdy gearbox giving a high torque (120 low speed (30 RPM) which is perfect for slowly raising a lowering a hen house door.

The motor has a wide diameter (6mm) sturdy shaft onto which it is easy to glue a spool or cog. With a 12.0V supply, this motor draws a super low 40mA (0.04 Amps) when there is no resistance up to a maximum of 500mA (0.5A) when working at its maximum

These motors are priced from £5-8 delivered (from HK / China), so they are also economical too. Click here for more information: 30 rpm high torque 12V geared motors.

There are many other uses for these low power high strength motors which we’ll be exploring soon.