Testing Car Battery Voltage Meter

LED car battery voltmeterPictured above is a car battery voltage meter which is designed to be inserted into the cigarette lighter socket of a vehicle to test and display the battery voltage – purchased for £1.76 including delivery from Hong Kong.

It is relatively well made if a bit plasticky, but certainly as good as should be expected for a device at this sort of price. Inserting it into the car cigarette lighter socket it displayed the battery voltage accurately to well within 0.1V, and when tested with a variable power supply gave similarly reliable readings with an input voltage from 6V to 16V.

LED voltmeter for 12V car battery

The LED numerical display is bright – if anything too bright as the voltmeter draws 40mA when it is on which is too high to leave connected to a battery all the time (taking 1Ah of charge from the battery per day).

We purchased this to test and to take apart for a project. Breaking it open was very easy.

taking apart an LED voltmeter

The plastic end cap is threaded onto the positive end of the cigarette lighter plug, and can be unscrewed (with a bit of force). Inside is a 5A fuse which should really be a 100mA fuse to properly protect the device.

Then the two sections of black plastic can then be prised apart to expose the innards.

Components inside the LED voltmeter

There is a small circuit board with an IC on it, the LED display, a large resistor, some other common components, and a TL431 adjustable precision zener shunt regulator which is used as the voltage reference.

We wanted this to stick on top of a solar charged 12V lead acid battery to display the battery voltage so we chopped off all the unnecessary bits and pieces leaving just the two wires for connection to the + and – terminals of the battery.

mini LED voltmeter for 12V batteryThe blue plastic cover is pretty much vital as without it it is very difficult to read the voltage from the display.

Finally, to reduce power consumption, we wired a small push to make button to the white positive input cable and connected that and the black negative cable to the terminals of the battery. Now, whenever the button is pressed and held, the battery voltage is displayed. This mini LED battery voltmeter is only 3.5 x 2.5 x 1.0 centimetres in size and does the job perfectly.

If you are interested in buying one of these car cigarette lighter LED voltmeters click here.

Solar Cell Coating Could Improve Efficiency by 6%

The journal Science had details today of research into a special coating for photovoltaic solar cells which could potentially increase the percentage of solar energy which is converted into electricity by 6%.

Solar panels do not convert all wavelengths of light into electricity – photons of light from the blue (higher energy) end of the spectrum are converted into heat if they are not reflected from the solar panel which a) means that that solar energy is wasted, and b) means that the solar panel gets hotter, which as our article (Effect of Temperature on Solar Panels) showed, reduces efficiency.

pantacene-solar-panels

Since the 1960’s it has been known that a material called pantacene (an organic semiconductor pictured above) has an interesting property. When a photon of light from the blue end of the spectrum hits pantacene, TWO electrons are generated. When a photon of light from the red end of the spectrum hits a normal solar cell, ONE electron is generated. Therefore by making a solar cell with a coating of pantacene, light from the whole visible spectrum can be exploited and the efficiency of the hybrid solar cell will be higher than the simple silicon solar panels currently available.

This is still very much in the prototype phase with many years of research still to come before it could become commercial. Pantacene though abundant, carbon-based, and organic, is currently expensive and technology has to be developed to enable the economical manufacture of hybrid solar panels.

Butanol – the Biofuel of the Future

Ethanol from crop waste, corn, and sugar beet etc is currently added in small percentages to petrol to reduce fossil fuel use. It has lower energy density than petrol (lower mileage), is corrosive to engines (cannot be used in high concentrations), and it absorbs water from the atmosphere which can cause engine problems. 

Butanol is a heavier alcohol without any of these problems, but is more expensive to process (ferment and distill) from crops than ethanol. New research has led to new families of catalysts which will enable existing ethanol plants to output butanol by adding one reactive conversion step at the end of their processing.

This brings us one step closer to butanol (renewable fuel biobutanol) being commercially viable as the biofuel of the future to replace petrol.

Take a look here at our new article Butanol vs Ethanol Fuel of the Future for more information.

Portugal 70% of Power from Renewables in Q1

The national grid operator in Portugal (Redes Energéticas Nacionais – REN) has announced that in the first quarter of 2013 70% of all power consumed was generated from renewables – a new record.

Surprisingly despite its sunny reputation and Southern European location, Portugal does not generate much electricity from solar PV – in fact just 0.7% of electricity generated in 2012 came from solar PV.

Castelo de Bode dam - Portugal hydro power plant

A huge 37% of Q1 2013 electricity generated in Portugal came from hydroelectric power – including from hydropower plants at Alqueva Dam (Europe’s largest dam) and Castelo de Bode Dam pictured above.

A further 27% of the power generated came from wind turbines, located primarily in the windy north east of Portugal.

Favourable weather conditions made a big contribution to this record, with hydro power generation up over 300% compared to the same period last year, and a 60% increase in wind power generation.

Portugal still have virtually no offshore wind turbines despite having a long windy stretch of Atlantic coastline to exploit, and very little solar PV despite being sun scorched. Therefore, with continued investment there is a great chance of seeing 100% of consumption being met by renewables soon in Portugal.

80 Watt 12V Monocrystalline PV Solar Panel – £69.98 inc Delivery!

Special offer of the week has to be these 80 Watt power monocrystalline PV Solar Panels offered as a pre-order item (to be despatched after 17th April 2013).

80 Watt Solar Panel - Special Offer

The panel, pictured above, has an anodised aluminium frame, 3.2mm tempered glass, and is 824 x 669 x 35mm and just 8kg. Best of all is the price – £64.99 plus £4.99. It comes fitted with standard MC4 terminated cables. It is fully weatherproof for outdoor use.

Click here for more information or to snap up one or more of these panels now: 80 Watt 12V PV Solar Panel.

New Solar Cell Efficiency Record – Spectrolab

Back in 2007 we announced that Spectrolab (a subsidiary of plane-maker Boeing) has set a new world record for solar cell efficiency at 40% with a multi junction solar cell with concentrated sunlight (with lenses or mirrors). That record was subsequently broken, but is still around 41%.

Now Spectrolab have announced that they have broken the world record for solar cell efficiency without solar concentration achieving 37.8% efficiency, and they believe that the technology they used to achieve this is capable of getting to efficiencies of eventually getting up to 45%.

high efficiency pv solar panels

Spectrolab specialise in making high efficiency multi-junction PV solar panels for use in space to provide power to satellites, but their technological advances will eventually work their way down to the consumer market. Increasing the efficiency of solar panels is important, because high efficiency means physically smaller panels which need less materials, cost less to transport, and can be used in more situations.

L298N Dual H Bridge Motor Drive Controller

An H Bridge is a electronic circuit which has an output voltage which can be in either direction. This is particularly useful when used with motors as reversing the polarity of the power supply to a motor causes it to rotate in the opposite direction.

In our article Automatic Hen House Door Controller we showed how  a pair of relays could be used to achieve this polarity reversal for motors, as making an H bridge can be a bit complicated and mistakes tend to lead to destructive short circuits. Fortunately now there are many ready made H bridge boards available relatively cheaply which make everything a lot simpler for the DIYer.

dual h bridge for motor control

Pictured above is one such H Bridge circuit. Like most it is actually a dual / double H Bridge and so it can be used to control the direction of motion (and on/off status) of one or two motors.

The row of three screw in-terminals pictured at the bottom of the image are for the +12V and GND input connections, and a +5V output connection respectively. The +5V comes from an onboard 5V regulator which can be used to directly power a microcontroller such as an Arduino or Picaxe which would usually be used to control the motor(s).

The pair of terminals on the left of the image connect to the two power inputs of the first DC motor, and the second pair of terminal on the right to the second motor (if used).

There are 4 yellow inputs on the bottom right of the board as shown in the image labelled IN1, IN2, IN3, and IN4. If a high logic signal is sent (by the microcontroller) to IN1, the first motor will turn in one direction. If a high logic signal is sent to IN2 then the first motor will turn in the other direction. IN3 and IN4 work in the same way with the second motor.

It is not actually necessary to use a microcontroller – microswitches and resistors can be used to control the motor(s) in some simple applications.

underside view of dual h bridge motor controller

This H Bridge circuit is based around the L298N from ST Microelectronics – a dual full bridge driver which can supply up to 2 Amps of output current to each motor.

Click here to purchase one of these: Dual H Bridge Boards. Prices start from just £2.50 including delivery (air mail from China – 3 weeks) to up to £10 from UK sellers. As it typically costs around £5.00 to purchase just the L298N chip from electronics suppliers in the UK, these boards are great value and speed up project development no end.

Testing LM2596 Variable Voltage Regulator

Our LM2596 Variable Voltage Regulator (discussed previously here: regulator with display) has finally arrived after its long journey from China.

LM2596 variable voltage regulator with display

The first image above shows the input voltage as being 13.8V (which was accurate to <0.1V). The second image below shows the output voltage which we set by adjusting the small brass screw in the blue potentiometer to be 5.0V (which was also accurate to <0.1V).

lm2596 with LCD voltage display

The build quality and quality of the components used is excellent throughout, the LCD is bright, and the addition of a red LED and a green LED to indicate whether the input or output voltage is being displayed is very useful. Selecting whether to display input or output voltage is achieved using a small button on the regulator board. In addition to screw-in terminals for connection of the input and output wires, there are also holes with solder pads in both fine and medium sizes so that different sizes of wire can be more securely attached if required.

The only bad point would be that there is no option to turn off the LCD when it is not needed – i.e. it needs three options (display input voltage, display output voltage, or display nothing) instead of the two it has. The LCD draws approximately 25mA all the time, so will take 0.6Ah of charge out of a battery every 24hrs which is a lot. Another 10mA seems to be the quiescent current lost in the regulator when nothing is connected to the output but it is still regulating voltage.

We can think of many uses for these voltage regulators which are made easier thanks to the on board display – first and foremost for small battery charging from a 12V battery, and/or powering USB charged devices (using a 5.0V output). For battery charging of say four series connected NiMH rechargeables, you would just set the output voltage to say 5.8 or 5.9V and connect it to the battery pack with the correct polarity.

Apart from having slightly high self-power consumption, these regulators are excellent quality and fantastic value.

If you are interested in purchasing one of these regulators, click here: LM2596 Voltage Regulators. Prices are around £3.50 each or £17 for five including air mail delivery from China.

Rust to Help Storage of Intermittent Renewable Energy

The main disadvantage of some renewable energy sources (particularly wind and solar) compared to fossil fuels is you cannot guarantee to have the power you need when and where you need it. Wind speeds are not stable, and it can be cloudy (certainly in the UK) and its always dark at night.

Rust for renewable energy storage - catalyst electrolyser

In order for a very high percentage of our power needs to ever be met by renewables, it is essential that new improved ways are found to store power so that it is available even when the sun is not shining and it is not windy. Otherwise we will need more fossil fuel power stations as fall backs to ensure that electricity demand can be reliably met at peak times.

One of the cleanest ways of storing power is to use surplus renewable electricity to break water down into its constituent parts – oxygen, and highly flammable hydrogen. The hydrogen stored at times of surplus is then burned to power a turbine to generate electricity at times when renewables cannot meet demand directly. Best of all, the waste product from burning hydrogen is…pure water.

Until now the catalysts (electrolysers) used to split water into hydrogen and oxygen have been expensive, exotic, and often toxic rare earth metals such as iridium oxide and ruthenium oxide. With such high production costs it had been thought that storing energy by splitting water would never be cost effective. But, recent research from University of Calgary in Canada has found that iron oxide (rust) combined with a few other inexpensive materials can be used as a catalyst at a cost of one thousandth that of existing commercial catalysts while working at 85-90% efficiency.

This ability to split water into hydrogen commercially using renewable energy will also greatly help the future of hydrogen fuel cell powered cars. It also has a great deal of potential for off grid renewable systems currently using batteries for storage, but which will soon hopefully generate their own hydrogen for a small hydrogen powered generator replacing their existing polluting and expensive to run diesel generator.