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This little device could save your life . . . You don’t want to be caught in a storm, especially if you are on a sports field, out boating, bushwalking or working in the open, on the farm or anywhere else where there is minimum shelter. If there is even a risk of a storm, take this Lightning Detector with you before venturing outdoors. Lightning Detector W hile most of us love the wide open spaces, they are definitely not the place to be if a thunderstorm is on the way. If there is a lightning strike nearby you could be in big danger of death or injury. And you don’t have to be hit directly – induction can kill you and so can the voltage gradient across the ground in the vicinity of a lightning strike. Our Lightning Detector can warn you of an approaching lightning storm and provides valuable time to take shelter safely indoors. And even if you’re not outdoors it can give you warning to disconnect vulnerable electrical appliances from the 230VAC mains supply. It provides audible and visual indication to warn of approaching thunderstorms. Lightning damage to electronic appliances Many people do not realise how vulnerable electronic equipment can be in a thunderstorm, even if it is not close by. Service organisations report a big surge in repair jobs 42  Silicon Chip by John Clarke after storms and just about all of this could be avoided simply by switching off and removing power plugs from the wall socket. Those appliances especially at risk include microwave ovens, TV sets, satellite receivers, mains powered computers (especially those also connected to the phone lines via a modem), washing machines and dryers. They should not be just switched off at the power point but the mains plug should be removed from the socket. TV antenna and satellite dish connections should be disconnected too. Many ovens incorporate electronic timers and power to these can be switched off at the “fuse” box. Apart from mains-powered computers, devices that are particularly prone to damage are fax machines and cordless telephone base stations. It is the fact that they are connected to both the 230VAC mains and the telephone wiring that provides a double whammy. During a big thunderstorm they should be disconnected both from the phone line and the mains power. siliconchip.com.au Of course, it is well known that any phones (apart from mobiles and cordless models) should not be used during a thunderstorm. So what to do? S1 +3V 1.5V POWER SUPPLY (Q1, LED3 & 4) LED2  BATTERY 3V POWER SUPPLY (2 x AA CELLS OR PLUGPACK INPUT) CONDITION To get a warning of imminent thunINDICATOR 1.5V derstorms, you need the SILICON CHIP Lightning Detector. It is a pocket-sized SINGLE CHIP PULSE unit that provides visual indication usOSCILLATOR AMPLIFIER AM RADIO EXTENDER (IC3) (Q2) ing a flashing LED and sounds an audible (IC1) (IC2, D3) PIEZO TRANSDUCER tone whenever lightning occurs in your COIL area. The greater the number of lightning DETECT  strikes, the more LED flashes and audible LED1 VR1 tone bursts are produced. SENSITIVITY For portable use it is powered with two alkaline AA cells, Battery life should Fig.1: the block diagram of the Lightning Detector. The early part looks be at least 1000 hours. For indoor use, similar to a radio receiver – which of course it is – but this radio receiver you can use a 6V-12V DC supply, such picks up just one thing: the RF pulse from a lightning strike within range. as a plugpack. One resistor needs to be chosen according to the DC supply voltage. When the exThe pulse extender produces a 200ms pulse and this ternal power supply is connected to the jack the socket, the lights the “detect” LED1. The pulse extender is necessary AA cells are automatically disconnected from the circuit. because the lightning strike pulses are too short in duration The principle of operation is based on detection of the to be noticed as a flash from the LED. broad-spectrum electromagnetic emissions produced by IC3 is an oscillator that runs for 200ms each time the lightning strikes. This is readily detected by a simple AM pulse extender produces a low signal and the resulting 4kHz (amplitude modulation) radio receiver. tone burst drives the piezo transducer which is resonant If you’ve ever been anywhere near an electrical storm at that frequency. with an AM radio turned on, you’ll have heard the crashes (static) of lightning strikes. Very large strikes can be heard Circuit details from a considerable distance away. The full circuit is shown in Fig.2. As mentioned, IC1 is We use a single AM radio IC which comprises a RF the TA7642 AM radio chip while CMOS 555 timers are used (radio frequency) amplifier, detector and AGC (automatic for the pulse extender IC2 and for 4kHz oscillator, IC3. The gain control). This was originally available in 1984 from circuit is powered from 3V but it will operate down to 2V. Ferranti Semiconductors as the ZN414Z but replaced by A 1.5V regulated supply powers IC1 while the amplifier, the MK484, now also obsolete. pulse extender (IC2) and the oscillator (IC3) are driven We have used the modern equivalent, the TA7642. It from the 3V supply. operates from a 1.2 to 1.6V supply and covers from 150kHz While most of the circuit is powered from the 3V supto 3MHz. This includes the normal AM radio broadcast ply rail, IC1 needs to be operated at between 1.2 and 1.6V. band (530kHz to 1.6MHz) but for our purposes, we are To provide for this we use a voltage regulator comprising not concerned with listening to broadcast radio stations. transistor Q1 plus infrared LED3 & LED4. These develop We simply monitor the whole spectrum covered by the a forward voltage of approximately 1V each which is reAM radio chip. markably constant over a wide range of current. Tests of several infrared LEDs from different manufacturers showed Block diagram that the forward voltage is around 1.09V at 1.6mA current The general arrangement of the Lightning Detector is dropping to 0.945V at 160A, ie, a current range of 10:1. shown in the block diagram of Fig.1. IC1 receives signals Stacking two infrared LEDs in series provides a reasonfrom a pickup coil. In an AM radio this pickup coil would ably stable 2V reference. The LEDs are fed via a 2.2kΩ normally be tuned to a particular frequency using a vari- resistor from the 3V supply and the 2V reference drives able tuning capacitor. the base of transistor Q1. This acts as a current buffer to We want to monitor a wide frequency range and so the supply IC1 with about 1.4V. This varies from 1.46V with a coil is left un-tuned. IC1’s output signal is noise bursts 3V supply down to 1.287V with a 2V supply. from lightning. IC1 is connected to the 1.4V Output from IC1 is typically supply via the 470Ω AGC resistor 15mV with a tuned coil but is at its output pin. A 100nF decouparound 2mV with the un-tuned ling capacitor at the output sets • Portable coil. This signal is amplified using the high frequency rolloff to 4kHz. • Battery or external power supply transistor Q2 and a sensitivity conOne end of the pickup coil L1 is trol sets the level applied to the fol• Visual and audible lightning indication connected to the high impedance lowing pulse extender comprising (around 3MΩ) input of IC1 while • Sensitivity control IC2 and diode D3. When lightning the other end is grounded via a • Battery condition indicator is detected, a noise-burst triggers 100nF ceramic capacitor. There • Reverse supply protection the pulse extender. is no parallel capacitor across Features siliconchip.com.au July 2011  43 +3V 2.2k C B A  K E LED3 (IR) 220k D3 1N4148 VR1 10k LIN 470 LED4  (IR) 10nF 8 7 C Q2 BC549C B TA7642 L1 I 100nF 100nF IC1 G E CER. 1 10k CER. 470nF 180k 22nF 6 5 1k CON1 A 22 A LED1 K POWER S1 PIEZO TRANSDUCER 1 1nF  OSCILLATOR A BATTERY  LED2 3V BATTERY (2 x AA CELLS) LIGHTNING DETECTOR K 100k K 10 F 16V A SC 5 +3V 180 D2 1N4004 B R1: FOR 12V INPUT -- 470  0.5W FOR 9V INPUT -- 330  0.5W FOR 6V INPUT -- 120  0.5W L1: STANDARD BROADCAST BAND FERRITE ROD ANTENNA 2011 3 IC3 7555 A DETECT K ZD1 3.9V 1W 8 4 2 PULSE EXTENDER D1 1N4148 R1 7 K AM RECEIVER 12V DC INPUT IC2 7555 2 100k 180k 4 3 6 O 100nF K A SENSITIVITY K 100k 100nF 100k 2.2k 100k 100nF A 100nF 470k Q1 BC547 10 F 16V 220k E BC547, BC549C, BC559 Q3 BC559 B C E TA7642 LEDS IN4148 A K 1N4004 A K K A C O I GND Fig.2: the three main functional areas of the circuit diagram are labelled the same as block diagram to enable you to trace the circuit operation through. As mentioned in the text, resistor R1 needs to selected depending on the DC power supply you use – it can handle anything from 6 to 12V. The battery supply is nominally 3V but it will operate down to 2V. L1. This means that the coil is un-tuned and will have a fully at 2V and we are inclined to assume that this IC does broadband response. Bias for the input of IC1 comes from also operate at 2V. a 100kΩ resistor connected to its output. Make sure you do not use bipolar 555 timers such as the IC1’s output is AC-coupled to the following common LM555CN or the TL555CP as these typically require 4.5V emitter amplifier, Q2. This has its emitter resistor bypassed or more for operation. with a 22nF capacitor to provide a gain of about 50 for freIC2 is the pulse extender which is set up as a monostable quencies above about 723Hz. Q2’s collector load comprises timer. Before triggering occurs, pin 3 is close to 0V and the the 10kΩ potentiometer VR1 and a 2.2kΩ resistor. VR1 is 470nF capacitor is held discharged at about 0.6V above 0V the sensitivity control. by diode D3. Pin 2 is held at 45% of the 3V supply, ie, at IC2 and IC3 are CMOS 555 timers and most manufacturers +1.35V, using the 220kΩ and 180kΩ voltage divider resistors. of these devices state that their version will operate down Triggering occurs when the noise signal fed to pin 2 pulls to 2V or less. These include the Intersil ICM7555IPA, Texas it below +1V. This sets pin 3 high and diode D3 is then Instruments TLC555CP, ST Microelectronics TS555CN and reverse biased. The 470nF capacitor then begins to charge National Semiconductor LMC555CN. The NXP (found- via the 470kΩ resistor. During this time, LED1 is lit (driven ed by Philips) ICfrom pin 3) When M7555CN guaranthe voltage across tees operation at 3V the 470nF capacitor over full automo- Supply voltage: reaches 2/3 of the 3V (2 x AA cells) [will operate down to 2V] tive temperatures. supply voltage, pin Plugpack: 6 to 12VDC at 30mA However, perfor- Current Consumption: 3 goes low and the Battery operation 1.5mA at 3V, 1mA at 2V, mance graphs show 470nF capacitor is DC plugpack operation 17mA at 12V operation with a Battery life: discharged via diTypically 1000h with Alkaline cells 2V supply at –55° IC1 supply: Typically 1.46V with 3V supply, 1.28V with 2V supply ode D3. C, 25°C and 125°C. Battery voltage indication: This is an unconDown to 2V Also samples of the Strike indication duration: ventional monosta200ms NXP ICM7555CN Transducer frequency drive: 4kHz ble timer arrangeoperate success- Frequency detection band: ment. Normally pin 150kHz to 3MHz Specifications 44  Silicon Chip siliconchip.com.au 2.2k 220k LED1 VR1 A K S1 A K IC3 7555 470nF 10 F 1nF 220k 180k 100k 10k 100k 2.2k PIEZO Q2 D2 CABLE TIES 22nF 10 F Q3 100nF 100nF 180 470k D3 4148 100nF IC2 7555 1k L1 10190210 R OT CETED G NI NT H GIL 10nF LED2 180k ZD1 D1 4148 22 R1* 100k 100k 100k 100nF CON1 470 LED4 LED3 A 100nF (-) 100nF IC1 + Q1 A * R1: SEE TEXT (DEPENDS ON VOLTAGE IN) + – TO BATTERY HOLDER TERMINALS Fig.3: everything (except the batteries) mounts on a single-side PCB. The component layout is shown above and, with the same-size photo at right, is self-explanatory. At right is Fig.4, the drilling guide for the end panel. There is no labelling on this panel; all controls are labelled on the front panel. Millimetre dimensions are the hole diameter required at each position. 7, the discharge, would be connected to pin 6 and would discharge the 470nF capacitor instead of using diode D3. Using D3 to discharge the capacitor frees pin 7 to perform another task. Because it can sink (pull down) to 0V, it is suitable for use as a reset control for the following oscillator, IC3. IC3 is connected in astable (free-running) mode, running at about 4kHzm to drive the piezo transducer. It is held in the reset condition, with its pin 4 pulled low by pin 7 (discharge) of IC2, when IC2 is not timing. Power supply As already mentioned, the Lightning Detector is powered from two AA-cells or a low voltage plugpack supply. When running from the AA cells, current flows via the closed contact in the power connector (CON1) and through the 22Ω resistor to the 0V supply. This resistor is included to prevent excess current if the cells are inserted back-to-front. When the cells are correctly inserted, the 22Ω resistor produces a minimal voltage drop (normally less than 33mV and less than 100mV with the detect LED lit). When running from a DC suppy, the AA cells are disconnected via CON1 (as noted above) and the incoming supply is regulated down to 3.9V using zener diode ZD1 and resistor R1. The value of this resistor depends on the DC supply voltage – anywhere from 6V to 12V will be suitable, with resistor values of 120Ω (6V), 330Ω (9V) or 470Ω (12V). The negative supply connects to the circuit ground siliconchip.com.au End Panel Drill Guide Switch 5mm LED 3mm LED 3mm Pot 7mm via the 22Ω resistor. Diode D1 reduces the 3.9V zener voltage supply to about 3.3V. We could have used 3.3V zener diode on its own without D1. However, we want to be able to run the circuit from two AA cells that provide a 3V supply. If a 3.3V zener diode were used, the cells would be discharged via the zener diode. So by including diode D1, current is prevented from flowing through the zener diode. The zener voltage is increased from 3.3V to 3.9V to compensate for the 0.6V diode drop. D1 also blocks reverse voltage to the circuit should the 12V supply be connected with reversed polarity. With reverse polarity, zener diode ZD1 is forward biased and clamps the voltage to no more than -0.6V below the 0V supply. D1 stops current flowing through the circuit backwards. Battery indication When the power is first switched on, LED2 provides indication of the battery condition. LED2 is driven via PNP transistor Q3 and its base is initially tied to 0V via the 10F capacitor. With the supply at 3V, Q3’s emitter is at about 0.6V and the LED is driven at maximum brightness. That is with about 2.4V (3V-0.6V) across the LED and 180Ω resistor. Assuming a LED forward voltage of 1.8V, this produces a current of about 3mA. At a lower supply voltage, the initial LED current is less and it will be dimmer. With a 2V supply, LED2 will be barely alight, indicating that the batteries should be replaced. July 2011  45 Parts List – Lightning Detector 1 PCB coded 04107111, 65 x 86mm 1 remote control case 135 x 70 x 24mm (Jaycar HB5610 or equivalent) 1 panel label 50 x 114mm 1 miniature PC mount SPDT toggle switch (Altronics S1421 or equivalent) (S1) 1 10k log potentiometer, 9mm square, PCB mount (VR1) 1 knob to suit potentiometer 1 switched 2.5mm PCB mount DC socket (CON1) 2 AA Alkaline cells 2 DIP8 IC sockets (optional) 1 tuning coil with ferrite rod (Jaycar LF-1020) 1 piezo transducer (Jaycar AB-3440, Altronics S 6140) 2 6mm spacers 2 M2.5 x 12mm screws 4 6mm self-tapping screws 2 100mm cable ties 6 PC stakes 1 50mm length of red light gauge hookup wire 1 50mm length of black light gauge hookup wire Semiconductors 1 TA7642 single chip AM radio (IC1) (Wiltronics X-TA7642) 2 7555 CMOS 555 timers (ICM7555IPA, TLC555CP, TS555CN, LMC555CN or ICM7555CN) (IC2,IC3) 2 3mm high intensity red LEDs (LED1,LED2) 2 5mm IR LEDs (LED3,LED4) 1 BC547 NPN transistor (Q1) 1 BC549C NPN transistor (Q2) 1 BC559 PNP transistor (Q3) 1 3.9V 1W zener diode (ZD1) 2 1N4148 switching diodes (D1,D3) 1 1N4004 diode (D2) Capacitors 2 10F 16V PC electrolytic 1 470nF MKT polyester 4 100nF MKT polyester 2 100nF ceramic 1 22nF MKT polyester 1 10nF MKT polyester 1 1nF MKT polyester Resistors (0.25W, 1%) 1 470k 2 220k 2 180k 5 100k 1 10k 2 2.2k 1 1k 1 470 1 180 1 22 1 of 120, 330 or 470 0.5W (R1 – see text) Whatever the supply, LED2 only lights momentarily and as the 10F capacitor begins to charge via the 100kΩ resistor, it dims and eventually goes out. The 220kΩ resistor across the 10F capacitor prevents the capacitor charging to any more than 2/3rds the supply. This provides a faster discharge of the capacitor when the supply is switched off. The 220 resistor is also used to discharge the capacitor when the supply is off so it is ready to flash the LED when power is reapplied. Construction The Lightning Detector uses a PCB measuring 65 x 86mm 46  Silicon Chip Here’s how the PCB fits inside the case. The top corners need to be shaped to fit the case mounting pillars but otherwise it’s a simple drop-in fit, secured by four selftapping screws . The two AA batteries which power the unit fit under the moulding at the bottom. and coded 04107111. The PCB and components are housed in a plastic case measuring 135 x 70 x 24mm. The PC board is designed to mount onto the integral mounting bushes within the box. Make sure the front edge of the PC board is shaped to the correct outline so it fits properly. It can be filed to shape if necessary using the PCB outline shape as a guide. Begin by checking the PCB for breaks in tracks or shorts between tracks or pads. Fix any defects, if necessary. Check the hole sizes for the PCB mounting holes and for the cable ties. These are 3mm in diameter. You can then insert the resistors and use the resistor colour code table to select each value and check each one with a digital multimeter. Then install the diodes; they must be mounted with the orientation as shown. Install the six PC stakes. IC2 & IC3 can be mounted on sockets or directly soldered to the PCB. When installing sockets and ICs, take care to orient them correctly – as indicated by the notch at one end. Capacitors can be mounted now. The electrolytic types must be oriented with the shown polarity. Make sure these capacitors are placed on the PCB so their height above the surface is no more than 12.5mm, otherwise the lid of the case will not fit correctly. Note that while provision is made for a capacitor across the L1 coil, as mentioned earlier one is not used in this circuit. It is included so that you can experiment with the radio IC by placing a tuning capacitor between the two PC stakes for the L1 coil and placing a fixed value (if required) capacitor to pad out the capacitor range. This will allow the reception of radio broadcast stations. Audio signal is available at the VR1 wiper. A coupling siliconchip.com.au plastic transducer tabs. Alternatively, two nuts can be used. Follow the wiring diagram to make the connections from the piezo transducer and battery terminals to the PC stakes on the PCB. Next, install the battery clips into the battery compartment. The two connected terminals are placed on the right hand side (as you look at the rear of the case with the compartment at the bottom). The spring terminal is placed to the top and raised section to the bottom. For the left side, insert the separate terminals with the spring terminal placed at the lower edge and the raised section to the top. On the compartment inside bend the two individual terminals to the outside of the compartment. You may need to stretch the contact springs so that the AA cells are held securely between the contacts. Looking end-on shows the two controls and two LEDs The PCB is secured to the base of the case using four M3 which mount on the end panel. Fig.5 (below right) is the x 6mm screws that screw into the integral mounting bushes same-size front panel artwork which can be photocopied in the box. Before fitting them in place, drill out the small or downloaded and printed, then glued in place. front panel for the LEDs, potentiometer and switch. A drill guide is available and is provided with the capacitor (say 100nF or so) is required front panel label. This can be used as a guide to connect this signal to an external Sensitivity Detect Power as to the drill hole positions. amplifier. The panel label for this project can eiMount IC1 and the transistors taking ther be photocopied (without infringing care to place each in its correct place. copyright) – see fig.5 – or for best results, If you happen to be using a Ferranti it can be downloaded from the SILICON CHIP ZN414Z from your IC collection for website (www.siliconchip.com.au). Go to IC1 note that the GND and Out pins the downloads section and select the month are reversed compared to the TA7642. and year of publication. You would have to place the IC in the When downloaded, print it onto paper, PCB oriented 180° to that shown on sticky-backed photo paper or onto plastic the overlay. film. For protection and long life, paper An MK484 has the same pin out as labels should be covered with either selfthe TA7642. The TA7642 has a greater adhesive clear film or (as we normally do) sensitivity in the lightning detector aphot laminated (laminators and sleeves are plication compared to the MK484 and very cheap these days and give a tough so given the choice, we recommend protective layer!). using the TA7642. We did not try a DC If printing on clear plastic film (overhead ZN414Z since this is not available. Input projector film) you can print the label as a The potentiometer (VR1) and the + mirror image so that the ink is behind the PCB-mounted switch S1 can now be film when placed onto the panel. Again, this soldered in. will give the label maximum protection. LED1 and LED2 mount horizontally Once the ink is dry, cut the label to size. but at a height of 6mm above the board The paper or plastic film is glued to the surface. Bend their leads 90° at 7mm panel using an even smear of neutral-cure back from the base of the LEDs, making silicone. For plastic film, if you are gluing sure the anode lead is to the left. it to a black coloured panel, use coloured L1 is a standard broadcast band coil silicone such as grey or white so the label pre-wound onto a small ferrite rod. can be seen against the black. There are actually two coils on the rod A hole in the panel is required directly but only one is used. Using your multimeter, find the coil that has the greatest above the piezo transducer. This can be first drilled in the plastic lid and then once the panel label is affixed, cut the resistance. With our prototype, the main winding measured about 11, while the separate antenna winding measured hole out using a sharp hobby knife. A small piece of dark fabric or loudspeaker foam 2. Connect the coil with the highest resistance to the PC (scrounged from an old pair of headphones) can be used to stakes. The ferrite rod is secured to the PCB using a pair of small cover the piezo transducer. Also a black bezel over the panel hole can improve the finish of the unit. These are secured cable ties. The piezo transducer is mounted using two 6mm long with a smear of neutral cure silicone. Our bezel came from standoffs and 12mm long M2.5 screws. The screws are the plastic dress plate that sits behind the nut of a Jaycar inserted from the underside of the PCB, pass through the PS-0192 stereo 6.35mm jack socket. Additionally, a cut out is required for access to the DC spacers and tap into the piezo mounting tabs. If you are using a different piezo transducer that has larger mounting holes socket. A rat-tail file can be used to make this hole in the lid. A suitable belt clip for the remote control box is available in the tabs, M3 screws could be used instead to tap into the SILICON CHIP siliconchip.com.au . July 2011  47 RESISTOR COLOUR CODES No. Value 4-Band Code (1%) 1 470kΩ yellow purple yellow brown 2 220kΩ red red yellow brown 2 180kΩ brown grey yellow brown 5 100kΩ brown black yellow brown 1 10kΩ brown black orange brown 2 2.2kΩ red red red brown 1 1kΩ brown black red brown 1 470Ω yellow purple brown brown 1 180Ω brown grey brown brown 2 22Ω red red black brown One of the following (R1): 1 470Ω yellow purple brown brown 1 330Ω orange orange brown brown 1 120Ω brown red brown brown 1 1 1 1 1 1 1 1 1 1 1 1 1 Capacitor Codes 5-Band Code (1%) yellow purple black orange brown red red black orange brown brown grey black orange brown brown black black orange brown brown black black red brown red red black brown brown brown black black brown brown yellow purple black black brown brown grey black black brown red red black gold brown Value F Value IEC Code EIA Code 470nF 0.47F 470n 474 100nF 0.1F 100n 104 22nF 0.022F 22n 223 10nF 0.01F 10n 103 1nF 0.001F 1n 102 the 22Ω resistor should be about 33mV with a 3V supply or less with a lower voltage supply. Check supply to IC1 at the emitter of Q1. This should be 1.46V with a 3V supply dropping to 1.287V with a 2V yellow purple black black brown supply. orange orange black black brown Adjust the sensitivity control fully brown red black black brown clockwise or back off if any indication persists. Test the Lightning Detector as from Altronics. The catalog number is H0349. (Contact a fluorescent light is being switched on. The switching on www.altronics.com.au). of conventional fluorescent tubes will cause the Lightning Detector to give a LED detect and tone indication with Testing each starter attempt to light the tube. Compact fluorescent Testing can be done with two AA cells or a DC supply. tubes tend to be indicated with a single flash and tone as Apply power and check that the power LED momentar- the tube lights rapidly. ily lights when the Lightning Dectector is switched on. The sensitivity control is included to prevent the Check the supply voltage by measuring across diode D2. Lightning Detector from producing an indication when This should be around 3V but may differ depending on there is no lightning. The control is adjusted clockwise the state of the cells or the tolerance of the 3.9V zener for maximum sensitivity to lightning but not so far as to SC diode when a DC power supply is used. Voltage across give false detection. What to Do in a Storm The best idea is to avoid getting caught outside in an electrical storm but sometimes, the best laid plans of mice and men. . . etc. How far away is the lightning? Watch for a flash of lightning. Then count or read off your watch the number of seconds until you hear the first crash of thunder (or crack if it is close!). Divide the number of seconds by three and you have a rough distance away that the lightning has struck. Anything less than 1km (ie, 3s) should be regarded as getting very dangerous. If you cannot get to shelter? If you are caught outside during an electrical storm, avoid conductors of electricity such as water, trees, poles, golf clubs, umbrellas and metal fences. If possible, keep away from open spaces (eg, the middle of a sports field) where you will be taller than the surroundings and definitely do not shelter under a tree. Crouch down, keeping your feet close together and wait out the storm. Groups of people should be spread out several metres apart. It is also a good idea to cover your ears with your hands to avoid hearing damage due to the noise of a close lightning strike. If possible, take refuge inside a vehicle or building. If inside a vehicle, close the windows and avoid touching the metal of the vehicle. Make yourself less of a target by lying down (eg on the back seat). Keep the vehicle away from trees or tall objects that may fall over in the storm. Avoid fallen power lines. Inside a building, keep windows and doors closed and keep 48  Silicon Chip away from windows, doors and fireplaces. Before the storm, unplug electrical appliances that may be susceptible to lightning damage. These include fax machines, telephones, microwave ovens, televisions and computers. To be doubly safe, unplug any computer communications devices from phone lines or cables (don’t forget routers etc). Avoid using electrical appliances and telephones until the storm has well and truly passed. (However, you can use a mobile phone if you have to – eg, to call for help). Avoid touching earthed fittings such as water taps, sinks, appliances and so on. If you are on a boat, keep low, dry, and away from metal conductors. Always check with the Bureau of Meteorology for storm forecasts before going out on a boat. In this way you could avoid boating in a storm. If you are a boat owner, make sure the boat is fitted with lightning protection that directs lightning safely to the water. This will help protect the occupants should they be caught out in a storm and also help protect the boat when left moored. And if someone near you is struck by lightning? Avoid the temptation to rush in and help – time is of the essence but there’s no point in two people being struck! As soon as it is safe to do so (ie, the danger has passed), commence standard A-B-C resuscitation. Check their response, clear the airway, and if necessary proceed with CPR. What? You don’t know CPR? Learn it today! siliconchip.com.au