IAN LANG ELECTRONICS

Fundamentals

Nobody likes getting electric shocks. Fewer still like getting their houses on fire. In these pages the aim is to teach in plain English the fundamental stuff about electricity starting with the fact that IT'S BLOODY DANGEROUS. With that in mind, lets get on with it.

 

Never consider anything too low powered to harm you. If you are resonably fit you can get away with messing about with batteries but if anything is plugged into the mains then make sure it's not just switched off at the socket but also unplugged. This applies even if it comes through an adaptor. Some adaptors are capable of giving out several Amperes of current and this will at best cause you a great deal of pain. If it goes through your chest cavity to ground it's enough to ensure your place sitting on a white fluffy cloud holding a harp, unless you're an evil engineer in which case Satan will take great delight in attaching electrodes to sensitive parts of your anatomy and sending a few sparks through. Your tastes might incline this way, I don't know (and don't want to know) but it strikes me that after a couple of lifetimes of it it might get a bit samey.

 

This leads us on to the subject of capacitors. The job of a capacitor is to build up a charge. Have you ever been tasered? A taser actually works by releasing the charge stored in a capacitor into your skin. Oh it hurts, it really does. Always make sure a capacitor is fully discharged before you start working anywhere near it. Discharge should be through a meaty bleed resistor.

 

High voltages will fry you if you are in contact with the ground. In dry air it takes 30,000 volts only one centimetre away to cause a big, painful spark to come into contact with you and if you're in contact with the ground at the same time it'll go through you like a pint of prune juice and turn you into a lump of coal.

 

Some components are made from stuff that will harm you. Arsenic is one. Batteries are a particular nasty thing. Some have acid in. If you need a lead acid battery buy a sealed one. Don't mess with acid even in a weakened state. It necrotises the skin. Think Phantom of the Opera.

 

Fuses are there for a reason, and the reason is that they stop explosions and fires. If a fuse blows there's a short circuit somewhere. Don't put a bigger rated fuse in unless you are absolutely certain that the components and wires it's supposed to be protecting can handle it. DO NOT BY-PASS FUSES. This is a certain way to calamity.

 

Multimeters- if you need to measure a voltage make sure the circuit is not live first. Attach your MM leads with crocodile clips or similar and then switch back on, standing away from the multimeter as you do it. Make sure you have selected the proper range and that the expected output is within your multimeter's capabilities. Don't measure resistances on a live circuit, you won't get a proper reading and you may fry your multimeter. High currents should not be measured- measure resistance and voltage and then work out the current using Ohm's Law.

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