Electricity is one mean monster you never want to mess with. It has its own rules which you ignore at your peril. Aside from the obvious ones – never work with live wires or use electrical devices near water – some are less obvious such as using the wrong type of component or not carrying out fail-proof voltage testing. However simple or complex your electronic project, here are ten important ways you can stay safe.
1) Discharge any capacitors.
Before working on any electrical equipment or appliance it’s crucial that you discharge all the capacitors, otherwise you might be in for a nasty shock or burn.
1. Stop any alternating current flowing through the capacitor by unplugging the electronic device.
2. Disconnect any capacitors that are removable.
3. To discharge the capacitor touch the capacitor leads with the wires of an electronic bulb, a volt meter or a 5- to 10-watt resistor. If using a bulb, it will gradually dim and turn off to indicate the progress of the discharge. If using a resistor, touch the capacitor leads for just a few seconds for discharging.
Some people discharge with a small screwdriver. However, the current discharged may be enough to melt the screwdriver’s tip, or the copper on the circuit board if the capacitor is still connected to it, as well as create sparks.
2) Don’t bodge it, replace it.
Electricity is too dangerous to risk a quick penny-pinching repair job. For instance, if you have a damaged length of cable never repair cuts with insulating tape; use a new length of cable instead.
3) Don’t cut corners. Only a fool uses the wrong tool.
Check and ensure you’re using the proper tools and equipment in any job. For example, when joining lengths of cable don’t bodge it with connector blocks covered in insulating tape or ‘splice’ wires by twisting them together, do a proper job using proper connectors instead.
4) Avoid live heat-sinks
Choose your heat-sink wisely, particularly if you’re working with mains electricity. As with any semi-conductor, a triac produces a lot of heat to switch the main electrical currents through the transistors. To dissipate the heat and prevent overheating a heat-sink is incorporated. A BTA08-600 triac is commonly used which has an insulated heat-sink connection to the mains voltage, whereas the BTB08-600, which is almost identical, is not insulated.
Although the non-insulated triac produces better thermal characteristics and is smaller, the insulated triac ensures that the heat-sink is not live so is safer to work with.
5) Cover those parts – they could be live.
Your electronic equipment may have a label on the back giving you a stark warning like “CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK DO NOT REMOVE COVER (OR BACK).” This basically means there are parts inside which are unprotected from the mains voltage. If you have removed the cover from a device like this, always remember to need to fix it back before connecting to the mains.
6) Protect against electronic static discharge.
To safeguard yourself and sensitive electronics against any static discharge always remember to get grounded or earthed first. “Earthed”, as the name suggests, refers to being connected to the earth or ground. One of the easiest ways is to be earthed is to wear an anti-static arm band connected by a wire to a metal cold water pipe (as this ends up in the earth or ground). As long as that pipe has eventual contact with the earth any static that builds up can be safely diffused through the earth rather than through you or via your tools to the sensitive electronics you’re working on. NB, a hot water pipe won’t work as it doesn’t have contact with the earth. Wearing cotton rather than man-made fibres is another added precaution you can take against static.
7) Consider switching from mains electricity to low voltage electricity.
If you’re an electronics newbie, the safest way to practice your hobby is to completely avoid working with mains voltage. Most electronic circuits use low voltages, powered by batteries or an external plug-in transformer which converts the voltage down to a safe voltage (e.g. AC current to a low voltage DC current). Make sure that the transformer has the appropriate voltage and rating for the type of circuit you’re using and the power supply it’s connected to.
8) Safety when soldering.
Aside from dangers of working with electricity, soldering wires in your electronics project poses a few dangers of its own. The solder can get seriously hot, and air pockets can get into the solder that when heated can splatter you in the face. Be sure to wear eye protection safety goggles, allow the solder to cool down before touching it, wash your hands after use (as it contains poisonous lead) and solder in a well ventilated room to avoid the build-up of its mild toxic and caustic fumes. It’s also important to use the correct voltage of soldering iron for your project.
9) Don’t overload your circuit.
Ensure that the cabling and all components in your circuit do not exceed the rating of the maximum current. This is especially important with heavy circuit loads such as lights and motors.
10) Test and test again.
To test there that your circuit is absolutely dead you should always use a voltage meter. But can you be absolutely sure your voltage meter is giving you a proper reading? It may seem paranoid but voltage meters can fail (however rarely). Bearing in mind that it’s always better to be safe than sorry, check that your meter is working properly on a known source of voltage and regularly inspect its body, probes and wires for any signs of wear or damage. It it’s faulty or unreliable, replace.
Louisa Logan is an electronic blogger, writing for sites like Element 14 and Farnell UK. She enjoys carrying out her own electrical experiments and has a passion for projects with Vishay capacitors and resistors.