Hello I thought I would start a new thread on the basics of electronics... Basic Electronic tools You'll need a few basic tools to complete your first project, however don't go mento and buy every tool under the sun. The most essential items you will need are a soldering iron and some solder - this is not normally provided with kits. You will also need some wire-cutters, wire-strippers and a pair of small pliers. Other items are also useful but they are not essential. Many suppliers sell basic tool kits, these could be better value but might not have all the tools you need. Here's a wee list of essential and optional tools... I have included the Maplin order codes where possible these codes may change or the product may become unavailable so use the nogga and look for an alternative if this is the case. Essentials: Tip tinner cleaner - such as order code JG06G this cleans, wets and tins the tip. Soldering iron - Antex 18 Watt type CS (code FY62S) or 25 Watt type XS (code FR12N). The XS model is probably better due to the higher power, but it is physically larger, and the 'bit' (the business end) is bigger. A full range of bits is available if you later decide you want a smaller bit. Solder - Solder comes in different thicknesses, 22SWG is thinner than 18SWG and is better for small joints. New legislation (RoHS) will prevent the use of lead solder after 2006 and many suppliers are now stocking lead-free solder. Maplin seem to no longer stock lead solder, but a small tube of lead-free solder (code N35BJ) should be fine. Alternatively last time I checked B&Q sold small tubes of tin/lead solder. Wire Cutters - Also called 'side cutters' these are used for cutting component leads close to the circuit board after soldering. I suggest Maplin's 'Snip Cutter' (code JH20W) or '155mm Side Cutters' (code GW49D). Wire Strippers - These are used to strip the insulation off wires you connect to your circuit. Strangely Maplin seem to have stopped stocking their simple 'Model 9' and their alternatives are all more heavy-duty (code FT44X might be suitable). You might need to try another supplier or a local shop for these. More complicated models aren't really worth the money for occasional hobby use. Pliers - Used for bending wires on components to fit into circuit board. These MUST be small - not the ones you use for plumbing! The range of pliers available is vast - I suggest the 'Miniature Long Nose Pliers' (code RL84F) or similar. Optional Extras: Screwdrivers - These are needed for some kits, not for others. A small straight type (code RM00A) and Medium cross - point type (code RM14Q) are most useful. You might well already have some suitable ones, so check what you need before buying Soldering iron stand - Stops you burning yourself, the cable lead or the table when the iron is not in use! Also this has a sponge to clean the iron. (code FR20W). I would count this as an essential actually due to safety reasons. Desoldering tool - Useful when you need to remove a solder joint for whatever reason. They work by sucking the molten solder into the pump, away from the joint. (code FR26D) Wooden board - If you don't have a work bench, use an old piece of shelving or similar to protect your table. If you don't have a board, buy a piece of chipboard or conti - board. Some people use even old wooden chopping boards. Test equipment - The only item of test equipment that's worth considering at this stage is a multimeter. A basic kit shouldn't require you to have one, although if it doesn't work it will be useful to find out what's wrong. If you do get one, choose a reasonable model so you don't out grow or get bored with it too soon. You could look at Maplin's 'PG10B' model (code GW18U). However, these are quite expensive, and not essential at this stage. Basic multimeters are available for under £10. KMAC.
Beginners Guide to Soldering So, you may have purchased a kit and some tools, now you're ready to start. When you're buying the kit get a few spare resistors and some small offcuts of stripboard (available from Maplin, the code for a small piece is JP46A). This will give you something to practice soldering with. When you've got all these it's time to get some soldering practice. It may help to print this page to refer to while practising This I do not mind if it helps you out. Read the whole page through before starting. Proceed as follows: Plug in the iron and wait about 5 minutes for it to heat up. Place the iron on something that won't burn, and make sure the 'bit' isn't touching anything, including the mains lead, ideally use a stand. Tin the bit - melt a small amount of solder onto the tip and wipe the hot iron on a wet sponge. Or use a Tip and Tinner Cleaner. If you don't have a stand (which includes a sponge) you will need a separate sponge. Make sure the sponge is damp - using a dry one will only mess up the sponge and won't clean the tip. This will put a layer of solder on the tip. You should only need to do this again really if you clean your tip. Bend the leads on the component with pliers to fit the board. Insert it into the board from the side without metal strips and bend the leads outwards on the other side to hold it in. Place the tip of the iron on the lead where it comes through the board on the side with the metal strips. Make sure it touches the lead and the board. Wait a second or two for the board and the lead to heat up. Don't leave it too long, however, or you will damage the component. This is particularly important with semiconductors - transistors, diodes, I.C.'s etc. Feed the solder into the joint until it forms a ring around the wire. It should stick properly to both the lead and the copper strip on the board. DO NOT carry the solder to joint on the tip of the iron, this almost invariably produces a bad joint. Remove the iron and allow the joint to cool naturally. DO NOT cool it by blowing on it. The joint should look volcano shaped with the lead sticking out of the 'crater'! If it is not shiny, or has formed into a blob then you have made a 'dry' joint. If the joint is not complete re-apply the iron and add a bit more solder. If you need to remove the solder, use a de-soldering tool or solder braid, or melt the solder and tap the edge of the board on the worktop to knock it off. Try again - practice makes perfect! When the joint is OK, use side cutters to cut the component lead off flush with the top of the solder. Repeat the process for the other leg(s) of the component. When you've finished soldering, clean the tip on the damp sponge and then re-tin it with fresh solder before you use the iron again. you unplug the iron. This protects the tin plating on the tip and prevents it oxidising (thanks Remember to keep the bit away from anything that it could melt until it is completely cold. Common problems: Too much solder - joint will form into a blob, solder may bridge between strips on the board. Remove ALL the solder as described above and try again. Too little solder - joint not complete, physically weak, possible not electrically sound either. Re-apply the iron and add a bit more solder. Solder will not stick - component lead and / or board may be greasy or tarnished. Generally you should clean the lead and the board before soldering them. Ideally keep the board in an air tight container when not working on it to prevent oxidisation of the surface. Don't rush to start building the project until you are sure you can produce good solder joints, as you will only spend more time later de-soldering bad joints, and may damage the components. When you're happy that your soldering is good, it's time to start construction. KMAC.
Beginners guide to Components Resistor: A resistor is a piece of material that obeys Ohm's Law. The name comes from its main property, it resists the flow of charge through itself, hence allowing us to control the current. Resistors can be made of various kinds of material, but whatever the choice it must conduct some electricity otherwise it wouldn't be of any use.. Two wires are connected to opposite ends of the resistor. When we apply a potential difference between the wires we set up a current from one wire to the other, through the resistor. The size of the current is proportional to the difference in voltage between the wires. The resistance (in units of Ohms) is defined as the ratio of the applied voltage, V (in Volts), divided by the current, I (in Amps), produced by the applied voltage. Resistors come in a wide variety of shapes and sizes, but the most common type is a cylinder with wires at the ends. The value is usually displayed using standard colour code. Most resistors have a value in the standard E12 series. Most of the resistors used in electronics have 'fixed' values, but resistors can also be made which have a controlled, variable resistance. These are sometimes called pots, and they're used for tasks like the volume control on a Hi-Fi amplifier. Capacitor: If you look at a catalogue of electronic components you'll find an enormous variety of sizes and types of capacitor. However, for most purposes we can divide capacitors into two basic types:- dielectric and electrolytic. A capacitor acts as a charge store. It contains a pair of metal plates separated by a thin sheet of insulating material. Left to themselves the plates are electrically neutral - the number of positive protons in each exactly equals the number of negative electrons. However, if we connect wires to the plates and apply and external voltage we can drag electrons off one plate and push them on to the other. This takes energy, i.e. we have to do work charging the capacitor. The result is a capacitor with one plate positively charged and the other negatively charged. The energy used to move charge is stored by this imbalance. If we connect two plates together with a resistor, the electrons 'rush back home' releasing their energy again. The voltage between the plates of a charged capacitor is proportional to the amount of charge moved. The charge/voltage ratio for any specific capacitor is called it's capacitance. The Diode: There are a number of different electronic devices which tend to be called diodes. Although they're made differently they all have three things in common. • They have two leads like a resistor. • The current they pass depends upon the voltage between the leads. • They do not obey Ohm's law! As an example I will use a is typical diode called a pn-junction. This allows me to explain behaviour of diodes. Remember, however, that there are other sorts of diodes which are built differently but show the same general behaviour. We create a pn-junction by joining together two pieces of semiconductor, one doped n-type, the other p-type. This causes a depletion zone to form around the junction (the join) between the two materials. This zone controls the behaviour of the diode. Junction field effect transistors: Junction field effect transistors (JFETs) come in two 'flavours', p-channel and n-channel. In each case a bar, or channel, of one type of semiconductor material is located inside a bulk material of the other kind i.e. p inside n, or n inside p. The explanation given below assumes we are talking about an n-channel device. You can explain the behaviour of the p-channel device by swapping everything around i.e. think of opposite signs for the voltage and current, and replace electrons with holes and vice-versa. Characteristic curves can be used to describe the behaviour of the JFET in detail. A pair of metallic contacts are placed at each end of the channel. When we apply a voltage between these, a current can flow along the channel from one contact to the other. The contact which launches charges along the channel is called the source, the one that 'eats' them at the other end is called the drain. In an n-channel device, the channel is made of n-type semiconductor, so the charges free to move along the channel are negatively (hence n) charged - they are electrons. In a p-channel device the free charges which move from end-to-end are positively (hence p) charged -they are holes. Remember that a hole is the absence of an electron. In each case the source puts fresh charges into the channel while the drain removes them at the other end. Bipolar Transistor: A Bipolar Transistor essentially consists of a pair of PN Junction Diodes that are joined back-to-back. This forms a sort of a sandwich where one kind of semiconductor is placed inbetween two others. There are therefore two kinds of Bipolar sandwich, the NPN and PNP varieties. The three layers of the sandwich are conventionally called the Collector, Base, and Emitter. Some of the basic properties exhibited by a Bipolar Transistor are immediately recognisable as being diode-like. However, when the 'filling' of the sandwich is fairly thin some interesting effects become possible that allow us to use the Transistor as an amplifier or a switch. What happens when we apply a moderate voltage between the Collector and Base parts of the transistor? The polarity of the applied voltage is chosen to increase the force pulling the N-type electrons and P-type holes apart. (i.e. we make the Collector positive with respect to the Base.) This widens the depletion zone between the Collector and base and so no current will flow. In effect we have reverse-biassed the Base-Collector diode junction. The precise value of the Base-Collector voltage we choose doesn't really matter to what happens provided we don't make it too big and blow up the transistor! So for the sake of example we can imagine applying a 10 Volt Base-Collector voltage. KMAC.
Beginners Guide - Testing & Troubleshooting Before you apply power, read the instructions carefully to check you haven't missed anything, and whether there are any specific instructions for switching on and testing. Check again that you have all polarity sensitive components the right way around, and that all components are in the correct places. Check off - board components are connected correctly. Check the underside of the board carefully for short circuits between tracks - a common reason for circuits failing to work. When you are sure everything is correct, apply power and see if the circuit behaves as expected, again following the kit manufacturers instructions. If it works, WELL DONE! You have your first working circuit - be proud of it! Skip the rest of this page !!! If it doesn't quite work as expected, or doesn't work at all, don't despair. The chances are the fault is quite simple. However, disconnect the power before reading on. Check the basic's first - is the battery flat? Are you sure the 'On' switch really is on? (Don't laugh, it's easily done) If the project has other switches and controls check these are set correctly. Next - check again all the components are in the correct place - refer to the diagram in the instructions. Look again at the underside of the board - are there any short circuits? These can be caused by almost invisible 'whiskers' of solder, so check for these with a magnifying glass in good light. Brushing the bottom of the board vigorously with a stiff brush can sometimes remove these. Pull the components gently to see if they are all fixed into the board properly. Check the soldered joints - poor soldering is the most common cause of circuits failing to work. The joints should by shiny, and those on the circuit board should be volcano shaped with the component wire end sticking out of the top. If any look suspect then redo them. Remove the solder with a solder sucker or braid and try again. Check for solder splashes shorting across adjacent tracks on the circuit board, especially where connections are very close such as on integrated circuits ('chips'). Solder splashes are most likely on stripboard. You can check for shorts using a multimeter set it to it's continuity range, or low resistance range. Be aware if you do this though, that there will be a resistance between some tracks due to the components. Any resistance below 1 ohm between tracks is likely to be a solder splash. Run the soldering iron between tracks on stripboard to remove any solder bridges. If the circuit still fails to work you will need to refer to the circuit diagram and take voltage readings from the circuit to find out what's wrong. You will need a multimeter to do this (see tools). Remember that if you find one fault such as a reversed component and correct it, it might have caused damage to other components. If you cannot get the kit to work, some suppliers have a repair service, e.g. Maplin's 'Get - you - working' service. It's difficult to offer more advice than this here, as there are many possible causes of the circuit not working. KMAC.
