Thursday, 29 October 2009

002 Hand Tools

Some tools are absolutely necessary for building radio equipment. The following short list should be shopped for, before attempting any practical work. These are the bare minimum required to assemble the projects detailed in this book, and may be all you ever need...

Soldering iron
Pliers
Cutters
Screwdrivers
Knife
Spanners
Trim-tool
Multimeter

We'll discuss each tool in turn, and suggest what to buy to get the best value and utility.

Soldering Irons

We use soldering irons to melt solder, which is an alloy designed to melt at relatively low temperatures. The solder is allowed to flow over the joint area where we wish to connect one component to another. The actual art of soldering is described in section 007 of this book.

Soldering irons can be bought very cheaply from discount shops; the quality of these will vary from tolerable to unpleasant, but they will be cheap, and will get you started. The power rating to look for is in the range 20 to 40 watts. Anything more powerful will be too large physically, and if the temperature is unregulated (highly likely in a cheap iron), then it will be difficult too achieve a clean soldered joint. Big irons are useful for heavy work, such as antenna work or soldering pieces of PCB material together. Besides the iron, you will need a damp cloth to wipe the tip of the iron on to remove the accumulated flux residue. Better-quality irons have a piece of special sponge material set into a small tray in the stand; keep this damp and wipe your iron's tip regularly.

I use three irons for work at home; a temperature-controlled soldering station, a 100W high-power iron and a small butane-powered portable. The soldering station is good for general work, and mine has a cleaning feature with rotating sponges inside the housing, which retains the moisture the sponges need to work. The 100W iron is useful for soldering pieces of copper-clad together to make cases or complex modules. Larger screening cans are best soldered with a big iron. The gas iron has a very small tip, and I use it for surface-mount devices. It has an integral flint wheel in the cap.

Pliers

You will need at least one pair of pliers. A pair of snipe-nosed pliers: get miniature 'electronic' types, as what you are working with will be small, and the leads may not be gripped by larger types. A pair of large, engineer's pliers will also prove useful for gripping larger items. One special pair to get if you decide to take your wiring skill to the next stage is the round-nosed plier. These, as their name suggests, have a pair of long, thin conical tips; these are used to curl wire into a ring shape for making 'mechanical' joints. I modify mine to be as versatile as possible by filing one of the tips smaller than the other, to make a wider variety of joint sizes.

Cutters

Cutters are available in a bewildering array of shapes and sizes. The ones to buy first are electronic side-cutters. These are for cutting thin copper leads on components, but can also cope with light-gauge copper connecting wire. Never use them on steel wire; they'll lose their edge or break. For very fine work, a pair of 'flush-cut' cutters can be added to the kit. If you anticipate cutting heavy cable, such as hard-drawn antenna wire, then a stronger pair will be needed. A farmer's fencing tool is great for this, as it includes a range of functions in the head, including a hammer and a nail-extractor.

Screwdrivers

Buy just two screwdrivers initially, and add to the range as you feel you need them. The ones you need are a small Pozidrive, and a 3mm flat-blade. Philips screwdrivers are different to Pozidrive; the angle is steeper and they only have four large flutes. Pozidrive tips have an additional four smaller flutes. They look similar, but you feel the difference when you try turning a tight screw. Extra screwdrivers can be bought as needed, a 6mm flat-blade and a larger Pozidrive are sensible additions. If you decide to buy a screwdiver kit which includes a handle and a range of interchangeable tips, then you have lots of options, including hex bits and Torx bits. Be careful about quality; poor alloy choice means that the tips will wear quickly and chew-up your screw heads.

Knives

Use whatever knife style you feel comfortable with. Here at G1INF, the favourite is a Stanley blade in a home-made handle. The choice is between fine blades with good access for detailed work, and heavy blades with fat handles for meatier cutting.

Spanners

The most likely spanner sizes you will need are 5.5mm (M3), 7mm (M4), 8mm (M5), 10mm (M6) and it would be wise to get a selection of larger sizes, or a small adjustable spanner, for working with control spindle nuts. Small kits of combination spanners (ring one end, open the other) are to be found in hardware stores, bargain shops and market stalls. These are ideal for light home use, but be sure you get that essential 5.5mm spanner. Tip - A 5BA spanner works on M3.

Trim-tool

Unless you have worked with radio or electronics before, you are unlikely to have seen a trim-tool. They are essential for setting-up trimmer capacitors. It is tempting for a beginner to use a small screwdriver to adjust a trimmer, but you'll soon learn by your mistake. Screwdrivers have a considerable metal mass, and this adds to the capacitance of the trimmer (and the circuit you're trying to tune). The process will be very frustrating, and although possible if you have the time to cut-and-try the over- or under-adjustment, it's far easier and quicker to use the real thing. Cheaply available from electronic suppliers, trim-tools are a tough plastic rod with a tiny piece of hard metal in each end. They do not appreciably change the capacitance, and you can adjust the tuning in 'real-time'. One word of warning - Trim-tools are not tough enough to be used as a screwdriver, so don't be tempted.

Multimeter

A vital first piece of test equipment is a small, cheap, digital multimeter. At the time of writing (2009), these could be bought for around £5 in bargain stores. There are cheaper models, but they may not have the ranges you require. Cheap analogue (moving-needle) meters are rarely worth buying; they are usually too insensitive. Digital meters have a high-impedance buffer amplifier before the ADC, and are very sensitive. A better-quality analogue meter has its uses. You can see trends in the measured value, and for some measurements it simply feels more comfortable to watch a needle swinging.

Minimum specification for a multimeter:

DC Volts ranges 0.5V to 500V
DC Current ranges 100mA to 10A
Resistance ranges 100 ohms to 2M ohms
Sensitivity - 20,000 ohms per volt (20K ohm / V)

Direct current (DC) voltage and DC current are the main parameters measured when testing a circuit. It is useful to check resistance in a number of situations. If you are unsure of a resistor's value, then measuring it with a meter will confirm it. Circuits can be checked (with the power off) with a resistance meter, and items like fuses and connectors can be analysed for faults.

The sensitivity is where many very cheap meters will fall by the wayside. The lower the sensitivity, the more current is taken from the circuit under test. If you apply a low-sensitivity meter to a high-resistance circuit, you will get a false reading, as much of the circuit's voltage will be drained by the meter. [graphic of meter loading]

One aspect of cheaper multimeters is the quality of the test leads. They will break long before the meter gives trouble, so note that both the pictured meters are fitted with home-made test leads. These are easy to make. Red 'bullet' crimp terminals are compatible with standard 4mm test connectors, and are cheap and easy to buy. A crimp tool for applying them should cost less than £3-.

Other Tools

Tools are seen by some as an object of desire in themselves. People collect tools, not because they need them, but because they look interesting, or they think they may one day have a use for them. If you want to amass a toolkit of your dreams, then go ahead, It's part of human nature. However, if you are fastidious about utility, then the tools above may be all you ever need. There are some extra tools worth considering, and they are described next.

Desoldering Pump

If you plan to make printed circuit boards, then a desoldering pump will be needed if you need to repair them. When a device is removed from a PCB, the hole invariably remains filled with solder, making it impossible to fit a replacement device. A desoldering pump is used with a soldering iron to remove the solder, leaving the hole open. They work like a back-to-front bicycle pump; you push the piston all the way into the cylinder until it latches, heat the joint to melt the solder and then apply the tip of the pump to the joint. Pushing the release button causes the piston to fly back under spring pressure, sucking the molten solder up the tip. The solder is collected in the cylinder, and will need to be emptied from time to time. Unscrew the tip carrier, and shake out the solder droplets. Any which remains stuck to the face of the piston can be released with a small flat-bladed screwdriver. Always wash your hands after this operation, as the finely-divided solder powder is easily ingested, and is toxic. There may be local regulations for the disposal of heavy metals, so either take advice from your local authority about disposal, or consider recycling the solder.

Wire Strippers

I have deliberately left wire stripper out of the list of essentials, because they are unnecessary for low-volume non-commercial wiring. I only have one wire stripper in my radio toolbox, and that is a special one for a particular fine, single-core wire I sometimes use when prototyping digital equipment. I keep wire strippers in my 'commercial' wirer's toolbox, because my clients expect me to use them, and I do. But at home, I have other ways.

There are at least three ways to take the insulation from the end of a wire without using wire strippers. The first, and least recommended, is to place the wire between your teeth and pull. The chances of chipping a tooth are high, and you run the risk of ingesting slivers of wire. Don't do it! Another way is to slice around the insulation with a knife, and pull off the resulting tube of insulation. This works well, but care must be taken not to cut the wire, or your fingers.

The most frequently-used method is to use your side-cutters. Grip the wire with your cutters, with the flat side of the cutters toward the end of the wire, and pull. It takes practice to remove the insulation cleanly, but once the knack is acquired, you won't look back. This method works well with multi-stranded wire, which is the commonest type. It is flexible, due to its rope-like structure, and the strands deform under the pressure of the cutters, so that more of the cut is applied to the insulation. When stripping single-core wire, make a rotating cut with the cutters before applying the pull.

Don't use this method if you are working in industry, as it is not approved by any employer I've met. You will inevitably mark or even cut through strands of wire when you're learning, but practice makes perfect.

In my experience, a cheap pair of strippers will cause more damage than the use of side-cutters, especially in inexperienced hands. Try the side-cutter method, and by all means invest in a pair of strippers if you feel the need. The type popular with installation electricians, which have a pair of jaws with a dozen or so tiny teeth, are ideal for everyday uses. For high-quality work, a pair of separation-jaw strippers will give first-class results. These are approved for use on aircraft and military equipment and are expensive.

As I mentioned in the first paragraph of this section, I keep a special stripper for miniature solid wire. It is specially designed to cut the insulation, and leave the core conductor intact. These, like the separation strippers described above, are not cheap. The one in the photograph has lasted the author for over twenty-five years.

Test Equipment

You will be able to do a lot of testing with just your multimeter. Its capabilities can be extended by making add-on modules, some of which are described in the projects section of this book. They will allow you to measure capacitance and radio-frequency power. There are other projects there which don't involve the multimeter; these include the noise generator, audio amplifier and gate dip oscillator. Other items of test equipment which will be useful to a radio experimenter are outlined in section 017, but as they are expensive and complex, they will not be discussed at length. The two main equipments in this category are the oscilloscope and the spectrum analyser; get an oscilloscope if you can, but check article 017 'Radio Frequency Testing' before you buy.

Care of Tools

I possess tools which date back to my apprenticeship, over thirty years ago. They've stayed with me because I've looked after them, and they've looked after me. Storage of tools is important, to keep them from damage (and from damaging people); an old adage - 'A place for every tool, and every tool in its place'. Keep your tools in a dedicated box, or set aside one or two drawers of your desk for them. Keep them clean; wipe them down with a dry (or slightly oily) cloth, and lubricate moving parts when needed. Pliers and cutters need their hinge joints oiled at least twice a year, more frequently if you use them full-time.

A useful way of storing test leads is to coil them individually, and pop them into small ziplock bags. Squeeze the air out before the seal shuts, and they snug down into a drawer or box very neatly without sprawling everywhere and tangling. If you have wall-space, hang them on hooks for easy access.

Instruments need special care. Check the battery occasionally. Some instruments use a tiny current, and the battery can degrade and leak before it is exhausted. Protect meters and other sensitive equipment from mechanical shock; moving-coils meters are particularly delicate, and a little attention to handling and storage will keep them safe. Protect them when storing, tarnsporting or even in use by means of polythene foam cushioning.

Other Workshop Facilities

A good stout bench, desk or table is needed to work on. I know amatuer constructors who cheerfully work on a bureau, wooden tray on the lap and even on the kitchen work surface. There have been designs published in the old paper magazines for special electronic hobbyist's work-stations.

A vice can be very handy; make sure it's well secured to the bench, and that the rear (fixed) jaw is overhanging the edge of the bench. Cupboards for storing equipment and components, small boxes for keeping things tidy, drawer-cabinets for small items. Take time to think how best to arrange your working space, and ask the rest of the household for their opinion!

Location

Think carefully before setting up shop in a shed or other outside structure. Is it dry? Does it freeze? Some devices (LCDs are an example) can be damaged by very low temperatures. Inside the home is best, but an outside shack can be a rewarding retreat if you can keep the temperature up and the damp down in winter. My mentor, Eric G3HTP (SK), kept his station under the stairs; he was quite comfortable, and far enough from the sitting-room not to disturb the family. I work in a lean-to extension at the back of our house, but I have used a metal shed, which made an excellent ground for my antennas.

Monday, 26 October 2009

24MHz HF Theremin

I've been wanting to blog this for a few months, but life got in the way of preparing enough material for release. I've updated the static site at g1inf4u with enough information for an experimenter to try their luck with one. The full link is here, and do please comment if you'd like more information.

The theremin is a 'mature' project; it's been around for a couple of years. The original still works, and I find it a great asset when I'm teaching the art of the Boatswain's Call. The two instruments are very close in character, and the way they are played. They share the distinction of being the only instruments whose pitch is controlled without the player's fingers touching it; only the distance from the tone-determining antenna or hole is relevant.

Theremins are relatively rare. I've just had to add the word to my netbook's dictionary, and few people recognise the word, either. The sound is unmistakeable, however, and while similar to a bowed saw, the range of frequencies is quite large. My theremin can make any tone from a low ten-hertz growl to a ten-kilohertz shrill.

I've seen pocket-sized theremins cropping up here and there, but none offer level control. I've used an ORP12 photocell with a white LED, and this gives a useful dynamic range. It would need a window amplifier to cut off the signal entirely, but then the circuit begins to get complex. Currently, it's simple and elegant.

Sunday, 25 October 2009

001 Health and Safety

When I was sixteen, I began my apprenticeship as an avionics / instrument technician. The first thing we did was to attend a lecture on industrial safety, complete with scary movies of industrial accidents and a long list of 'thou shalt not' behaviour modes. This was before we'd even seen the workshop which would be our daytime 'home' for the next forty weeks.

It would be wrong of me to treat my readers any differently; safety first and always. This brief post will outline the essentials of radio experimenter's safety knowledge, but be aware that the author is not a H&S professional, and the reader is advised to take local expert advice before beginning work.

The potential hazards include:

Risk of burning. Soldering irons have a very hot functional end; the temperature is usually set to around 360 degrees C, but may be higher where an unregulated iron is used. Molten solder is at the same, high temperature, and because it is a liquid (and a heavy one), it can flow, drop or spray and cause burns.

Risk of cutting / abrasion / amputation. Some tools used have functional sharp edges; knives, hacksaws, chisels, etc. Always cut away from your body / hand / other parts. Take great care when cutting thin sheet materials; the edges will easily cut you.

Risk of puncture wounds. Some tools have functional sharp points, and care must be taken to avoid being stabbed by your own spike, needle, needle-nose pliers etc. Tightening a cable tie with pliers is particularly hazardous; the tie may break, and the pliers will move fast. Take care with cut wire ends. Larger wire sizes make sharp, stiff spikes.

Risk of poisoning. Some of the chemicals and materials used in electronics are dangerous. Do not open electronic components. Many contain susbstances hazardous to health, such as beryllia, polychlorinated biphenyls and lead alloys. Solder may contain lead in high proportion. Always wash your hands after handling solder.

Risk of respiratory irritation. Be very careful when cutting fibreglass panels; the dust is a respiratory irritant. Wear a dust mask, and if possible operate a vacuum cleaner by the work when cutting. Solder contains a resinous 'flux', which will vapourise when heated. Make sure you have adequate ventilation, and use a small fan if possible to draw the fumes away from you.

Risk of electrocution. Do not use mains power for your projects. The risks far outweigh the convenience; you can change a battery, but you only get one life. Make sure you electric-powered tools (including soldering iron and bench lamp) are in good condition, with no frayed or damaged wires. If in doubt, get a qualified electrician to inspect them.

Risk of radio-frequency burns. The projects, as published, do not produce enough power to cause significant danger of RF burns, but you should be aware that even modest RF energy can produce very painful and potentially dangerous burns on the skin.

This list is by no means exhaustive, and other safety information will be included in future articles as necessary.

I repeat once more - I'm not an expert - take advice if you are at all unsure. Work safe!

Basic Skills - Introduction

In support of the projects, I will be releasing some skill-related posts. These articles give the reader an introduction to each skill, and will also give links out to any resources the author finds during his research. The content is based on the author's own experience and learning, but there's a lot more to know.

The set begins as it should, with words of caution. Electronics assembly and experimentation is potentially hazardous, and the reader must make him / herself aware of these hazards. This first 'Health and Safety' post is by no means definitive. Safety information will be given occasionally as the topical need arises in future posts.

Take note that the author is not a Health and Safety professional, and whilst the advice given in this blog is given in good faith, the reader assumes all responsibility for his / her own safety. If in any doubt, take professional advice before undertaking any potentially hazardous operation.

List of forthcoming posts:
001 Health and Safety. Safety first, and always.
002 Hand tools. Outline of basic radio-construction hand tools. Other tools will be introduced and discussed topically, later in the series.
003 Basic fitting skills 01 - Hacksawing, filing, finishing. How to cut metal.
004 Basic fitting skills 02 - Drilling. How to make holes.
005 Basic fitting skills 03 - Tapping and threadcutting. How to make threads.
006 Electronic skills 01 - Cable preparation. How to strip cables and wires.
007 Electronic skills 02 - Soldered joints. How to make a joint, and solder it.
008 Electronic skills 03 - Wirewrapping. How to make joints without solder.
009 Electronic skills 04 - PCB making. How to make your own printed circuit boards.
010 Electronic skills 05 - PCB assembly. How to fit devices to a PCB.
011 Electronic skills 06 - Elementary panel wiring. How to wire-up electronic equipment.
012 Electronic skills 07 - Advanced panel wiring. Advanced techniques, including lacing.
013 Electronic skills 08 - Prototyping with stripboard. How to make projects using stripboard.
014 Electronic skills 09 - RF prototyping with copperclad. How to 'skywire' circuitry.
015 Electronic skills 10 - Basic circuit testing. How to make sure your project works.
016 Electronic skills 11 - Audio frequency testing. How to check for sound quality.
017 Electronic skills 12 - Radio frequency testing. How to check that new radio.
018 Light fabrication 01 - Sheet work. How to cut and fold cabinets.
019 Light fabrication 02 - Soldering. How to join sheet materials with solder.

There is no timeline here because these 'skills' posts will be interspersed with the regular Project posts. When a significant number are published, I'll add a sidebar navigation to allow easy access to both the skills and the projects.

Thursday, 22 October 2009

Simple AF Amplifier

The Simple Audio Frequency (AF) Amplifier. An easy and useful introduction to home-build electronics, this project will take a low-level audio-frequency signal and boost it to 200 times its original strength. It has a level control to adjust the output for comfort, and will drive a pair of iPod / MP3 player headphones, or a small loudspeaker. It uses a 9V battery (PP3 / MN1604), and requires no setting-up or test equipment. To make it, you will need the following parts:
  1. LM386 audio amplifier device
  2. 10k logarithmic pot with switch
  3. 1uF 16V electrolytic capacitor
  4. 10uF 16V electrolytic capacitor
  5. 100uF 16V electrolytic capacitor
  6. Red 5mm LED
  7. 1K-ohm resistor (1/8 watt)
  8. 3.5mm stereo jack socket
  9. 2-off 4mm banana sockets
  10. Thin insulated wire (150mm)
  11. PP3 battery clip
  12. PP3 9V battery
  13. 100x55mm single-sided copper-clad board
An experienced constructor would find most (or all) of this in their junk-box, but a newcomer to the art will need to buy these things new. I plan to market a kit of parts for this project, along with all those which will follow in the weeks and months ahead. Two big-name suppliers of components are Farnell ( http://uk.farnell.com/ ) and RS Components ( http://rswww.com ). Farnell may be the better bet for the non-corporate buyer, and they carry the stereo socket ( p/n 1280747 ), whilst RS do not. You will have to buy the sockets in multiples of five, as that is their packet quantity. No worries - you''l find uses for the other four in other projects and experiments. Another source of components is from old or broken equipment; see my article - http://www.lulu.com/content/e-book/component-harvesting/5327360 for more information.

You will of course need tools, and solder. Soon, I'll be adding teach-in articles (including videos) on tools and techniques; but for now, unless you already have the skills and tools, ask someone who knows how before attempting to make this project. Stick around! I'll tell you how it's done. I've spent over thirty years in the electronics industry, in several varied jobs, and I've picked-up a lot of knowledge and skills down the years. I intend to pass it all on to you.

The panel drilling is very straightforward. There are nine holes, and you'll need 3mm, 5mm, 6mm, 8mm and 10mm drill bits. Drill all holes initially with the 3mm bit; this makes it much easier to start the larger drills, and this first drilling size is called a 'pilot hole'. Make sure you clamp the panel when drilling. If the drill bit snatches the panel, it'll whip round and catch your hand. A G-clamp with a piece of wood to spread the load makes a good makeshift clamp. Clean the raised burr from around the hole edges with a larger-sized drill bit (hand-held), and then buff-up the copper surface with scouring pad ready for soldering.

Mount the sockets and pot first, locating them in their holes and carefully tightening their nuts. With care, a pair of snipe-nosed pliers may be used to tighten the nut of the stereo socket. Bend pins 3 and 4 of the LM386 up, and then outward, level with the top surface of the plastic case. These will be soldered to the panel as 'ground' connections. Turn the LM386 over. With the writing-side down, you have the remaining six pins sticking upright like a dead insect. Connection to these pins is now easy, and they are clear of the panel. Bend the 10uF capacitor's leads around as in the layout picture, and solder the capacitor to pins 1 and 8 of the LM386. These pins are at the 'notch' end of the device. Now add the remaining components. The red LED is pushed through the panel, and it's cathode lead is soldered directly to the panel. This is different to the circuit diagram; the diagram shows the resistor in between the cathode of the LED and the panel. It will work either way round; this is a good example of the flexibility which can be employed in electronics. Things aren't always this easy or straightforward, but I haven't the space now. I'll expand on this and much more, later.

Connect a PP3, a pair of headphones, and switch on. A buzzing will be heard in the headphones if the input socket is touched. What can you amplify? Try a magnetic (moving-coil) microphone, or an electric guitar. Search the web for 'crystal set' radio designs; the output can be amplified by this project. If you want to use a computer-type microphone (electret), it will need a power supply. This can be done by connecting a 47k resistor between the input socket and the switched side of the power switch. This will put around two volts on the microphone.

This simple circuit is simpler than normal for an LM386-based amplifier. I've left out three components; and these may be added if the amplifier is unstable or noisy. They will not normally be necessary, but you should be aware of them. A 100uF capacitor can be added between pin 6 of the LM386 and the panel, with the + of the cap to pin 6. This 'decouples' the power supply, stopping spurious signals getting into the device via the power supply. It also helps to stabilise the voltage, acting as a reservoir. Two other devices normally used in circuits of this nature are a 10-ohm resistor and a 100nF capacitor in series, connected from pin 5 (the output) and the panel. This 'Zobel network' helps to cancel-out the reactance of the speaker's coil, but if headphones are used the inductive reactance is too small to be of consequence. If you hear popping or howling when using a speaker, add the Zobel components.

Next week, I'll offer up some skills. There's a lot to learn, and the basics need covering first. When I was trained as a wirer, many years ago, we were instructed to wire-up panels fitted with tagstips and terminals, and the joints were made such that they held together mechanically. The units we made had to work before they were soldered. The wires had to be laid straight, and the stripping accurate. Any deviation from the rigorous standards, and the instructor pushed a screwdriver through the wire, and politely asked us to 'do it again!'. I'm not that overbearing; but I will teach you all I know about wiring, fitting and electronics assembly. Valves, Transistors, ICs, panel wiring, PCBs, wirewrapping, soldering, stripboard, the lot.

Theory will be added into the mix as required. I will not be teaching Maxwell's Laws of Electromagnetism, but I will tell you why you don't need them.

Sunday, 18 October 2009

Cheap and Easy 4mm Connectors


An interim post; I felt it was worth sharing. I have used red bullet crimp connectors for some years as a cheap alternative to 4mm 'banana' plugs, which are used for test and measurement connections. Only the red ones work; the yellow and blue crimps are too big. Earlier today, I found it was easy to use the female crimps to make workmanlike sockets for use in test equipment.

All you need is a red female bullet crimp, and a pair of M8 nuts. It's simple. Use a nut to cut a shallow thread in the body of the crimp, and then use a pair of nuts to mount the crimp in the front panel of your new home-brewed meter, power supply, generator, whatever. I found it easier if the wire was already crimped into the terminal; the flattened, crimped section can be held with pliers while the nut is wound up the barrel of the crimp terminal.

For a really smart finish, you need a powerful soldering iron. A 100-Watt soldering iron has enough power to solder an M8 nut to a piece of FR4 copperclad. Drill an 8mm hole in the panel, lightly assemble a nut to the rear of the panel with a short bolt in the hole, and heat the nut. When it's hot enough, flow a little solder around the nut. Just add enough to give a 3mm 'fillet' joint. Wait until the nut has cooled before winding the crimp barrel into it; if you are tempted to do this in a hot nut, the crimp will shrink with the heat and drop out!

These crimp terminals are sold in motor factors, DIY stores and good, old-fashioned hardware shops. You'll find the M8 nuts in the same places. The connectors made in this way are fully compatible with 4mm banana plugs and sockets, and the tooling is cheap, too. Buy the simple pressed-steel cheap one you see in the photos; you can pay a lot more, but these work well enough for our purposes. Besides, you get a wire stripper, screw cutter and wire cutter in the tool as well.

Thursday, 15 October 2009

Back to Basics

I've decided to start over. New ground rules for myself, and heaps of benefits for readers.

(1) I will post updates here regularly, every Thursday. If anything can't wait, it'll get posted, but the Thursday post is the routine.

(2) The amateur construction ebook will have its projects posted as news items here, with links to PDFs as they are completed. The project PDFs are free for anyone to download, anytime, anywhere. All I ask is that you download, and not link to them. 'Bandwidth thieves' will be dealt with.

That's it! Just a little more commitment and organisation this end. Enjoy.


So, starting over means back to square one? Yes, and it's real basic. The first project is a fundamentally useful one, and it has just ten components, including all connectors and the FR4 panel it's built on. I can't claim originality for this one; it's straight out of the data-sheet for the LM386 audio amplifier. Anyone with basic electronic tools can build this, and the parts will cost you around £3-50 total. If I were to present this as a kit, it'll cost you £7-50 including post and packing to UK mainland, battery not included. That's a thought I'm going to mull over.

The LM386 amplifier is available in a variety of sub-types; the only ones worth noting are the N-1 and N-4. The N-1 is the cheapest, and will deliver around 300mW. The maximum voltage is 12V, making it ideal for use with a 9V PP3 battery. For higher voltages and more power, the LM386N-4 can use up to 18V and supply 1000mW (a whole watt) of audio power, great for small speakers. Its Farnell code is 1184987, and they sell it for 57p.
Next post here will include links to this first project, and give an overview of the next. I'll also include links to things I've discovered while researching 'out there', a practice harking back to the original purpose of blogging; a list of links and commentaries on websites.

Tuesday, 13 October 2009

New Way of Business at G1INF

I have on my bureau, alongside my netbook, a small lump of FR4 which has seen more prototype radios than the skip behind one of my old salt mines. It's about to get another ride on the resin-cored express, and this time it's a very simple little project.

I've rationalised the way I'm going to present projects. I'll start small, and build up to meatier jobs. The progress will be rendered here in the Notes, and written-up in full as a project at g1inf4u.

Mystified? I'll reveal all in a couple of days.

Friday, 2 October 2009

Diversion into sales

I'm letting the new radio percolate for a few days, while I sort out some sale stock for my eBay account. I've built up a significant amount of surplus over the years, and I'm disposing of some of it to make room, and funds, for the kits project. I'll be releasing the stuff onto the lists over the weekend, and I'll update here with links and information on the items available.

Another thread of the business is the information products. I'll be unable to commit any serious time to this for the next few weeks, as the hardware sales will take precedence. The only new information likely to be published will be for the kits!