marți, 4 noiembrie 2014

Curious C-Beeper

Curious C-Beeper

Curious C-Beeper is a fun to build little probe that can be used to quickly detect the capacity of capacitors in pF nF range, test their stability with temperature changes, find broken wires, locate wires, trace wires on PCBs, and to locate live wires behind the walls without touching them. The circuit uses three transistors to make a most unusual capacitance beeper probe. When a capacitor is touched to the probe, the probe beeps at a frequency that varies with capacitance. The frequency change is so steep with capacitance that tiny capacitors may be precisely matched or an exact fixed value may be selected to replace a trimmer in a prototype. If the user has reasonably moist skin, simply holding one lead of the capacitor to be tested while touching the other lead to the probe is all that is necessary. The user's body forms the other connection through the beeper's metal case. When the beeper is properly adjusted it draws only 10 uA with nothing touching the probe - no power switch is required. This design is optimized for capacitors less than about 0.1 uF (100 nF). Large capacitors give a low frequency "clicking" sound and small capacitors sound a tone that increases as the capacitance decreases. Many decades of frequency change occur over the beeper's range giving even the more tone-deaf among us sufficient change to discern slight differences in capacitance. The entire device is powered by two CR2032 lithium cells that fit into TicTac box. The use of power switch is unnecessary since the circuit consumes almost no power when not being used.

Curious C-Beeper 

The Curious C-Beeper will become indispensable in virtually no time and has many uses such as:

Quickly match capacitors and trimmers. Forget the capacitance meter when matching parts from the parts bin or selecting a fixed value to replace a trimmer - the "fingers as conductors" feature makes the C-Beeper super-fast when searching for that perfect value.

Easily detect tiny variations when a capacitor is heated or cooled to quickly discriminate between NPOs and "Stable" dielectrics. General purpose and temperature compensating dielectric are quite easy to spot.

The C-Beeper makes an excellent cable fault locator - the end with the open will have less capacitance and beep at a much higher pitch or not at all. A break along an unshielded bundle can be spotted by grabbing the bundle at various points while listening for the capacitance change.

Identify which wire is which at the end of a bundle without stripping back the insulation. Touch the bare wire at one end with the C-beeper probe and pinch the still-insulated wires at the opposite end. The right wire will drop the pitch.

Identify traces on unpopulated PCBs right through solder mask - touch the C-beeper to the exposed end of the trace and use a finger to follow the trace across the board.

Check the value of feed through capacitors after they are installed - a difficult operation with a capacitance meter.

Identify varicap diodes. They beep at a much lower pitch than regular diodes.

Make a small flat plate electrode and line voltage electric fields may be detected. Follow wires behind walls and ceilings or determine if wires are "hot" without touching them. The C-Beeper's tone is modulated by the AC voltage causing a warbling sound. Circuits with lamp dimmers, solid-state switches or fluorescent bulbs are especially easy to detect due to the harmonics on the line.


List of components:
C1 trimmer capacitor 30pF
C2 1nF
D1 1N4148
LED1 LED3MM
Q1 BC559C
Q2 BC559C
Q3 BC549C
R1 1M
R2 2M
R3 5M
R4 2M
R5 1M5
R6 33k
R7 33k
R8 270R
SG1 Piezoelectric Speaker

The probe tip is made ​​from silver wire 0.8 mm. The box brings out the ground through a screw. C1 trims the capacitance set point for LED and Piezoelectric Speaker.


Curious C-Beeper


Curious C-Beeper


Curious C-Beeper 

LM386 Utility Amplifier

LM386 Utility Amplifier

It's always handy to have a little amp kicking around to trace audio signals, test mics, CD tape and TV audio outputs. You know, something that doesn't weigh a lot and isn't clumsy. There are tons of uses for this little circuit. There are a couple of versions of this amplifier chip. Both are 8 pin DIP packages and the difference between the two are apparent by their part numbers. Either are suited for this circuit provided the supply voltage does not exceed the recommended 5 to 12 volt DC range. Power output can range from about 325 mW to about 750 mW within this supply range when using an 8 ohm speaker. Power it with batteries or a small DC supply...why not solar cells or a little windmill generator?

LM386 Utility Amplifier

The circuit shown has gain of about 200. VR1 is the volume control. The voltage rating of the DC blocking capacitor C1 should exceed the supply voltage of any piece of equipment you want to probe if you're using this as a signal tracer. Tube amp circuitry supply rails can exceed 600VDC, so make sure you choose C1 with this consideration in mind.

Parts
C1, C2 10uF 16V electrolytic
C3 .1uF capacitor
C4 .05uF capacitor
C5 220uF 16V electrolytic
R1 10 ohm 1/4w resistor
U1 LM386 amplifier
VR1 100K "A" taper pot
SPKR1 8 ohm speaker

Mini FM Transmitter

Mini FM Transmitter

Here's how to build your own mini FM transmitter. It transmits FM waves so you could easily receive the signals on your mobile phone, radios, etc. As the name and the picture indicates it is very small and is approximately the size of a 9v battery clip. With this FM transmitter you could start your own mini FM station. The circuit uses BC547 transistor to amplify the signal and then frequency modulate it. It uses "frequency modulation" most commonly known as FM, the same principal to transmit audio signals captured by the microphone.

Mini FM Transmitter 

Lets start with getting all the parts.

Components

BC547 Transistor
An microphone
A variable capacitor 47pf
An Inductor (see steps for description)
4.7k Resistor
330ohm resistor
1n capacitor (102)
10p capacitor
9V battery
LED(optional)

Tools

Soldering Iron
An FM receiver (any mobile phone)


I got almost all of the components from a pile of old PCBs I had in an old forgotten box. All I had to get was the BC547 and the electret microphone. Actually I did find the BC547 in an old PCB but i was not sure if it would work. It looked quite burnt to me. The old PCBs had many components resistors, crystals, diodes, etc. I may use them some day and for know back in the box.

I had to de-solder the parts of the old board, for those who don't know how to solder and de-solder there is a bunch of instructables that describe how to do this and learning to solder is not a hard task.

First of all lets start with cutting up a PCB to the required size. The size to compare is a 9v battery clip, it might look quite small in the beginning but don't worry it would hold all the components just fine. Use a sand paper for smoothing the sides of the PCB and to clear out any rough edges.

Make sure to get a PCB with big holes as the variable capacitor pins won't go in the standard size holes.

You can get the microphone at a local hardware store. And be sure to get some male pins to hold the microphone in place refer the picture as to how to solder the microphone in place.

Why not use some wires to hold the microphone?

I would not suggest wires as when you tape the circuit if the last few steps you would not get a clear audio. I tried it and got a lot of noise. I got lesser noise when I used the male pins soldered to the microphone.

Once you're done with the PCB and know where and how to solder the microphone now it's time to complete the rest of the circuit. Follow the circuit above and solder all of the components. Make sure not to leave any space between any of the components if you need to get the circuit small. For the inductor use 0.5mm wire and 8 turns, with each turn with a diameter of 6mm.

And for the antenna just use a thin 5cm long wire. For more stability you could center tap the coil and solder the antenna to the center tap.

Also If you notice the circuit has a LED in it, it is used to show when the circuit is functional. I did not add the LED in my circuit because it was draining my battery faster.

Once you got the circuit like the one in the above picture, it's time to cover it with tape. I used wiring tape to cover the whole circuit except the microphone and the variable capacitor. This is an important step as when you proceed to the next step, where you tune to the required bandwidth. Touching the circuit (mainly the coil) with your fingers would lead to severe noise.

You could also use a heat sink instead of tape, I used tape because I wanted to experiment withe circuit so I did not want it to be permanent.

Now it's time to tune the circuit to a required bandwidth, you could do this in two ways.

Use your mobile phone to find the signal
Manually tune the variable capacitor to match a frequency

The first step is recommended all you have to do is power the circuit and turn on auto find bands on your mobile. Your mobile would scan for channels and all you have to do is look for your transmitter (play some music in front of the transmitter) on that list.

The second method is time consuming, in this method you have to turn on your radio and the circuit. Keep the radio at a specific channel, and then tune the variable capacitor extremely slowly. When you hear stuff on the radio maybe a song that you are playing stop and the bandwidth on the radio is the required bandwidth.

After using the 9v battery circuit for some time I thought of replacing the battery with rechargeable Li-ion batteries. If you have viewed my previous instructables you would have seen that I use these batteries a lot.

The rechargeable batteries provide longer transmission than the common 9v battery.


Mini FM Transmitter


Mini FM Transmitter


Mini FM Transmitter 

How Google's New App can organize you

Last week Google introduced a radical new mail app, built on top of Gmail, that promises to cut through the pain of managing your inbox. Countless apps and extensions have promised to relieve the suffering of email, and I'm always open to trying another one. I spent the past few days using Inbox as my primary email app, and here's how it works.

 Inbox's approach is focused on giving you access to the most important information first, eliminating the need to dig through emails for essentials such as attachments, photos, and travel details. Its smart reading function abandons the classic chronological presentation of email in favor of grouping similar messages together and prioritizing them by importance.

 The main dashboard, titled simply, "Inbox," acts as a feed of all your incoming mail, which is placed into smart categories Inbox calls "bundles." Your Inbox comes with a set of pre-categorized bundles such as travel, purchases, updates, and social media, but you can also create your own bundles and tell Inbox what kind of messages to automatically throw in there.

 Bundles are similar to the "Labels" and "Categories" you're already using on Gmail. The difference here is that Inbox presents your emails in the bundles themselves, and the bundles move up and down your timeline as new emails arrive. For example, I took a label I already had in Gmail titled "Pop Mech," and enabled bundling in its settings. Now, anytime an email arrives that fits into the parameters I've set for that bundle, such as all emails from certain people, with certain email domains, or containing certain keywords, it will automatically be placed in the "Pop Mech" bundle, and the entire bundle will appear at the top of my inbox with the most recent email in bold.



Located in the bottom right corner of the dashboard is a red circle with a plus in the center you'll recognize from some of Google's other mobile apps. You can hover over it on the web app or simply press it on the mobile app to compose an email to any of your most recent contacts, or to compose a reminder that will be pinned to the top of your Inbox. 

Like Gmail, Inbox scans all of your emails, but here the most important content in each message is highlighted and previewed so you don't have to open each email. For example, PDF and photo attachments will appear below the subject, as will recent purchases, flight information, and other reservations, making it easy for the user to preview that content straight from the Inbox. This is by far my favorite feature of the app. With just a glance, I can navigate the essentials all in one view. 

Inbox also gives you multiple options for individual or bulk actions on your email, such as "Pin," which saves that message to the top of your Inbox, effectively acting as a "to-do" reminder (implying that people don't only use email for messaging, but also to organize their day-to-day priorities). There's also "Snooze," which allows you to defer that message to a later time, at which point that email will pop back up at the top of your Inbox, and "Done" which doesn't delete the email but places it in a separate category to signify that you've already taken care of it. Inbox includes helpful shortcuts, too. Swiping an email left will snooze it, while swiping right will mark it as done. 

The "Snooze" and "Done" folders are easily accessible from the top of the sidebar, and you can access all pinned items from the thumbtack toggle in the top right corner of the inbox. To activate a bulk action in the mobile app, press and hold any email in that folder for approximately 3 seconds to check or uncheck multiple messages. My only quarrel with this is that there's no similar one-step action for sending emails to the trash folder. Instead, you have to push the "options" button, then hit "Trash." While the web app doesn't allow you to select multiple emails for bulk actions, you can still "sweep" all items in that bundle as "done." 


The mobile app and web app are almost identical, with the web app also giving you quick access to Google Hangouts, Google Drive, and your other Google notifications. One final (and major) setback is that unlike popular email management apps like Outlook or Mailbox, Inbox only works with Gmail accounts. 

Although my first reaction to Inbox was an overwhelming anxiety over its unfamiliar presentation and initially unclear functionality, its features have proven quite useful over the few days I've been using the app, especially the preview function for important content. Being able to see what I need without opening each email saves time and, along with Inbox's bundle feature, adds to the organizational appeal Google is clearly striving for. 

This is a smart mailbox for the busy user who simply has too many emails to manage with a basic mail app. Despite a few minor complaints, the app offers a definite upgrade from the classic Gmail app. Inbox does more than just organize your email; it streamlines the process of checking and composing them, too. Now go bug your friends for invites, or request one from Google

Seen on www.popularmechanics.com

Animated Necklace with LED

With the maker faire this month I decided to make some bling to bring. Having made 80 of these necklaces in august that I brought with me to burning man this year, the process is now super refined and easy. The cost to make one of these is very cheap, bordering on about 1.50 each. But the coolness factor is off the charts. At burning man I had a box of several colors of LED’s as well as some color fading ones. The color fading ones were by far the most popular. Anyway here is the how to…
The Acrylic:
For this project we will be using 2 thicknesses of acrylic. A .220 – .250 and a .120 – .125 thickness. Acrylic is ideal for this project over lexan for instance due to how it plays with the light from the LED’s.
The LED’s:
For this project you will need one 5mm led of your color. As stated before the color fading ones are very cool, UV will have a very short run time, 8-16 hours and red leds the longest run time.
Screw :
The screws you will want for this project are about .120 and .450 long. Ideally they will have a flat head on them so the don’t stick out to far. You can use what you have laying around or hit the home center for ideas and a minor price gouging.
Battery:
We picked up these batteries on ebay for about .50 each in larger lots. The 3V CR2026 is the ideal thickness for this project and should last 3-7 days in these necklaces.
A Pattern:
For this project we used Corel draw… yes I said Corel draw… Wow… one more time to reaffirm to myself… Corel draw… ok… that’s X4 if anyone cares to know. This app believe it or not is very very good for rapid pattern dev and works very will with the epilog mini systems. It also will export any format under the sun and is natively supported by Ponoko. Here is the file for this pattern(right click, save as).
So here we go. The laser is raster etching the words and vector cutting the top layer of the necklace that holds the LED and the pattern we want to display. The epilog mini 45 system realy zips through this material with ease.
Click here for the rest of the project.

12V Fluorescent Light Inverter

This is a low voltage 12V fluorescent inverter for powering two 20W or single 40W fluorescent tube. It's a circuit you can put together from junk box components and is a very simple to build. The transformer is hand-wound on a ferrite rod from an old transistor radio and the winding wire can be salvaged from an old transformer. The cost of powering the circuit is about 22 watts and this will produce the same light output as 60 watt incandescent light bulb.


12V Fluorescent Light Inverter

With a normal fluoro operating on the 240v mains, a ballast (or choke) is needed in series with the tube to limit the current after the tube has "struck". This ballast dissipates about 10-20 watts for a 20 watt tube and reduces the efficiency of the circuit. 

If the ballast is replaced with an electronic circuit and high-frequency transformer, the losses are less than 5 watts. Furthermore, if we do not drive the tube as hard as the 240v version we can get even better efficiency. 

The size of tube, you will need, will depend on the area you wish to illuminate and the battery capacity you have available, however it is important to realise that the higher wattage tubes offer the greatest efficiency. 

This is because they have a longer length and larger diameter (than say an 8 watt tube) and give more light over a larger area. That's why we have concentrated our design on the 40 watt tube. You can get plenty of circuits and devices that power the 4, 6 and 8 watt tubes but nothing has been done for the 40 watt variety. 

There is another range of tubes, commonly called the "compact fluoro" or high efficiency fluoro. These are a folded fluorescent tube having a rating of either 11 watts, 13watts or 18watts. They are not covered in this project as they are expensive to boy and more difficult to drive. They are actually driven VERY HARD and if you feel one after it has been turned on for a few minutes you will find the tube is quite warm. 

They are not really suitable for indoor use as they take a while to come on and don't give enough illumination for an average room. We have tried the whole range of these tubes and come to the conclusion that they are only suitable for outdoor use as a decorative lamp or for partially illuminating a dark area. 

This is one of those situations where the old-style product is the best. I think you will find that the glitter of the compact lamp has almost faded by now as the public has come to realize they are not the whiz bang invention of the century and have not taken over any of the areas already serviced by the tungsten lamp or standard fluoro. 

After all, you can buy a 100watt globe for less than $1.00 and a compact lamp costs about $20.00. It will take more than 5 years for the savings in electricity to equal the cheap 100 watt globe. 

The one problem that lets compact lamps down is the electronic circuitry. The electrolytics in the base are driven very hard and tend to dry out after a few years. We have found lots of discarded bases (with tube) with this problem. 

Apart from this, the fluorescent lamp has a number of advantages over incandescent lighting. The main one is efficiency. 

This is due to the fact that it's a cold light, in comparison to incandescent light where the light is produced by the heating of a piece of wire. 

The other advantage is the light does not come from a point source and thus it is more-evenly spread over a larger area. 

Fluorescent lighting is approximately 400% more efficient than incandescent lighting (50 Lumens/watt compared to 12 Lumens/watt for a 100 watt tungsten lamp), although there are some losses in the ballast. A 20 watt tube (plus 10-20 watts for the ballast) gives the same light output as a 100 watt lamp, when it is heavily driven in the 240v mode. 

For a normal household, the lighting component of the electricity bill is only a fraction of the total and doesn't warrant a house to be converted to fluorescent lighting. 

But if you are considering setting up a home in a remote area, where mains electricity is not available, you will appreciate the advantage of high-efficiency lighting. 

With modern electronic circuits, fluorescent lamps can be designed to operate very efficiently and with this project you can build the circuit yourself and operate it from a 12v supply.


THE 12V SUPPLY 

In any low-voltage situation the greatest component of consumption is lighting. This is because all the other appliances have been converted to some other form of energy. The fridge has been converted to gas. the toaster has been thrown out, the jug has been changed to a saucepan or kettle on a fuel stove and the electric fry pan has been forgotten. 

All that has been left is the lighting and a few small appliances such as the washing machine, portable TV and drill (12v rechargeable type). 

When considering the sort of lighting you need, you must take into account the type of work you will be carrying out such as eating, reading, repairing etc. 

For some of these, the light from a camp-fire will be sufficient while for repair work you will need the highest level of illumination. 

To provide the required level there are two choices. The standard 12v globe, and the fluorescent tube. 

I have not considered the use of gas lighting as they remove the oxygen from the air, produce a lot of heat and are potentially very dangerous. 

If you need to carry out fine, detailed work, you will need a standard 12v globe or even a 50 watt halogen lamp. 

However for general room illumination, a 20 watt fluorescent will be adequate. 

Let's see how we can make a 20 watt inverter. 

The project we will be describing is not designed to drive any of the compact (or folded) fluorescent tubes as they are driven much harder than ordinary tubes and get quite warm after only a few minutes of operation. 

This heating represents wasted energy and in this project we are trying to save as much energy as possible. 

Folded tubes are also less efficient than ordinary straight tubes as they have two or four tubes running beside each other and when they are illuminated, some of the light from one tube will hit against the walls of the others and be lost. 

The folded tube is not suitable for indoor use. All the tubes I have bought have been a failure. Some took a long time to come on - up to 10 seconds to "strike." 

The other disappointment is the weak output for the first 10 minutes or so. They take about 10 minutes to "get going." 

I have an 18 watt compact lamp in my room at the moment and cannot read the pages I am preparing. It's another invention that has "missed the bus" -they are just not quite good enough.
I am going to replace it with a 100 watt globe and come back. 

While in the process of changing the globe, I compared the 18 watt compact fluoro with our circuit driving two 20 watt tubes and found them to almost the same. They are equivalent to a 60 or 75 watt clear globe and is perfectly ok for general lighting in a room. 

There is an enormous difference between the circuit for a fluoro operating on 240v AC and one that operates on 12v DC.


20 WATT FLUORO 

The wattage of a fluorescent tube is a characteristic of its size and vice versa; the wattage determines the size. That's why a 20 watt tube is 2 feet long and a 40 watt tube is 4 feet long.
The design of a tube is a complex mathematical equation (a lot of experimentation has gone into its design). 

The tubes are filled with a gaseous mixture that produces ultra-violet light when operating and this light hits against the walls of the tube to excite the coating on the inside to produce visible light. 

The gas and the coating are all poisonous and the emission of the ultraviolet waveform from an uncoated tube is quite dangerous to the eyes, so experimenting with tubes other than operating them as per this project is to be avoided. 

You can buy uncoated tubes (called ultraviolet tubes) for lighting effects, EPROM erasing, special heating, and germicidal applications. Do not use any of these tubes in this project as the voltage we are producing will create different effects and damage your eyes.


12v INVERTER 

Now for the 12v version. 

The circuit doesn't require many components but its operation is quite complex. The clever component is the transformer. It performs 3 functions. 

Firstly it is acting as a feedback component for the transistor to create an oscillator circuit. Secondly it is providing a high voltage (over 1 000 volts) to strike the tube and keep it struck and thirdly it is supplying spikes of energy to illuminate the tube. 

The circuit is shown in figure 1 and we will take a detailed look at how the transformer carries out the three functions. 

The transformer in this project is not a lethal device as the output wattage is slightly below the value that produces electrocution. However the output is in excess of 1,000v and the ends of the secondary winding should not be touched when the transformer is operating. 

To get a shock you must touch both ends at the same time - it is not sufficient to touch one end and any other part of the circuit as the secondary is an isolated winding. 

Even a simple transformer such as the one we are winding in this project will demonstrate a number of interesting features. One of them is the ability to step-up a voltage. This is the main purpose in this project as we require a voltage of approximately 1,000v to strike the tube.
Another interesting feature is the availability to get positive or negative voltage (phase) from a separate winding on the transformer, simply by connecting the winding around one way or the other. In this project we connect the winding to get positive feedback so that a single transistor will drive the circuit.


HOW THE OSCILLATOR WORKS 

The oscillator works on positive feedback. This positive feedback comes from a separate 13 turn winding on the transformer called the feedback winding. 

The cycle starts by turning on the transistor a fair bit via the 180R resistor on the base and this causes current to flow in the primary winding. The flow of current causes magnetic flux to be produced by the winding and this passes through the ferrite core. The feedback winding is also wound around the core and the magnetic lines pass through this winding and produce a voltage.
The winding is connected to the transistor so that the voltage from the winding ASSISTS the voltage from the 180R resistor and causes the transistor to turn on harder. 

Thus more current flows through the primary winding and the magnetic flux increases. This causes more voltage to be produced in the feedback winding and the transistor turns on even harder. 

This continues until the transistor is fully turned ON and maximum current is flowing in the primary winding. 

Now comes the important part. 

Even though maximum current is flowing in the primary winding and maximum flux is produced in the core, this flux is a steady flux and not an increasing flux. 

The only time a voltage is produced in a secondary (or feedback) winding is when the flux is INCREASING (or decreasing). When the flux is stationary, the voltage in any of these windings ceases to be produced. 

Thus we come to a point in the cycle where the current in the primary is a maximum but the voltage in the feedback winding is zero. 

The only current flowing into the base of the transistor comes from the turn on resistor but this is note enough to fully turn the transistor ON and so the transistor turns off a small amount. 

This has the effect of reducing the flux in the ferrite rod and we now have a situation where the flux is DECREASING. This changes the situation in the feedback winding. The voltage in the feedback winding is now produced in the OPPOSITE DIRECTION and the transistor begins to turn off even more. 

The magnetic flux begins to collapse very quickly and this produces a very high reverse voltage on the base of the transistor (up to about 25v) to turn the transistor off completely. 

This is how we get a positive and negative voltage for the transistor. 

This is quite an amazing achievement as the voltage through the primary doesn't change direction - it merely increases and decreases in value - but the voltage from any of the other windings changes direction! 

The collapsing magnetic flux cuts the turns of the secondary winding and produces a voltage of about 2.5v per turn in the 450 turns, making a total of about 1 ,000 appearing across the ends of the tube. This is sufficient to strike the tube and as we mentioned above, the resistance (or impedance) of the tube reduces as more current flows. In our case the voltage across the tube is about 400v (this voltage depends on how hard the tube is driven and is riot a fixed value). 

When the magnetic flux has almost fully been converted to electrical energy, the 180R turn-on resistor on the base of the transistor starts the cycle over again. 

The voltages produced by the transformer are very spiky and the gas in a fluorescent tube is very quick to react to these spikes. The gas produces ultraviolet light that strikes the fluorescent material on the inside of the tube and causes it to produce visible light. 

The tube forms part of the load for the transformer and has an effect on quenching the spikes to the transistor so it is not advisable to operate the transformer without the tube connected.

PARTS LIST
1 – 2R2 1/4watt (for testing)
1 - 47R 1/4watt
1 - 180R 1watt
1 - 47k
1 - 100k mini rim pot
1 - 100ngreencap
1 - 100u 16v electrolytic
1 - BC338 transistor
1 - TIP 3055 transistor
1 - on/off switch
1 - 12mm bolt and nut for transistor
1 - heat-sink 5cm x 10cm
1 - ferrite rod 10mm dia x 8m long
1 - 30m winding wire .28mm dia
1 - 4m winding wire .61 mm dia
(wire diameters are NOT critical)
1 - insulation tape either sticky tape
or masking tape
1 - interlayer insulation - paper

Extras:
2 - 20 watt fluorescent tubes
1 - box to house project
1 - 6m of figure-8 flex to go between inverter and tube(s)

WINDING THE TRANSFORMER
The ferrite core of the transformer is an antenna rod from an old transistor radio. You could use a slab antenna but we have chosen a 10mm diameter rod, 8cm long and the first winding to be wound on it is called the primary. 

This consists of 58 turns of wire spaced slightly apart so that is occupies the centre 6cm of the rod. The first thing to do is wind two layers of insulation around the rod so that the wire does not touch the rod and create a short. 

Leave the first 8 - 10cm of wire and start winding with the thick .61mm wire. But firstly hold the end of the wire in place with a short piece of sticky tape folded over itself and stuck along the length of the rod, where the winding is to be placed. Continue winding and fix the other end in a similar manner, leaving 8 - 10 cm for connecting to the rest of the components. 

Place one layer of paper over this winding and secure both the start and end of the paper with sticky tape. Make sure this insulating paper is tight by rolling it like a cigarette before sticky-taping. 

The next layer is called the feedback winding and consists of 13 turns of the thin .28mm wire, wound in a spiral fashion so that it takes up the full length of the 6cm. 

Terminate both the start and finish of the winding with sticky tape to prevent it unwinding. Cover this with a layer of insulation. 

Now, for the final winding, called the secondary. 

This consists of 450 turns of .28mm wire, wound in 3 layers of 150 turns. 

The winding does not have to be neat and you could quite easily jumble-wind the turns and it would work perfectly ok, however there are two factors to remember. 

The voltage between the start and finish of this winding will be about 1,000 volts and the insulation on the wire is only about 100v. So the start and the finish must not be near each other. This also applies to most of the other turns so the best way to prevent the inner-turn sorts is to carefully wind the turns side-by side. 

This also produces the best results. 

Leave 8 - 10 cm of wire and hold the start in place with a piece of sticky-tape folded over itself and stuck to the insulation. Wind 150 turns neatly across the 6cm of the transformer and hold the last turn in place with sticky tape before placing a layer of insulation over the winding. Continue with the next layer and one more, making a total of 450 turns. 

Cover the last layer with insulation, tin the ends of each of the windings with a hot soldering iron and plenty of solder and the transformer is complete. 


CONNECTING THE TRANSFORMER 

The transformer has 6 wires. 

The two high voltage wires from the secondary can be connected around either way to the tubes. 

Either lead of the primary, can be connected to the collector, and the other end connects to the positive of the battery and 180R resistor. Now comes the difficult part. 

The feedback winding must be connected to the base and the join of the resistors so that the transistor gets positive feedback. You can do this by marking the start of the primary winding and the start of the feedback winding and connecting them in a particular way, but if you are wrong, a very high current will flow and the transistor will be damaged. We have devised a fail-safe method that doesn't rely on you having to remember which is the start of each of the windings, or the direction of the winding. It's called trial and error with safety resistor. 

Place the 2R2 safety resistor in the positive line as shown in the circuit diagram and connect the feedback winding any way you wish. Turn the project ON AND OFF very quickly. If the fluoro's don't come on immediately, the feedback winding is around the wrong way. The safety resistor will only allow 5amps to flow thorough the circuit and the transistor will not be damaged.


12V Fluorescent Light Inverter


12V Fluorescent Light Inverter


12V Fluorescent Light Inverter

12V Fluorescent Light Inverter