building circuits on breadboards

7/31/2019 Building Circuits on Breadboards

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Building Circuits on BreadboardsUses of BreadboardsA breadboard is used to make up temporary circuits for testing or to try out an idea. No soldering is

required so it is easy to change connections and replace components. Parts will not be damaged so they

will be available to re-use afterwards. The photograph shows a circuit on a typical small breadboardwhich is suitable for building simple circuit with one or two IC chip.

Connections on BreadboardsBreadboards have many tiny sockets (called 'holes') arranged on a 0.1" grid. The leads of most

components can be pushed straight into the holes. ICs are inserted across the central gap with

their notch or dot to the left. Wire links can be made with single-core plastic-coated wire of

0.6mm diameter (the standard size).Stranded wire is not suitable because it will crumple whenpushed into a hole and it may damage the board if strands break off. The diagram shows how the

breadboard holes are connected.NE555

The top and bottom rows are linked horizontally all the way across. The power supply is

connected to these rows, + at the top and 0V (zero volts) at the bottom. I suggest using the upper

row of the bottom pair for 0V, then you can use the lower row for the negative supply withcircuits requiring a dual supply (e.g. +9V, 0V, -9V).

The other holes are linked vertically in blocks of 5 with no link across the centre. Notices how

there are separate blocks of connections to each pin of ICs.


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Large BreadboardsOn larger breadboards there may be a break halfway along the top and bottom power supply

rows. It is a good idea to link across the gap before you start to build a circuit, otherwise youmay forget and part of your circuit will have no power!THEELECTRONICS

CLUB

Building a Circuit on BreadboardConverting a circuit diagram to a breadboard layout is not straightforward because the

arrangement of components on breadboard will look quite different from the circuit diagram.When putting parts on breadboard you must concentrate on their connections, not their positions

on the circuit diagram. The IC (chip) is a good starting point so place it in the centre of the

breadboard and work round it pin by pin, putting in all the connections and components for eachpin in turn.

Monostable Circuit Diagram

The best way to explain this is by example, so the process of building this 555 timer circuit on

breadboard is listed step-by-step on the next page.

The circuit is a monostable which means it will turn on the LED for about 5 seconds when thetrigger button is pressed. The time period is determined by R1 and C1 and you may wish to try

changing their values. R1 should be in the range 1kW to 1MW.Time Period, T = 1.1 R1 C1


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IC pin numbersIC pins are numbered anti-clockwise around the IC starting in the bottom left-hand corner, nearthe notch or dot. The diagram shows the numbering for 8-pin and 14-pin ICs, but the principle is

the same for all sizes.NE555

555 Timer IC Pin configuration

555 Timer IC Packages
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The 555 Timer IC is available as an 8-pin metal can, an 8-pin mini DIP (dual-in-package) or a

14-pin DIP.

This IC consists of 23 transistors, 2 diodes and 16 resistors. The explanation of terminals

coming out of the 555 timer IC is as follows. The pin number used in the following discussion

refers to the 8-pin DIP and 8-pin metal can packages.

555 timer IC 14 pin configuration

Pin 1: Grounded Terminal. All the voltages are measured with respect to this terminal.

Pin 2: Trigger Terminal. This pin is an inverting input to a comparator that is responsible for

transition of flip-flop from set to reset. The output of the timer depends on the amplitude of theexternal trigger pulse applied to this pin.

Pin 3: Output Terminal. Output of the timer is available at this pin. There are two ways inwhich a load can be connected to the output terminal either between pin 3 and ground pin (pin 1)

or between pin 3 and supply pin (pin 8). The load connected between pin 3 and ground

Supply pin is called the normally on loadand that connected between pin 3 and ground pin is

called the normally off load.
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Pin 4:Reset Terminal. To disable or reset the timer a negative pulse is applied to this pin due to

which it is referred to as reset terminal. When this pin is not to be used for reset purpose, itshould be connected to + VCC to avoid any possibility of false triggering.

Pin 5:Control Voltage Terminal. The function of this terminal is to control the threshold and

trigger levels. Thus either the external voltage or a pot connected to this pin determines the pulsewidth of the output waveform. The external voltage applied to this pin can also be used to

modulate the output waveform. When this pin is not used, it should be connected to groundthrough a 0.01 micro Farad to avoid any noise problem.

Pin 6: Threshold Terminal. This is the non-inverting input terminal of comparator 1, whichcompares the voltage applied to the terminal with a reference voltage of 2/3 V CC. The amplitude

of voltage applied to this terminal is responsible for the set state of flip-flop.

Pin 7:Discharge Terminal. This pin is connected internally to the collector of transistor and

mostly a capacitor is connected between this terminal and ground. It is called discharge terminal

because when transistor saturates, capacitor discharges through the transistor. When thetransistor is cut-off, the capacitor charges at a rate determined by the external resistor and

capacitor.

Pin 8:Supply Terminal. A supply voltage of + 5 V to + 18 V is applied to this terminal with

respect to ground (pin 1).

Components without suitable leadsSome components such as switches and variable resistors do not have suitable leads of their own

so you must solder some on yourself. Use single-core plastic-coated wire of 0.6mm

diameter (the standard size). Stranded wire is not suitable because it will crumple when pushedinto a hole and it may damage the board if strands break off. THE

ELECTRONICSCLUB

Building the example circuitBegin by carefully insert the 555 IC in the centre of the breadboard with its notch or dot to the

left. Then deal with each pin of the 555:

Pin 1: Connect a wire (black) to 0V.

Pin 2: Connect the 10k resistor to +9V.


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Connect a push switch to 0V (you will need to solder leads onto the switch)

Pin 3: Connect the 470 resistor to a used block of 5 holes, then...Connect LED (any color) from that block to 0V (short lead to 0V).

Pin 4: Connect a wire (red) to +9V.

Pin 5: Connect the 0.01F capacitor to 0V.

You will probably find that its leads are too short to connect directly, so put in a wirelink to an unused block of holes and connect to that.

Pin 6: Connect the 100F capacitor to 0V (+ lead to pin 6).

Connect a wire (blue) to pin 7.Pin 7: Connect 47k resistor to +9V.

Check: there should be a wire already connected to pin 6.

Pin 8: Connect a wire (red) to +9V.Finally

Check all the connections carefully.

Check that parts are the correct way round (LED and 100F capacitor).

Check that no leads are touching(unless they connect to the same block).

Connect the breadboard to a 9V supply and press the push switch to test the circuit.If your circuit does not work disconnect (or switch off) the power supply and very carefully re-

check every connection against the circuit diagramNE555

CLUB


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SOLDERING

How to SolderFirstly it's best to secure the work somehow so that it doesn't move during soldering and affect

your accuracy. In the case of a printed circuit board, various holding frames are fairly popular

especially with densely populated boards. The idea with a holding frame is to insert all the parts on

one side (this may be referred to as "stuffing" or "populating" the board), hold them in place with a

special foam pad to prevent them from falling out, turn the board over, and then snip off the wires

with cutters before making the joints. The frame saves an awful lot of turning the board over and

back again, especially with large boards. Other parts could be held firm in a modeller's small vice,

for example.

Solder joints may need to possess some degree of mechanical strength in some cases, especially

with wires soldered to, say, potentiometer or switch tags, and this means that the wire should be

looped through the tag and secured before solder is applied. The down side is that it is more

difficult to desolder the joint (see later) and remove the wire afterwards, if required. Otherwise, in

the case of an ordinary circuit board, components' wires are bent to fit through the board, inserted

flush against the board's surface, splayed outwards a little so that the part grips the board, and

then soldered.

In my view -- opinions vary -- it's generally better to snip the surplus wires leads off first, to make

the joint more accessible and avoid applying a mechanical shock to the printed circuit board (PCB)

joint. However, in the case ofsemiconductors, I often tend to leave the snipping until after the joint has been made, since the

excess wire will help to sink away some of the heat from the semiconductor junction. Integrated

circuits can either be soldered directly into place if you are confident enough, or better, use a dual-

in-line socket to prevent heat damage. The chip can then be swapped out if needed.

Parts which become hot in operation (e.g. some resistors), are raised above the board slightly to

allow air to circulate. Some components, especially large electrolytic capacitors, may require a

mounting clip to be screwed down to the board first, otherwise the part may eventually break off

due to vibration.

The perfectly soldered joint will be nice and shiny looking, and will prove reliable in service. I would

say that the key factors affecting the quality of the joint are:

o) Cleanliness

o) Temperature

o) Duration


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o) Adequate solder coverage

A little effort spent in soldering the perfect joint save a considerable amount of time in

troubleshooting a defective joint in the future. The basic principles are as follows.

Really Clean: Firstly, and without exception, all parts -- including the iron tip itself -- must be clean

and free from contamination. Solder just will not "take" to dirty parts! Old components or copper

board can be notoriously difficult to solder, because of the layer of oxidation which builds up on

the surface of the leads. This repels the molten solder and this will soon be evident because the

solder will "bead" into globules, going everywhere except where you need it. Dirt is the enemy of a

good quality soldered joint!

Hence, it is an absolute necessity to ensure that parts are free from grease, oxidation and other

contamination. In the case of old resistors or capacitors, for example, where the leads have started

to oxidize, use a small hand-held file or perhaps scrape a knife blade or rub a fine emery cloth over

them to reveal fresh metal underneath. Strip board and copper printed circuit board will generally

oxidize after a few months, especially if it has been fingerprinted, and the copper strips can be

cleaned using an abrasive rubber block, like an aggressive eraser, to reveal fresh shiny copper

underneath.

Also available is a fibre-glass filament brush, which is used propelling-pencil-like to remove any

surface contamination. These tend to produce tiny particles which are highly irritating to skin, so

avoid accidental contact with any debris. Afterwards, a wipe with a rag soaked in cleaning solvent

will remove most grease marks and fingerprints. After preparing the surfaces, avoid touching the

parts afterwards if at all possible.

Another side effect of having dirty surfaces is the tendency for people to want to apply more heat

in an attempt to "force the solder to take." This will often do more harm than good because it may

not be possible to burn off any contaminants anyway, and the component may be overheated. In

the case of semiconductors, temperature is quite critical and they may be harmed by applying such

excessive heat.


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Before using the iron to make a joint, it should be "tinned" (coated with solder) by applying a few

millimeters of solder, then wiped on a damp sponge preparing it for use: you should always do this

immediately with a new bit. You can re-apply a very small amount of solder again, mainly to

improve the thermal contact between the iron and the joint, so that the solder will flow more

quickly and easily.

Normal electronics grade solder is usually 60% lead - 40% tin, and it contains cores of "flux," which

helps the molten solder to flow more easily over the joint. Flux removes oxides which arise during

heating, and is seen as a brown fluid bubbling away on the joint. Acid fluxes (e.g. as used by

plumbers) must never be applied. Other solders are available for specialist work, including

aluminum and silver-solder. Different solder diameters are produced, too; 20-22 SWG (19-21 AWG)

is 0.91-0.71mm diameter and is fine for most work.

Temperature: Another step to successful soldering is to ensure that the temperature of all theparts is raised to roughly the same level before applying solder. Imagine, for instance, trying to

solder a resistor into place on a printed circuit board: it's far better to heat both the copper PCB

and the resistor lead at the same time before applying solder, so that the solder will flow much

more readily over the joint. Heating one part but not the other is far less satisfactory joint, so strive

to ensure that the iron is in contact with all the components first, before touching the solder to it.

The melting point of most solder is in the region of 188C (370F) and the iron tip temperature is

typically 330C to 350C (626F to 662F).

Now is the time: Next, the joint should be heated with the bit for just the right amount of time --

during which a short length of solder is applied to the joint. Do not use the iron to carry molten

solder over to the joint! Excessive time will damage the component and perhaps the circuit board

copper foil too! Heat the joint with the tip of the iron, then continue heating whilst applying solder,

then remove the iron and allow the joint to cool. This should take only a few seconds, with

experience. The heating period depends on the temperature of your iron and size of the joint -- and

larger parts need more heat than smaller ones -- but some parts (semiconductor diodes, transistors

and integrated circuits), are sensitive to heat and should not be heated for more than a few

seconds. Novices sometimes buy a small clip-on heat-shunt, which resembles a pair of aluminium

tweezers. In the case of, say, a transistor, the shunt is attached to one of the leads near to the

transistor's body. Any excess heat then diverts up the heat shunt instead of into the transistor


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junction, thereby saving the device from over-heating. Beginners find them reassuring until they've

gained more experience.

Solder Coverage: The final key to a successful solder joint is to apply an appropriate amount of

solder. Too much solder is an unnecessary waste and may cause short circuits with adjacent joints.

Too little and it may not support the component properly, or may not fully form a working joint.

How much to apply, only really comes with practice. A few millimetres only, is enough for an

"average" PCB joint, (if there is such a thing).

PICTORIAL VIEW OF SOLDRING

Clean the iron "bit" (tip) using a damp sponge. The ironfeatured here is an Ungar Concept 2100 Soldering Station.

A useful product is Multicore's Tip Tinner Cleaner (TTC) - a15 gramme tin of special paste which cleans and "tins" theiron, in one go.


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Insert the components and splay the leads so that the partis held in place.

It's usually best to snip the wires to length prior tosoldering. This helps prevent transmitting mechanicalshocks to the copper foil.

Apply a clean iron tip to the copper and the lead, in order toheat both items at the same time.

Continue heating and apply a few millimetres of solder.Remove the iron and allow the solder joint to cool naturally.

It only takes a second or two, to make the perfect joint,which should be nice and shiny. Check the Guide fortroubleshooting help.


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An example of a "dry" joint - the solder failed to flow, andinstead beaded to form globules around the wire.

Soldering Tools

The only tools that are essential to solder are a soldering iron and some solder. There are, however, lots ofsoldering accessories available

Different soldering jobs will need different tools, and different temperatures too. For circuit board work you willneed a finer tip, a lower temperature and finer grade solder. You may also want to use a magnifying glass.Audio connectors such as XLR's will require a larger tip, higher temperature and thicker solder. Clamps and

holders are also handy when soldering audio cables.

The Soldering Iron/Gun

The first thing you will need is a soldering iron, which is the heat source used to melt solder.

Irons of the 15W to 30W range are good for most electronics/printed circuit board work.

Anything higher in wattage and you risk damaging either the component or the board. If you

intend to solder heavy components and thick wire, then you will want to invest in an iron of

higher wattage (40W and above) or one of the large soldering guns. The main difference

between an iron and a gun is that an iron is pencil shaped and designed with a pinpoint heat

source for precise work, while a gun is in a familiar gun shape with a large high wattage tip

heated by flowing electrical current directly through it.

A 30W Watt Soldering Iron A 300W Soldering Gun


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For hobbyist electronics use, a soldering iron is generally the tool of choice as itssmall tip and low heat capacity is suited for printed circuit board work (such asassembling kits). A soldering gun is generally used in heavy duty soldering suchas joining heavy gauge wires, soldering brackets to a chassis or stained glasswork.

You should choose a soldering iron with a 3-pronged grounding plug. The groundwill help prevent stray voltage from collecting at the soldering tip and potentiallydamaging sensitive (such as CMOS) components. By their nature, solderingguns are quite "dirty" in this respect as the heat is generated by shorting acurrent (often AC) through the tip made of formed wire. Guns will have much lessuse in hobbyist electronics so if you have only one tool choice, an iron is whatyou want. For a beginner, a 15W to 30W range is the best but be aware that atthe 15W end of that range, you may not have enough power to join wires orlarger components. As your skill increases, a 40W iron is an excellent choice asit has the capacity for slightly larger jobs and makes joints very quickly. Be awarethat it is often best to use a more powerful iron so that you don't need to spend a

lot of time heating the joint, which candamage components.

A variation of the basic gun or iron isthe soldering station, where thesoldering instrument is attached to avariable power supply. A solderingstation can precisely control thetemperature of the soldering tip unlikea standard gun or iron where the tiptemperature will increase when idle

and decrease when applying heat to ajoint. However, the price of a solderingstation is often ten to one hundredtimes the cost of a basic iron and thus

really isn't an option for the hobby market. But if you plan to do very precise work,such as surface mount, or spend 8 hours a day behind a soldering iron, then youshould consider a soldering station.

There are several things to consider when choosing a solderingiron.

Wattage adjustable or fixed temperature

power source (electric or gas)

portable or bench use

Wattage


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It is important to realise that higher wattage does not necessarily mean hotter solderingiron. Higher wattage irons just have more power available to cope with bigger joints. Alow wattage iron may not keep its temperature on a big joint, as it can loose heat fasterthan it can reheat itself. Therefore, smaller joints such as circuit boards require a lesserwattage iron - around 15-30 watts will be fine. Audio connectors need something bigger

- I recommend 40 watts at least.

Temperature

There are a lot of cheap, low watt irons with no temperaturecontrol available. Most of these are fine for basic soldering, butif you are going to be doing a lot you may want to consider avariable temperature soldering iron. Some of these simply havea boost button on the handle, which is useful with larger joints, others have athermostatic control so you can vary the heat of the tip.

If you have a temperature controlled iron you should start at about 315-345C (600-

650F). You may want to increase this however. Use a temperature that will allow you tocomplete a joint in 1 to 3 seconds.

Power

Most soldering irons are mains powered - either 110/230v AC,or bench top soldering stations which transform down to lowvoltage DC. Also available are battery and gas powered. Theseare great for the toolbox, but you'll want a plug in one for yourbench. Gas soldering irons loose their heat in windy outsideconditions more easily that a good high wattage mains powerediron.

PortabilityMost cheaper soldering irons will need to be plug into the mains. This is fine a lot of thetime, but if there is no mains socket around, you will need another solution. Gas andbattery soldering irons are the answer here. They are totally portable and can be takenand used almost anywhere. They may not be as efficient at heating as a good highwattage iron, but they can get you out of a lot of hassle attimes.

If you have a bench setup, you should consider using asoldering station. These usually have a soldering iron and

desoldering iron with heatproof stands, variable heat, and aplace for a cleaning pad. A good solder station will be reliable,accurate with its temperature, and with a range of tips handy itcan perform any soldering task you attempt with it.

Solder


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The most commonly used type of solder is rosin core. The rosinis flux, which cleans as you solder. The other type of solder isacid core and unless you are experienced at soldering, youshould stick to rosin core solder. Acid core solder can be tricky,and better avoided for the beginner.

Rosin core solder comes in three main types - 50/50, 60/40 and63/37. These numbers represent the amount of tin and lead are present in the solder,asshown below.

Solder Type % Tin % LeadMelting Temp

(F)

50/50 50 50 425

60/40 60 40 371

63/37 63 37 361

Any general purpose rosin core solder will be fine.

Troubleshooting GuideThe solder won't "take": If grease or dirt are present, desolder and clean up the parts. Or, the materiasimply not be suitable for soldering with lead/tin solder.

The joint is crystalline or grainy-looking:The parts forming the joint may have been moved beforeallowed to cool, or the joint was not heated adequately (too small an iron or too large a joint).

The solder joint forms a "spike": The joint was probably overheated, burning away the flux.

If you are unlucky enough to receive burns which require treatment, here's what to do:

First Aidfor Burns

Most burns from soldering are likely to be minor and treatment is simple:

Immediately cool the affected area under gently running cold water.Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended). If ice is reaavailable this can be helpful too, but do not delay the initial cooling with cold water.

Remove any rings etc. before swelling starts Apply a sterile dressing to protect against infection.

Do not apply any creams or ointments.The burn will heal better without them. A dry dressing, such as a clean handkerchief, may be apyou wish to protect the area from dirt.

Seek medical attention if the burn covers an area bigger than your hand.

To reduce the risk of burns:

Always return your soldering iron to its stand immediately after use.


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Allow joints and components a minute or so to cool down before you touch them. Never touch the element or tip of a soldering iron unless you are certain it is cold

How to DesolderA soldered joint which is improperly made will be electrically "noisy," unreliable, and is likely to get worse over t

may even not have made any electrical connection at all, or could work initially and then cause the equipment to

a later date! It can be hard to judge the quality of a solder joint purely by appearances, because you cannot say

joint actually formed on the inside, but by following the guidelines there is no reason why you should not obtain

results.

A joint which is poorly formed is often called a "dry joint." Such a joint usually results from dirt or grease prevent

solder from melting onto the parts properly, and is often noticeable because of the tendency of the solder not to

"spread," but to form beads or globules instead, perhaps partially. Alternatively, if it seems to take an inordinate

time for the solder to spread, this is another sign of possible dirt and that the joint may potentially be a dry one.

There will undoubtedly come a time when you need to remove the solder from a joint: possibly to replace a faul

component or fix a dry joint. The usual way is to use a desoldering pump which works like a small spring-loaded

pump, only in reverse! (More demanding users using CMOS devices might need a pump which is ESD safe.) A spr

loaded plunger is released at the push of a button and the molten solder is then drawn up into the pump. It may

one or two attempts to clean up a joint this way, but a small desoldering pump is an invaluable tool especially fo

work.

Sometimes, it's effective to actually add more solder and then desolder the whole lot with a pump, if the solder particularly awkward to remove. Care is needed, though, to ensure that the boards and parts are not damaged b

excessive heat; the pumps themselves have a P.T.F.E. nozzle which is heat proof but may need replacing occasio

An excellent alternative to a pump is to use desoldering braid, including the famous American "Soder-Wick" (sic)

Adcola "TISA-Wick" which are packaged in small dispenser reels. This product is a specially treated fine copper b


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which draws molten solder up into the braid where it solidifies. The best way is to use the tip of the hot iron to p

short length of braid down onto the joint to be desoldered. The iron will subsequently melt the solder, which wi

drawn up into the braid. Take extreme care to ensure that you don't allow the solder to cool with the braid adhe

the work, or you run the risk of damaging

PCB copper tracks when you attempt to pull the braid off the joint.

I better to buy a small reel of de-soldering braid, especially for larger or difficult joints which would take several

attempts with a pump. It is surprisingly effective, especially on difficult joints where a desoldering pump may pro

struggle.

How to Use a Multimeter

A multimeter is an instrument used to check for AC or DC voltages, resistance or continuity of electrical compone

and small amounts of current in circuits. This instrument will let you check to see if there is voltage present on a

etc. This article will discuss analog meters.

Steps
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Multimeter with selector set to the "Off" position. This meter has only two jacks.

Becoming Familiar With the Parts of a Multimeter.

Inspect the meter. Starting from the top and working to the bottom: The dial. This has the arc shaped scales vis

through the window. The pointer indicates values read from the scale.

The pointer or needle, this is the thin black line at the left-most position in the dial face window in the image. Th

needle moves to the value measured.

Arc shaped lines or scales on the meter dial face. May be different colors for each scale but will have different va

These determine the ranges of magnitude.

A wider mirror like surface shaped like the scales mentioned previously might also be present. The mirror is used

reduce parallax viewing error by lining up the pointer with its reflection before reading the value the pointer is

indicating. In the image, it appears as a wide gray strip between the red and black scales.

A selector switch or knob. This allows changing the function (volts, ohms, amps) and scale (x1, x10, etc.) of the m

Many functions have multiple ranges. It is important to have both set correctly, otherwise serious damage to the

or harm to the operator may result. Most meters employ the knob type like the one shown in the image, but the

others. Regardless of the type, they work similarly. Some meters (like the one in the image above) have an "Off"

position on this selector switch while others have a separate switch to turn the meter off. The meter should be s

when stored.

Jacks or openings in the case to insert test leads. Most multimeters have several jacks. The one pictured has just

One is usually labeled "COM" or (-) for common and negative. This is where the black test lead is connected. It w

used for nearly every measurement taken. The other jack(s) is labeled "V (+) and the Omega symbol" (an upside

horseshoe) for Volts and Ohms respectively and positive. The + and - symbols represent the polarity of probes w

for and testing DC volts. If the test leads were installed as suggested, the red lead would be positive as compareblack test lead. This is nice to know when the circuit under test isn't labeled + or -, as is usually the case. Many m

have additional jacks that are required for current or high voltage tests. It is equally important to have the test le

connected to the proper jacks as it is to have the selector switch range and test type (volts, amps, ohms) set. All

correct. Consult the meter manual if unsure which jacks should be used.

Test leads. There should be (2) test leads or probes. Generally, one is black and the other red.
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Battery and fuse compartment. Usually found on the reverse, but sometimes on the side. This holds the fuse (an

possibly a spare) and the battery that supplies power to the meter for resistance tests. The meter may have mo

one battery and they may be of different sizes. A fuse is provided to help protect the meter movement. Sometim

there is more than one fuse. A good fuse is required for the meter to function. Fully charged batteries will be req

for resistance / continuity tests.

Zero Adjustment. This is a small knob usually located near the dial that is labeled "Ohms Adjust", "0 Adj", or simi

is used only in the ohms or resistance range while the probes are shorted together (touching each other). Rotate

knob slowly to move the needle as close to the 0 position on the Ohms scale as possible. If new batteries are ins

this should be easy to do - a needle that will not go to zero indicates weak batteries that should be replaced.

Use the Ohm Function to Measure Resistance

Multimeter with selector set to "Ohms". This meter only has a single Ohms range.

Set the multimeter to Ohms or Resistance (turn meter on if it has a separate power switch). Understand that resand continuity are opposites. The multimeter measures resistance in ohms, it can not measure continuity. When

is little resistance there is a great deal of continuity. Conversely, when there is a great deal of resistance, there is

continuity. With this in mind, when we measure resistance we can make assumptions about continuity based on

resistance values measured. Observe the meter indication. If the test leads are not in contact with anything, the

or pointer of an analog meter will be resting at the left most position. This is represents an infinite amount of res

or an "open circuit"; it is also safe to say there is the no continuity, or path between the black and red probes. Ca

inspection of the dial should reveal the OHM scale. It is usually the top-most scale and has values that are highes

left of the dial (a sideways "8" for infinity) and gradually reduce to 0 on the right. This is opposite of the other sca

they have the lowest values on the left and increase going right.

2 .Connect the black test lead to the jack marked "Common" or "-"

3.Connect the red test lead to the jack marked with the Omega (Ohm symbol) or letter "R" near it.
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4.Set the range (if provided) to R x 100.

5.Hold the probes at the end of the test leads together. The meter pointer should move fully to the right. Locate

"Zero Adjust" knob and rotate so that the the meter indicates "0" (or as close to "0" as possible). Note that this p

is the "short circuit" or "zero ohms" indication for this R x 1 range of this meter. Always remember to "zero" the

immediately after changing resistance ranges.

6.Replace batteries if needed. If unable to obtain a zero ohm indication, this may mean the batteries are weak a

should be replaced. Retry the zeroing step above again with fresh batteries.

7.Measure resistance of something like a known-good lightbulb. Locate the two electrical contact points of the b

They will be the threaded base and the center of the bottom of the base. Have a helper hold the bulb by the gla

Press the black probe against the threaded base and the red probe against the center tab on the bottom of the b

Watch the needle move from resting at the left and move quickly to 0 on the right.

8-Change the range of the meter to R x 1. Zero the meter again for this range. Repeat the step above. Observe h

meter did not go as far to the right as before. The scale of resistance has been changed so that each number on scale can be read directly. In the previous step, each number represented a value that was 100 times greater. Th

really was 15,000 before. Now, 150 is just 150. Had the R x 10 scale been selected, 150 would have been 1,500. T

scale selected is very important for accurate measurements. With this understanding, study the R scale. It is not

like the other scales. Values at the left side are harder to accurately read than those on the right. Trying to read

on the meter while in the R x 100 range would look like 0. It would be much easier at the R x 1 scale instead. Thi

when testing resistance, adjust the range so that the readings may be taken from the middle rather than the ext

left or right sides.

9.Test resistance between hands. Set the meter to the highest R x value possible. Zero the meter. Loosely hold a

in each hand and read the meter. Squeeze both probes tightly. Notice the resistance is reduced. Let go of the prand wet your hands. Hold the probes again. Notice that the resistance is lower still. For these reasons, it is very

important that the probes not touch anything other than the device under test. A device that has burned out wi

show "open" on the meter when testing if your fingers provide an alternate path around the device, like when th

touching the probes. Testing round cartridge type and older style glass automotive fuses will indicate low values

resistance if the fuse is lying on a metal surface when under test. The meter indicates the resistance of the meta

surface that the fuse is resting upon (providing an alternate path between the red and black probe around the fu

instead of trying to determine resistance through the fuse. Every fuse, good or bad, will indicate "good".

Use the Volts Function to Measure Voltage

1.Set the meter for the highest range provided for AC Volts. Many times, the voltage to be measured has a value

unknown. For this reason, the highest range possible is selected so that the meter circuitry and movement will n

damaged by voltage greater than expected. If the meter were set to the 50 volt range and a common U.S. electr

outlet were to be tested, the 120 volts present could irreparably damage the meter. Start high, and work downw

the lowest range that can be safely displayed.


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2.Insert the black probe in the "COM" or "-" jack.

3.Insert the red probe in the "V" or "+" jack.

4.Locate the Voltage scales. There may be several Volt scales with different maximum values. The range chosen

selector knob determines which voltage scale to read. The maximum value scale should coincide with selector k

ranges. The voltage scales, unlike the Ohm scales, are linear. The scale is accurate anywhere along its length. It w

course be much easier accurately reading 24 volts on a 50 volt scale than on a 250 volt scale, where it might look

is anywhere between 20 and 30 volts.

5.Test a common electrical outlet. In the U.S. you might expect 120 volts or even 240 volts. In other places, 240 o

volts might be expected. Press the black probe into one of the straight slots. It should be possible to let go of the

probe, as the contacts behind the face of the outlet should grip the probe, much like it does when a plug is inser

Insert the red probe into the other straight slot. The meter should indicate a voltage very close to 120 or 240 vol

(depending on type outlet tested). Remove the probes, and rotate the selector knob to the lowest range offeredgreater than the voltage indicated (120 or 240). Reinsert the probes again as described earlier. The meter may in

between 110 and as much as 125 volts this time. The range of the meter is important to obtain accurate measur

If the pointer did not move, it is likely that DC was chosen instead of AC. The AC and DC modes are not compatib

correct mode MUST be set. If not set correctly, the user would mistakenly believe there was no voltage present.

could be deadly. Be sure to try BOTH modes if the pointer does not move. Set meter to AC volts mode, and try a

Whenever possible, try to connect at least one probe in such a way that it will not be required to hold both while

making tests. Some meters have accessories that include alligator clips or other types of clamps that will assist d

this. Minimizing your contact with electrical circuits drastically reduces that chances of sustaining burns or injury

Use the Amps Function to Measure Amperes

1.Determine if AC or DC by measuring the voltage of the circuit as outlined above.

2.Set the meter to the highest AC or DC Amp range supported. If the circuit to be tested is AC but the meter will

measure DC amps (or vice-versa), stop. The meter must be able to measure the same mode (AC or DC) Amps as

voltage in the circuit, otherwise it will indicate 0.
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Be aware that most multimeters will only measure extremely small amounts of current, in the uA and mA ranges

is .000001 amp and 1 mA is .001 amp. These are values of current that flow only in the most delicate electronic c

and are literally thousands (and even millions) of times smallerthan values seen in the home and automotive cir

that most homeowners would be interested testing. Just for reference, a typical 100W / 120V light bulb will draw

Amps. This amount of current would likely damage the meter beyond repair. A "clamp-on" type ammeter would

ideal for the typical homeowner requirements, and does not require opening the circuit to take measurements (

below). If this meter were to be used to measure current through a 4700 ohm resistor across 9 Volts DC, it would

done as outlined below:

3.Insert the black probe into the "COM" or "-" jack.

4.Insert the red probe into the "A" jack.

5.Shut off power to the circuit.

6.Open the portion of the circuit that is to be tested (one lead or the other of the resistor). Insert the meter inse

with the circuit such that it completes the circuit. An ammeter is placed IN SERIES with the circuit to measure cu

cannot be placed "across" the circuit the way a voltmeter is used (otherwise the meter will probably be damage

Polarity must be observed. Current flows from the positive side to the negative side. Set the range of current to

highest value.

7.Apply power and adjust range of meter downward to allow accurate reading of pointer on the dial. Do not exc

range of the meter, otherwise it may be damaged. A reading of about 2 milliamps should be indicated since fromlaw I = V / R = (9 volts)/(4700 ) = .00191 amps = 1.91 mA.

8.If you're measuring the current consumed by the device itself, be aware of any filter capacitors or any elemen

requires an inrush (surge) current when switched on. Even if the operating current is low and within the range o

meter fuse, the surge can be MANY times higher than the operating current (as the empty filter capacitors are a

like a short circuit). Blowing the meter fuse is almost certain if the DUT's (device under test) inrush current is ma

times higher than the fuses rating. In any case, always use the higher range measurement protected by the high

rating (if your meter has two fuses), or just be careful.

Switching Regulator DC/DC

Step-Up, Step-Down & Buck-Boost Small Size & High Efficiency!

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When you are going to check any part for continuity, you must remove the power. Ohm meters supply their own

from an internal battery. Leaving power on while testing resistance will damage the meter.

If the multimeter stops working, check the fuse. You can replace these at places like Radio Shack etc.

Warnings

Always check meters on known good voltage sources to verify operational status before using. A broken meter t

for volts will indicate 0 volts, regardless of the amount present.

Never connect the meter across a battery or voltage source if it is set to measure current (amps). This is a comm

to blow up a meter.

Respect electricity. If you don't know something, ask questions and research the subject.

Things You'll Need

Multimeter. Consider a digital meter instead of the older analog types. Digital meters usually offer automatic ranand easy to read displays. Since they are electronic, the built-in software helps them withstand incorrect connec

and ranges better than the mechanical meter movement in analog types.

Digital multimeter with four jacks for test probes. The digital display removes guess work when reading.
http://www.wikihow.com/Image:Fluke-87-III-True-RMS-Multimeter-4569.jpg

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