report on ehw

8/2/2019 Report on EHW

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Report on

1Fire Alarm(Analog project)

2.Traffic Signal System (Digital Project)

Projects

In Electronics hardware workshop

T.E. Electronics & Telecommunication -Semeste

2011-2012

CERTIFICATEProject entitled

1.Fire Alarm(Analog project)

2.Traffic Signal System (Digital Project)

Submitted

For term work in Electronics Hardware work shop Semester-V is approved.Guide Examiners------------------------ Internal: ------------------------------


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(Name of Internal Guide)

External: ------------------------------------------------------

Head of Department---------------------------

PrincipalContents

Sr. No. Page Title Page No

1 List of tables and figures** 2

2 Fire alarm 3

1.1. Introduction

1.2 Circuit Diagram

1.3 Component values

1.4 Circuit Description

1.5 Applications and Future scope

3 Traffic signal system

2.1. Introduction

2.2 Circuit Description2.3 Application and future scope

2.4 Result and conclusion

3 References


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List of Figures

FigureNumber

Name PageNumber

1.2 Circuit diagram of Fire Alarm 4

2.1 Circuit diagram ofTraffic signal system 5

2.2 Pin diagram & Timing diagram of counter 4017

FIRE ALARM

1 .1 INTRODUCTION

The primary function of a fire alarm is to alert the occupants of a building to thepresence of a fire. It may also perform other functions. For instance, the system can bedesigned to simultaneously alert the fire department by means of a direct or relayedsignal where a rapid response by the fire department is essential. The US Fire

Administration says "Don't Forget the Smoke Alarms". Even though fire sprinklers areeffective life safety devices you still need smoke alarms. Some fires can begin assmoldering fires that produce smoke and gases but don't generate enough heat toactivate the sprinklers. Smoke alarms are needed to provide warning for thesesituations.

1.2 CIRCUIT DIAGRAM


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1.3 COMPONENT VALUES

R1,R3,R7,R8 470

R2 33K

R4 560

R5 47K

R6 2.2K

C1 10F

C2 0.04F

C3 0.01F

D1 1N4001

IC NE- 555

TH1 10K


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LS1 8 ,1W

T1 BC548

T2 BC558

T3 SL100B

1.4 CIRCUIT DESCRIPTION:

In this fire alarm circuit, a thermistor works as the heat sensor. When temperature increases, itsresistance decreases, and vice versa. At normal temperature, the resistance of the thermistor (TH1)

is approximately 10 kilo-ohms, which reduces to a few ohms as the temperature increases beyond

100C. The circuit uses readily available components and can be easily constructed on anygeneral purpose PCB. Timer IC NE555 (IC1) is wired as an astable multivibrator

oscillating in audio frequency band. Switching transistors T1and T2 drive multivibrator NE555

(IC1).The output of IC1 is connected to npn transistor T3, which drives the loudspeaker (LS1) togenerate sound. The frequency of IC1 depends on the values of resistors R5 and R6 and capacitor

C2.

When thermistor TH1 becomes hot it provides a low-resistance path to extend positive voltage to

the base of transistor.T1 via diode D1 and resistor R2. Capacitor C1 charges up to the positivevoltage and increases the on time of alarm. The higher the value of capacitor C1, the higher the

forward voltage applied to the base of transistor T1 (BC548).Since the collector of transistor

T1isconnected to the base of transistor T2,transistor T2 provides positive voltage to reset pin 4 ofIC1 (NE555). Resistor R4 is used such that IC1 remains inactive in the absence of positive

voltage Diode D1 stops discharging of capacitor C1 when the thermistor connected to the positive

supply cools down and provides a high-resistance (10-kilo-ohm) path. It also stops the conductionof T1. To prevent the thermistor from melting, wrap it up in mica tape.The circuit works off a 6V-12V regulated power supply. LED1 is used to indicate that power to the

circuit is switched on

1.5 APPLICATION AND FUTURE SCOPE:

Some Fire Alarm Systems utilize Emergency Voice Alarm Communication Systems(EVACS) to provide pre-recorded and manual voice messaging to building occupants.

Voice Alarm systems are typically used in high-rise buildings, arenas and other large"defend-in-place" occupancies such as Hospitals and Detention facilities where totalevacuation is difficult to achieve.Voice-based systems are especially useful during fire,security, weather and similar events, and provide response personnel with the ability toconduct orderly evacuation and notify building occupants of changing eventcircumstances


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TRAFFIC SIGNAL SYSTEM

2 .1 INTRODUCTION

Traffic lights , which may also be known as stoplights , traffic lamps , traffic signals , signallights , robots or semaphore are signalling devices positioned at road intersections,pedestrian crossing and other locations to control competing flows of traffic. Traffic

lights were first installed in 1868 in London, and today are installed in most cities aroundthe world. Traffic lights alternate the right of way of road users by displaying lights of astandard colour (red, yellow/amber, and green), using a universal color code (and aprecise sequence to enable comprehension by those who are color blind).

2.2 CIRCUITDIAGRAM:


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Fig.2.1

2.3 COMPONENT VALUES:

R1,R2,R3 470

R4 22KR5 100K

C1 0.1F

C2 1F,16v

C3 10F,16v

LEDS RED,AMBER,GREEN

POT 1M

IC NE- 555

IC COUNTER-4017

2.4 COUNTER IC 4017:

The 4017 IC is a 16-pin CMOSdecade counterfrom the 4000 series. It takes clockpulses from the clock input, and makes one of the ten outputs come on in sequenceeach time a clock pulse arrives.

Pinout & Timing Diagram
http://en.wikipedia.org/wiki/CMOShttp://en.wikipedia.org/wiki/CMOShttp://en.wikipedia.org/wiki/Counterhttp://en.wikipedia.org/wiki/Counterhttp://en.wikipedia.org/wiki/CMOS


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Fig .2.2

Pinnumber

Name PURPOSE

1 6 The 6th sequential output

2 2 The 2nd sequential output

3 1 The 1st sequential output

4 3 The 3rd sequential output




8 0 V, VDD The connection to the 0 V rail




12 COCarry out output - outputs high on counts 0 to 4, outputs low on counts 5 to 9 (thus a transition from low

to high occurs when counting from 9 back to 0)

13 LE Latch enable - latches on the current output when high (i.e. the chip counts when LE is low)

14 CLK Clock in
http://en.wikipedia.org/wiki/File:4017-chip.png


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15 RST Reset - sets output 1 high and outputs 2 through 10 low, when taken high

16+9 V,

VCCThe connection to the +VCC rail (voltage between +3 V and +15 V)

2.5 CIRCUIT DESCRIPTION:

This project operates red, amber and green LEDs in the correct sequence for a singleUK traffic light. The time taken for the complete red - red & amber - green ambersequence can be varied from about 7s to about 2 minutes by adjusting the 1M preset.Some amber LEDs emit light that is almost red so you may prefer to use a yellow LED.The 555 a stable circuit provides clock pulses for the 4017 counter which has tenoutputs (Q0 toQ9). Each output becomes high in turn as the clock pulses are received.

Appropriate outputs are combined with diodes to supply the amber and green LEDs.The red LED is connected to the 10 output which is high for the first 5 counts (Q0-Q4high), this saves using 5 diodes for red and simplifies the circuit.


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2.6 APPLICATION AND FUTURE SCOPE

The separation of conflicting streams of traffic in time can reduce the chances of right-

angle collisions. They can increase the traffic capacity at intersections .Automotivetechnologies are gaining ground in modern road traffic-control systems, since thenumber of road vehicles and passengers is rapidly growing. There is a perpetual needfor safety-critical traffic automation, and traffic engineering makes the dynamic or staticanalysis and the synthesis of automotive vehicle technologies possible. The main goalof engineering is the planning and management of traffic systems.

Appendix ADesign and Manufacturing of Printed circuit Board (PCB).

What is PCB?

A printed circuit board, or PCB, is used to mechanically support and electrically connectelectronic components using conductive pathways, or traces, etched from coppersheets laminated onto a non-conductive substrate. It is also referred to as printed wiringboard (PWB) or etched wiring board. A PCB populated with electronic components is aprinted circuit assembly (PCA), also known as a printed circuit board assembly(PCBA).PCBs are rugged, inexpensive, and can be highly reliable. They require muchmore layout effort and higher initial cost than either wire-wrapped or point-to-pointconstructed circuits, but are much cheaper and faster for high-volume production.

Prior to manufacuring PCB, one needs tp prepare layout for the circuit. In thelayout preparation we need to consider the placement of varous devices andcomponents used in the circuit, the size of the component. The layout prepartionis done using varoius EDA (Electronics Design Automation) softwares such asORCAD, EGLE, EXPRESS PCB, DIPTRACE etc. following tips and guidelinesshould be taken into account in layout preparations.

Tips on PCB DesigningAt the start of design process, designer must follow these details:

11. Accurate actual sizes of the components being used.22. Electrical connections between components.33. Component mounting data.44. PCB area.55. Conductor width and spacing.


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On the bass of above data, a designer must follow the following points:11. All components must be represented.22. There can be no crossovers in tracks. A crossover will result in shorting of

tracks .33. Always keep point to point conductor runs as straight and as short as

possible. When unable to use straight lines, use diagonal lines. Combinationof straight lines, diagonal lines and 90 degree bends should be used fortrack layout.

44. Avoid looped runs.55. Polarity marks should be drawn for power terminals, diodes, electrolytic

capacitors and any such polarized components.66. Place all resistors, capacitors, diodes etc. parallel to each other and parallel

to PCB.77. Try to group components together on the basis of functional block,

component type, and similarity in dissipation, size or polarity.

18. Put high wattage resistors and power semiconductors away from the centreof the PCB. Keeping such components near edges facilitates putting up ofheat sinks.

29. Keep a margin of at least on all sides to allow a space between boardedges and actual components. This space can be used only for mounting ofconnectors, or PCB mounting screws.

310. Keep number of jumpers minimum.411. Mount the components as close to each other as possible, leaving only

minimum space required between to service the components. Typicaldistance between transistors and ICs will be around 1/8 or .

512. For currents up to 1A, use track size of 1/16 or 1.5mm approx. For higher

currents increase the track width approximately.613. Spacing between tracks is a function of the voltage. Typical values are

0 150 V 1/32150 300V 1/16301 500V 1/8114. Make use of power and ground bus concepts to simplify the track layout.215. Think of symmetry while arranging components. Try to spread the

component weight evenly across PCB.316. Try to place large and small components alternately.

GUDELINES FOR PREPARING COMPONENT LAYOUT.11. Ensure that you have all the required components with you.22. Note down accurate measurements of each component.33. Show PCB mounting holes at the corners at 70mmX70mm.44. Distribute the components evenly over the area. You need not mark this

area. Only make sure that this entire area is used.55. Ensure that heavier components are towards the centre.66. Keep components with heat sinks, power resistors, ICs near centre.


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77. All axial lead components should be placed either horizontally orvertically.(i.e. parallel to PCB edges)

88. Pads for external wire connection, or the components where external wireis terminated directly, should be towards the edges of PCB.

99. For axial lead component like resistor, distance between the mounting

holes will be (body length in mm +6 mm) minimum.1010. While deciding the component position, think of connected componentsand place the components in such a way that path length between twoconnected components is minimum.

1111. You need not accommodate transformer, power supply& signal sourceon the PCB. Provide pads to terminate external wire or you can solder theexternal wire directly onto the appropriate component lead. In such casetake care to locate that component towards the edges of PCB.

1212. Show at least the mounting holes for every component. Showingcomponent out line (Shape & size) is preferred but not must.You will proceed to make track layout only after your component layout is

corrected & approved.

I. Preparation of layout using DIPTRACE

11. Open the DIPTRACE Software.

START Programs DipTrace PCB lyout.

Following window will be seen on the monitor.

12. Standard components sizes such as resistors, capacitors, transistors and ICswith various package types, are available in the library of the DipTrace. The

list of the components is displyed alphabetically on the left of the Diptracelayout window. Select, Drag and drop the required component as shownbelow. As the components are placed on the Top layer of the PCB, whileplacing the components, select the layer settings shown with arrows. Theproperties of the components such as rotation can be changed by selectingthe component and right clicking.

13. After the placement of the components. Select the bottom layer and make alltheconnections using the traces available in Menu bar shown with arrows in thefollowing figure. Following figure is a layout for the Transitorised common

emitter Amplifier. The Text is used to name the components or its value onthe top layer. The width of the traces etc can be changed by selecting thetrace and right click.

14. After the connections are complete click Run Autorouter button in thetoolbar to form a board of your prepared layout.


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15. The photo chemical process of PCB manufacturing needs the negative of thelayout. The Dip trace software can give the printout of the layout as it is

1(Positive) or negative of any layer. But we need the negative of the bottomlayer. The following steps should be followed to get the print out.

In Dip Trace window click File Preview. The preview window will be opened

only if the printer is connected to your PC. Use the laser printer only to takethe printout of your layout negative. Do the settings in the preview window asshown below. The printout should be mirror image of the negative. Get theprintout on the A4 size Butter Paper. Depending on the darkness of the black

Area which is actually the unwanted copper, the multiple printouts can betaken and can be overlapped.

II FABRICATION OF PRINTED CIRCUIT BORD1 Introduction

The method of making your own Printed Circuit Board is described in the

following guideline..Even if you have never fabricated a PCB before, with a little practice you will beable to produce PCB of professional grade for prototyping or even a finishedproduct.The manual artwork method of PCB design is the method used by mostmanufacturers of PCBs. With this method, extremely accurate, high densityprinted circuit boards can be constructed, since the artwork can be produce 1, 2or 4 times the size of the final PCB. This method consist of applying tapes,donuts pad, multi pad configurations (for integrated circuit) letters, numbers andwords, to a sheet of Mylar film.

If the artwork is done by computer aided design, please ensure that the

output is on an accurate good quality laser, and not a dot matrix printer, aspinholes will lead to defects in the final PCB.There are commercial photo-sensitive resist, which are very practical forproducing circuits on PCB. Placing the circuit design on a negative helps actualproduction of circuits. Exposing the negative while in contact with coated (photosensitive) circuit board is done first. Then developing and other processes arerequired to form the circuit boards.There are durable photosensitive resist of organic. Solvent solutions which areUltra Violet Light sensitive. These can be processed and used easily inlaboratory.The resist may be applied in double coats in a dip coating machine. With a dipcoater the resist is coated very accurately on the required PCB laminate anddried it is then exposed to contact with negative with the design to an actinic lightsource (U. V.). The non-exposed parts are dissolved by developing with therecommended developing solution.This leaves the circuit resist on the required parts of the metal on the PCB. Thenon coated or unprotected metal may be etched in an etching solution such asferric-chloride solution. After etching and washing the resist is removed with the


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required solvent and a very accurate circuit configuration is left on the circuitboard.While drilling the board be sure that drill bit is sharp. Best result for glass epoxyboard material will be maintain with carbide tipped drill bit, but you can use anordinary high speed steel (HSS) drill bit if that is all you have. For most

component proper drill size is 1 mm. diameter and for integrated circuit .8mm isused. The specified drill sizes are not critical, but it is good if we dont use toolarge drill since it makes it more difficult to get a proper solder connection.ProcessIn photo transfer processes cleanliness is very important. This applies to all stepsyou follow to achieve the desired results. Whether you are making metal labels orProfessional grade PCBs, please ensure that your work tables, apparatus, tanks,trays are completely free from dirt and dust.

Cleaning the Laminate-Before the metal surface (in case of the bare PCB Copper laminate) is coated with

photo resist, clean the surface thoroughly, so as to make it completely free of physical &chemical contamination .It is advisable to clean the metal by solvents liketrichloroethylene to remove traces of grease or oil. Contaminants such as cupric-oxide,dirt etc can be removed by applying abrasives like pumic powder. Traces of suchcleaning powder should then be removed by washing the metal plates under runningwater and scrubbing it with a soft brush or pad. The surface should then be quickly andthoroughly dried with forced warmed air.Coating the Laminate-Photo resist can be applied precisely and economically by using a dipping process,done by a Photo resist Dip Coater.Dip coating is the best method of photo resist coating . Ti is used when the number of

Laminates to be coated is high and generally both the side of the laminates are to becoated. Stainless steel tank is used for storing the photo resist coating material. Youhave to dip or immerse the laminate in the tank containing photo resist and withdraw itslowly (withdrawal at rate of 30 to 40 cm/minutes) .Therefore the motorizedarrangement for this operation is required.It is difficult to predict a particular coating thickness needed for specific applicationbecause the coating methods and the equipments used change from user to user. It istherefore best to determine the optimum coating thickness experimentally.ThinnerUse of thinner is to be done very carefully. The use of thinner will depend upon themethod of coating you are following.(Photo resists viscosity -12 secs FC4).The thinneris used to dilute the photo resist , as it tends to get thick during non use.Pre-baking

After coating the laminate, allow it to dry naturally for minimum 5 minutes. Tis helps toevaporate the solvents completely. If the coating is thick it is also desirable to bake thelaminate in PCB curing machine with controlled temperature at 30- 45 C for about 10minutes.

All operation related to coating and pre-baking are to be carried out in safe (yellow) lightExposure


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The coated laminate is normally exposed in contact with photographic negative orpositive. Photo resist is sensitive to ultra violet radiations and therefore an Ultra-violettubes based ,UV exposure unit can be used for exposure.The time of exposure depends on many factors e.g. the source of light, thickness ofcoating, distance between the source of light and printing down frame etc.

The time of exposure depends on many factors e.g. the source of light and printingdownFrame etc.For double side PCBs it is desirable to use double sided sandwich glass for printingframeDevelopment-The exposed plate should be placed into the solvent based developer. This willremove unexposed areas of the photo resist and will show a colorless resist imagewhich has plastic-like appearance. The total development time is between 60-90seconds.The developer gets exhausted after continuous use and it is necessary to keep a

periodical check on it. The exhausted developer creates scum in the non-image areas,When such

trouble occurs, developer should be replaced and the container of the old developershould be cleaned before pouring fresh developer in it.Washing-Immediately after development is over, wash it in running water on neutral PH. Afterwashing and drying , dyeing is carried out to improve the visibility of the image and tofind out any cracks or broken line and to facilitate the same for the purpose ofretouching before etching.Dying the image-

Immerse the dried plate in the dye developer bath. The surface of the board is coveredwith a dye-developer. The board is put under running water of neutral PH in order towash off the dye stain from the unexposed area, which results into a clean dyed imageof photo resist and dry.

A dyed image can show you pinholes in the image areas that may be due to uncleanprinted frame or dusty, negative or positive. Occasionally black spots appear in theresist areas. These may be due to foreign matters in the resist coating, which is acontinuously used without filtration. It is better to repair these defects in the image areaotherwise they may become the source of trouble in further process.Etching-This is an important and critical step in the chemical processing of the direct-etchedBoards. Although basically this operation aims at chemical, removal (etching) ofunwanted copper portion (non-image area). The operation must bear in mind theimportant of the definition tolerance possible, under cutting and contamination of aboard substrate due to enchants. Good results can be obtained by carefully studying thevarious aspects of the operation.Ferric Chloride is one of the most widely used enchants for copper and copper alloys .The main reason for its popularity is the low cost. Commercially it is available in lumpsor ready to use solutions of different strengths.


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Various methods are used while chemically removing the unwanted copper from thelaminates.

1A. In the proto-Etch Etching machine, the laminates are put in a tank filled withenchant agitated by a pump & a heater .The heater helps the enchant to becomewarm and helps to each PCBs faster. Fresh enchant is available to the surface

areas while the dissolved metal from the surface is rinsed awaysimultaneously .A sensor is provided for maintaining temperature.2B. IN the Oscillating spray etching machine, the technique of spraying the etchant

with moving nozzles, has double side etching either in horizontal and verticalpositioning to production is the greatest advantages of these machines but thecost of equipment is more.Whatever the method you follow for etching the laminate, please do not forget tocleaned the etched boards after the etching is complete.

Resists Removal:

After the etching or plating job is complete it is desirable to remove theresist from the image area, photo resist stripper is used to remove theresist from PCB the cleaned surface should be washed with water anddried quickly.

Trouble Shooting:

Problem Causes

11. Exposed coating has a spongy a) Inadequate exposure time appearance or matfinish afterb)Thick coating development.

12. Exposed coating peels off2a) Inadequate exposure time during development.3b) Very thick coatingc) Laminate surface not sufficient clean

3. Exposed coating does not develop a) Pre-baking beyond 50C for longer time.4. Dyed- image does not look intense a) Thin coating.

Protective Coating (Tinning):

Roller tinning unit is used for solder coating of PCB to provide an effectiveprotection against corrosion and ensuring along storage life and improveSoldering properties. After cleaning & fluxing, the PCB to be solder coated is

passed between two rotating rollers the one at the bottom being the tinned rollerwhich partially dips into a solder bath and the top silicon rubber covered idleroller. The hot solder on the timed roller transfer on to the copper patterns of thePCB.

Drilling:


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The drilling of PCB is done for making holes on the conductor pattern forinserting the component leads to the solder side of the PCB

III. PCB Designing and Manufacturing guide lines11. Circuit Diagram

Use: PCB layout, artwork, troubleshooting, users manual and assembly.

Information:

1a. All symbols drawn from the standard symbol drawing. whichare updated as and when required.

2b. Component nos. (R1, C1 etc.) as per final componentlayout or component assembly.

3c. Component values with complete specifications.

4d. All pins, used or unused.

5e. Description of connectors.

6f. All test points (numbered).

7g. All components including decoupling capacitors andjumpers.

8h. Any other information. E.g. Jumper meaning. Portaddresses etc.

2Refer: System specifications12. Writing Diagram

Use: Assembly, testing, Installation & troubleshooting.

Information:

2a. Wiring related to physical parts.

3b. Connector details as pin numbers and types.

4c. Colour codes as of all wires, if any.

5d. Wire sizes.

6e. Ferrule identification number and signal name.

Refer: Wiring diagram including wire length etc.13. Component List


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Use: R& D, testing, Formulation of parts list

Information:

0 a. Component number (one item written on one line) as on thecircuit diagram as well as component layout or assembly

diagram.

1 b. Complete description.

2 c. Manufacturers item code/ Part no.

3 d. Remarks for alternatives or special instructions.

2Refer: Circuit diagram, wiring Diagram, Component layout, Parts list (Billof Material), Structure diagram

4. Component Layout

Use: Assembly, Testing, TroubleshootingInformation:

1a. All Components Number in Sequence either horizontal or vertical.2b. Back annotated to the circuit diagram.3c. Mechanical fixing if any.4d. PCB size and shape.5e. All Components outlines as per actual dimensions.6f. Components numbers as per standard circuit symbol.7g. Silk screen (optional).

Refer: Circuit Diagram, Component layout (Bill of Material) and Drilling Details

5. Parts ListUse: Purchase, Production Planning and inventory controlInformation:

1a. Part No.2b. Components Number.3c. Full Description with make and options.4d. Supplier Name.5e. Quantity per sub-assembly or assembly, whichever preferable.6f. Location in stores7g. Remarks.

Refer: System Specifications6. Drilling DetailsUse: PCB ManufacturingInformation:

1a. Drill size.2b. After or before plated through holes (PTH) normally after PTH.3c. Standardized color codes.4d. Viewing side.


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5e. Non-Plated through holes as mounting holes.6f. PCB number.

7. ArtworkUse: PCB Manufacturing

Information:1a. PCB number, normal or mirror as per the side of PCB.2b. Revision of artwork.3c. Component side, solder side or layer no.4d. Exact PCB dimensions in 1:1 scale.5e. The side that is matched while taking films.

Refer: Circuit Diagram, Component Layout, Drilling Details8. Films

Use: PCB ManufacturingInformation:

1a. PCB number, normal or mirror as per the side of PCB.2b. Revision of artwork.3c. Component side, solder side or layer no.4d. Exact PCB dimensions in 1:1 scale.5e. The side that is matched while taking films.

Refer: Circuit Diagram, Component Layout, Drilling Details

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