5V Power Supply Circuit

For the electronics enthusiast, having a 5 volt DC power supply around in your lab can be very useful. Many op amps, micro controllers, and other digital ICs  run off 5 volts (although most now take a range of 3-15 volts) . Here is how to build a very simple 5 volt DC power supply that can deliver up to 1.5A of current. You will need to solder together the various components.

This circuit can be used for 12V, 9V by replacing LM7805 with 7812 for 12V and 7809 for 9V.

Step 1: Circuit Diagram

 Step 2: Components Required
1. IC1:      LM7805
2. D1-D4: 1N4007
3. C1: 1000uF/25V
4. C2: 100uF/25V
5. LED: Red Color
6. 1KOhm Resistor 1/4 watt
7. PBT2 Connectors : Qty. 2

 Step 3: PCB Layout and Development
Download PCB Layout PDF 1:1 Scale

Metal Detector Circuit

An induction balance (IB) metal locator has a good depth of penetration and distinguishes well between ferrous and non-ferrous metals. It is also capable, to a large extent, of rejecting iron and also tin foil This is a boon for anyone who is searching for coins or noble metals. My aim with this design was to create a 'minimalist' device — one that would work well but without all the bells and whistles of the expensive, commercial designs. I found that it was possible, with just a handful of components, to design a high-quality metal locator.

Simple, but it works

An IB metal locator is usually far more complex than the design shown here. The reason for the simplicity is that I have dispensed with analogue circuitry, and instead used a digital transmitter and receiver. As the search coils pass over metal, only digital signals of a certain amplitude break through to a peak detector (IClb). Since these are in the audio range, they are immediately transferred to the piezo sounder or headphones. On testing the sensitivity of this design in air, with optimal tuning and using a 25mm-diameter brass coin, it gave a clear signal at 150mm, and a 'screaming' signal at 110mm. It was also able to detect a pin at 30mm.

Note that these figures may not apply in the ground, where depth of penetration will depend largely on the mineralisation present.
In contrast, the locator is far more reluctant to pick up tin foil. A tin foil disk of the same size as the brass coin was only detected at half the distance in air. This rejection of tin foil is due in part to the metal locator's low frequency, which avoids what is called skin effect.
Besides this, if the two coils are positioned as described, ferrous metals (iron) are, to a very large extent, rejected — to such an extent, in fact, that a 25mm diameter brass coin weighing seven grams looks the same to the metal locator as a lump of iron weighing 20 times as much. Large nonferrous objects are detected at half a metre distance and more.
The locator's power consumption is conveniently low. It draws around 10mA, which means that it may be powered off a small 9V battery. If an alkaline battery is used, this will provide about 48 hours' continuous use. In my experience, the number of coins that are found on a beach in an hour or two should easily make up for the cost of batteries!
Finally, while the stability of the locator is not the best, it's by no means the worst either. Re-tuning is necessary from time to time, especially in the first few minutes of use. One soon becomes accustomed to giving the Fine Tune knob an occasional tweak — perhaps with every 40 or 50 sweeps of the search head.
Circuit description
The search head of a typical IB metal locator contains two coils: a transmitter (Tx) coil and receiver (Rx) coil.
In this case, the Tx coil is driven by a square wave oscillator, which sets up an alternating magnetic field in the coil. The Rx coil is then positioned in such a way that it partly overlaps the Tx coil. By adjusting the amount of overlap, a point can be found where the voltages in the Rx coil 'null' or cancel out, so that little or no electrical output is produced. A metal object which enters the field then causes an imbalance, resulting in a signal.
The transmitter (IC1a) is a standard 555 oscillator configuration, using one half of the ICM7556IPD dual low power CMOS version of this IC.
Do NOT use the  NE556N IC, by the way.
IC1a oscillates at about 700Hz, determined by R/C components around pins 1, 2 and 6. The 680R resistor limits the current passing through the Tx coil.

The receiver section (IC1b) is pre­ceded by a simple yet sensitive preamplifier stage, based on Q1, which amplifies the signal received from the Rx coil. This is fed directly to IC1b, which is used here as a high-perfor­mance sine-square converter. Its input at pins 8 and 12 is biased by the divider formed by the 10k resistor and pots VR1-VR3, so that only pulses of a certain amplitude break through to output pin 9.
There is a point at which, with careful adjustment, the signal is just breaking through in the form of a crackling sound. When the locator's output is adjusted to a fast crackle, the presence of metal turns this into a 'scream'. This is heard from the piezo sounder or through standard headphones. The 7556 IC allows up to 100mA of output current, therefore no further amplification is required.
Winding the coils
The one drawback to any IB metal locator design is its need for two coils, which must be very carefully and rigidly positioned in relation to one another. Sometimes there's no room even for a fraction-of-a-millimetre error in positioning these coils. While this particular design makes things easier than usual, the placement of the coils will still require some patience. On the other hand, the winding of the coils is relatively easy. Each coil also includes a electrostatic (Faraday) shield, which helps to minimise ground effect.
The winding of the (identical) coils is not critical and a little give and take is permissible.
I used 30SWG (0.315mm) enamelled copper wire, winding 70 turns on a circular former, 120mm in diameter.
I created the former with a sheet of stiff cardboard with 12 pins stuck through it at a suitable angle (the heads facing slightly outwards). The coil was wound clockwise around the pins, then temporarily held together with stubs of insulating tape passed under the coil and pressed together over the top. The coil may be jumble-wound (that is, you don't have to wind the turns on side-by-side in neat layers).
Once this has been done, the pins are removed, and a second coil is wound in the same way. In each case, mark the beginning and end wires. Each coil is then tightly bound by winding insulating tape around its entire circumference.
Now we add a Faraday shield to each coil. This is accomplished with some long, thin strips of aluminium foil. First scrape the enamel off each coil's end wire. Solder a 100mm length of bare wire to the winding wire, and twist this around the coil, over the insulating tape. This provides electrical contact for the Faraday shield.
Beginning at the base of this lead, the foil is wound around the circumference of the coil, so that no insulating tape is still visible under the foil but the foil should not complete a full 360°. Leave a small gap (say 10mm) so that the end of the foil does not meet the start after having gone most of the way around. Do this with both coils. Each coil is now again tightly bound with insulating tape around its entire circumference.
Attach each of the coils to its own length of quality single-core screened audio cable, with the Faraday shield in each case being soldered to the screen. Do not use stereo or twin-core microphone wire to run both leads together; this may cause interference between the coils.
Gently bend the completed coils until each one is reasonably flat and circular, with each end wire facing away from you, and to the right of the beginning wire. Now bend them further until they form lopsided ovals like capital Ds (see Fig. 2). The backs of the Ds overlap each other slightly in the centre of the search head. This is the critical part of the operation, which we shall complete after having constructed the circuit.
Last of all, wind strips of absorbent cloth around each coil (I used strips of thin dishwashing cloth such as Chux), using a little all-purpose glue to keep them in place. Later, when epoxy resin is poured over the coils, this cloth meshes the coils into the resin.
Construction
The PC board of the Matchless Metal Locator measures 48mm x 42mm, and is coded 04106021. There are not many components, so it should be easy to assemble the board using the PC board overlay diagram in Fig. 3.
With the exception of the CMOS IC, component values and types are not critical. The one critical component is the ICM7556IPD CMOS IC. I also tried the TS556CN IC in this position — it worked, but not as well.
Begin board assembly by soldering the nine terminal pins, the 14-pin dual-in-line socket for IC1 and the resistors. Continue with the capacitors, diodes and Q1.
Once soldering is complete, carefully check the board for any solder bridges, then use some short lengths of quality screened microphone wire to attach the piezo sounder, VR2 and VR3, with the screen (or braid) always being wired to 0V. If you wish, add a socket for headphones in parallel with or in place of the piezo sounder. Use insulated hookup wire to attach the battery and switch S1, keeping the leads short. Finally, attach the screened cables from the coils, with the screen again going to 0V, and insert IC1 in the DIL socket. Note that IC1 is static sensitive, and requires careful handling (discharge your body to earth before handling).
Fig. 5 shows the suggested hardware construction, using PVC piping and joints. Bend the base of the metal locator's shaft under very hot water to obtain the angle shown. Alternatively, a swivel joint may be made.
The entire electronics (apart from the search coils) is mounted in a metal case, ensuring that no part of the underside of the PC board is touching the case. The adjustment slot for VR1 should be accessible via a small hole in the case. Mount VR2 and VR3 where quick and easy adjustment is possible.
A metal case is essential, otherwise the circuit is affected by electrostatic coupling (or capacitive effects). The metal case is connected to 0V, through the tab on the copper side of the PC board.
I was unable to obtain a purpose-made metal case in my city (Cape Town), but found that good quality metal sweet tins were readily available, so I used one of these. They are also considerably cheaper than similarly sized electronics enclosures and of course you get the sweets as well!
Setting the coils
A completed PC board is needed before we can 'pot' the coils. These are potted with epoxy resin in a hard plastic dinner plate, the sort you'd find in a picnic set. Any plastic plate of suitable size will do, on condition that it is rigid. (A tip: don't pinch them from the family picnic set....)

First place the coils on top of one another — ensuring that they are correctly orientated, with each end wire facing away from you, and to the right of the beginning wire. Adjust both VR2 and VR3 to their midpoint. Adjust VR1 to about 90kQ. Then attach a 9V battery and switch on. The circuit will most likely be screaming; that is, beeping loudly and continuously. Now slowly move the coils apart. When they are somewhere past the halfway point, the headphones will fall silent. This is where the voltages in the Rx coil 'null'. Continue to move the coils apart. At a precise point just before the coils no longer overlap at all — the headphones will begin to scream again (there may or may not be a low-level beep just before this).
It is at this precise point, and not a fraction of a millimetre either way, that the coils need to be set.
Take an indelible marker pen and mark out holes in the lower plate around both coils. These holes are used to pass cable ties through, to hold the coils tightly to the plate. Also use a cable tie to hold the audio cables to the plate. Use some Blu-tak to tightly seal the holes underneath the plate before pouring in the resin — epoxy resin can be very 'runny' and sticks faster than many glues.
Also at this point carefully bend the coils at the centre of the plate until you reach the exact balance at which there is neither silence nor screaming in the piezo sounder/headphones, but just a crackle. A little drift should not matter at this point.
Now you are ready to mix and pour the resin. Use a modest amount of catalyst, so that there will be not too much heat and shrinkage in the resin. Pour the resin over the cloth which surrounds the coils, so as to soak it, and keep on pouring at least until the entire bottom of the plate is covered with resin.
The circuit may no longer function correctly at this point until the resin has hardened, so make no more adjustments at this stage, but switch the circuit off and leave it for 24 hours or so.
I potted two sets of coils (that is, two complete search heads). The first worked perfectly, precisely as I had set it in the plate. The second contracted slightly as the resin set, so that no settings of VR2 or VR3 would produce a tone in the headphones. However, this is where the design of the Matchless Metal Locator shows its flexibility. By turning VR1 clockwise, the circuit was again functioning normally when VR2 and VR3 were set to their midpoint.
How to use it
Keep the search head away from all metal — and "noisy" computer equipment — and switch on. Adjust potentiometers VR2 (Tune) and VR3
(Fine Tune) to their mid-points. Then adjust VR1 with a screwdriver or plastic alignment tool until the metal locator is just at the point where a crackle is heard, between silence and a scream (or between a low-level hum and a scream). Use the tune and fine-tune knobs for any further tuning.
A fast crackling sound produces the best results. Move a coin over the search head and the piezo sounder should scream.
In actual use, the adjustment of the metal locator will be affected by the mineralisation of the ground you are searching, as well as temperature and voltage variations. So as mentioned earlier, readjustments to VR3 and VR2 are inevitable from time to time.
That's really all there is to it.

Dark Activated Lamp

This circuit Turns on lamp at Night. The lamp remains on till morning and then turns off. This eliminates the need of switching the lamp on/off daily and also helps to light the premises of the house when the occupants are out of station. Very useful for solar powered lamps.

The circuit utilizes the light sensing property of LDR to activate the circuit. The LDR (Light Dependent Resistor) has very high resistance as high as 10 Meg ohms in dark which reduces to a few Ohms in bright light. Resistor R6 (10k) and the LDR forms a potential divider that gives a variable voltage to the base of Q2 Transistor. The Transistor Q2 is connected to base of Q1 through R1.

During day time LDR gets sunlight and it conducts. This increases the voltage at base of Q2. So Q2 gets in conduction mode and reduces the base voltage of Q1 (2N2222). Thus Lights remains off during day time.

When the light level decreases at sunset, LDR cease to conduct and the voltage level at base of Q2 Transistor decreases so it turns off transistor Q2. This will increases voltage at base of Q1 conducts. This turns on the lamp. This condition remains until LDR illuminates in the morning and then the lamp turns off.

Step 1: Circuit Diagram

Step 2: Components Required

1. LDR

2. BC548

3. 2N2222

4. 10K, 4.7K, 100Ohm Resistors

5. 1N4007 Diode

6. Bright white LEDs

Dark Activated Relay

This dark activated switch can trigger a relay to operate an AC lamp at Night. The lamp remains on till morning and then turns off. This eliminates the need of switching the Porch lamp or Backyard lamp daily and also helps to light the premises of the house when the occupants are out of station.

The circuit utilizes the light sensing property of LDR to activate the circuit. The LDR (Light Dependent Resistor) has very high resistance as high as 10 Meg ohms in dark which reduces to a few Ohms in bright light. Resistor R6 (10k) and the LDR forms a potential divider that gives a variable voltage to the base of Q2 Transistor. The Transistor Q2 is connected to base of Q1 through R1.

During day time LDR gets sunlight and it conducts. This increases the voltage at base of Q2. So Q2 gets in conduction mode and reduces the base voltage of Q1 (2N2222). Thus relay remains off during day time.

When the light level decreases at sunset, LDR cease to conduct and the voltage level at base of Q2 Transistor decreases so it turns off transistor Q2. This will increases voltage at base of Q1 conducts. This activates the relay and the AC load connected to the NO (Normally Open) contacts of the relay turns on. This condition remains until LDR illuminates in the morning and then the lamp turns off. Diode D1 protects Q1 from back e.m.f when RL1 switches off.

Step 1: Circuit Diagram

Step 2: Components Required

1. LDR

2. BC548

3. 2N2222

4. 10K, 4.7K, 330Ohm Resistors

5. 1N4007 Diode

6. 12V Relay

Automatic Upper Dipper Light Control

Driving the highway with your high-beam headlights can really increase your visibility, but can be a blinding hazard for other drivers. This simple circuit can be wired into your headlight switch to provide automatic switching between high and low beam headlights when there is oncoming traffic. It does this by sensing the lights of that traffic. In this way, you can drive safely with your high-beams on without blinding other drivers.

Circuit Diagram:

Components Required:
1. 2N2222  Transistor
2. 10K Ohm 1/4 Watt Resistor
3. 12V Relay
4. LDR

Note: LDR should me mounted in such a way so it points toward the front of the car with a clear line of site. Suitable places are on the dashboard, in the front grill, etc.

ICL7107 Autorange Voltmeter

This circuit note describes a technique for auto-ranging a battery operated DVM suitable for panel meter applications. Also, circuit ideas will be presented for conductance and resistance measurement, 9V battery and 5V supply operations, and current measurement.

In the field of DVM design, three areas are being addressed with vigor: size, power dissipation, and novelty. The handheld portable multimeter has gained in popularity since low power dissipation devices enabled battery operation, LSI A/D converters reduced IC count, and novelties such as conductance, automatic range scaling, and calculating were included to entice the user. 

Auto Ranging Circuitry:

The control signals necessary for auto-ranging are overrange, under-range, and clock. The over-range and underrange inputs control the direction of a scale shift, becoming active at the completion of an invalid conversion and remaining active until a valid conversion occurs. The clock input controls the timing of a scale shift. This signal should occur only once per conversion cycle, during a time window which will not upset an ongoing conversion and must be disabled after valid conversions.

Auto-range is achieved in two steps:

1. Measure the input and compare it with range that is >2V, >20V and >200V. this is achieved using LM324 operational amplifier.

2. Shifting of range selector switch is done using CD4051 it selects the correct input.

3. Shifting of decimal point according to input voltage is done using 74138 3:8 decoder IC.

For questions related to circuit post comments and follow us on google+ and Facebook for more intersting circuits

Adjustable 0-35V 3Amps DC Power Supply

In this project we are designing 3Amps 0-35V Adjustable power using LM2576. It is Switching regulator. It has many benefits such as It does not require any Heat sink, You can give higher Input voltage at input.

The LM2576 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving 3A load with excellent line and load regulation. These devices are available in fixed output voltages of 3.3V, 5V, 12V, 15V, and an adjustable output version.

Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation and a fixed-frequency oscillator.

The LM2576 series offers a high-efficiency replacement for popular three-terminal linear regulators. It substantially reduces the size of the heat sink, and in some cases no heat sink is required.

A standard series of inductors optimized for use with the LM2576 are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies.

Other features include a specified ±4% tolerance on output voltage within specified input voltages and output load conditions, and ±10% on the oscillator frequency. External shutdown is included, featuring 50 μA (typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions.

Step 1 : Components Required 
1. LM2576
2. 100uH 3A Inductor
3. 1K Resistor
4. 1000uF Capacitor Qty.2
5. PBT2 Connector Qty. 2
6. 3.3K Pot

Step 2 : PCB and Circuit Development
Adjustable Power Supply Circuit Diagram:

Adjustable Power Supply PCB Layout:

Pin diagram of LM2576:

Step 3 : Download PCB Layout
1. Power Supply Layout pdf

Dual Adjustable DC Power Supply

Dual adjustable power supply circuit using LM317 and LM337. With PCB design. For experimenting electronic circuits and project we require variable power supply.It requires center tap transformer. 

The LM317 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to use and require only two external resistors to set the output voltage. Further, both line and load regulation are better than standard fixed regulators. Also, the LM317 is packaged in standard transistor packages which are easily mounted and handled.

In addition to higher performance than fixed regulators, the LM317 series offers full overload protection available only in IC’s. Included on the chip are current limit, thermal overload protection and safe area protection. All overload protection circuitry remains fully functional even if the adjustment terminal is disconnected. Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors in which case an input bypass is needed. An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve very high ripple rejection ratios which are difficult to achieve with standard 3-terminal regulators. Besides replacing fixed regulators, the LM317 is useful in a wide variety of other applications. Since the regulator is “floating” and sees only the input-to-output differential voltage, supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e., avoid short-circuiting the output. Also, it makes an especially simple adjustable switching regulator, a programmable output regulator, or by connecting a fixed resistor between the adjustment pin and output, the LM317 can be used as a precision current regulator. Supplies with electronic shutdown can be achieved by clamping the adjustment terminal to ground which programs the output to 1.2V where most loads draw little current.

For applications requiring greater output current, use LM338 series (5A) data sheets. For the negative complement, see LM337 series data sheet. 

Features :

•  Guaranteed 1% output voltage tolerance (LM317A)
•  Guaranteed max. 0.01%/V line regulation (LM317A) 
•  Guaranteed max. 0.3% load regulation (LM117)
•  Guaranteed 1.5A output current 
•  Adjustable output down to 1.2V
•  Current limit constant with temperature
•  P+ Product Enhancement tested
•  Output is short-circuit protected

Step 1: Components Required

1. LM317 Qty.1

2. LM337 Qty.1

3. 1000uF Capacitors Qty. 2

4. 1N4007 Diodes Qty. 4

5. 240 Ohm 1/4 Watt Resistors Qty. 2

6. 4.7K Pot Qty. 2

7. Heat Sink for TO-220 Package Qty.2

8. PBT3 Connectors Qty.2

Step 2: Circuit Design and PCB Development

Dual Adjustable Power Supply Circuit Diagram

Dual Adjustable Power Supply PCB Layout

Step 3: Download Required Files

1. Dual Adjustable Power Supply Circuit Diagram pdf

2. Dual Adjustable Power Supply PCB Layout pdf

Step 4: Follow us on Google+ Facebook

1. For questions related to circuit comment here

LED Chaser Circuit

LED chaser or Rolling LEDs are widely used in decoration purpose, We are presenting a simple LED chaser using CD4017 and CD40106. 

Lets see how the LED chaser circuit works ?

CD4017 is Decade counter. Its output is connected to LEDs through current limiting resistors, This circuit can operate on +9V battery. CD40106 is hex inverter. We have build oscillator using CD40106 NOT gate (inverter) to generate clock pulses for counter. You can adjust the LED rolling speed by changing R11 value or chainging C1 capacitor value.

Step 1: Major Components Required

1. CD4017  Qty. 1

2. CD40106   Qty. 1

3. 2.2K Resistors Qty. 11

4. 4.7uF and 4.7KOhm for Clock Circuit

5. +9V Battery

Step 2: PCB Development of LED Chaser Circuit

Step 3: Download Required Files for Development

1. LED Chaser Circuit pdf

2. LED Chaser PCB Layout pdf

Step 4: Follow us on Google+ and Facebook

for any questions comment here

DIY Electronic Dice

We are living in a digital world, So why not to make a digital electronic dice for game. Here We are presenting a compact Electronic Dice with PCB design. You can break the PCB in two if you want to reduce the Dice size. It works on +5V.

Dice have 1 to 6 count. So we are using 7 LEDs that displays the patterns same as Dice. It consists of 7490 Counter IC and CD4093 NAND gate IC. Binary counter is configered to count a 3-bit value such that it can diplay Dice numbers in proper way. This counter is resets when it gets 7 count that will not be displayed. To reset the counter IC2A and IC2B two NAND gates are used in such a way that it makes AND gate and another reset comes from QA. When QA, QB, QC all three bits become High Counter gets reseted. To drive 4 LEDs we have used BC548 transistor.

We need the pulses that are generated at very high frequecy. When Switch S1 is pressed these puses are fed to counter, we can not predict how many pulses fed to counter so we can't predict the what nuber is going to displayed on the dice. Clock pulses are generated using NAND gate oscillator is formed using R9 and C1. For more details on how to make oscillator using NOT gate ? Click here.

Step 1: Circuit and PCB Development

PCB Layout of electronic Dice

Step 2: Download Required Files

1. Circuit Diagram pdf

2. PCB Layout pdf

Step 3: Test the circuit

1. Follow us on Google+

2. Share

3. For any questions comment below

ICL7107 Ammeter Design

Digital Ammeter using ILC7107. In this project we will learn how to make digital Ammeter using ICL7107 ? and many basic fundamentals of Ammeter design.

Designing of Digital Ammeter is basically a process of converting a voltmeter into a Ammeter.

We know that V=I x R. From this we can say that Voltage is directly proportional to the current (V = I) flowing  through resistance. In ammeter this resistance is call Shunt. Shunt resistance have very small value and it will  not affect the load voltage. Most commonly 75mV shunts are available in market. Or you can use low value resistance.

We are measuring voltage across the Shunt resistance that is directly proportional to the current. But practically we have to keep this voltage drop below 0.1V (100mV). So we need a amplifier to amplify this voltage. Another function of amplifier is to match the current readings with display. i.e. is called scaling.

The Intersil ICL7106 and ICL7107 are high performance, low power, 31/2 digit A/D converters. Included are seven segment decoders, display drivers, a reference, and a clock. The ICL7106 is designed to interface with a liquid crystal display (LCD) and includes a multiplexed backplane drive; the ICL7107 will directly drive an instrument size light emitting diode (LED) display. The ICL7106 and ICL7107 bring together a combination of high accuracy, versatility, and true economy. It features autozero to less than 10μV, zero drift of less than 1μV/oC, input  bias current of 10pA (Max), and rollover error of less than one count. True differential inputs and reference are useful in all systems, but give the designer an uncommon advantage when measuring load cells, strain gauges and other bridge type transducers. Finally, the true economy of single power supply operation (ICL7106), enables a high performance panel meter to be built with the addition of only 10 passive components and a display.

Working:

We have designed basic Ammeter using design steps given in data sheets. It displays 3 digits i.e. 99.9 Amps maximum. Actually ICL7107 have 3 and 1/2 Display we are not using 1/2(half) display. Reference voltage of 100mV is generated using 1.2 V Zener and Variable resistor forms a voltage divider. Input is divided by 100K and 100Ohm resistor to get 200mV in-proportion. 

Lets see Ammeter Desing Calculations:
Shunt Calculations: 
(Note: Discription is given with referance to Simulated Circuit, Check Resistor names in Developed PCB Circuit)

1. If you are using low value resistor

  Vin=RShunt x Imax

If you are using Standard Shunt that are commonly available with voltage specificaion i.e. Vin = 75mV. (Voltage Across Shunt at Max Amps)

Example : 100Amps 75mV, 50Amps 75mV

Vo is voltage given at Vin Pin(31)
Rin=R6=R7
Rf=R4=R9

1. Calculations for 100Amps Shunt
Vin=75mV
Vo=RF/Rin(Vin)

Where:
Vin = 75mV
Vo=100mV (~99.9mV)

Assume Rin=10K
Find Rin=?

Rin=R6=R7
Rf=R4=R9

2. Calculations for 50Amps 75mV Shunt
Vin=75mV
Vo=RF/Rin(Vin)

Where:
Vin = 75mV
Vo = 50mV
In this case if you calculate like this display will show 99.9 at 50Amps
for proper scaling 
50Amps =>> 75mV
50mV ==>> Display Shows 50.0

So in this case Vo must be 50mV

Assume Rin=10K (You can assume Rin in the range of 10K to 50K)
Find Rin=?

Rin=R6=R7

Rf=R4=R9

How to ? 
Components Value Selection:
Integrating Resistor:
Both the buffer amplifier and the integrator have a class A output stage with 100μA of quiescent current. They can supply 4μA of drive current with negligible nonlinearity. The integrating resistor should be large enough to remain in this very linear region over the input voltage range, but small enough that undue leakage requirements are not placed on the PC board. For 2V full scale, 470kΩ is near optimum and similarly a 47kΩ for a 200mV scale. Select 47KΩ (Resistor Connected at Pin 28) Vbuf

Integrating Capacitor:
The integrating capacitor should be selected to give the maximum voltage swing that ensures tolerance buildup will not saturate the integrator swing (approximately. 0.3V from either supply). In the ICL7106 or the ICL7107, when the analog COMMON is used as a reference, a nominal +2V fullscale integrator swing is fine. For the ICL7107 with +5V supplies and analog COMMON tied to supply ground, a ±3.5V to +4V swing is nominal. For three readings/second (48kHz clock) nominal values for ClNT are 0.22μF and 0.10μF, respectively. Of course, if different oscillator frequencies are used, these values should be changed in inverse proportion to maintain the same output swing. An additional requirement of the integrating capacitor is that it must have a low dielectric absorption to prevent roll-over errors. While other types of capacitors are adequate for this application, polypropylene capacitors give undetectable errors at reasonable cost. (Capacitor Connected at Pin 27 Select 0.22uF)

Auto-Zero Capacitor (Pin 29):
The size of the auto-zero capacitor has some influence on the noise of the system. For 200mV full scale where noise is very important, a 0.47μF capacitor is recommended. On the 2V scale, a 0.047μF capacitor increases the speed of recovery from overload and is adequate for noise on this
scale.

Reference Capacitor: (Pin 34, 33):
A 0.1μF capacitor gives good results in most applications. However, where a large common mode voltage exists (i.e., the REF LO pin is not at analog COMMON) and a 200mV scale is used, a larger value is required to prevent roll-over error. Generally 1μF will hold the roll-over error to 0.5 count in this instance.

Oscillator Components:
For all ranges of frequency a 100kΩ resistor is recommended and the capacitor is selected from the equation:

Reference Voltage:
The analog input required to generate full scale output (2000 counts) is: VlN = 2VREF. Thus, for the 200mV and 2V scale, VREF should equal 100mV and 1V, respectively.

Development of PCB:
Step 1: Circuit Diagram and Components required
1. 7-Segment Display Common Anode Qty. 3
2. ICL7107, and IC Base 40 Pin
3. LM7805
4. 1N4007
5. Other Capacitors and Resistors
6. OP07 Operational Amplifier
Download PDF File

Step 2: PCB Layout 
Download PCB Layout pdf

Step 3: Assemble Components and Test the circuit
1. Comment if you have any questions.
2. Like, Share, Follow us on Google+

Wireless AC Mains Detector Circuit

Wireless mains voltage detector, This circuit detects the presense of AC voltage in wire without physical contact. It is very useful to detect multicore wire fault detection, where you can detect exact location of the open circuit fault.

It consist of CD4033. CD4033 consists of a decade counter and 7 segment decoder. In this circuit we have kept clock input of CD4033 open. so it can pick any noise i.e. is generated by AC voltage and starts counting. The 7 segment display will start counting randamly when it detects AC supply. Circuit operates at 9V DC battery. 2.2K Ohm resistor is used for current limiting of 7 segment display.

Circuit Diagram of Wireless AC Mains Detector:

PCB Layout of Wireless AC Mains Detector:

Download Required Files:

1. pdf PCB Layout for PCB Development (1:1 size Not Mirrored)

Follow us on Google+ for more interesting stuff

Digital Temperature Indicator

The circuit given here is of digital temperature indicator with LED 7-segment display using the ICL7107. It measures temperature from 00.0 C to 99.9 C. ICL7107 is a 3 1/2 digit A/D converters with LED 7-Segment Driver. We convert 99.9mV Voltmeter into a Temperature indicator first we design 99.9mV Voltmeter.

The Intersil ICL7106 and ICL7107 are high performance, low power, 31/2 digit A/D converters. Included are seven segment decoders, display drivers, a reference, and a clock. The ICL7106 is designed to interface with a liquid crystal display (LCD) and includes a multiplexed backplane drive; the ICL7107 will directly drive an instrument size light emitting diode (LED) display. The ICL7106 and ICL7107 bring together a combination of high accuracy, versatility, and true economy. It features autozero to less than 10μV, zero drift of less than 1μV/oC, input  bias current of 10pA (Max), and rollover error of less than one count. True differential inputs and reference are useful in all systems, but give the designer an uncommon advantage when measuring load cells, strain gauges and other bridge type transducers. Finally, the true economy of single power supply operation (ICL7106), enables a high performance panel meter to be built with the addition of only 10 passive components and a display.

Working:
We have designed basic 99.9mV DC Voltmeter using design steps given in data sheets. It displays 3 digits i.e. 99.9mV maximum. Actually ICL7107 have 3 and 1/2 Display we are not
using 1/2(half) display. Reference voltage of 100mV is generated using 1.2 V Zener and Variable resistor forms a voltage divider. Input is divided by 10K and 1.1KOhm resistor (divide by 10) to get proportional temperature scale. Block diagram gives clear idea about how it works.

 How to ? 
Components Value Selection:
Integrating Resistor:
Both the buffer amplifier and the integrator have a class A output stage with 100μA of quiescent current. They can supply 4μA of drive current with negligible nonlinearity. The integrating resistor should be large enough to remain in this very linear region over the input voltage range, but small enough that undue leakage requirements are not placed on the PC board. For 2V full scale, 470kΩ is near optimum and similarly a 47kΩ for a 200mV scale. Select 47KΩ (Resistor Connected at Pin 28) Vbuf

Integrating Capacitor:
The integrating capacitor should be selected to give the maximum voltage swing that ensures tolerance buildup will not saturate the integrator swing (approximately. 0.3V from either supply). In the ICL7106 or the ICL7107, when the analog COMMON is used as a reference, a nominal +2V fullscale integrator swing is fine. For the ICL7107 with +5V supplies and analog COMMON tied to supply ground, a ±3.5V to +4V swing is nominal. For three readings/second (48kHz clock) nominal values for ClNT are 0.22μF and 0.10μF, respectively. Of course, if different oscillator frequencies are used, these values should be changed in inverse proportion to maintain the same output swing. An additional requirement of the integrating capacitor is that it must have a low dielectric absorption to prevent roll-over errors. While other types of capacitors are adequate for this application, polypropylene capacitors give undetectable errors at reasonable cost. (Capacitor Connected at Pin 27 Select 0.22uF)

Auto-Zero Capacitor (Pin 29):
The size of the auto-zero capacitor has some influence on the noise of the system. For 200mV full scale where noise is very important, a 0.47μF capacitor is recommended. On the 2V scale, a 0.047μF capacitor increases the speed of recovery from overload and is adequate for noise on this
scale.

Reference Capacitor: (Pin 34, 33):
A 0.1μF capacitor gives good results in most applications. However, where a large common mode voltage exists (i.e., the REF LO pin is not at analog COMMON) and a 200mV scale is used, a larger value is required to prevent roll-over error. Generally 1μF will hold the roll-over error to 0.5 count in this instance.

Oscillator Components:
For all ranges of frequency a 100kΩ resistor is recommended and the capacitor is selected from the equation:

Reference Voltage:
The analog input required to generate full scale output (2000 counts) is: VlN = 2VREF. Thus, for the 200mV and 2V scale, VREF should equal 100mV and 1V, respectively.

Development of PCB:
Step 1: Circuit Diagram and Components required
1. 7-Segment Display Common Anode Qty. 3
2. ICL7107, and IC Base 40 Pin
3. LM35 Temperature Sensor
4. LM7805
5. 1N4007
6. Other Capacitors and Resistors

Download PDF Circuit Diagram

Step 2: PCB Layout 
Download PCB Layout pdf
Download Component Placement Diagram pdf

Step 3: Assemble Components and Test the circuit
1. Comment if you have any questions.
2. Like, Share, Follow us on Google+