Inductance Meter Adapter Circuit

This is a design circuit for measure inductance of the inductor labeled LX which is the inductance to be measured. The o/p of the circuit is a TTL square wave whose frequency relates to the inductance being measured. The inductance meter adapter output is connected to a frequency meter and the inductance is calculated from the frequency. This is the figure of the circuit;

The center operate of the circuit is the buffer colpitts oscillator(the first stage) which resonates with the unknown inductance to give a Sine wave of a particular frequency . The frequency of the sine wave is a function of the unknown inductance and the four 1000pF capacitors. The output sine wave is amplified by the second transistor and is then rectified by the capacitor and diode combination that follows. The rectified sine wave now having only positive excursions is buffered by the third transistor and is then fed to the 74ls393. Counter IC which is configured as a divide by 256 counter. The output of the IC pin 6 and ground is connected to the frequency meter.

The parts:
The 7805 regulator powers the IC and the last 2 transistors
The circuit operates from a 9V battery which also feeds the regulator
The Ic consists of two counters in one package of 14 pins hence you need just one.
PIN 14 is VCC and PIN 7 is ground
The ic is TTl IC

Diode Thermometer Circuit Using 1N4148

This is a design circuit of thermometer. When power transistors are used, they may tend to overheat. Likewise resistors may also overheat in the event of faults or short-circuits. The knowledge of their temperatures may be advantageous. Here’s the figure of the circuit;

 

Measuring the temperature of a bodies, depends upon the establishment of thermo-dynamic equilibrium between the body and the device used to sense the temperature. In practice, this condition is rarely attained since it is difficult to establish complete instantaneous equilibrium. Hence great care must be exercised in choosing a method suited to the problem so that satisfactory conditions for temperature measurements are obtained. Temperature sensors possess thermal characteristics dependent largely on their size and shape and the materials from which they are made.

Celsius Thermometer Circuit

This is a design circuit of the Celsius thermometer in the diagram is based on the well-known Type LM334 from National Semiconductor. This IC is a sensor that provides a current which is directly proportional to the temperature in kelvin (K). Unfortunately, this is a quantity that is not suitable for use in most practical applications. This is the figure of the circuit;

 

In the circuit, therefore, the sensor is set to 1 µA K–1 with P1 and the offset of 273 K removed with P2. This renders the output voltage of the sensor directly proportional to the temperature in degrees Celsius (° C) and this makes the circuit suitable for a great many applications (since 1K=1° C). Circuit IC2 is arranged as a 2.5 V reference voltage source. The current setting of the sensor is determined by the resistance between the adjust pin and earth. If the earth is made virtual by raising the potential at the adj pin, the zero point can be shifted as desired. Calibration is best done by using a good domestic thermometer as reference. Start by short-circuiting IC2 and adjusting P1 until the reading of meter M1 shows a current value numerically equal to the ambient temperature plus 273. If, say, the room temperature is 25°C, adjust P1 until the meter reads 298 µA. Then, remove the short-circuit from IC2 and adjust P2 until the meter reads a current whose numerical value is equal to the room temperature, that is, 25 µA. The circuit draws a current not exceeding 1 mA, so using two AA size (AM3, MN1500, LR6, SP/HP7) batteries as power source will give a life of a couple of years.

Water Level and TDS Sensor

This is a design circuit for watel level sensor using TLC555 is a monolithic timing circuit fabricated using the Lin-CMOS* process.  Due to its high impedance inputs (typically 1012 Ohms), it is capable of producing accurate time delays and oscillations while using less expensive, smaller timing capacitors then the NE555. This is the figure of the circuit;

Like the NE555, the TLC555 achieves both mono stable (using one resistor and one capacitor and astable (using two resistors and one capacitor) operation.  In addition, 50% duty cycle astable operation is possible using only a single resistor and one capacitor.  It operates at frequencies up to 2 Mhz and is fully compatible with CMOS, TTL, and MOS logic.  It also provides very low power consumption (typically 1 mW at VDD = 5V) over a wide range of supply voltages ranging from 2 volts to 18 volts.

Digital LED Voltmeter Circuit Using ICL7107

This is a design circuit for digital voltmeter with LED display. It’s ideal to use for measuring the output voltage of your DC power supply. It includes a 3.5-digit LED display with a negative voltage indicator. It measures DC voltages from 0 to 199.9V with a resolution of 0.1V. The voltmeter is based on single ICL7107 chip and may be fitted on a small 3cm x 7cm printed circuit board. The circuit should be supplied with a 5V voltage supply and consumes only around 25mA. The use of 7805 5V voltage regulator is highly recommended to prevent the damage of ICL7107, 555 ICs and to extend the operating voltages. This is the figure of the circuit;

 

Parts list of The Digital LED Voltmeter:
R1 = 8K2 R1 = 8K2
R2 = 47K / 470K R2 = 47k / 470K
R3 = 100K R3 = 100K
R4 = 2K R4 = 2K
R5, R6 = 47K R5, R6 = 47k
R7 = 0R / 4K7 R7 = 0R / 4K7
R8 = 560R R8 = 560R
C1,C5, C6, C8, C9 = 100n C1, C5, C6, C8, C9 = 100n
C2 = 470n / 47n C2 = 470n / 47n
C3 = 220n C3 = 220n
C4 = 100p C4 = 100p
C7 = 10-22u C7 = 10-22U
D1, D2 = 1N4148 D1, D2 = 1N4148
IC1 = ICL7107 IC1 = ICL7107
IC2 = NE555 IC2 = NE555
OPTO = CA 10 pin FTA = CA 10 pin

Low Voltage AC Voltmeter Circuit

This is a design circuit for AC voltmeter for measuring low AC voltages. The main component of this circuit is an operational amplifier (such as the 741 or 351), configured as an amplifier whose feedback circuit is a diode bridge full-wave rectifier. This is the figure of the circuit;

The op amp's output current in both the positive and negative cycles flows through it in only one direction.  In effect, the average of the op amp's output ac current io, which passes through the ammeter as a dc current, is measured by the ammeter. With full wave rectification, the meter current is given by: io = 0.9 Vin/R, or Vin = 1.1 ioR.  Note that this project requires calibration so that the meter will register the rms value of the input voltage Vin.
 

Digital Voltmeter Circuit

This is a design circuit for digital voltmeter circuit. The integrated circuit ICL7107 is a 3-1/2 digit LED A/D convertor. It contains an internal voltage reference, high isolation analog switches, sequential control logic, and the display drivers. The auto-zero adjustment mechanism ensures zero reading for 0 volts input. The circuit is classic design and you can be sure that it will work fine. However, for better result, it is recommended to design a proper PCB for minimum voltage drift and noise. This is the figure of the circuit;

Connect the positive and negative probes PLG1 and PLG2 to two points of the electric circuit you would like to know their electric potential difference or simply voltage. You have to set the selector switch S2 to proper voltage range you expect those two points would have. To calibrate the volt-meter, use the potentiometer P1. Adjust it to read correct voltage on the display by connecting probes to a known voltage source. You may need to use another calibrated volt-meter in this case.

Low Voltage AC Voltmeter Circuit

This is a design circuit for AC voltmeter for measuring low AC voltages. The main component of this circuit is an operational amplifier (such as the 741 or 351), configured as an amplifier whose feedback circuit is a diode bridge full-wave rectifier. This is the figure of the circuit;

The op amp's output current in both the positive and negative cycles flows through it in only one direction.  In effect, the average of the op amp's output ac current io, which passes through the ammeter as a dc current, is measured by the ammeter. With full wave rectification, the meter current is given by: io = 0.9 Vin/R, or Vin = 1.1 ioR.  Note that this project requires calibration so that the meter will register the rms value of the input voltage Vin.
 

Barometer Signal Conditioner Circuit

This is a circuit for a complete barometric pressure signal conditioner that operates from a single 1.5V battery. We can get the best accuracy and stability if we use bonded strain gauge and capacitive-based transducer,  but they are expensive.  This design introduce a new type of semiconductor transducer that achieves 0.01″ Hg (inches of mercury) uncertainty over time and temperature.  This would be suitable for portable application since it uses only a single cell battery. This is the figure of the circuit;

 

The 6 k Ohm transducer T1 need exactly 1.5mA excitation current, so it needs a relatively high voltage source.  Non-inverting input of A1 senses T1’s current by monitoring the voltage drop across the resistor string in T1’s return path. The inverting input of A1 is fixed by the 1.2V LT1004 reference. The  output of A1 biases the 1.5V powered LT1110 switcher. This switcher produces two outputs from L1.   The rectified and filtered voltage from pin 4 is used to supply the power for  A1 and T1.  A1’s output, in turn, closes a feedback loop at the regulator. This loop control the step-upped voltage to give a constant current of   1.5mA through T1.  This circuit design produce  the required high excitation voltage while minimizing power consumption. This is done by making the switching regulator produces only enough voltage to satisfy T1’s current requirements. Pin 1 and 2 of Li produce a fully floating, boosted voltage, which is rectified and filtered to power A2. Since A2 floats with respect to T1, it can look differentially across  T1 outputs (pin 10 and 4). Practically, pin 10 acts as ground and pin 4′s output is measured by A2 using this reference point.

The gain of A2 is set to  provide a convenient scale of 3.000 V = 30.00″ Hg. Calibrating this circuit is easy, just adjust R1 for 150mV across the 100 Ohm resistor in T1′s return path.  This step set the T1 current to the  calibration point  as specified by the manufacturer.  Next, adjust the scale to match the factor of 3.000V=30.00″Hg by adjusting R2.  Even if the pressure standard is not available, we can calibrate the circuit using individual calibration data provided by the manufacturer.  This circuit maintain 0.01″Hg accuracy over months over a wide range ambient pressure shift.  This portable device is also give interesting altitude indication if we take it when driving over hills and freeway overpasses, since 0.01″Hg corresponds to about 10 feet increase from sea level. This circuit draws 14mA from the battery, permitting the circuit to operate for 250 hours if we use a single D cell battery.

Milivolt Meter Circuit Using Op Amp LM11

This circuit is design for milivolt meter circuit. This circuit is using LM11. This circuit has requirements analogous to those discussed for the ammeter. This is the figure of the circuit;

In the most-sensitive position, the range resistor is zero and the input resistance equals R1. As voltage measurement is desensitized by increasing the range resistor, the input resistance is also increased, giving the maximum input resistance consistent with zero stability with the input open. Thus, at full-scale, the source will be loaded by whatever multiple of the noise current is required to give the desired open-input zero stability.

[Schematic circuit source: National Semiconductor Notes]

Temperature Monitor for Microprocessor Systems Circuit

This is a design circuit for monitoring the temperature. This circuit is used an NE1617A. This is the figure of the circuit;

Voltage And Current Noise Tester Circuit

This is a simple design circuit for tester circuit. This circuit is based on LM791. This is the figure of the circuit.


Using large resistor value make the current noise dominate since it is coupled into the resistance and thus voltage noise and thermal noise become negligible compared to the current noise. The output voltage is specified as Vout and input voltage as Vin and box noise enabled is checked.

[Schematic circuit source: National Semiconductor Notes]

Single Television Conversion Terrestrial Tuner Evaluation IC Circuit

This is a design circuit for conversion tuner. This circuit is based on MAX3540 single chip IC. This is the figure of the circuit.


This television tuner draws only 760mW of power from a +3.3V supply voltage. The MAX3540 is designed to convert NTSC or ATSC signals in the 54MHz to 860MHz band to a 44MHz intermediate frequency (IF). The MAX3540 includes a variable-gain low-noise amplifier, multi band tracking filters, a harmonic-rejection mixer, a low-noise IF amplifier, an IF power detector, and a variable-gain IF amplifier. The MAX3540 also includes fully-monolithic VCOs and tank circuits, as well as, a complete frequency synthesizer. This highly integrated design allows for low-power tuner-on-board applications without the cost and power-dissipation issues of dual-conversion tuner solutions. The MAX3540 is specified for operation in the 0°C to +85°C temperature range, and is available in a leadless 48-pin flip-chip (fcLGA) package.

[Schematic circuit source: MAXIM Application Notes]

Open Loop And Phase Test Circuit

This is the simple design circuit for test circuit. This circuit is based on LM791 for control the operation. This is the figure of the circuit;


When testing the open loop and phase, the user should choose an upper frequency limit that goes beyond the unity gain bandwidth of the amplifier. The capacitor is chosen to be large to provide roll off (f=1/2 πR1C2) so that even if the op amp tested has very low frequency dominant pole, the simulation shown a smooth transition and 20 dB per decade roll off.

[Circuit source: National Semiconductor Notes]

Security Monitor Circuit Using LM386

This is a circuit diagram of security system. You can use this in the garden and listening to unusual sounds, or maybe just the sounds of wildlife. If you have a car parked at a remote location, the microphone will also vote on anything in this area. Cable can be seen or hidden, screened cable is not required and you can use a cable or speaker bell wire if desired. In principle this circuit is there are two parts, a remote microphone preamp, and an audio amplifier based on the National Semiconductor LM386 audio amplifier. This is the figure of the circuit.


Remote microphone preamps is using ECM to monitor the vote. A direct coupled amplifier 2 stage built around Q1 and Q2 microphone strengthen weak signals. R2 preset functions as a control, and C1 provides some high frequency roll into the overall audio response. Q1 is run at a low collector current for a high signal to noise ratio, while the Q2 collector biased to around half of the maximum dynamic supply voltage range. Power supply for the preamp is fed through R10 and R6 from the 12V supply. C4 ensures that the preamp power supply is separated and there is no ac voltage is present on the electrical network. Amplified audio output is from the collector of Q2 to be fed into the supply line through a 220u capacitor C6.

Q2 output impedance is low, the relatively high value of C6. C6 also has a second purpose of allowing the audio signal output through, while blocking dc voltage. In the end part of this circuit is a 10u capacitor C7, bringing home the amplified audio to listen to the location. The first signal further amplifier voltage gain x10 amplified using TL071. C8, a capacitor 22p more a response rolls off high frequencies above 100kHz. This is required as a long wire may take a little radio interference. After amplification by op-amps, audio finally passed to the LM386audio amplifier . R14 acts as a volume control. R13 and C12 to prevent the possibility of instability in the LM386 and recommended by the manufacturer. Audio output is about 1 watt into 8 ohm loudspeaker, distortion of about 0.2%.

High Impedance DC Voltmeter

This is a project schematic for voltmeter circuit. This circuit is using digital system. This circuit is based on LM324 single chip IC. Here’s the figure of the circuit.


This circuit is of a comparator circuit, can be measured with a step 1Volt, car battery voltage. Hint voltage to the battery voltage ratio, which is applied to the inverting input of the amplifier, with a reference voltage produced by the diode D1, such as the current value so good thermic stability. With the RV1, we set the voltage gradient that we want. In this circuit is to use a type LM324 comparator.

Wind Meters Circuit

This is a design circuit for gauges simple wind meter. This circuit is work with based on transistors. Here’s the circuit figure of wind meters circuit:


Working principle of this circuit are the transistors Q1 and Q2 are used to feel the wind. The relationship between thermal impedance and the surrounding transistors utilized wind speed here. Transistors Q1 and Q2 is the cable that VCE of Q1 is higher than Q2 and therefore power dissipation will be higher. The wind causes the cooling so that Q1 VCE of changes. Which ended at different power dissipations and the different variations detected by R10.This voltage op amp and strengthened to generate comparable Fout wind speed. To air is still Fout will 0V and at 75 m / s wind speed will Fout 2.5V. A voltmeter FSD Fout 3V is connected across the terminal and ground can be used as a screen. The circuit requires 5V DC voltage. To work properly, the air must pass through two transistors (Q1 and Q2). Most of the resistors are not used here are the standard values. So, you should use a combination (series or parallel) resistors to achieve certain values. Please note that the resistor values is very important in this circuit.

Audiometer Circuit Using AT89S51

This is a design for audiometer circuit. This audiometer is an instrument used for the diagnosis threshold of human hearing to give some particular audio frequency and also a certain level of intensity. Raised from the signal generator sinus and selected using a multiplexer 4051. Amplitude or intensity of sound can be arranged through the DAC. Use as bait with the audio signal. Voltage to references from the DAC, so the output can be set with accuracy Vref/255. This is the figure of the connection of the circuit.


Procedure for programming the audiometer circuit is initial view will display the form fields Name and Date patients now on the Character LCD screen, which can be entered via the keyboard. After the data in the content of the system will wait for the emphasis the Enter key when keyboard enter key is pressed the system will start working on procedures audiometer. Through the multiplexer 4051 then selected the most low frequency, 125 Hz and data on the issue with the DAC will be issued with the signal frequency and amplitude particular. Interruption through the system timer 0, mode with 16 bit then remove the signals that can be set to increase amplitude for every 10 seconds: 0:05 x 200 = 10 seconds if the patient does not press the button, when 10 patients amplitude still does not listen to the sound of the automatic frequency raised to a higher level and again at the lowest amplitude. By using an external system interruptions 0, then we can do so that interruptions can be patient when the system starts listening to a sound. When patients hear then press the button so that there will be a process data storage dB and Frequency at the time. When the process is completed the system will re-open the data-data that have been stored for the data storage process is done.

Setting Time Test Circuit Using JFET

This is a circuit for testing the time. This circuit is built using JFET. This is the simple form. Here’s the schematic circuit diagram of the time test circuit.


Settling time is tested with the LF155/6 connected as unity gain inverter and LF357 connected for AV = −5. The FET used to isolate the probe capacitance. The output = 10V step. AV = −5 for LF357. [Schematic source: National Semiconductor, Inc].

Audio Frequency Meter

This is a circui for audio frequency meter. This circuit uses 555 IC as a mono stable multi vibrator (one-shoot trigger). A mono stable multi vibrator can act as a frequency-to-voltage converter because it produces a fixed pulse width, with the repetition rate/density is proportional to the triggering input frequency. This is the figure of the circuit.


For resistor R1, because it set the measurement range, it’s better to use a rotary switch to select different values for different ranges. For the ampere meter, you can use analog or digital ampere meter. A cheap dual-slope ADC digital meter is suitable because its averaging characteristic, but a fast digital multimeter can also be used although it may show some uncertainty because of their fast sampling.