Logic probe testerLogic testers are simple but very helpful devices in testing digital circuits. A logic probe can be designed in many different ways. In this particular design, a combination of discrete and TTL logic components is applied to test different logic levels. This logic tester can test and display three different logic levels: the “0″ and the “1″ levels including the undefined logic state also known as “never mind”.

If the tested voltage level is below 1 volt, the logic tester will recognize it as a logical “0″. In that case, the emitter-collector junction of T2 conducts and the D5 LED lights up optically displaying a “logic 0″. If the tested voltage is between 1 volt and 2 volts, both T1 and T2 does not conduct and the XOR gate U1 receives two dissimilar logic states at its inputs. The XOR output becomes positive and the D6 LED lights up signalling a “never mind” logical state. The same thing happens by a open input or when testing a blind IC pin.

When the tested point is above 2 volts, the D4 LED lights up signalling a logical “1″ state. Another plus of the featured circuit is the fact that it uses a 7486 IC for the XOR gate. Since this IC has 4 gates inside, the circuit can be expanded to build a four channel logic analyzer.

Logic probe tester circuit diagram

1Hz to 1MHz Frequency Meter with Digital Display

Overview

The circuit was designed to create a low cost frequency meter that will cover the range of 1 Hz to 1

MHz with a digital indication using three 7-segment displays.

Terminology

o 7805 – a 3-terminal 1A positive voltage regulator with output transistor safe area

compensation, internal short circuit current limiter, output voltage of 5V, 12V, and 15V, internal thermal overload protection, no external components, and current output in excess of 0.5A

o 4026 – a decade counter where the count advances as the clock input becomes high and has

a maximum current of about 1 mA with a 4.5 V supply and 4 mA with a 9 V supply, which can light the appropriate segments of a common cathode 7-segment display

o 4583 – a 4-bit single-chip microcomputer designed with CMOS technology using a simple,

high-speed instruction set, equipped with four 8-bit timers, a 10-bit A/D converter, interrupts, oscillation circuit switch function, and used in application with remote control transmitter

o 4007 – a 1000 Watt solid state band-specific amplifier that covers a frequency range of 400-

450 MHz and provides an excellent 3rd order intercept point, high gain, and a wide dynamic range by utilizing Class A/AB linear power devices

o 556 – a dual timer that is highly stable device for generating oscillation or accurate time

delays used in pulse width/position modulation, sequential timing, time delay generation, linear ramp generator, precision timing, and pulse generation due to its features such as normally open and normally off output, temperature stability, output and supply TTL compatible, adjustable duty cycle, and operates in both astable and monostable mode

Circuit Explanation

The input signal is being regulated by IC1 as it performs the functions of a Schmitt trigger which is a

discrete comparator with hysteresis, whose output has two possible states just like other

multivibrators. The hysteresis refers to the difference between the positive and negative thresholds.

It changes the signal to a level that is acceptable as an input for IC2-3-4. The input of pin1 on IC2

contains the tenth pulse which produces the carry pulse in the pin5 of IC3. Simultaneously, this

scenario causes the zero indication in DIS1 while the IC3 causes a one indication of DIS2. In the

event that the tenth pulse is reached by the input of IC3, DIS2 will indicate zero while the DIS3 will

show one. With the display in the right order, the total indication would be 100.

The output of IC4 pin5 can be used to turn ON the decimal point in DIS1, showing the exceeding

measurements. One half of double timer IC5A begins the timing while switch S1 interrupts the time

in 1sec or 1ms. The second half IC5B produces an indication in 2 or 3sec during the interruption with

the interruption initiated by a RESET pulse. The connection of Q1 & IC1 should be far from input

jack to prevent high frequency parasitic signals. A low frequency in the input is applied by using S1

while the TR2 regulates the suitable frequency meter source with a 9V supply.

Part List

R1= 8.2Mohm

R2-9= 100Kohm

R3= 470Kohm

R4= 470 ohm

R5-6-7= 10Kohm

R8= 3.3Mohm

C1-2= 1uF 63V Mylar

C3= 47uF 16V

C4= 100nF 63V

C5= 2.2uF 16V

C6= 10uF 16V

C7= 10nF 63V Mylar

C8-10= 1nF 63V Mylar

C9= 1uF 16V

TR1= 1M ohm trimmer

TR2= 1Kohm trimmer

Q1= 2N930

IC1= 4583

IC2-3-4= 4026

IC5= 556

IC6= 4007

IC7= 7805

DS1-3=Display 7 Seg. Comm. Cath.

S1= ON-OFF mini switch

S2= 1X2 mini switch

Application

The digital frequency meter can be reliably used in laboratories by covering the frequency areas of

all the trade generators. Other types of frequency meters are used in a variety of industries such as

monitoring of vibration levels from heavy equipment, verifying the RF frequency signals of electronic

circuitry, and used with RF signals to provide high degree of measurement accuracy with data

calibration.

Simple pH Meter Circuit, A Low Cost Adapter for Your Digital VoltmeterPosted on May 20, 2009 by Adam

What is A pH Meter?

A pH meter is actually a precise voltmeter that measures the generated

voltage of a pH electrodes. The requirement of such meter is high input

impedance and has the gain of voltage-pH conversion. The standard pH

probe generate voltage about 59 mV per pH, so all we need is a pre-

amplifier with high impedance input and with gain = 16.7 to give 1 Volt

per pH. Here is the schematic diagram of the pH meter circuit:

pH Meter Circuit

This pH meter circuit use a high input impedance high gain op-amp

TL081. The transformer voltage is center tapped 15V (15V-0V-15V).

Multi-turn variable resistor is recommended for the zero, slope, and

reference variable resistors. Current consumption of this pH meter

circuit should be very small, so the 7812 and 7912 regulator IC won’t

need any heat sink.

pH Meter Calibration

To calibrate our pH meter circuit, follow these steps:

Null the amplifier by shorting the pH probe input to ground.

Measure the voltage between output + and ground. Adjust the zero

potentiometer until the voltmeter reading show zero volt (or close

to zero).

Now connect pH probe input to a 413 mV voltage source. You can

use a potentiometer to make a simple 413 mV voltage source. After

connecting the input to 413 mV source, then measure the + output

and ground using the digital voltmeter and you should read 7.00

volt. If not then adjust the slope potentiometer until you get the

closest reading to 7.00 volts.

Short the pH probe input to ground. Connect the digital voltmeter

voltmeter between – output and + output. Now adjust reference

potentiometer until the voltmeter show 7.00 volts. This corresponds

to the neutral pH of 7.

Connect the pH probe input to a pH electrodes (pH probe/sensor),

now the pH meter is ready to use. The voltmeter reading in volts

would be direct conversion of pH. pH value of 7 would be read as 7

volts, pH 3 as 3 volts, etc.

With low cost digital voltmeter (DVM), we can easily obtain 0.05 pH

accuracy if we follow the calibration method as described above.

Digital LED Voltmeter Using ICL7107 October 22nd, 2009 | Author: admin

This circuit is a circuit diagram 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. The following is a schematic drawing:

Parts list of The Digital LED Voltmeter:R1 = 8K2 R1 = 8K2R2 = 47K / 470K R2 = 47k / 470KR3 = 100K R3 = 100KR4 = 2K R4 = 2KR5, R6 = 47K R5, R6 = 47kR7 = 0R / 4K7 R7 = 0R / 4K7R8 = 560R R8 = 560RC1,C5, C6, C8, C9 = 100n C1, C5, C6, C8, C9 = 100nC2 = 470n / 47n C2 = 470n / 47nC3 = 220n C3 = 220nC4 = 100p C4 = 100pC7 = 10-22u C7 = 10-22UD1, D2 = 1N4148 D1, D2 = 1N4148IC1 = ICL7107 IC1 = ICL7107IC2 = NE555 IC2 = NE555OPTO = CA 10 pin FTA = CA 10 pin

Description.The circuit given here is of a very useful and accurate digital voltmeter with LED display using the ICL7107 from Intersil. The ICL7107 is a high performance, low power, 3.5 digit analog to digital converter. The IC includes internal circuitry for seven segment decoders, display drivers, reference voltage source and a clock. The power dissipation is less than 10mW and the display stability is very high.The working of this electronic circuit is very simple. The voltage to be measured is converted into a digital equivalent by the ADC inside the IC and then this digital equivalent is decoded to the seven segment format and then displayed. The ADC used in ICL7107 is dual slope type ADC. The process taking place inside our ADC can be stated as follows. For a fixed period of time the voltage to be measured is integrated to obtain a ramp at the output of the integrator. Then a known reference voltage of opposite polarity is applied to the input of the integrator and allowed to ramp until the output of integrator becomes zero. The time taken for the negative slope to reach zero is measured in terms of the IC’s clock cycle and it will be proportional to the voltage under measurement. In simple words, the input voltage is compared to an internal reference voltage and the result is converted in a digital format.The resistor R2 and C1 are used to set the frequency of IC’s internal clock. Capacitor C2 neutralizes the fluctuations in the internal reference voltage and increases the stability of the display.R4 controls the range of the voltmeter. Right most three displays are connected so that they can display all digits. The left most display is so connected that it can display only “1” and “-“.The pin5(representing the dot) is connected to ground only for the third display and its position needs to be changed when you change the range of the volt meter by altering R4. (R4=1.2K gives 0-20V range, R4=12K gives 0-200V range ).Circuit diagram.

Notes. Assemble the circuit on a good quality PCB. The circuit can be powered from a +/_5V dual supply. For calibration, power up the circuit and short the input terminals. Then adjust R6 so

that the display reads 0V. The ICL7107 is a CMOS device and it is very sensitive to static electricity. So avoid

touching the IC pins with your bare hands. The seven segment displays must by common anode type. I assembled this circuit few years back and it is still working fine.

Digital Voltmeter and Ammeter Using CA3161E and CA3162E

Overview

The circuits were designed using two A/D converters to create a voltmeter and ampere meter.

Terminology

o 1N4001 – a 1.0 Amp Silicon rectifier with voltage range of 50 to 1000 Volts and possessing

features such as guaranteed high temperature soldering, high current capability, diffused junction, low reverse leakage, utilizes void-free molded plastic technique for low cost construction, and carries Underwriters Laboratory Flammability Classification of 94V-0 by its plastic package

o BC557 – PNP general purpose transistors used for amplification and switching due to its low

current and low voltageo CA3162E – a monolithic analog to digital converter that provides 3 digit multiplexed BCD

output with features such as availability of extended temperature range version, over range indication, maintains delay with hold inhibits conversion, high speed (96Hz) and low speed (4Hz) conversion rate, internal timing with no external clock required, differential input, capable of reading 99 mV below ground with single supply, ultra stable internal band gap voltage reference, and dual slope A/D conversion

o CA3161E – a monolithic integrated circuit that performs the BCD to seven segment decoding

function and features constant current segment drivers, low standby power dissipation, pin compatible with other industry standard decoders, eliminates the need for output current limiting resistors, constant current segment outputs, and TTL compatible input logic levels

o 7805 – a 3-terminal 1A positive voltage regulator with output transistor safe area

compensation, internal short circuit current limiter, output voltage of 5V, 12V, and 15V,

IC2 N IC4=CA3161E

internal thermal overload protection, no external components, and current output in excess of 0.5A

o Voltmeter – a device or an instrument used for measuring the electrical potential difference

between two points of either alternating current or direct current electric circuito Ammeter – also known as amperemeter, is an instrument used for the measurement of

electric current flow in terms of the unit called ampereo 7 Segment LED – is a form of electronic display device for displaying decimal numerals that is

an alternative to the more complex dot-matrix displays also known as seven-segment indicator

o Diode Bridge – also known as bridge rectifier which has four diodes arranged in a bridge

configuration where the output voltage has the same polarity with either polarity of the input voltage

Circuit Explanation

The circuits are designed with the combination of CA3161E and CA3162E to imposing a complete 3-

digit display using a binary coded decimal to 7-segment display/decoder. The combination of the two

converters offers a complete digital readout system with a minimum number of external parts.

Although the circuit provides precise measurements of the voltage in the terminal and the current

that flows within the circuit, they are very basic even for an inexperienced user. The CA3162E

corresponds to the IC1 and IC3 in both circuits which functions as the A/D converter for 3-digit

display while CA3161E corresponds to the IC2 and IC4 which drives the 7-segment decoder.

From the first figure, which represents the voltmeter, the input comes in series with resistor R1. It is

then combined with resistor R3 that creates a voltage divider operation which produces an output

voltage that is a fraction of its input voltage. IC1 CA3162E has its pin 10 and 11 receive the input

power. The variable resistor RV1is being adjusted just enough to produce a display in the 7-segment

which is zero in all the 3 digits. The external voltage in the input has value around 900 mV. The

resistor RV2 will operate to adjust and rectify the 900 mV source to produce the necessary display.

Doing this will require checking on the voltage for precision and good quality.

In figure 2, which represents the ampere meter, no resistor exists in the input stage thus, creating a

drop in the voltage that is proportional to the value of current flowing into the circuit. Since this circuit

utilizes the same type of IC, pins 10 and 11 of IC3 would be receiving the input voltage. the variable

resistor RV4 will provide the necessary adjustment to provide a zero display on all the 3 digits in the

7-segment display. The positive input is connected to the positive pole of the battery while the

negative input has the 10 ohm resistor at 10 W connected in the negative pole. Variable resistor

RV3 is adjusted to produce 0.9 A current in the display. To ensure this value, an external ammeter is

used for measurement.

In both circuits, the voltage or current converter converts the input voltage applied between pins 10

and 11 to a current that charges the integrating capacitor (C4 and C9) for a predetermined time

interval. The V/I converter will be disconnected from the integrating capacitor and a constant current

source of opposite polarity is connected. The original value of the number of clock counts will be

restored which elapsed before the charge. The comparator senses the restoration which in turn

latches the counter. The count is then multiplexed to the BCD outputs.

Application

Voltmeters contain very high resistance and are connected in parallel across the component through

which the voltage is being measured. The black or negative lead of the voltmeter is connected

normally to the negative terminal of the component like the power or battery supplies while the red or

positive lead of the voltmeter to the positive side of the component. Alternatively, alligator clips can

be used in case of the black lead since it can be permanently connected to 0V while the red probe

measures other points for voltages.

In using the ampere meter, it should be placed in series with the component though which current is

being measured. In order to prevent the reduction of that current as it flows through the device, it

should be designed with a low internal resistance. Ampere meters for both AC and DC can be made

of dynamometer, hot-wire, or moving-iron.

Simple Diode Zener Tester Circuit DiagramThis is a tester circuit, used to test the zener diode voltage operation. This circuit helps you to measure the Zener operation voltage while you can not see the mark on the zener diode. This circuit also more accurate then digital volt meter measurement.

Put the zener diode on the J1 connector, and put the digital volt meter at J2 connector.Component list :

1. Q1=2N53632. D1=1N40023. C1=470uF 50V4. S1=ON/OFF5. T1=220Vac//12Vac 300mA6. DZ=Diode Zener7. D.V.M=Digital Volt Meter

simple transistor tester circuit diagram

Tags: circuit, detector, diagram, Tester, transistor

This is a simple transistor tester circuit diagram, this circuit diagram is used to test the transistor value. You will need 2 constant current sources because this circuit operates to test both of NPN and PNP transistors.

transistor tester circuit diagramThe potentiometer are use to set the current input which used to test the transistor. This circuit is very efficient with error tolerance only 2%, smaller then ordinary multitester.parts :1. D1 = D2 = LED2. T1 = TUN3. T2 = TUP4. R1 = R2 = R3 = 8k2 OHM5. Trimpot P1 = P2 = 100k OHMRelated posts:

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LED based transistor tester

john

January - 11 - 2010

4 Comments

Description.Here is the circuit of a very simple transistor tester which used two LEDs for displaying the condition of a transistor. Both PNP as well as NPN transistors can be tested using this circuit. Quad 2 input CMOS NAND gate IC CD4011B is the heart of the circuit. Out of the four NAND gates inside the IC, only three are used here and they are used as NOT gates by shorting their input terminals. Gates U1a, U1b, resistor R1 and capacitor C1 forms a square wave oscillator. The frequency of this oscillator can be adjusted by using R1. The output of the oscillator is inverted using the gate U1c. The inverted oscillator output is connected to the base of the transistor under test through the resistor R2 and the non inverted oscillator output is connected to the emitter of the transistor under test using the resistor R3.The status of the LEDs D1 and D2 reveals the condition of the transistor under test. If red LED is ON, It indicates that the transistor under test is a good NPN. If green LED is ON, it indicates that the transistor under test is a good PNP. If both LEDs are ON, it indicates that the transistor under test is short. If both LEDs are OFF, it indicates that either the transistor is bad or you may have connected it incorrectly.Circuit diagram.

Notes. The circuit can be easily assembled on a Vero board. Use 5V DC for powering the circuit. All unused pins of the IC must be connected to ground.

Logic Digital Tester by LM324

This is Logic Digital Tester Circuit. It uses the level input about 5V and use the integrated circuit LM324. Be Main Part electronics perform Drive All LED. Then use Current very low about 10mA by have potentiometer be formed fine the value threshold give just right with the level logic digital both of 3 the level that use by LED1(Green) be the level high and LED2(Red) Be the level LOW and The LED3(Yellow) be the level High IMR . The detail is other please see in the circuit please sir.

Digital Step-Km CounterMax. range: 9.950 meters with two digitsSlip it in pants' pocket for walking and jogging

Circuit diagram

Parts:R1,R3 22K 1/4W ResistorR2 2M2 1/4W ResistorR4 1M 1/4W ResistorR5,R7,R8 4K7 1/4W ResistorR6 47R 1/4W ResistorR9 1K 1/4W ResistorC1 47nF 63V Polyester CapacitorC2 100nF 63V Polyester CapacitorC3 10nF 63V Polyester CapacitorC4 10µF 25V Electrolytic CapacitorD1 Common-cathode 7-segment LED mini-display (Hundreds meters)D2 Common-cathode 7-segment LED mini-display (Kilometers)IC1 4093 Quad 2 input Schmitt NAND Gate ICIC2 4024 7 stage ripple counter ICIC3,IC4 4026 Decade counter with decoded 7-segment display outputs ICQ1,Q2 BC327 45V 800mA PNP TransistorsP1 SPST Pushbutton (Reset)P2 SPST Pushbutton (Display)SW1 SPST Mercury Switch, called also Tilt SwitchSW2 SPST Slider Switch (Sound on-off)SW3 SPST Slider Switch (Power on-off)BZ Piezo sounder B1 3V Battery (2 AA 1.5V Cells in series)

Device purpose:This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot lights after every 50 meters of walking. A beeper (excludable), signals each count unit, which occurs every two steps. A

normal step is calculated to span approx. 78 centimeters, thus the LED signaling 50 meters lights after 64 steps or 32 mercury switch's operations, the display indicates 100 meters after 128 steps and so on. For low battery consumption the display lights only on request, pushing P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together. Obviously this is not a precision meter, but its approximation's degree was found good for this kind of device. In any case, the most critical thing to do is placement and sloping degree of the mercury switch inside the box.

Circuit operation:IC1A & IC1B form a monostable multivibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divide by 64. Q2 lights the dot of D1 every 32 pulses counted by IC2. IC3 & IC4 divide by 10 each and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each monostable count. Q1 drives the piezo sounder and SW2 let you disable the beep.

Notes:Experiment with placement and sloping degree of mercury switch inside the box: this is very critical.Try to obtain a pulse every two walking steps. Listening to the beeper is extremely useful at this setting's stage.Trim R6 value to change beeper sound power.Push P1 and P2 to reset.This circuit is primarily intended for walking purposes. For jogging, further great care must be used with mercury switch placement to avoid undesired counts.Current consumption with display disabled is negligible, therefore SW3 can be omitted.