The development of digital techniques led to the creation of logical probes. The proposed logical probe is simple and easy to operate. The probe has a large input resistance, it was possible to achieve the use of CMOS structures.
The principle of operation of the probe is very simple (see Figure). When the probe is connected to a controlled point, where "0" is present, or the last "truncated", on the conclusions 8, 10, 12 of the DD1 chips of the device there is a log. "1", therefore, on the eight-seated indicator, "0" is depicted. When the probe is connected to the controlled point, where "1" is present, then the log of the DD1 chip (8,10,12) is installed log. "0", so segments A, F, E, D goes out and depicted log. "1". Diode VD1 protects the device from incorrect polarity of supply voltage.
CONDACTOR C1 prevents the probe self-excitation. The probion consumes a current of 17.5 ... 20 mA and operates at a voltage of 3 to 15 V. Power supply from the chains of the test device.
Design. The probe is mounted on two printed circuit boards from one-sided foil textolite.
On the first board, all elements are placed, except HG1, and the second board houses HG1. The first fee is better to place in the housing of the 20 mm syringe, and the second. On the knob of the syringe. The role of the probe plays the needle of the syringe.
Installation. Conclusions 1.6 need to be removed, and the microcircuit is "sideway", with 10-14 conclusions.

Details. CONDENSER C1 type KM-5, km-6, resistors R1 ... R3 type MLT-0,125, Diode VD1 Any small, chip K561LN2 (can be replaced by KR156LN2 or K564LN2), an eight-segment signogenerator - any similar one.
In establishing the device does not need.
Literature Radіoamator 3.2000 Author - K.Gerasimenko, PGT Krasnopolye, Sumy region.

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The logical probe is essentially a measuring device, an integral part of the laboratory of a specialist in a digital technique, which determines the presence of logical levels at the TTL chip conclusions and helping radio amateurs during repair and designers when debugging their radio-electronic devices.

Logical probe

The proposed logical probe is simple and reliable, indicates not only logical "0" and "1", but also intermediate states.

At the calibration, the scheme can be simplified, eliminating the "extra" elements, thereby increasing the attractiveness of the device for radio amateurs.

Logic TTL probe with advanced features

A description of the scheme and design of an uncomplicated probe for four logical levels, which can also fix single pulses and pulse sequences, and having a built-in generator, which helps to check the operation of meters.

Counter frequency meter

The proposed version of the Prober To determine the logical levels of TTL logic, shows the dynamics of occurring processes in the test devices and allows you to evaluate the frequency of the controlled signal (up to 2 MHz), the duty cycle, the number of pulses; Using a logical pulsator (pulse generator) it is possible to check registers, counters.

Logical Probe on Als342b

The article is a kind of reference sheet and tells about the signs of the indicators, their characteristics and classification. The diagram of the logical probe on the decimal indicator of ALS342B, its description and design is also provided.

The conclusions of most elements located on one side of the printed circuit board are closed through the edge of the board and subfalls to the contact sites located on the reverse side of the board. Needle probe Vpyana in the groove of the printed circuit board. Capacitor C2 consists of two connected parallel capacitors K53-16 to 10 μF.

In the probe, you can apply CT361 and CT373 transistors with any letter indexes, it is possibleand other silicon vicochastic transistors of the corresponding type of conductivity. Diodes can be replaced with any low-power silicon (v 3 V 4) and Germany (V 5, V b). Microcircuits - for similar other TTL series.

Explore logical devices in static and dynamic modes allows the Prober proposed by N. Pastushenko and A. Zhizchenko (G Kiev).

The printed diagram of the probion is depicted in fig. 3.

In the absence of a signal at the entrance of the elementdi .1 - Low logical level, on the entrances of the elementsd 1.2, D1. 3 D1 .4. - tall. The indicator segments will not shine. If a level corresponds to a logical "1", then on the output of the elementdi .i. there will be a logical "O", at the outputd 1. 2 - logical "1", elementsd1. 3 and D 1. 4 remain in the initial condition. In this case, segments are glowingb. and C and the number "1" is indicated. When there is a logical "O" at the input, then at the output of the elementsdi .2, D 1.3 and D 1.4 there will be a high logical level and the segments of A b will be lit,d, E, F.

When submitting for a probe input to thempulses with a frequency of up to 25 g C alternation of numbers "O" and "1" is distinguishable by the eye. At frequencies above 25 Hz, the effect of C1 capacitor begins to affect. As a result, the brightness of the glow of the segmentd. the letter "P" indicates the sequence of pulses with a high frequency at the input of the probe.

The probion feeds directly from the test device. If you have a nutrition +5 in a segment A (point).

In the probe used resistors MLT-0.125. Capacitors K50-6. Instead of chipk 133LA 8. you can apply the K155L8 chip.

In fig. 4 shows the location of parts on the printed circuit board from the double-sided foil glassstolite, and in fig. 5 - drawings of both sides of the printed circuit board. Appearance The probique is shown in the photo (Fig. 6)

Prober with sufficiently large input resistance and high-definition of response at certain levels of input voltage is proposed by V. Piratinsky and S. Shakhnsky from Moscow.

The transition zone from a state at which the indicator LED is on with full brightness, into a state in which the LED is lit to be 30 mV for the upper limit of the logical level "0" (-0.4 V) and 80 mV for the lower limit of the logical level " I "(+2.4 V).

The probe is characterized by a small energy consumed from the power source of the tested device, which is no more than 12 mA.

In fig. 7 shows principled electrical circuit Prober. It consists of two independent thresholds, one of which corresponds to the level "0". And the other level "I".

When the voltage at the input of the probe has a value from 0 to +0.4 V. Transistorsv 7 and V 8 threshold circuit "1" closed and red LEDv 5. does not burn. In the threshold scheme "0" transistorv 9. closed, and transistorvI 0. open and burns green LEDv 6. . Indicating the presence of the logical level "0".

With the potential at the input of the probe from +0.4 V to +2.3 in transistorsv 7 and V 8 still closed, transistorv 9. opened, and the V10 is closed. At the same time both LEDs are not lit. The same is observed if there is no signal at the input input.

No indication, so. indicates that. That there is no potential at the input or it has an intermediate value with respect to logical levels.

At the voltage at the input of the probe above +2.3 in transistorsv 7, V 8 threshold scheme "I"(V 7, V 8 fully open at the potential above +2.4 V) and the red LED lights upv 5, indicating the presence of the logical level "1". The threshold scheme "0" is in the same time. Diodes VI -v 4. serve to increase the voltage at which the threshold scheme "I"

Current transmission coefficienth. 21E. The transistors should be at least 400. Diodes VI-V4 KD103 (K102) are inappropriate. All resistors OMLT 0.125 - 5%.

Find a platoon using a voltage divider connected to a +5 V source, feeding the required voltage level to the plug input.

By changing the resistance of the resistorr 7. across Mascasgreen LEDv 6. at the level of the input voltage of 0.4 V, and the resistance to resistancer 5. - ignition of the Red LEDv 5. in the level of input voltage +2.4 V. For the convenience of adjusting resistorsr 5. R 7 you can temporarily replace variables.

Probil, developed by Muscovite V. Kopylov,

Also has high input resistance (RVX \u003d 200 com). But in contrast to the Probrier of V. Pirates and S. Shakhhansky registers and impulses. It has protection against overvoltages in the input (up to ± 250 V) and from the wrong power of the polarity of the power supply.

The concept of the probique is shown in Fig. eight

Through the RI resistor the signal enters the field of field transistorv 3. through the input voltage limiter on diodes VI.v2. From the output repeater, the signal is fed to emitter repeatspruce performed on transistorsv 4 yv 5, which reduce the inputs of the chips on each other in each other and shifted the levels of signals entering the elements.d1. 1, D 1. 2. With the ratings indicated on the schemer 2- R 5, the threshold thresholds of the response "1" and "2" are equal, respectively, 0.4 V and 2.4 V. To use the probe during chains control with other thresholds, it is necessary to choose these resistors. With input voltage exceeding the logical "I" threshold voltage on the outputs of the elementsd1. 1 and d 2.2, a logical "0" appears and the segment is glowingd. lED indicator H1 (sign "1"). At the inlet voltage below the logical "0" threshold voltage at the outputd 1. 2 The logical "1" appears. at the exitd 2. 1 - logical "0" and ignite through a resistorr 10 - segment F, via resistor R11 and diodev 6 - Segments A, B, G (The "0" sign is indicated) if the input voltage is in the interval between the logical "0" and "i" thresholds (intermediate level), the logical "i" on the outputsd 2.1 and D 2.2 cause the appearance of "0" at the exitd 2.3. and shine segments with. B,g. (The knowledge is indicated by "P"). Capacitors C2. C.3 eliminate excitation during transition modes.

The pulse detection is based on the start of the simultor on the front and the decline in each input pulse. Negative pulses for starting a waiting multivibrator performed on elementsd1. 4, D 2. 4, C5 and RI 3, form at the output of the elementd 2.3. each time the input signal moves from "0" to "1" and back, and their duration depends on the duration of the front and the decline in the input pulses. The "Point" segment is connected to the output of the standing multivibrator, which flashes twice to each input pulse at the frequency of the last less than 20 Hz and with sufficient duration. At the frequency of the input impulsion, more than 20 Hz flashes merge into a continuous glow. At the input signal. Close to Meandra, simultaneously with the point the signs "0" and "I" are indicated. Moreover, their relative brightness depends on the strength of the pulses. With a large or small duty, only one of these signs is indicated.

The probe is assembled on a double-sided printed circuit board of a foil fiberglass with a thickness of 1.5 mm. The location of the conductors from the part side is shown in Fig. 9, and from the opposite side - in fig. 9. b.

The probe used chips of the K155 series, MLT-0,125 resistors, KM5A condensers (C2. SZ), km6 (C /, C4) and K53-4 (C5, C6).

Section: [Constructions of simple complexity]
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The simple logic probe Designed for repair and adjustment digital circuits. For ease of use, the power supply of this logical probe is made from the power source, from which the device under study is powered. When repairing schemes using the K561 and K176 microcircuits, it will be 9 volts, and 5 volts for schemes using 155 and 555 series.

Description of the work of the probe

The logical level indicator in the logical probe serve two LEDs connected in parallel. For their glow, two transistors VT1 and VT2 are answered. When entering the probe logical probe log. 0, the transistor VT1 is locked, and VT2 is open due to the flowing current through the resistors R2, R3 in its base electrocups.

The VT2 transistor unlocks, and thus ignites the green LED. When entering the probe logical probe log. 1, transistor VT1 is unlocked, and VT2 closes, because there is no current of its base. Dispiration VT1 allows you to turn on the red LED, and the green LED goes out at the same moment.

In the event that a signal from a certain frequency appears on the probe, it will turn on both red and green LED. In the diagram, any LEDs similar by parameters with AL307 can be applied. Transistors can be replaced by KT315, CT3102.