SU1357884A1 - Device for checking assembly of printed circuit boards - Google Patents

Abstract

The invention can be used to automatically control electrical circuits. The device for controlling the mounting of printed circuit boards contains a contact block 7 with terminals 8-11, switch 12 with keys 13-16, resistor 17, power supply 18, display unit 19, coincidence element 20, current comparator 21, control unit 22 and testing Em card 1 with radio elements 2-6. The device increases the reliability of the control. 3 il. fi cl from 01 oo oo 4:

Description

. one

The invention relates to the automatic control of electrical circuits and can be used to control circuits of printed circuit boards without dismantling the monitored board,

The purpose of the invention is to increase the reliability of the control.

FIG. 1 shows a diagram of the proposed device; in fig. 2 - current comparator circuit; in fig. 3 is a current-voltage characteristic of dynamic feedback.

The checked card 1 with radio elements 2-6 is connected via the contact block 7, 1; {meyu1atsii terminals 8-11 for connecting the test object, with a commutator 12, having keys 13-16, which is connected through a resistor 17 a power supply 18 and a display unit 19, the output of which is connected to the first input of the coincidence element 20, the second input of the coincidence circuit is connected to the output of the current comparator 21, and the output of the coincidence element 20 is connected to the input of the control jump 22, the output of which is control for the switch.

The current comparator 21 (FIG. 2) contains an operational amplifier 23 covered by dynamic feedback 24 having a special current-voltage characteristic and a threshold unit 25 connected to the output of the operational amplifier.

Dynamic feedback is performed on a high resistance resistor and Zener diodes (Fig. 3).

The threshold unit 25 is a conversion link between the analog output of the operational amplifier and the digital output of the current comparator, i.e. it is an analog-to-code converter. The identification unit 19 functions as a threshold device, the output of which contains a signal only when the input signal is greater than a certain threshold level, otherwise the output of the display unit is zero, which entails an indication of the presence of a short circuit in the test. my chains.

A prerequisite for reliable operation of the device is the occurrence of at least part of the radio elements between the current-carrying (printed circuit board conductors. The absence of all radio elements is unlikely.

The device works as follows.

Object 1 control (printed circuit board with installation) via contact b. sec 7 is connected to the output of switch 12.

Upon a command from the control unit 22, the key 13 is triggered, connected via pin 8 of the tested circuit to the commutator 12. All other control circuits are connected to the first input of the current comparator 21 through the corresponding contacts of the contact block 7, the second entrance

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five

five

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five

common

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which is connected by bus.

The input current at the first input of the comparator is compensated by the current in negative feedback, while maintaining the equality of the potentials of the first and second inputs. Moreover, at the output of the current comparator, a fault is formed even at a very low input current, which indicates the presence of a contact (no break) in the circuit under test.

If there is a short circuit between the circuit to be tested and any other circuit of the object, then the input of the display unit 19 closes to the first input of the current comparator 21 through the resistance of the short softening.

If the input of the display unit has a voltage lower than a certain threshold level, then there is no signal at its output and it indicates the presence of a short circuit.

In the absence of a short circuit at the input of the display unit, a voltage is formed that is greater than the threshold level, while the output of the display unit is formulated with the health signal of the circuit under test, which is fed to the input of the coincidence element.

At the output of the current comparator 21, the output signal is generated only if there is at least a small current at its input. The current at the input of the comparator is only present if the contact device is in good condition and there is no open circuit. Thus, the signal at the comparator output indicates the absence of an open circuit in the test of my circuit.

This signal is fed to the second input of the match. Only when there are two signals at the input of the coincidence element 20, an output signal is received at its output, which enters the input of control unit 22, after which the control unit issues a command in which the next switch key 12 connects the circuit under test to the device and the previous one returns to its original state the

The process is repeated.

The resistance of the elements of the control object (printed circuit board with installation) can be in the range from several ohms to several mega-ohms.

The resistance of the resistor 17 is selected

of CONDITIONS

  /

-R,

 - resistance of resistor 17;

 - the voltage of the power source, the magnitude of which is limited by the allowable voltage, which is not destructive. for the object of control; / Ki - current in the circuit during a short circuit (its value is not up to, it is necessary to exceed the maximum input current of the comparator, for whom

po, m comparator retains its properties, namely the equality of the potentials of the first and second inputs);

-resistance between short-circuited chains of the control object;

-resistance between the contacts of the contact device and the chains of the object of control.

Claims (1)

Invention Formula A device for controlling the mounting of printed circuit boards, containing a power source, a resistor, a control unit, an indication unit, a switch, the first outputs of a switch 15 with a current comparator output, an element output connected to the first resistor output and that coincidence connected to the input of the control unit with the first input display unit, second board. the output of the resistor is connected to the first output of the power source, the output of the control unit is connected to the control input of the switch, the information inputs of which are connected to the terminals for connecting the test object, characterized in that, to increase the reliability of the control, a coincidence element and a current comparator are inserted into the device, the first input of which is connected to the second outputs of the switch, the second input of the current comparator is connected to the second output of the power source and to the second input of the display unit, the output of which is connected to the first the input of the match element whose second input is connected with the output of the current comparator, the output of the coincidence element is connected to the input of the control unit. the output of the resistor is connected to the first output of the power source, the output of the control unit is connected to the control input of the switch, the information inputs of which are connected to the terminals for connecting the test object, characterized in that, to increase the reliability of the control, a coincidence element and a current comparator are inserted into the device, the first input of which is connected to the second outputs of the switch, the second input of the current comparator is connected to the second output of the power source and to the second input of the display unit, the output of which is connected to the first the input of the match element whose second input is connected .2 Compiled by M. Haenko Editor O. GolovachTekhred I, VeresKorrektor O. Kravtsova Order 5505/46 Circulation 730 Subscription VNIIPI USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, Rau Shska nab. 4/5 Production and printing company, Uzhgorod, ul. Design. four