SU1499453A1 - Device for protection against contact chatter - Google Patents

Abstract

The device can be used to eliminate signal bounce from mechanical contacts in automation and measurement technology. The aim of the invention is to simplify the device by inserting a Schmitt trigger 4 with logic 2I-NOT at the input and diode 8 into the discharge circuit, the time of the driving capacitor 7, which allows to eliminate the signal bounce in a wide range. The device also contains a mechanical contact 1, the first 2 and the second 6 resistors, the trigger 3. 1 Il.

Description

one

(21) 4108723 / 24-21

(22) 08/20/86

(46) 07.08.89. Bul ff 29 (72) A.N.Sharakhov

(53) 621.384 (088.8)

(56) USSR Copyright Certificate No. 930623, cl. H 03 K 5/153, 1980.

USSR Author's Certificate No. 1239847, cl. H 03 K 5/01, 1983.

(54) DEVICE FOR PROTECTION FROM DRABEZ | Contact GA

(57) The device can be used

It is designed to eliminate signal bounce from mechanical contacts in automatics and measurement technology. The aim of the invention is to simplify the device by introducing a Schmitt trigger 4 with LOGIC-2I-NE at the input and a diode 8 into the discharge circuit, the time of the output capacitor 7, which allows eliminating signal bounce in a wide range. The device also contains a mechanical contact 1, the first 2 and the second 6 resistors, the trigger 3. 1 Il.

with

CD

sd

OO

The invention relates to a pulse technique and can be used in automation devices, remote control, computing and measuring equipment.

The purpose of the invention is to simplify the device.

The drawing shows the functional diagram of the device for; protection from bounce contacts.

The device for protection against bounce of contacts contains a mechanical contact 1, the first resistor 2, the trigger 3 Schmitt trigger 4, (executed on the AND-NE element), the delay element 5 consisting of the RC circuit (resistor 6, capacitor 7) and diode 8. Moreover, the common output of the RC circuit is connected to the anode of diode 8, the first input of the Schmitt trigger 4, the first output of the second resistor 6, the second output of which is connected to the power supply bus, and the first output of the capacitor 7 to the common bus of the device. The first pin of pin 1 is connected to the common bus. The cathode of the diode 8 is connected to the second output-contact 1, the first output of the resistor 2, the inverse input of the installation in the unit state of the trigger 3 and the second input of the Schmitt trigger 4, the output of which is connected to the inverse input of the installation in the zero state of the trigger 3, the output of which It is connected to the output bus 9 of the device. In this case, the second terminal of the resistor 2 is connected to the power supply bus of the device.

The device works as follows.

In the initial state, the contact 1 is open, therefore a high logical level, specified through the resistor 2 from the power source, goes to the second Schmitt trigger 4 input. After time T, the capacitor 7 is charged through the resistor 6 to the high logic level and at the output of the I- element It is NOT a logic low that sets trigger 3 to the zero state. Since the time T is less than the time of establishing other processes when the power source is turned on, the pulse generated at the trigger output, if it is set to one at the time of switching on, does not affect the operation of other devices and, moreover, can be used to bring the FRIENDS5C devices to the original state.

When contact 1 is closed, a signal begins to arrive at the input of the device, the level of which is determined by the potential of the common bus of the device containing bounce. The first bounce pulse that arrived at the inverse of the installation in the unit state of the trigger 3, on the output bus 9 sets a high logic level. In addition, the same pulse causes a fast discharge of the capacitor 7 through the diode 8 to the common bus of the device, therefore, a low level appears at the first input of the NE-4 element and a high logic level at its output. At the end of the first bounce pulse, a high voltage level arrives at the device input. Capacitor 7 starts charging. The time of its charge T is chosen so that during the time interval between adjacent bounce pulses it cannot be charged to the level perceived by the Schmitt trigger 4 as a high logic level of voltage, therefore in the time intervals between bounce pulses at the inverse input of the zero state Trigger 3 is always high logic level, and on the output bus is also a high logic level. The next 1B bounce pulse causes the discharge of capacitor 7. During the action of the signal corresponding to the stable closed position of contact 1 (also a low voltage level), the capacitor 7 is discharged, therefore the duration

I;

THIS plot to work the device. no effect

When the switching is completed, the contact 1 returns to the steady position Open. At the input of the device, there is a high voltage level corresponding to the stable open position of the contact 1, and after a time T the capacitor 7 is charged to the level perceived by the Schmitt trigger 4 as a high logic level. Since a high logic level is also present at its second input, a low logic level is formed at the output of the Ymitta 4 trigger, which sets the trigger 3 to the zero state. Thus, when switching contact 1 on the output bus 9 of the device, a pulse impulse is formed, whose leading edge coincides with the leading edge of the first bounce pulse, i.e. with the start of the switch.

The output impulse of the device provides reliable overlapping of everything. switching process. Due to the fact that it is not the duration of the bounce pulses that is analyzed, but the time intervals of the niches, the device is not critical to the duration of contact retention in the On state and is operable in the case of continuous bounce. The presence of auto-correction of the initial state of the trigger reliably protects the device from being set to the forbidden state.

Claims (1)

Invention Formula A device for protection against chatter of contacts, containing a single-pole Q 49% 53b a switch, the first terminal of which is connected to the common bus, and the second is connected to the first output of the first resistor and the S input of the RS flip-flop, which is the device output, and R, the input to the Schmitt trigger output, the first input of which is connected to the first terminals A second resistor and a capacitor connected by its second output to a common bus, the second output of the first resistor is connected to the power supply bus, characterized in that, in order to simplify the device, a diode is inserted into it, and the Schmitt trigger is provided as a two-input element AND NOTthe second () Schmitt trigger input is connected to the second output of the single-pole switch and the cathode of the diode, the anode of which is connected to the first input of the Schmitt trigger, and the second output of the second resistor is connected to the power source bus. 15 20