SU1539977A1 - Device for protection of contacts from chatter - Google Patents

Abstract

The invention relates to automation and computing and can be used to form a single pulse. The purpose of the invention is to increase reliability by simplifying the device. The contact bounce protection device contains a single-pole switch 1, a resistor 2, an element of NE-3, an inverter 4, an RC circuit from a current-limiting resistor 5 and a capacitor 6, a Schmitt trigger 7, an output bus 8. Simplification of the device is provided by the proposed construction scheme. 2 Il.

Description

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The invention relates to automation and computing and can be used to form a single pulse.

The aim of the invention is to increase reliability by simplifying.

FIG. 1 is a schematic diagram of the device; in fig. 2 - time diagrams of his work.

The device contains a single-pole switch 1, a resistor 2, an element AND-HE 3, an inverter 4, an RC-chain consisting of a current-limiting resistor 5 and a capacitor 6, a Schmitt trigger 7, the first terminal of the switch 1 connected to the common bus, and the second the first input of the element is NE-3, the input of the inverter 4 and through the resistor 2 with the power bus. The output of the inverter 4 is connected to the series-connected current limiting resistor 5, the capacitor 6 and the output of the NAND 3 element. The trigger input of the Imitat 7 is connected to the circuit connecting the limiting resistor 5 and the capacitor 6, and the output to the second input of the NAND element 3 and to the output bus 8.

The device works as follows.

In the initial state1, the logical unit is present at the inputs of the inverter 4 and the NOT-3 element, the capacitor 5 is discharged, and its two plates have zero potential, which creates the state of the logical unit at the Schmitt trigger 7 output. This state of the circuit is stable. When the contact is closed (Fig. 2, a), the first pulse passing through the AND-HE element 3 and the capacitor 6 sets the Schmitt trigger 7 to the zero state (Fig. 2, b), which causes the locking element J – HE for passing the bounce pulses and holding the state of logical zero at its output.

The bounce pulses at the output of inverter 4 (Fig. 2, b) are filtered on an RC chain, which has a time constant much longer than the period of bounce pulses, as a result of which the voltage on the capacitor plate remains almost unchanged (Fig. 2, c. ), at the exit

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Schmitt trigger 7 holds a zero potential (Fig. 2, d), and at the output of the element AND-HE 3, respectively, the level of the logical unit (Fig. 2, e). In this position, the circuit is located until the contacts are opened. When the contacts open, the chatter pulses at the output of the inverter 4 (Fig. 2.6) are filtered again, do not lead to significant changes in the voltage on the capacitor 6 plate (Fig. 2, s), thereby maintaining at the output of the Schmitt trigger 7 zero potential (Fig. 2, d), with the result that the AND-HE 3 element remains closed for the passage of bounce pulses. At the end of the bounce, the inverter 4 is set to the zero state and the capacitor 6 starts to slowly charge through the current limiting resistor 5. reducing the potential on the plate (Fig. 2, c), and when the trigger threshold of the Schmitt 7 is reached, it translates it into a state of logical unit (Fig. 2, d), which leads to the establishment at the output of the element AND-NOT 3 zero potential (Fig. 2, d). In this case, the capacitor 6 is quickly discharged through the low-impedance output of the AND-HE element 3 (Fig. 2, c), and the circuit is again set to its initial steady state (Fig. 2),

Claims (1)

Invention Formula A device for protection against chatter of contacts, containing a single-pole switch, the first contact of which is connected to the common bus, and the second contact with the first input of the NAND element and through 1 resistor to the power bus, Schmitt trigger, the input of which is connected to the first capacitor plate and the first output of the current-limiting a resistor, the second output of which is connected to the output of the inverter, is about the fact that, in order to increase the reliability by simplifying the device, the output of the AND-NE element is connected to the second capacitor plate and the second input to you Schmitt trigger trigger, and the inverter input is connected to the second switch-switch. $ J 6 UUUL ... llIUUir PLG ish FIG. I