DD130194B1 - CIRCUIT ARRANGEMENT FOR CONTACT BLOWING - Google Patents

Description

197414 -

Λ -

Circuit arrangement for Kontaktentprellung

Field of application of the invention

This circuit arrangement for Kontaktentprellung is used wherever applications work together with mechanical switching elements and electronic circuits. For example, in data processing on input devices and data display devices ·

Characteristics of the known technical solutions In the "Electronics" 3/72, page 99 and "electronics" 12/75, page 73 circuit arrangements are recorded for Kontaktentprellung.

In "Elektronik" 3/72., The British company Plessey Switching Controls has developed a circuit arrangement. A seven-digit dual counter is driven by a clock generator with usually a clock frequency of 500 kHz, thus constantly to let count the seven-digit dual counter, so that all coming for the 7-bit words embossed bit pattern at its зіеЬеп outputs in rapid succession are repeated , After a keystroke, a conductive connection is established between one of the decoder outputs and one of the multiplexer inputs, so that the signal "L" occurs at the output of the multiplexer only in the case of a particular bit pattern, and no signal occurs in all other combinations. To the clock generator and

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to stop the dual counter so that the 7-bit word corresponding to the pressed key stops on the seven output lines of the dual counter, seven AND gates are supplied to the parallel outputs. Pressing the AND gates takes over the output signal of the multiplexer.

Furthermore, from the "electronics" 12/75, page 73 a keyboard encoder with Kontaktentprellung known, to generate coded signals a numeric keypad is shown with a BCD output. The outputs of the decimal counter (BCD code) are converted by a decoder into a "1 out of 10" code. If the desired digit is selected with one of the keys from 0 to 9, it is stored in a memory. In this case, a two-phase clock plays an important role in the generation of two planks, the second plank triggers the decimal counter. If a switch is closed, the pulses are repeated after every ten cycles, as long as the switch is closed X3t. The signal propagation time in the decoder results in a time shift relative to the clock. Due to finite rise times in the decimal counter, needle pulses are a Polge. A time constant L .j must be long enough to cover the contact bounce with certainty. Become within f. pressed several keys, only the first pressed key is considered.

The published patent application 2409345, ANT: 27.2.74, Title: "Breaker-free circuit" anticipates the fact mentioned in the preamble of the claim of the invention description "Circuit arrangement for Kontaktentprellung" fact that a mechanical switching element, led via switching resistance and negator to the input of a univibrator , used for debouncing. The characterizing part of the claim of invention of the "Circuit arrangement for contact

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contravention goes far beyond the disclosure of the above-mentioned OS in the inventive idea and the resulting circuit arrangement and represents a new independent solution.

Object of the invention

This circuit arrangement for Kontaktentprellung has the goal that, compared to the prior art, a significantly economical component consumption and a faster switching behavior is achieved ·

Explanation of the essence of the invention

The consequence of this is that in fast electronic circuits several processes can be triggered by such a mechanical switch, although there is a demand to have only one action triggered. Therefore, the state of the art correspondingly large time constant canceled and a superimposition of the codes are prevented when a second key dss mechanical switch is printed ·

The object of this circuit is that a strong bouncing switch emits only a single signal, with the first signal swing, which gives off the switch with the least time delay, an output signal is available and that the output signal is only switched off when the Ausschaltprellungen of Switch has subsided "

According to the invention this is achieved in that in the circuit arrangement for Kontaktentprellung an input to another univibrator is arranged directly after a mechanical switching element with the switching resistance · The output of the former univibrator is as an input of the second univibrator and the output of the second univibrator is at the first Univibrator fed back · Furthermore, the output of the former univibrator as reset input and

.4- 197414

the output of the second univibrator is connected as an input to an edge-triggered D flip-flop, which is arranged without an actuating input.

embodiment

Prerequisite for the individual switching properties are that in the idle state at the output 7; 11 of the two univibrators 6, 10, the potential H (high) is · When switching the univibrators 6, 10 are the outputs 7, 11 of the two univibrators 6; 10 for the hold time ¹ Xf of the univibrators 6; 10 to the L potential (low) · At the two inputs of the respective univibrators 6, 10, which form a conjunction, a potential H (high) must be, so that the univibrator 6 or · 10 can be triggered · Y / during the holding time f take the univibrators 6; 10 no signal. The edge-triggered D-type flip-flop 14 is equipped with a set and reset input 12, whereby only the reset input 12 is used · With the positive switching edge at the input 13, the value applied to D is switched to the output 15 дди _иа · The switching state with the L-potential at the reset input 12 sets the output 15 Т _auf to the switching state H ·

If the mechanical switching element 1, z. As a key or a switch, closed, so is due to the inverter 3, briefly placed at the input 4 of the univibrator 6 da3 Η potential. The input 5 of the univibrator 6 is already at rest at the H potential. Thus, the univibrator 6 is triggered immediately and the output 7 of the univibrator 6 goes to the L potential · The L potential at the input 9 of the univibrator 10 is prevented in that, as a result of the bouncing of the switch 1, the univibrator 10 is also triggered. The hold time f 1, of the univibrator is adjusted so long that the known bounce time of the switch 1 is bridged.

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With the L-Potentiai at the reset input 12 of the D flip-flop 14, the output 15 Τ »,,« of ^the D flip-flop 14 is switched to the H potential. After expiration of the hold time Oi, the output 7 of the univibrator 6 returns to the Η potential and thus the input 8 of the univibtator 10 also has the Η potential · After the mechanical switching element 1 has opened, the potential at the input 4 is above the switching resistor 2 of the univibrator 6 pulled from the univibrator 10 to the Η potential, while at the input 4 of the univibrator 6, due to the negator 3, an L potential is applied · The univibrator 10 is thus triggered immediately and the resulting L-potential on Output 11 of the univibrator 10 locks on the input 5 of the univibrator 6, the univibrator 6 itself, so that the univibrator 6 can not be triggered by subsequent Preller of the mechanical switching element 1. After expiration of the hold time ^ _{2 of} the univibrator 10, the potential at the output 11 jumps from L to H · This positive switching edge switches the L-potential applied to D of the D-flip-flop 14 to the output 15 t . the L potential gets "With that, the switching cycle is completed and all the switching elements of this circuit are back in their resting state ·

Claims (2)

-6- 197414 invention claim 1 · Circuit arrangement for contact debouncing, wherein a mechanical switching element (1) with a switching resistor (2) via an inverter (3) to the input (4) of a univibrator (6) which drives a edge-triggered D flip-flop (14), is connected, characterized in that directly after the mechanical switching element (1) with the switching resistor (2) an input (9) to another univibrator (10) arranged that in each case an output (7) of the univibrator (6) as input ( 8) of the univibrator (10) and
an output (11) of the univibrator (10) as input (5) fed back to the univibrator (6) and that the output (7) of the univibrator (6) also as a return input (12)
and the output (11) of the univibrator (10) is connected as an input (13) to an edge-triggered D flip-flop (14). 2. Circuit arrangement according to item 1, characterized in that the edge-controlled D flip-flop (14) is arranged without control input · For this 1 page drawings