DE1788034C3 - Electronic timing element, especially for the digital control of machines - Google Patents

Description

7) lies.

2. Timing element according to claim 1, characterized in that that the transistor (1) via at least one resistor (2; 3; 4) or via diodes with can be controlled by a common series resistance.

3. Timing element according to claim 1 or 2, characterized in that the tap of the potentiometer (5) connected to the time capacitor (9) via a resistor (35) and that between this; Resistor (35) and the negative DC supply voltage line (6) a capacitor (27) is provided.

4. Zeitgüed according to one of claims 1 to 3, characterized by a voltage measuring device (30) ! wipe the tap of the potentiometer (5) and the positive DC supply voltage line

5. Timing element according to claim 4, characterized by a changeover switch (28) for optional connection the tap of the potentiometer (5) with the voltmeter (30) or with a parallel to the voltmeter (30) arranged resistance (29), the resistance value of which corresponds to the internal resistance of the voltmeter (30).

6. Timing element according to claim 5, characterized by a further contact (32) of the switch (28), via which the timer on the output side in the idle state when the voltmeter (30) is switched on is held.

7. timing element according to claim 6, characterized in that the further Koniakt (32) with the Output transistor (14) as a threshold amplifier provided Schmitt trigger (13) is connected in such a way that when another is closed Contact (32) of the output transistor (14) during the recharging of the time capacitor (9) remains controlled.

constant power source is charged. The charging process da-iert until the breakdown voltage of a Zener diode in the emitter circuit of a transistor on the output side Threshold amplifier is reached and the time capacitor discharges via the conductive Zener diode « will. The time is set by changing the steepness of the capacitor charging current Help change an ohmic resistance in the constant current source. This is the time setting range limited downwards, d. h_ that short times and thus also the time zero are not set can, since the steepness of the capacitor charging current can not be chosen arbitrarily large without the Constant current source from overload damage

takes.

The invention is based on the object of a timer of the aforementioned type to the effect that the time setting range downwards is not limited.

According to the invention, this object is achieved by the im Characteristics of claim 1 specified features

The invention relates to an electronic timing element as described in the preamble of claim 1 benen type. Such a timing element is known ("Electronics", 1967, Issue 7, pp. 207 to 212, Fig. II).

In the known timing element, the collector-emitter path of a transistor, which is switched on in the idle state and thus short-circuits the timing capacitor, ie keeps it free of charge, lies parallel to the timing capacitor. When a control signal is applied, the transistor blocks, whereby the time capacitor of the Kon- JSl.

a major difference in the function of the invention Timing element compared to the known timing element is that the time capacitor in the Initial state is charged and when the electronic switch is closed, an adjustable potential jump with a reversal of sign is subjected, its Height can be kept as small as desired by setting the potentiometer accordingly, so that even the shortest times do not require an increase in the charging current. This completes the normal time adjustment The potentiometer setting can be changed without changing the steepness of the capacitor charging current. One can thus change the steepness of the capacitor charging current of a time domain switchover Reserved.

A potential jump of the time capacitor with sign reversal is in an electronic Zeitgüed known per se (Siemens-Zeitschrift, 1959, issue 10, pp. 602 and 603), but there, too, the setting of the Time range by changing the steepness of the discharge current, which limits the time range downwards will. In addition, the charging voltage of the time capacitor runs according to an exponential function.

Advantageous designs of the timing element according to the invention emerge from claims 2 to With the measures according to claim 2 can be a coupling of the invention in a simple manner Reach timing element to a digital control device, in particular for an injection molding machine, without that this - especially with a large number of inputs - the operational reliability is reduced. With the measures of claim 3 can significantly increase the interference immunity of the timing element according to the invention will. In the formation of the timing element according to the invention according to claims 4 to 7 is the time-determining position of the potentiometer tap can be detected with a simple voltmeter that 1 in turn can be switched to all other timing elements of the relevant control device. Farther can be a simple potentiometer through these measures any tolerance and linearity can be used without a calibrated scale.

■ · In the drawing, an embodiment of the invention is shown. The figure shows the circuit diagram of a timing element according to the invention.

The electronic timing element shown starts up so-

17 8δ

soon a transistor 1 controlled via one of three input resistors 2, 3 and 4 ond therefore conductive will. The number of these input resistances can vary considerably depending on the operating voltage and dimensioning multiply without reducing operational reliability. If several, e.g. B. more than 20, OR inputs are required, diodes connected in parallel with a series resistor are used used. A potentiometer 5 is connected to the operating voltage via the transistor 1 that is switched through a DC supply voltage source with a negative line 6 and a positive line 7 placed, wherein a lamp 8 indicates the switching state and lights up when the transistor 1 is activated. As a result of Voltage loading of potentiometer 5 becomes> 5 the voltage at the left assignment of a previously charged time capacitor 9 is lowered, namely in Depending on the position of the tap on potentiometer 5. At the same time, the Capacitor voltage also the potential of the right assignment of the time capacitor 9, creating a by then Conducting transistor 10 in the charging circuit of the time capacitor 9 is blocked and the time capacitor 9 is discharged via the potentiometer 5 and the transistor 20 of a constant current source 11. After his The time capacitor 9 is discharged from the DC supply voltage source via the potentiometer 5 and the re-conductive transistor 10 is charged again, to one of the division ratio of the Potentiometer 5 dependent voltage. The base of the transistor 10 is used to protect it from overvoltages connected in series with a diode 12.

The transistor 10 is part of a Schmitt trigger 13 which has a further transistor 14. When the transistor 1 is blocked, the base of the transistor 14 is supplied with current from the positive line 7 via the potentiometer 5 and a resistor 15, and the transistor 14 is therefore turned on. During the timing of the timer, i. During the discharge of the time capacitor 9, the transistor 14 receives a base current via the resistors 16 and 17 and therefore remains conductive. The transistor 14 is only blocked when, with the transistor 1 still turned on, the transistor 10 becomes conductive again after the time capacitor 9 has discharged, so that the base of the transistor 14 via the resistor 15 and the conductive transistor 1 as well as the resistor 16 and the conductive transistor 10 is connected to the negative line 6. The transition of the transistor 14 from the conductive to the blocking state > ⁿ represents the information to which a machine control connected downstream of the timing element responds. The Schmitt trigger 13 is followed by an inverter stage with a transistor 18 which conducts when the transistor 14 is blocked, as a result of which the voltage at an output terminal 19 becomes practically zero. This state lasts until the control signal at the resistors 2, 3, 4 disappears and the transistor 1 blocks again.

As is readily apparent from the above, ho is due to the linear discharge of the time capacitor 9 via the transistor 20 of the constant current source It the elapsed time exactly proportional to the divider voltage set on potentiometer 5, the. as already mentioned, is equal to the charging voltage of the time capacitor 9.

Different resistances can be used in the circuit of the constant current source 11 by means of a switch 21 22 and 23 can optionally be switched on in order to set the discharge duration of the capacitor 9 or the time range to change the timing element, for example by one or more powers of ten. A thermistor is used for temperature compensation of the constant current source 11 24 provided. Capacitors 26 and 27, which can be electrolytic capacitors, as well as a Resistor 35 ensure better immunity to interference of the timing element according to the invention.

As can also be seen from the figure, the tap of the potentiometer 5 is via a switch 28 and a resistor 29 is connected to the positive line 7. Upon actuation of the switch 28, this connection is separated and the tap of the potentiometer 5 via a voltmeter 30 to the positive line 7 connected. The value of the resistor 29 corresponds to the value of the internal resistance of the voltmeter 30. The display value of the voltmeter 30 is therefore a measure for the potentiometer 5 set time during which the timer should take effect. By changing the potentiometer setting As mentioned, the duration of the timer can be set, the set Value can be read on the voltmeter 30, for example on a calibrated scale. Over a line 31 to the voltage measuring device; 30 can do this can be connected to other timers.

In order to prevent that during the measurement with the voltmeter 30, i. h .. while laying down of the time range, the machine control is controlled via the timer, is another contact 32 of the switch 28 is provided, which via resistors 33 and 34, the transistors 14 and 1 in the conductive State controls. As a result of this control, the time capacitor 9 discharges in the above described way; in the subsequent recharging of the time capacitor 9, however, remains the In contrast to its normal operation, transistor 14 is conductive, since it is still through resistor 33 and the closed contact 32 is connected to the positive line 7. The one from the downstream machine control as information evaluated transition of the transistor (14) from the conductive to the blocking State is therefore omitted.

Proper functioning of the timer assumes, as mentioned, that a control signal at least is present at one of the resistors 2, 3 or 4 until the time capacitor 9 is completely discharged and is recharged. This means that the signal duration of the control signal is greater than the delay duration of the timer must be. In order to also use the timing element according to the invention for shorter signals, To be able to end, the transistor 1 is replaced by a bistable multivibrator, which is replaced by any A short control signal is set, which corresponds to the switching on of the transistor 1. Resetting the bistable multivibrator takes place after the delay time of the timing element by its output signal at exit 19.

1 sheet of drawings

Claims (1)

Patent claims: 1. Electronic timing element, especially for the digital control of machines, with one of its A transistor, which is provided as an electronic switch, and a time capacitor, the one with its one assignment to a constant current source for linear capacitor charging and a threshold amplifier, characterized in that the time capacitor (9) with its other assignment on the tap of a potentiometer (5), which in turn Via the emitter-collector path of the transistor (I) to a DC supply voltage source (6,