JPH0343728B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic timer with a built-in momentary relay for self-holding, and its purpose is to prevent malfunction due to external impact.

An electronic timer that is equipped with a CR time limit circuit or an oscillation counting circuit and has a built-in instantaneous relay to enable self-holding is not only easy to wire because it does not require external self-holding wiring, but also can be easily connected to an external electric controller. This is to prevent malfunctions, but if an electromagnetic switch is installed in the vicinity of this electronic timer, the operating shock will last about 10 milliseconds at 100G. When used in an operating circuit, the coil of instantaneous relay 1 and switching transistor 2 are connected to power supply 3, 3,
The coil of the time limit relay 4 is connected in parallel to the switching transistor 2 together with the switching transistor 5, and the switching transistor 5 is driven by the time limit signal from the time limit circuit 6.
The above-mentioned shock is applied to instantaneous relay 1 and its normally open contact Ta is instantaneously closed, causing electronic timer T to self-hold as shown in Figure 2, causing an accident to occur in the external device. .

Note that PB is a push button switch for starting the timer.

The present invention has been made in order to improve the above-mentioned conventional situation.

Examples of the present invention will be described below with reference to FIG.

11 is an instantaneous relay whose coil is connected to a switching transistor 1 via a light emitting diode 12.
3. Connect the resistor 14 in series with the power supply 15, the base of which is connected to one end of the power supply 15 in series with the voltage dividing resistors 16 and 17, and connect the capacitor 18 between the midpoint of the voltage dividing resistors 16 and 17 and the other end of the power supply 15. is connected.

The time limit relay 19 has its coil connected in parallel to a light emitting diode 20, a switching transistor 21, a switching transistor 13, and a resistor 14, and a diode 22 connecting the base of the switching transistor 13 and the collector of the switching transistor 21. , base time limit circuit 23
It is connected to the time limit signal terminal.

This timer is used by connecting to the operating circuit shown in Figure 2, and generally the push button switch PB is
Since the pulse width during ON operation lasts from 50 milliseconds to 100 milliseconds, the switching transistor 13 is made up of the resistor 16 and capacitor 18 mentioned above.
The delay time is set to 20 to 30 milliseconds.

Therefore, in normal operation, the push button switch
When PB is operated, switching transistor 1
When the base of 3 is delayed by resistor 16 and capacitor 18, enough base current flows for switching,
It turns on, the instantaneous relay 11 operates, it enters a self-holding state, and is held even if the finger is removed from the push button switch PB, the time limit starts, and after the predetermined time limit ends, a time limit signal is output from the time limit circuit 23, and the switch is pressed. The switching transistor 21 is turned on, and the time-limiting relay 1 is turned on.
9 works. When the power is cut off, both relays return to normal. Incidentally, the capacitor 18 is discharged through the diode 22 when the time limit relay 19 is activated, so that a predetermined delay is always obtained.

Next, if an external shock is applied to this timer and the contacts of the instantaneous relay 11 are accidentally closed, the shock will end before the switching transistor 13 turns on due to the delay of the resistor 16 and capacitor 18. , it will not accidentally enter a self-holding state. Note that it is possible to change the delay time constant as appropriate depending on the type of external impact and the type of push button switch, etc., and is included in the present invention.

By having the configuration described above, the present invention has the following features:
Even if the self-holding contact malfunctions due to an external shock, the switching transistor will not self-hold because the delay circuit will delay the ON operation for self-holding, and this will prevent malfunction from occurring due to external shock. No self-holding electronic timer can be obtained.

[Brief explanation of drawings]

1 and 2 show a conventional example of the present invention, with FIG. 1 being a circuit diagram and FIG. 2 being an operating circuit diagram. Third
The figure is a circuit diagram showing an embodiment of the present invention. 11: Instantaneous relay, 13: Switching transistor, 15: Power supply, 16: Resistor, 18: Capacitor, 19: Time limit relay, 21: Switching transistor, 23: Time limit circuit.

Claims (1)

[Claims] 1. In a self-holding electronic timer that has a built-in instantaneous relay for self-holding and a time-limited relay for time-limited output, and drives the time-limited relay with a time-limited circuit that outputs a time-limited signal such as a CR time-limited circuit or an oscillation counting circuit, switching transistors and A self-holding electronic timer characterized in that a coil of an instantaneous relay is connected in series with a power source, and a delay output of a CR delay circuit connected in series with the power source is connected to the base of the switching transistor.