JPS636914A - Timer device - Google Patents

Abstract

PURPOSE:To eliminate mis-start of an electronic switch due to a leakage current, to decrease a current giving to parts except a timer circuit and to reduce waste full power consumption by connecting a series circuit comprising a base, an emitter and a light emitting diode across a current sensing resistor and connecting a series resistor to the emitter of a 2nd transistor (TR) whose base is connected to the collector of a 1st TR. CONSTITUTION:The series circuit comprising the base, the emitter of the TR 12 and the light emitting diode 15 is connected across the current sensing resistor 11 and the collector of the TR 12 is connected to a negative power supply terminal via a resistor 14. Further, the emitter of the TR 13 is connected to a positive input terminal of a timer circuit 7 via a resistor 16 and the collector is connected to the other input terminal of the timer circuit 7. The light emitting diode 15 is lighted to display it when the timer circuit 7 counts the time and the resistor 16 is selected to make the voltage amplification factor of the TR 13 into the unity. Thus, the malfunction of the TR 13 due to noise is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a timer device that is started by turning on a power source using an electronic switch, such as a proximity switch, through which a leakage current flows when turned off.

[Prior art and its problems]

Most timer devices are configured to turn on the power using an electronic switch to start a timer circuit and perform a predetermined operation after a predetermined time. However, electronic switches generally have a large amount of leakage current when they are off, and this leakage current has the drawback of causing the timer device to start incorrectly. In order to deal with the drawbacks of conventional electronic switch 2, on/off element 2a, and resistors 4, 5 of smoothing circuit 3 are connected to the positive end of power supply 1, as shown in FIG.
, timer circuit 7 through a series circuit of Zener diode 6.
, the other input end is connected to the negative end of the power supply, and a bypass resistor 8 is connected between the resistor 5 and the Zener diode 6 and to the negative end of the power supply. . 2b is on when electronic switch 2 is off;
Off element 2aKi is a so-called leakage resistance through which leakage current flows, 9 is a smoothing capacitor connected to the connection point of both resistors 4.5 and the negative terminal of power supply 1, and 10 is a predetermined period of time that has passed since the timer circuit 7 started. This is the output transistor that turns on.

With such a circuit configuration, when the switch 2 is off, current flows from the power supply 1 to the bypass resistor 8 via the leakage resistor 2b and the smoothing circuit 3. Therefore, the resistance at this time is 8
If the zener voltage of the zener diode 6 is kept high in spite of the voltage drop, the timer circuit will not start erroneously due to this leakage current.

However, in such a timer device, when the switch 2 is turned on and a predetermined voltage is applied, the current flowing through the bypass resistor increases, resulting in increased power consumption, so the power source must be increased. Moreover, the heat generated by the current flowing through the bypass resistor lowers the reliability of surrounding electronic components, which in turn lowers the reliability of the entire timer device. Of course, if the current capacity of the bypass resistor is increased, only heat generation can be prevented, but this increases the size and has the drawback of increasing the size of the device.

[Purpose of the invention]

An object of the present invention is to provide a highly reliable timer device that does not malfunction due to leakage current, consumes less power even when a predetermined voltage is applied, and therefore does not generate unnecessary heat.

[Key points of the invention]

The gist of the present invention is to provide a timer device having a timer circuit that starts when a switch connected to a power source is closed and a voltage is applied between input terminals, and a current detecting resistor connected between the switch and the timer circuit, and a current detecting resistor connected between the switch and the timer circuit. A first transistor having a pace and an emitter connected to both ends of a detection resistor, and a pace current supply resistor having an emitter and a collector connected between the input terminals and a pace current supplying resistor between the pace and collector, and a pace connected to the first transistor. A second transistor connected to the collector detects the current flowing to the timer circuit via a current detection resistor, and when this current is only a leakage current, the first transistor is turned off and the second transistor is connected to the collector. A pace current is passed through the transistor of
Furthermore, when a predetermined voltage is applied to the timer circuit and a predetermined current flows through the current detection resistor, the first transistor is turned on and the second transistor is turned off, so the timer circuit can be started and wasteful bypass current is eliminated. This means that it will not flow. Note that if a series circuit of a pace, emitter, and light emitting diode is connected to both ends of the current detection resistor, and a series resistor is connected to the emitter of the second transistor, this light emitting diode will display the operating status of the timer circuit, and A resistor connected to the emitter of the second transistor increases the voltage amplification factor of this transistor to 1, making it possible to prevent noise voltage from malfunctioning this transistor and, by extension, malfunctioning the timer circuit.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2. Here, parts and circuits that have the same role as those in FIG. 3 are given the same reference numerals, and detailed explanation thereof will be omitted.

In Figure 1, a power supply 1, an electronic switch 2) a smoothing circuit 3
, the timer circuit 7 including the transistor 10, etc. are the same as those of the conventional one. This embodiment differs from the conventional one in that instead of the Zener diode 6 and bypass resistor 8 shown in FIG.
The point is that a leakage current countermeasure circuit consisting of the following is provided. That is, a current detection resistor 11 is connected in series between the resistor 5 of the smoothing circuit 3 and the input terminal of the timer circuit 7, the pace and emitter of a transistor 12 are connected to both ends of this resistor 11, and the collector of this transistor 12 is It is connected to the negative power supply terminal via a resistor 14. The emitter and collector of the transistor 13 are connected between the input terminals of the timer circuit 7, and the base thereof is connected to the collector of the transistor 12. The current detection resistor 11 keeps the transistor 12 in the off state in case of leakage current;
When the current increases to a predetermined value, the transistor 12 is turned on, and the resistor 14 is set so that the current increases to a predetermined value.
The transistor 13 is set to have a sufficiently small value with respect to the operating current of It has a sufficiently large hFE.

With this configuration, when the switch 2 is off, a voltage is applied to the timer circuit 7 via the leakage resistor 2b. However, at this time, the voltage drop across the resistor 11 due to the leakage current is small and the transistor 12 is off, so current flows through the transistor 13 from its emitter base to the resistor 14, turning on the transistor 13 and turning on the timer circuit 7. The input terminals are short-circuited to prevent the timer circuit 7 from starting. Next, when the switch 2 is closed, a large current flows through the resistor 11, and this voltage drop turns on the transistor 12. Since the voltage drop across the resistor 14 becomes high, the base current of the transistor 13 is blocked, and the transistor 13 is turned off. Therefore, a predetermined voltage is applied to the timer circuit 7 and the timer circuit 7 is started. The current of the timer circuit 7 keeps the transistor 12 on.

Then, after a predetermined time period, the transistor 10 is turned on. Figure 2 shows an embodiment different from that in Figure 1, in which the power supply 1, electronic switch 2) smoothing circuit 3, timer circuit 7, etc. are the same as in Figure 1, but the current detection resistor A series circuit consisting of the base and emitter of a transistor 12 and a light emitting diode 15 is connected to both ends of the transistor 11, and the collector of the transistor 12 is connected to the negative power supply terminal via a resistor 14. Further, the emitter of the transistor 13 is connected to the plus input terminal of the timer circuit 7 via the resistor 16, and the collector is connected to the other input terminal of the timer circuit 7.

The light emitting diode 15 emits light to indicate when the timer circuit 7 is measuring time, and the resistor 16 is set so that the voltage amplification factor of the transistor 13 is 1 to prevent malfunction of the transistor 13 due to noise. . Since the other operations are the same as those in FIG. 1, their explanation will be omitted.

〔Effect of the invention〕

According to the present invention, the current supplied to the timer circuit is detected by a current detection resistor, and if the supplied current is a small value such as a leakage current, the input terminal of the timer circuit is short-circuited. No false starts due to switch leakage current,
In addition, the current flowing through circuits other than the timer circuit is small, so there is no extra power consumption or heat generation, and the device is resistant to noise. It is also excellent because it can display the operating status of the timer circuit.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram showing an embodiment of a timer device according to the present invention, FIG. 2 is a wiring diagram showing an embodiment different from FIG. 1, and FIG.
The figure is a wiring diagram showing an example of a conventional timer device. 1...Power supply, 2...Electronic switch, 7
...Timer circuit, 11... Current detection resistor, 12.13... 12 Transistor Fig. 1 Fig. 2

Claims (1)

[Scope of Claims] 1) A timer device having a timer circuit that starts when a switch connected to a power source is closed and a voltage is applied between input terminals, comprising: a current detection resistor connected between the switch and the timer circuit; A first transistor having a base and an emitter connected to both ends of the current detection resistor, an emitter and a collector connected between the input terminals, a base current supply resistor being connected between the base and the collector, and a base to the first transistor. A timer device comprising: a second transistor connected to a collector of the transistor. 2) In the timer device according to claim 1,
A timer device characterized in that a series circuit of a base, an emitter and a light emitting diode is connected to both ends of the current detection resistor, and a series resistor is connected to the emitter of the second transistor.