JPH08181592A - Changeover circuit for time of timer - Google Patents

Abstract

PURPOSE: To reduce the effect of external noise by mounting a changeover section having a switch means turning on/off a field-effect transistor externally onto a printed circuit board. CONSTITUTION: A time constant circuit comprising resistors R1 to R3 and a capacitor C1 is connected to a timer IC 1 mounted on a printed circuit board B and a time of the timer IC 1 is set by the time constant circuit. Each source of FETs Q1 , Q2 is connected to each connecting point among the resistors R1 to R3 and drains connect to ground. Gates of the FETs Q1 , Q2 are connected to a changeover section 2 via lead wires L1 , L2 led from the printed circuit board B. Contacts r1 to r3 of a switch SW1 of the changeover section 2 are selected to turn on/off the FETs Q1 , Q2 and to switch the time of the timer IC 1. The charge discharge current of the time constant circuit flows to the printed circuit board B only via the FETs Q1 , Q2 and is not supplied to the lead wires L1 to L3 , the effect of external noise is not caused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a timer time switching circuit for switching a timer time of a timer unit mounted on a circuit board and for timing a predetermined timer time from outside the circuit board.

[0002]

2. Description of the Related Art Conventionally, a mono-multi timer IC1 that outputs a high-level or low-level pulse signal during a time limit by a trigger input from the outside for a predetermined fixed time (timer time) is printed on a printed circuit board B. It is installed in and used as a timer unit. FIG. 5 is a schematic circuit configuration diagram showing a conventional configuration. The timer IC ₁ has a resistor R ₁
~R series circuit ₃ and the capacitor C ₁ is externally attached. That is, from the timer IC ₁ to these resistors R _{1 to} R ₃
By flowing a charge and discharge current through the ground line to the series circuit and the capacitor C _1, the time constant determined by a combined resistance value and the capacitance of the capacitor C ₁ of the resistor R ₁ to R ₃ timer time of the timer IC1 is set to Has been done.

Then, the timer time of the timer IC1 is preset.
To switch from outside the substrate B, the timer time switching
The road is added. This timer time switching circuit is
R₁~ R₃Resistance of series circuit of₁And resistance R₂Connection point with
And resistance R₂And resistance R₃Printed circuit board B from the connection point with
Each of the lines out of the, and the contact point r corresponding to each line
₁, R₂And contact point r that is not connected to any line₃Provided
And their contact point r₁~ R₃Print selectively
Switch SW connected to the ground line of board B₁The
Switch SW provided outside the lint board B₁At each contact r
₁~ R₃To change the charging / discharging current flow path.
Change the combined resistance value related to the timer time.
You can change the timer time in 3 steps
It is a scam. That is, the switch SW₁Is a contact
r₁When connected to₂And resistance R₃Contact with
Since the continuation point is grounded to the ground line, the charging / discharging current is
Resistance R₃Does not flow to the time constant at this time, that is,
Timer time is resistance R₁, R ₂Combined resistance value and capacitor
C₁It depends on the capacitance value of. In the same way, switch S
W₁Is the contact point r₂, R₃Flow of charge and discharge current when connected to
Route changes, which causes the timer time to switch
Of.

[0004]

By the way, the charge / discharge current flowing through the capacitor C ₁ generally has a current value of several μA to several hundred μA, and as shown by the arrow in the drawing of FIG. It flows from B to the ground lines of the printed circuit board B through the lead lines L from the contacts r ₁ to r ₃ and the switch SW ₁ . Here, the lead wire L is always exposed to external noise, and if external noise is placed on the lead wire L while the charging / discharging current is flowing through the lead wire L,
Or not timer IC1 is operated at the time limited to the timer time as set by the switch SW ₁ due to the influence of noise, or problems such as timer IC1 to malfunction there is a problem that occurs.

An object of the present invention is to solve the above problems and to provide a timer time switching circuit in which the influence of external noise is reduced.

[0006]

In order to achieve the above object, a timer for switching a timer time of a timer unit mounted on a circuit board for limiting a predetermined timer time from outside the circuit board. A time switching circuit, which has a time constant circuit composed of a plurality of resistors and capacitors, sets a timer time according to the time constant of the charging / discharging operation of the time constant circuit, and a plurality of resistors. 1 or a plurality of field effect transistors for changing the charging / discharging current path of a time constant circuit composed of a capacitor are mounted on a circuit board, and 1
It is characterized in that a switching unit having switch means for turning on / off a plurality of field effect transistors is provided externally to the circuit board.

According to a second aspect of the present invention, in order to achieve the above object, there is provided a timer time switching circuit for switching a timer time of a timer unit mounted on a circuit board for timing a predetermined timer time from outside the circuit board. , A timer constant setting section having a time constant circuit composed of a plurality of resistors and capacitors and setting a timer time according to a time constant of charging / discharging operation of the time constant circuit, and a time constant composed of a plurality of resistors and capacitors A switching unit having one or a plurality of field-effect transistors for changing a charging / discharging current path of a circuit mounted on a circuit board and having a switching means for turning on / off the one or a plurality of field-effect transistors is externally attached to the circuit board. In addition, the ON / OFF control signal of the field effect transistor output from the switching unit is supplied via the inverter logic circuit.

According to a third aspect of the present invention, in order to achieve the above object, there is provided a timer time switching circuit for switching the timer time of a timer unit mounted on a circuit board and for timing a predetermined timer time from outside the circuit board. , A timer constant setting section having a time constant circuit composed of a plurality of resistors and capacitors and setting a timer time according to a time constant of charging / discharging operation of the time constant circuit, and a time constant composed of a plurality of resistors and capacitors One or a plurality of light-triggered field effect transistors that change the charging / discharging current path of the circuit are mounted on a circuit board, and light-emitting elements optically coupled to the one or a plurality of field effect transistors are caused to emit light. It is characterized in that a switching unit provided with a switch means for turning on / off the field effect transistor is provided externally to the circuit board.

The invention of claim 4 is the first to third aspects of the invention.
In the invention, the switch portion for changing the charging / discharging current path of the time constant circuit including at least a plurality of resistors and capacitors is mounted on the circuit board.

[0010]

According to the invention of claim 1, there is provided a timer time setting section which has a time constant circuit composed of a plurality of resistors and capacitors, and which sets a timer time according to a time constant of charge / discharge operation of the time constant circuit. Switch means for mounting on the circuit board one or more field effect transistors for changing the charge / discharge current path of a time constant circuit composed of a plurality of resistors and capacitors and for turning on / off the one or more field effect transistors By externally providing the switching unit provided with the circuit board, the path of the charging / discharging current flowing in the time constant circuit can be changed without drawing it out of the circuit board. It only flows to the outside, and the influence of external noise can be reduced.

According to another aspect of the present invention, there is provided a time constant circuit comprising a plurality of resistors and capacitors, and a timer time setting section for setting a timer time according to a time constant of charge / discharge operation of the time constant circuit. Switch means for mounting on the circuit board one or more field effect transistors for changing the charge / discharge current path of a time constant circuit composed of a plurality of resistors and capacitors and for turning on / off the one or more field effect transistors A switching unit equipped with a switch is provided externally to the circuit board, and the on / off control signal of the field effect transistor output from the switching unit is supplied through the inverter logic circuit, so that the charging / discharging current flowing in the time constant circuit. Since the path of can be changed without drawing it out of the circuit board, the charging / discharging current will flow only inside the circuit board, and the influence of external noise It is possible to reduce the.

According to the third aspect of the present invention, there is provided a time constant circuit comprising a plurality of resistors and capacitors, and a timer time setting section for setting the timer time according to the time constant of the charge / discharge operation of the time constant circuit. , One or a plurality of light-triggered field effect transistors that change the charge / discharge current path of a time constant circuit composed of a plurality of resistors and capacitors, and one or a plurality of field effect transistors, respectively. By providing a switching unit externally provided on the circuit board, the switching unit having switching means for turning on / off each field effect transistor by causing the light-emitting element optically coupled to emit light, the path of the charging / discharging current flowing in the time constant circuit is provided. Since it can be changed without drawing it out of the circuit board, the charging / discharging current flows only in the circuit board, and the time constant circuit and the switching unit are electrically connected. Because it is insulated, it is possible to further reduce the influence of external noise.

According to the structure of the invention of claim 4, the switch part for changing the charging / discharging current path of the time constant circuit including at least a plurality of resistors and capacitors is mounted on the circuit board, so that only the external switching part is provided. Not only that, the timer time can be switched on the circuit board by using the switch unit.

[0014]

【Example】

(Embodiment 1) FIG. 1 is a schematic circuit configuration diagram showing a first embodiment of the present invention. As shown in FIG. 1, the basic configuration of this embodiment is common to that of the conventional example, and the common parts are denoted by the same reference numerals and the description thereof is omitted.

In this embodiment, a series circuit of resistors R _{1 to} R ₃ externally attached to the timer IC ₁ and a capacitor C ₁
A timer time setting unit is composed of a time constant circuit consisting of
Further, the resistance R ₁ and the resistance R ₁ of the series circuit of the resistances R ₁ to R ₃ are
N-channel field effect transistors (hereinafter abbreviated as FET) Q ₁ and Q ₂ for switching whether to connect the connection point with ₂ and the connection point between the resistor R ₂ and the resistor R ₃ to the ground line. And these FETs
The switching section 2 provided outside the printed circuit board B turns Q ₁ and Q ₂ on and off.

The FETs Q ₁ and Q ₂ have their sources connected to the connection point between the resistors R ₁ and R ₂ and the connection point between the resistors R ₂ and R _{3, respectively,} and their drains connected to the ground line. Further, a resistor R ₀ is provided at the gates of the FETs Q ₁ and Q _2.
And a pull-down resistor Rd, one end of which is connected to the ground line through a low-pass filter including a capacitor C ₀
Since the gates of the FETs Q ₁ and Q ₂ are connected to the ground line by the pull-down resistor Rd, the FETs Q ₁ and Q ₂ are normally off.

Lines are drawn from the gates of the FETs Q ₁ and Q ₂ to the outside of the printed circuit board B, and contact points r ₁ and r ₂ corresponding to the lines are provided on the lead lines L ₁ and L _2. Yes, and a leader line L that is not connected to any line
_A contact point r ₃ is provided at ₃ . Further, a capacitor C ₂ for stabilizing the power supply voltage is mounted on the printed circuit board B, and a switch is connected to a lead line L ₃ drawn out of the printed circuit board B from the non-ground side terminal of the capacitor C _2. S
W ₁ is provided so that the contacts r _{1 to} r ₃ can be selectively connected to the capacitor C ₂ . That is, in this embodiment, the switching unit 2 is constituted by the contacts r _{1 to} r ₃ and the switch SW ₁ .

Here, the switch SW₁Contact r₁(Also
Is the contact r₂), FETQ₁(Or
FETQ₂) Gate is switch SW₁Power through
FETQ is pulled up to pressure₁(Or FET
Q₂) Can be turned on. And FETQ₁
(Or FETQ₂) Turns on, the resistance R₁And resistance
R ₂Connection point (or resistance R₂And resistance R₃Connection with
Point) is FETQ₁(Or FETQ₂) Via gra
The path for charging / discharging current flows because it is grounded to the ground line
Change and change the combined resistance value related to the timer time.
You can switch the timer time. At this time,
The discharge current is FETQ as shown by the arrow in FIG.₁(Also
Is FETQ₂) To the ground line,
Lead line L drawn out of the substrate B₁~ L₃Flow
Not. Also, switch SW₁Contact r₃Switch to
For example, FETQ₁, Q₂Both are off, in this case
Is the charging / discharging current is the resistance R₁~ R₃And capacitor C₁Only
Flow, of course leader line L₁~ L₃Does not flow to.

According to the above configuration, the external noise is exposed.
Leader line L₁~ L₃Without charging and discharging current to
The timer time is set by the switching unit 2 provided outside the printed circuit board B.
Can be switched, leader line L₁~ L₃Outside coming to
Prevent the influence of incoming noise on the timer IC1
If the timer time is different from the set time, the timer IC1
It is possible to prevent malfunction. In addition, this embodiment
In, FETQ ₁, Q₂Resistor R to the gate of₀Over
And capacitor C₀A low-pass filter consisting of
Therefore, noise resistance can be further improved.

(Embodiment 2) FIG. 2 is a schematic circuit configuration diagram showing a second embodiment of the present invention. As shown in FIG. 2, the basic configuration of the present embodiment is common to that of the conventional example and the first embodiment, the common parts are denoted by the same reference numerals, and the description thereof will be omitted. Only the part that is described will be described.

In this embodiment, the FET is the same as the first embodiment.
Q₁, Q₂Connect a pull-down resistor Rd to the gate of
Inverter instead of grounding to land line
Three₁, 3₂And pull-up resistor Ru to connect to the power supply
It is characterized by that. Contact point r of switching unit 1₁,
r₂Is the leader line L₁, L₂Through the inverter 3
₁, 3₂And the pull-up resistor Ru.
Switch SW₁Leader line L with_FourPrinted circuit board
It is grounded to the B ground line.

Therefore, in the switching unit 2, the switch S
W₁Contact r₃When switching to, pull-up resistor
Inverter 3 via Ru₁, 3₂Has a high level of confidence
No. is input, so FETQ₁, Q₂The gate is low
Turns off at the level. In this case, the charge / discharge current is the resistance R
₁~ R₃And capacitor C₁Flows only through the resistance R₁~ R ₃
Combined resistance value and capacitor C₁With the capacity value of the timer time
Is decided.

On the other hand, the switch SW in the switching unit 2₁To
Contact point r₁(Or contact r₂), The inverter
Data 3₁(Or inverter 3₂The input side of
Ji SW₁Since it is grounded to the ground line via
Converter 3₁(Or inverter 3₂) Input is low
It becomes a level. As a result, the inverter 3₁(Or
Converter 3₂) Output becomes high level, so FET
Q₁(Or FETQ₂) Turns on, and the charge / discharge current
The flow path of is changed and the timer time is switched. Was
However, also at this time, as in the case of Example 1, charge and discharge
Current is FETQ ₁(Or FETQ₂) Via gra
To the outside of the printed circuit board B.
Leader line L₁~ L₃Does not flow to.

According to the above configuration, the timer time can be switched by the switching unit 2 provided outside the printed circuit board B without flowing a charging / discharging current to the lead lines L _{1 to} L ₃ exposed to external noise. Therefore, it is possible to prevent the influence of external noise that arrives on the leader lines L _{1 to} L _{3 from} being exerted on the timer IC 1, and prevent the timer time from being different from the set time and the timer IC 1 from malfunctioning. In the present embodiment as well, as in the first embodiment, since the low pass filter including the resistor R ₀ and the capacitor C ₀ is provided at the gates of the FETs Q ₁ and Q ₂ , the noise resistance can be further improved.

(Embodiment 3) FIG. 3 is a schematic circuit configuration diagram showing a third embodiment of the present invention. As shown in FIG. 3, the basic configuration of the present embodiment is common to that of the conventional example and the first embodiment, the common parts are denoted by the same reference numerals, and the description thereof will be omitted. Only the part that is described will be described.

This embodiment is based on the FETs of the first and second embodiments.
Q _1, instead of Q _2, MOS output of the photo-coupler PC
It is characterized by using ₁ and PC ₂ . That is, the sources of the MOSFETs Q ₁ and Q ₂ forming the photocouplers PC ₁ and PC ₂ are connected to the connection point between the resistors R ₁ and R ₂ and the connection point between the resistors R ₂ and R _3. , The drains of the MOSFETs Q ₁ and Q ₂ are grounded to the ground line of the printed board B.

On the other hand, each MOSFET Q₁, Q₂And optical coupling
Being a photo coupler PC₁, PC₂Light emitting die
Aude LED₁, LED₂Pulls its anode to the power supply
It is up and the cathode is a leader
L₁, L₂It is connected to. Therefore, switching
Switch SW in section 2₁Contact r₃Switch to
Light emitting diode LED₁, LED₂Drive to
Since no current flows, MOSFETQ₁, Q₂Is triggered
It turns off without fail. In this case, the charge / discharge current is the resistance R ₁
~ R₃And capacitor C₁Flows only through the resistance R₁~ R₃of
Combined resistance value and capacitor C₁With the capacity value of
Decided.

On the other hand, when the switch SW ₁ is switched to the contact point r ₁ (or the contact point r ₂ ) in the switching unit ₂ , the light emitting diode LED ₁ (or the light emitting diode LED ₂ )
Has a switch SW ₁ and a current limiting resistor R ₄
Since it is grounded to the ground line via the, a drive current flows through the light emitting diode LED ₁ (or the light emitting diode LED ₂ ). As a result, the light emitting diode LED
₁ (or light emitting diode LED ₂ ) emits light and MO
The SFETQ ₁ (or MOSFET Q ₂ ) is triggered and turned on, the path through which the charging / discharging current flows is changed, and the timer time is switched. However, also at this time, as in the case of the first and second embodiments, the charging / discharging current is the MOSFET Q.
Leader line L drawn to the outside of printed circuit board B by flowing to the ground line through ₁ (or MOSFET Q ₂ ).
_It does not flow to _{1 to} L ₃ .

According to the above configuration, the timer time can be switched by the switching unit 2 provided outside the printed circuit board B without flowing a charging / discharging current through the lead lines L _{1 to} L ₃ exposed to external noise. Therefore, it is possible to prevent the influence of external noise that arrives on the leader lines L _{1 to} L _{3 from} being exerted on the timer IC 1, and prevent the timer time from being different from the set time and the timer IC 1 from malfunctioning. Moreover, in this embodiment, by using the photocouplers PC ₁ and PC ₂ , the switching unit 2, the resistors R _{1 to} R ₃ and the capacitor C _{1 are used.}
Since the time constant circuit composed of is electrically insulated, the noise resistance can be further improved as compared with the first and second embodiments.

(Embodiment 4) FIG. 4 is a schematic circuit configuration diagram showing a fourth embodiment of the present invention. As shown in FIG. 4, the present embodiment is the same as the first embodiment except that a switch unit 4 for switching the timer time on the printed circuit board B is added, and other configurations are the same as those of the first embodiment. It is common, and the common parts are denoted by the same reference numerals and the description thereof will be omitted.

In this embodiment, the resistors R ₁ and R _{2 are}
And the contacts r _a and r _b provided by pulling out the line from the connection point with the resistor R ₂ and the resistor R ₃ and the contact r _c not connected to any other circuit part, and the contacts r _{a to} r. A switch SW ₂ for selectively grounding _c to the ground line of the printed circuit board B is mounted on the printed circuit board B to form the switch unit 4. Here, the switch SW ₂ contacts r _a (or, contact r _b) is switched on, irrespective of the switching unit 2 provided outside of the printed circuit board B, the connection point between the resistors R ₁ and R ₂ (or, The connection point between the resistors R ₂ and R ₃ ) is grounded to the ground line and the timer time is switched. That is, in the switching unit 2, the switch SW ₁
Is switched to the contact r ₃ , the timer time can be switched by the switch SW ₂ of the switch unit 4 on the printed circuit board B, and conversely, the switch S of the switch unit 4 can be switched.
If W ₂ is switched to the contact r _c , the timer time can be switched by the switch SW ₁ of the switching unit 2.

According to the above construction, in addition to the construction of the first embodiment, the switch section 4 is mounted on the printed board B, so that the switch section 4 on the printed board B can also switch the timer time. There is an advantage that the usability as a timer time switching circuit can be improved. In this embodiment, the switch part 4 is added to the structure of the first embodiment, but the same effect can be obtained by adding the switch part 4 to the structure of the second or third embodiment. Needless to say.

[0033]

According to the invention of claim 1, there is provided a timer time switching circuit for switching a timer time of a timer unit mounted on a circuit board and for timing a predetermined timer time from the outside of the circuit board, wherein a plurality of resistors and capacitors are provided. And a time constant circuit having a time constant circuit configured to set a timer time according to the time constant of the charge / discharge operation of the time constant circuit, and a charge / discharge current path of the time constant circuit composed of a plurality of resistors and capacitors. By mounting one or a plurality of field-effect transistors for changing the number on the circuit board, and externally providing a switching unit equipped with switch means for turning on and off the one or a plurality of field-effect transistors on the circuit board, Since the path of the charging / discharging current flowing in the time constant circuit can be changed without drawing it out of the circuit board, the charging / discharging current will flow only in the circuit board. It is possible to reduce the influence of noise, the timer time may change under the influence of the noise, the timer unit is an effect that it is possible to prevent the malfunction.

According to a second aspect of the present invention, there is provided a timer time switching circuit which is mounted on a circuit board and switches the timer time of a timer section for timing a predetermined timer time from outside the circuit board. Has a time constant circuit that consists of a timer time setting unit that sets the timer time according to the time constant of the charging / discharging operation of this time constant circuit, and changes the charge / discharge current path of the time constant circuit consisting of multiple resistors and capacitors. 1 to a plurality of field effect transistors are mounted on a circuit board, and a switching unit having switch means for turning on and off the one to a plurality of field effect transistors is provided externally to the circuit board and is output from the switching unit. By supplying the ON / OFF control signal of the field effect transistor via the inverter logic circuit, the charging / discharging current flowing in the time constant circuit is circulated. Since it can be changed without drawing it out of the board, the charging / discharging current flows only in the circuit board, and the influence of external noise can be reduced. There is an effect that it is possible to prevent the section from malfunctioning.

According to a third aspect of the present invention, there is provided a timer time switching circuit for switching a timer time of a timer unit mounted on a circuit board for timing a predetermined timer time from the outside of the circuit board, which comprises a plurality of resistors and capacitors. Has a time constant circuit that consists of a timer time setting unit that sets the timer time according to the time constant of the charging / discharging operation of this time constant circuit, and changes the charge / discharge current path of the time constant circuit consisting of multiple resistors and capacitors. One or a plurality of light-triggered field effect transistors are mounted on a circuit board, and light-emitting elements optically coupled to the one or a plurality of field effect transistors are caused to emit light to turn on / off each field effect transistor. By providing the switching unit equipped with the switch means externally to the circuit board, the path of the charging / discharging current flowing in the time constant circuit is drawn out of the circuit board. It is possible to change without the charge and discharge current stops flowing only only the circuit board,
Moreover, since the time constant circuit and the switching unit are electrically insulated, the influence of external noise can be further reduced, and it is possible to prevent the timer time from changing or the timer unit malfunctioning due to the influence of noise. There is an effect that it can be surely prevented.

According to the invention of claim 4, the switch part for changing the charging / discharging current path of the time constant circuit composed of at least a plurality of resistors and capacitors is mounted on the circuit board, so that not only the external switching part but also the switching part is attached. The timer time can be switched using the switch section on the circuit board, and the usability of the timer time switching circuit can be improved.

[Brief description of drawings]

FIG. 1 is a schematic circuit configuration diagram showing a first embodiment.

FIG. 2 is a schematic circuit configuration diagram showing a second embodiment.

FIG. 3 is a schematic circuit configuration diagram showing a third embodiment.

FIG. 4 is a schematic circuit configuration diagram showing a fourth embodiment.

FIG. 5 is a schematic circuit configuration diagram showing a conventional example.

[Explanation of symbols]

1 Timer IC 2 Switching unit R _{1 to} R ₃ Resistance C ₁ Capacitor Q ₁ and Q ₂ Field effect transistor B Printed circuit board

Claims (4)

[Claims] 1. A timer time switching circuit which is mounted on a circuit board and switches a timer time of a timer section for timing a predetermined timer time from outside the circuit board, the time constant circuit comprising a plurality of resistors and capacitors. A timer time setting unit that sets a timer time according to the time constant of the charging / discharging operation of the time constant circuit, and one to a plurality of changing the charging / discharging current path of the time constant circuit including a plurality of resistors and capacitors A timer time switching circuit, wherein a field effect transistor is mounted on a circuit board, and a switching unit having switch means for turning on / off one or a plurality of field effect transistors is externally provided on the circuit board. . 2. A timer time switching circuit for switching a timer time of a timer unit mounted on a circuit board for timing a predetermined timer time from outside the circuit board, the time constant circuit comprising a plurality of resistors and capacitors. A timer time setting unit that sets a timer time according to the time constant of the charging / discharging operation of the time constant circuit, and one to a plurality of changing the charging / discharging current path of the time constant circuit including a plurality of resistors and capacitors A field effect transistor is mounted on a circuit board, and a switching unit having switch means for turning on and off one or a plurality of field effect transistors is externally provided on the circuit board and is output from the switching unit. A timer time switching circuit, characterized in that the ON / OFF control signal is supplied via an inverter logic circuit. 3. A timer time switching circuit which is mounted on a circuit board and switches the timer time of a timer unit for timing a predetermined timer time from outside the circuit board, the time constant circuit comprising a plurality of resistors and capacitors. A timer time setting unit that sets a timer time according to the time constant of the charging / discharging operation of the time constant circuit, and one to a plurality of changing the charging / discharging current path of the time constant circuit including a plurality of resistors and capacitors A light-triggered field-effect transistor is mounted on a circuit board, and a switch means is provided for turning on and off each of the field-effect transistors by causing one or a plurality of field-effect transistors to respectively emit light-emitting elements. A timer time switching circuit characterized in that a switching unit is externally provided on a circuit board. 4. The timer time according to claim 1, wherein a switch section for changing a charge / discharge current path of a time constant circuit including at least a plurality of resistors and capacitors is mounted on a circuit board. Switching circuit.