JPH037399B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an iron that automatically detects if the iron has been left unattended with the power turned off.

Conventional Technology Conventionally, a mercury switch has been used as a sensor for detecting whether the iron has been turned off. In other words, when the iron is used, the mercury moves due to the reciprocating motion of the iron, turning the contacts on and off, and when not in use, the contacts remain on or off, and this voltage is detected to determine whether the iron is in use or not. The purpose was to determine whether the device was in use and to detect if the device had been forgotten to turn off.

Problems to be Solved by the Invention In such a conventional mercury switch system, it was necessary to contain the mercury, and it was difficult to construct the switch.

Means for Solving the Problems The present invention eliminates the conventional mercury switch method and uses a light-receiving and emitting element consisting of a light-emitting diode and a phototransistor.While the iron is in use, a ball rolls on the light-emitting diode and phototransistor. Since the bulb is stopped when the iron is not in use, the output signal is held high or low, and this voltage change is detected to notify the user that the power has been turned off. This is done by passing the output current of the phototransistor through a specified resistor, applying the voltage across the resistor between the base and emitter of the transistor, and setting the voltage between the base and emitter of the transistor to a specified value. Detection is performed by a detection circuit consisting of a switching circuit that utilizes the characteristic that the base current does not flow unless the base current exceeds a value (hereinafter referred to as V _BE ), and this detection circuit and a light emitting diode are connected in series to generate the necessary power for the detection circuit. It is configured to allow current to flow through the light emitting diode.

Effect With this configuration, when the bulb is not above the light emitting diode and phototransistor (a small amount of light output from the light emitting diode enters the phototransistor due to diffuse reflection inside the case), a small amount of current flows through the phototransistor. At this time, the voltage applied between the base and emitter of the transistor is small, and the transistor is off when it is below the transistor's V _BE . On the other hand, when the sphere is above the light emitting diode and phototransistor, the light emitted from the light emitting diode is reflected by the sphere and enters the phototransistor.
Therefore, a large current flows through the phototransistor,
A large voltage exceeding V _BE is applied between the base and emitter of the transistor, turning the transistor on.

In this way, while the iron is in use, the rolling of the ball turns the transistor on and off, allowing a signal to be obtained. Also, when the iron is not in use, the bulb stops at or above the phototransistor and light emitting diode.
The transistor is held off or on. Is this transistor on or off?
Detects whether it is held on or off,
Determines whether the iron is in use or not and detects if you forget to turn off the power.

Furthermore, since the detection circuit and the light-emitting diode are connected in series, the current required for the detection circuit is passed through the light-emitting diode, and the light-emitting diode does not require a separate current, so the circuit can be completed using a simple power supply circuit with low current consumption. is configured.

Embodiment An embodiment of the present invention will be described below based on the drawings. FIG. 1 shows an embodiment of the iron power-off detection circuit according to the present invention. V _AC is the alternating current supply voltage,
The voltage is dropped by resistor _R1 and rectified by diode _D1 . Capacitors C ₁ and C ₂ are smoothing capacitors, and ZD ₁ is a constant voltage Zener diode. LED is a light emitting diode, with resistor R ₂
Limits the current flowing to the LED. _Q1 is a phototransistor, _Q2 is a transistor, resistor _R3 carries the output current of phototransistor _Q1 , and the voltage drop across resistor _R3 is applied between the base and emitter of transistor _Q2 . Emitter of transistor Q ₂ ,
The voltage across the terminals of the resistor R ₄ connected between the ground becomes the output voltage V ₀ . The detection circuit consisting of Q ₁ , Q ₂ , R ₃ , and R ₄ is connected in series with the light emitting diode LED, and this is connected to the DC power supply V _C1 , so that the current flowing through the detection circuit flows to the light emitting diode LED. It is configured so that no separate LED current is required. That is, LED and Q ₁ , Q ₂ , R ₃ , R ₄
The part becomes the circuit part of the present invention.

FIG. 2 shows the circuit section and sensing element section of the present invention.
Reference numeral 1 denotes a case attached to an iron, in which a ball 2 is placed, and by moving the iron, the ball 2 rolls and passes over a light receiving/emitting element 3 containing a phototransistor and a light emitting diode. When the bulb 2 is not on the light emitting/receiving element 3, the transistor _Q2 is off and the output voltage _V0 is low; when it is on the light emitting/receiving element 3, the transistor _Q2 is on and the output voltage V0 is _low . Get high. Output voltage at this time V ₀
The waveform of is shown in FIG. Figure 3a shows when the iron is being used, the ball is rolling, and _V0 is a repeating signal of high and low. b is when the iron is not in use, the bulb is not on the light receiving/emitting element, and the output voltage V ₀
is kept low. c is also a time when the iron is not in use, the bulb is stopped on the light emitting/receiving element, and the output voltage V ₀ remains high.

The switching circuit constituting the detection circuit will be described in detail with reference to FIG. In FIG. 4A, i _P is the output current of phototransistor Q ₁ , and a voltage of magnitude V _B =i _P ×R ₃ is applied between the base and emitter of transistor Q ₂ . When the current value of i _P is small, V _B is small, and when V _B < V _BE , transistor Q ₂ is not turned on, and a voltage of V ₀ = i _P ×R ₄ is generated. i _P
becomes large and V _B > V _BE , the transistor
A base current flows through Q ₂ , transistor Q ₂ becomes an active region, and V ₀ =(i _P +i _C )×R ₄ . Furthermore i _P
When becomes large, transistor Q ₂ is completely turned on, and V ₀ ≈V _DD (V _DD : DC power supply voltage).

The situation at this time is shown in Figure 4B, where the vertical axis shows the output voltage.
V ₀ is shown with the output current i _P of the phototransistor plotted on the horizontal axis. When i _P is greater than or equal to i ₁ , transistor Q ₂ is off, when i _P is between i ₁ and i ₂ , transistor Q ₂ is in the active region, and when i _P is greater than or equal to i ₂ , transistor Q ₂ is fully turned off. It becomes ON. By changing the size of resistor R ₃ , the values of i ₁ and i ₂ can be set to appropriate values. Therefore, when the ball is not on the light receiving/emitting element, the resistor is set so that i _P is smaller than i ₁ , and when the ball is on the light receiving/emitting element, the resistance is set so that i _P is larger than i ₂ . All you have to do is set R ₃ .

FIG. 5 shows another embodiment in which the resistor R ₃ of FIG.
This is an example in which Q2 is not inserted between the base and emitter of transistor _Q2 , but between the base and ground. The operation is similar to that shown in FIG.

FIG. 6 shows yet another embodiment, in which a transistor
A PNP type transistor is used for _Q2 , and its operation is similar to that shown in Figure 4, but it has the advantage that the retarder current is small when the insulation resistance of the printed circuit board decreases. This is advantageous when the light emitting diode and phototransistor need to be placed in close proximity on the same printed circuit board, as shown in FIG.

In Fig. 6, when the sphere is not above the light emitting/receiving element, a very small current i _P flows through the phototransistor Q ₁ , and R ₃ flows between the base and emitter of the transistor Q ₂ .
A voltage of ×i _P is applied. When the insulation resistance of the printed circuit board deteriorates and cannot be ignored, a leakage current of approximately (V _C1 -V _DD )/r flows, where r is the insulation resistance. At this time, the voltage across the resistor R ₃ is R ₃ ×{i _P +(V _C1 −V _DD )/r}. However, in the case of the circuit shown in Figure 1, the leakage current is V _C1 /r, and the voltage across the resistor R ₃ is R ₃ × {i _P +V _C1 /r}
Therefore, the circuit shown in FIG. 6 is more advantageous in terms of leakage current.

Effects of the Invention As described above, according to the present invention, it is possible to detect when the iron is not in use with an extremely simple circuit configuration, and to prevent forgetting to turn off the power. It can reduce current consumption and is extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a power-off detection circuit showing an embodiment of the present invention, Fig. 2 is a diagram illustrating detection by a ball passing over a light receiving/emitting element, and Fig. 3 is a waveform of the output voltage. 4 are explanatory diagrams of the operation of the circuit of FIG. 1, and FIGS. 5 and 6 are circuit diagrams showing different embodiments. LED...Light emitting diode, _Q1 ...Phototransistor, _Q2 ...Transistor, _R3 , _R4 ...Resistor, 2...Ball, 3...Receiving/emitting element.

Claims (1)

[Scope of Claims] 1. A light emitting/receiving element consisting of a light emitting diode and a phototransistor that receives the light emitting output of the light emitting diode, a ball that rolls over the light emitting/receiving element by using an iron, and an output current of the phototransistor. a detection circuit that applies the voltage across the first resistor between the base and emitter of the transistor, and extracts the voltage between the emitter of the transistor and ground as a power-off detection voltage. , a circuit for detecting a forgetting to turn off the power of an iron, which includes the detection circuit and the light emitting diode connected in series. 2 The detection circuit detects the emitter of the phototransistor,
The phototransistor and the transistor 2. A power-off detection circuit for an iron according to claim 1, comprising a circuit that connects a collector of said transistor to a DC power source and extracts the voltage between the emitter of said transistor and ground as a detection voltage. 3 The detection circuit detects the emitter of the phototransistor.
connected to the base of the NPN transistor and connected to ground potential via the first resistor;
The emitter of the transistor is connected to a ground potential via a second resistor, the phototransistor and the collector of the transistor are connected to a DC power supply, and the circuit extracts the voltage between the emitter of the transistor and the ground as a detection voltage. A circuit for detecting a forgetting to turn off the power of an iron according to claim 1. 4. The detection circuit connects the collector of the phototransistor to the first DC power supply via the first resistor, the base of the PNP transistor, and the emitter of the transistor to the first DC power supply. The emitter of the phototransistor is connected to a second DC power source having a lower voltage value than the first DC power source, the connector of the transistor is connected to ground via a second resistor, and the collector of the transistor is connected to a second DC power source having a lower voltage than the first DC power source. 2. The iron power-off detection circuit according to claim 1, comprising a circuit that extracts the voltage between the ground and the ground as a detection voltage.