JPH0236280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature display device for electric heating appliances such as irons and ovens.

Generally, this kind of equipment reaches a high temperature of around 250℃.
It is dangerous as it may cause burns or burn other objects. Therefore, after use, this type of equipment must be left alone until the temperature drops. However, it would be convenient and less dangerous if it were possible to display how much the water has fallen.

The object of the present invention is to display this by blinking the display when the temperature drops to a non-hazardous temperature of about 50°C.

The case of ironing will be explained below as an example. In FIG. 1, voltages of alternating currents 1 and 2 are applied to a heater 4 via a bidirectional three-terminal controlled rectifier element 3. In order to obtain a DC power source for an electronic circuit, the AC power sources 1 and 2 are rectified by a diode 5, voltage is dropped by a resistor 6, and smoothed by a smoothing capacitor 7 to become a DC power source. The temperature adjustment volume 8 is designed so that a voltage corresponding to each temperature click point can be obtained at its output terminal, and if the temperature is set to 140°C, the voltage of the comparison amplifier of the zero volt switching circuit 10 consisting of an IC is set to 140°C. The voltage is applied to one of the three terminals. The other four terminals of the comparison amplifier have a resistance of 1 due to the resistance change of the thermistor 11 for temperature measurement.
A voltage correlated with the temperature determined by the ratio to 1' is applied. When the temperature is low, the resistance of the thermistor 11 is high, so the voltage at the four terminals is low.

Therefore, the circuit 10 outputs a gate pulse from the 6th terminal, turns on the element 3 by zero-volt switching, and causes current to flow through the heater 4. When it is heated and the temperature rises, the resistance of the thermistor 11 becomes smaller and the voltage of the 4 terminals of the circuit 10 becomes the same as that of the 3rd terminal.
The gate pulse from the terminal disappears and element 3 turns off.
becomes.

The temperature is controlled as described above, but the temperature is displayed using the light emitting diode only during temperature fluctuations corresponding to the voltage drop of the two Zener diodes 12 and 13 connected to the output terminal 9 of the volume control 8. indicator (hereinafter referred to as LED) 15 lights up, and if the temperature fluctuates above or below this, LED 1
4 or LED16 lights up. This means that a voltage higher than the voltage drop of the Zener diode 12 than the set voltage of the volume is applied to the + input terminal of the comparison amplification means 17 made of an IC, and a voltage higher than this voltage is applied to the - terminal of the means 17. applied. In other words, when the temperature reaches such a high temperature that the resistance of the thermistor 11 becomes low, the output of the means 17 becomes L, and the LED 1
4 lights up. A voltage lower than the set voltage by the voltage drop of the other Zener diode 13 is applied to the + terminal of the means 18, and a voltage lower than this voltage is applied to the - terminal of the means 18. In other words, when the temperature of the thermistor 11 becomes low and the resistance increases, the means 1
The output of 8 becomes H, and the LED 16 lights up. At this time, the cathode of the LED 16 is L, so it lights up. The reason for this is that the + terminal of means 19 is 50
The voltage is set at a voltage equivalent to a low temperature of 140°C, and the - terminal is connected to the voltage equivalent to the thermistor currently set at 140°C, which is at a much higher voltage than the + terminal, so the output is L. Therefore, the + terminal of the means 20 also becomes L, and its output also becomes L. In other words
The cathode of the LED 16 is L. The display is performed in this way, but assuming that the forward voltage drop across diodes 12 and 13 is equivalent to a temperature of approximately 20 degrees Celsius, if the set value is 140 degrees Celsius, LED 15 will light up within ±20 degrees Celsius. .

After use in this manner, unless element 3 is turned on by turning off the 6-terminal gate circuit of circuit 10 or cutting off 3 terminals of one of the comparators of circuit 10, the iron will cool down and the thermistor 11 will output The voltage at the negative terminal of the means 19, which can also be called a point, decreases. At that time, up to the set value of -20℃, LED15 will
When you go down beyond that, LED 16 lights up and is displayed. When the temperature reaches around 50°C, the - terminal of the means 19 becomes lower than the + terminal of the means 19 to which a voltage equivalent to 50°C is applied, so the output of the means 19 becomes H.
Therefore, since the output of the means 19 has been L until now, the + terminal of the means 20 which was set to L through the resistor 21 is dissolved, and the + input terminal is changed to H through the resistor 21.
Therefore, the output also becomes H. Therefore, the cathode of the LED 16 becomes H, so the LED 16 turns off. On the other hand, the capacitor 24 is gradually charged through the resistor 23 and its potential becomes higher, and the - terminal becomes higher than the + terminal, so the output of the means 20 becomes L.
LED 16 lights up again. and capacitor 2
While the charge of 4 is being discharged through the resistor 23, the output is L, so the LED 16 continues to light up.
However, if it is almost discharged, +
A voltage is applied to the terminal, and when the - terminal becomes lower than that voltage, the output becomes H. Therefore LED
16 goes out again, and charging of the capacitor 24 begins. By repeating this, the LEC 16 repeats blinking. A so-called blinking multivibrator circuit is formed. This blinking causes the user to
I know that the temperature has dropped below ℃.

FIG. 2 shows another embodiment in which a part of the circuit shown in FIG. 1 is changed, and parts having the same function are given the same numbers as in FIG. 1. This figure 2 shows how to blink the LED 16 for blinking display by connecting means 20 in parallel.
This is an attempt to bypass the lighting current of the LED 16 to cause it to blink, and FIG. 1 shows an attempt to insert means 20 in series with the LED 16 to intermittent the lighting current of the LED 16 itself. Therefore, in FIG. 2, the output of the means 19 is connected to the negative input terminal of the means 20, and a diode 25 is inserted therein. In the figure, 26 indicates a diode.

In operation, first, the output of the means 19 is L until the temperature drops to around 50 DEG C., so the - input terminal of the means 20 is L. Therefore, the output of the means 20 is H
Therefore, the current of the LED 16 is not bypassed and the LED 16 is lit. When the temperature further decreases from this state and the resistance value of the thermistor 11 increases, the potential at the connection point, that is, the voltage at the - input terminal of the means 19 decreases. When the voltage drops below the + input terminal of the means 19, the output becomes H. That is, the means 20 -
The input terminal, which had been set to L until now, is now in a free state. Therefore, the means 20 causes self-oscillation as explained in FIG. 1, and the output changes from H to L at a constant cycle.
When the current is L, the current of the LED 16 is bypassed, so the LED 16 turns off, and when it is H, the current is not bypassed, so the LED 16 blinks repeatedly.
Obtain the exact same effect as shown in the figure. The above explanation is for LED
This is the case of 16, but this principle can be applied to other cases.
It is also possible to blink the LEDs 14 and 15 individually or all the LEDs at once.

In this way, the present invention has a display that flashes to let you know when the temperature has dropped to a point that is not dangerous for burns, so you can complete the work by storing the equipment in a designated box, etc., without leaving it unattended forever. Can be done. Also, the area can be opened for children's play. In addition, the present invention is inexpensive because it does not blink using a dedicated display, but instead uses a display for other purposes. Furthermore, when ICs are used, they are generally commercialized in packs of 2 or 4, so when limited to Figures 1 and 2, only 3 are needed for other purposes. , totally left over 1
Since only the attached resistors and capacitors are increased, it can be obtained at low cost.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a circuit diagram of another embodiment of the present invention. 1, 2...AC power supply, 4...Heater, 14,1
5, 16...display body, 17-20...comparison amplification means, 22, 23...resistor, 24...capacitor.

Claims (1)

[Claims] 1. An indicator that indicates that the temperature is lower than the set temperature, and a means that operates at a voltage that corresponds to a temperature range that does not cause burns, fire, etc. when the heater of the heating device is turned off and cooled. , and a multivibrator that turns on and off according to this output, and the multivibrator causes the display body to blink in the above temperature range.