JPS5857716B2 - timer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a timer, and in particular, it is possible to set a long time, displays the elapsed time or remaining time, and automatically controls the on/off of the device when the set time is reached. It was made so that it could be done.

An example of a timer according to the invention will now be explained with reference to the figures.

In Figure 1, 1 is a clock pulse generator that generates clock pulses of a constant frequency, and a series circuit of a resistor 2 and a capacitor 3 that constitute a charging circuit, a discharging transistor 4, and a comparison amplifier are purchased. Transistors 5 and 6
and voltage dividing resistors 7 and 8 that provide a reference voltage to the comparison amplifier.
and a switching transistor 9.

When the power is turned on, a charging current flows to the capacitor 3 through the resistor 2, and the voltage across the capacitor 3, that is, the base voltage 8 of the transistor 5, is applied to the resistor 2 as shown in FIG.
and rises with a time constant determined by capacitor 3, and this rises with a time constant determined by capacitor 3.
and the voltage at the connection point of 8, that is, the reference voltage given to the base of the transistor 6.

When the voltage exceeds the voltage VB, the transistor 5 is turned on, which turns on the transistor 9, which turns on the transistor 4, and the charge in the capacitor 3 is discharged through the transistor 4, and the voltage VB instantly drops to the ground potential.

Therefore, transistor 5 is turned off, transistors 9 and 4 are also turned off, and capacitor 3 is charged again.
Repeat the same thing as above.

Therefore, a clock pulse SP of a constant period is obtained at the collector of the transistor 5, as shown in FIG.

In this case, as shown by the broken line in Fig. 2, when the power supply voltage +VOO changes and the way the voltage VB rises changes, the reference voltage Vo also changes at the same time, so regardless of the fluctuation of the power supply voltage +cc First, the frequency of clock pulse SP is held constant.

A counter 10 counts the above-mentioned clock pulses Sp from the clock pulse generator 1.

This counter 10 has m flip-flop circuits 11m.
...111 are connected in cascade, and the count value is taken out as an m-bit code.

12 is a digital-to-analog converter which converts the output of the counter 10 into an analog signal and generates a comparison signal whose value changes according to elapsed time.

This DigiCrew analog converter 12 includes transistors 13 to 15 and switching transistors 16n corresponding to the upper n (n2m) bits of the counter 10.
...161, transistor 16n...16,
connected in series, each with a resistance value of 2°-IR...
... Consists of a resistor R and a transistor 17,
The series circuits of the switching transistor and the resistor are connected in parallel with each other, and the output of the flip-flop circuit 11n...11 of the upper n bits of the counter 10 is the base of the switching transistor 16n...16. is supplied to

The base voltage of the transistor 13 is held constant, and the collector of the transistor 14 is connected to the transistor 1.
6n...16. ■ When only the transistor 16n is turned on.

When only transistor 16□ is on, a current of 2n-2■o flows, and when only transistors 163 and 161 are on, a current of (2n
-3+20-1) IO flows, and so on, a current proportional to the output code of the upper n bits of the counter 10 converted into an analog value flows.

A current proportional to the collector current of the transistor 14 flows through the transistor 15, and a current proportional to the current flowing through the transistor 15 flows through the transistor 17.

Therefore, as shown in FIG.
Every time the counter 10 counts 2m-n clock pulses SP, for example every minute, a comparison current IC flows which increases stepwise by a constant value.

A time setting circuit 20 generates a reference signal having a value corresponding to a set time.

It consists of transistors 21 to 25 and a setting variable resistor 26, and the variable resistor 26 has a so-called B-type resistance characteristic.

Since the base voltage of the transistor 21 is held constant, as the position of the movable element is moved away from the ground end, the potential of the movable element and hence the base voltage of the transistor 24 rises, and the current flowing through the transistor 24 increases.

Since a current proportional to the current flowing through the transistor 24 flows through the transistor 25, the current flowing through the transistor 25 is determined by the position of the mover of the variable resistor 26.

Therefore, if a certain period of time is set according to the time scale provided in connection with the variable resistor 26, as shown in FIG. flows.

30 is a comparison circuit, and the above-mentioned comparison current ■.

is compared with the reference current (2), and when the former reaches the latter, that is, when the elapsed time becomes equal to the set time, an output in a constant state is generated.

This is because transistors 31 and 3 constitute the comparison amplifier.
2 and a switching transistor 33, the base of the transistor 31 is supplied with a constant reference voltage VD of, for example, 1, while the base of the transistor 32 is connected to the collector of the transistor 17 of the Digicrew analog converter 12 and the time setting circuit. It is connected to the collector of 20 transistors 25.

Furthermore, 40 is a meter circuit connected to the comparison circuit 30, that is, connected to the base of the transistor 32, which includes a transistor 41 having a diode configuration and a transistor 42.
and a meter 43.

As mentioned above, the comparison current c, which increases stepwise by a constant value every time a certain period of time passes, flows through the collector emitter of the transistor 17 of the digital-to-analog converter 12, while the time setting circuit 20 A reference current of a constant value corresponding to a preset time flows through the emitter collector of the transistor 25.

Therefore, while the elapsed time has not reached the set time and the comparison current IC is smaller than the reference current A, the difference between them M=I, -I
A current of O, that is, a current that decreases stepwise by a constant value every time a certain period of time passes, as shown in FIG. 3, flows through the meter circuit 4.
0, and a current proportional to this current IM flows into meter 4.
It flows to 3.

Since the current IM (= IA l-0) is proportional to the difference between the set time and the elapsed time, that is, the remaining time, this remaining time is displayed by attaching a time scale to the make 43. .

On the other hand, the base voltage of the transistor 32 of the comparison circuit 30 is
Well, as shown in Figure 3, the current IM (-Iiichi ■o)
The transistor 31 is turned off and the transistor 32 is turned on while the elapsed time does not reach the set time, but when the elapsed time reaches the set time, the transistor 31 is turned off and the transistor 32 is turned on. That is, when the current IC reaches the current IA, the base voltage (18) sharply drops to become lower than the base voltage VD of the transistor 31, and the transistor 31 is turned on and the transistor 32 is turned off.

When the transistor 31 is turned on, the transistor 33 is turned on, and as shown in FIG. A trigger pulse PD is obtained from a trigger pulse forming circuit 50, which is supplied to a flip-flop circuit 52 through an OR circuit 51 and is inverted.

Therefore, for example, when the switch 53 is operated in advance, a trigger pulse is appropriately supplied from the trigger pulse forming circuit 54 to the flip-flop circuit 52 through the OR circuit 51, and the flip-flop circuit 52 is in a reset state. If the device 55 is turned off, when the set time is reached and the flip-flop circuit 52 is reversed by the trigger pulse PD, it becomes set and the device 55 is dynamically turned on.

Conversely, if the flip-flop circuit 52 is set in advance and the device 55 is turned on, when the set time is reached and the flip-flop circuit 52 is reversed by the trigger pulse PD, it will be in the reset state. Then, the device 55 is automatically turned off.

According to the above-described timer according to the present invention, the time setting circuit obtains a reference signal having a value corresponding to the set time,
In addition, clock pulses of a constant frequency are counted by a counter, and a comparison signal whose value changes according to the elapsed time is obtained from the count value, and the two are compared. It has the advantage of being easy to configure.

Furthermore, the configuration is simplified because the frequency of the clock pulse is always constant, instead of changing the set time by changing the frequency of the clock pulse as in the conventional configuration.

Furthermore, the remaining time can be displayed by the meter, and the device can be turned on or off when the set time is reached using a simple configuration.

Note that the comparison current ■ obtained by the digital-to-analog converter 12.

It may be configured such that the elapsed time is supplied to a meter circuit and the elapsed time is displayed by the meter.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an example of a timer according to the present invention, and FIGS. 2 and 3 are waveform diagrams for explaining each. 1 is a clock pulse generator, 10 is a counter, 12 is a digital-to-analog converter, 20 is a time setting circuit, 26
30 is a comparison circuit, 40 is a meter circuit, and 43 is a meter.

Claims (1)

[Claims] 1. A clock pulse generator that generates clock pulses of a constant frequency, a counter that counts the clock pulses, and a digital circuit that converts the output of this counter into an analog signal and generates a comparison signal whose value changes depending on the elapsed time. - Comprising an analog converter, a time setting circuit that generates a reference signal with a value corresponding to a set time, and a comparison circuit that compares the comparison signal with the reference signal and generates an output when the former reaches the latter. The equipment is controlled by the output of the comparison circuit, and the comparison signal from the digital-to-analog converter is supplied to the meter to display the elapsed time, or the comparison signal and the reference signal are supplied to the meter. A timer that is supplied to display the remaining time.