JPH0334247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a device that uses a microcomputer as a control center, and when the output port of the computer is destroyed for some reason such as an electrical shock, the electrical load driven by the computer is powered off. The present invention relates to an electrical load drive device that prevents the device from remaining on.

For example, in order to electrically control a gas main valve in a computer-controlled thermal device, it is being considered to electrically open and close a solenoid valve using a microcomputer. It is required that such electrical loads be operated reliably so that they do not go into an operating mode different from the internal commands of the computer.

The purpose of the present invention is to provide a load driving device that satisfies the above requirements.Specifically, the present invention is capable of detecting an abnormality in the output port of a microcomputer that controls the load, and at the same time turning off the power to the load in the event of an abnormality. It is an object.

Therefore, the basic feature of the present invention is to use at least two output ports to drive a load, taking advantage of the fact that the probability that multiple output ports fail simultaneously is extremely low in a microcomputer. .

FIG. 1 shows an embodiment of the present invention, in which reference numeral 1 is a microcomputer, 2 is a gas solenoid valve as a load, 3 is an AC 100V commercial power supply, 4 is a photo coupler as a detection means, and 5 is an alarm buzzer. ,
Vcc is a DC power supply, R1, R2, and R3 are base bias resistors of transistors Tr1, Tr2, and Tr3, respectively, and R4, R5, and R6 are transistors, respectively.
Base leak resistance of Tr1, Tr2, and Tr3, R7 is an input series resistance of the input port 11 of the microcomputer 1, R8 is a pull-up resistor, R9 is a resistor for limiting the current flowing to the photo coupler 4,
Diode D1 and capacitor C1 are for rectifying and smoothing AC100V commercial current 3, RY1 is a relay as a switch for inputting gas solenoid valve 2, and D2 is a free holing diode.

Note that the base inputs of transistors Tr1 and Tr2 are connected to output port 0 of microcomputer 1, respectively.
1 and 02, and as shown in FIG. 2, it is configured as a logic circuit so as to energize and drive the relay RY1 under the logical product condition H.H of high level (H level).

In the above configuration, in normal operation, the microcomputer sets the output port 02 to H level based on the control program of the transistor Tr.
2 is in the on state, and in this state, by generating H level and L level electrical signals to output port 01, relay RY1 is energized.
By deenergizing the solenoid valve 2 and turning on and off the power circuit of the solenoid valve 2, the valve can be driven to open and close.

In order to close the solenoid valve 2, a safety operation is performed as shown in the control program shown in FIG. That is, in order to close the gas electromagnetic valve 2, the port 01 is changed from the H level to the L level, and after a certain delay time (DELAY), the input port I1 is checked. At this time, if the output port 01 is destroyed for some reason and the load circuit remains powered on, the AC100V commercial power supply 3 will be rectified and smoothed by the diode D1 and the capacitor C1.
A current flows through the photo diode of the photo coupler 4, and since the transistor switch of the photo coupler 4 is also on, a level signal is applied to the input port I1 of the microcomputer 1. Therefore, when checking input port I1, if it is level, output port 01
is determined to be abnormal, the computer sets output port 02 to level, deenergizes the relay gas, closes gas solenoid valve 2, sets output port 3 to H level, and sounds alarm buzzer 5. .
In addition, setting a certain delay time (DELAY) is
This is to prevent erroneous judgments due to response delays of the transistor Tr1, relay RY1, and photocoupler 4, and discharge time of the capacitor C1.

Note that since the output port of a computer is generally at L level (open or grounded) in the event of a failure, it is particularly effective to set the load operating condition to H.H as in the above embodiment. However, it is also possible to change the operating conditions if necessary.

FIG. 4 shows another embodiment of the present invention, in which the operating condition of the load is the AND condition of H and L as shown in FIG. In FIG. 4, the diode D3 is provided to prevent the transistor Tr1 from being turned on by the emitter-collector saturation voltage of the transistor Tr2.

Further, if necessary, a lamp or the like may be used instead of the buzzer 5.

As described above, in the present invention, since the microcomputer self-checks for abnormalities in the output port and operates safely, there is an excellent effect that it is almost impossible to accidentally hold the load in the driven state.

[Brief explanation of the drawing]

FIG. 1 is an electrical wiring diagram showing an embodiment of the present invention;
FIG. 2 is a truth diagram showing the logical operating conditions of transistors Tr1 and Tr2 in FIG. 1, FIG. 3 is a flowchart showing the main points of the computer control program in FIG. 1, and FIG. FIG. 5 is an electrical wiring diagram showing essential parts of another embodiment, and FIG. 5 is a truth diagram showing logical operating conditions of transistors Tr1 and Tr2 in FIG. 4. 1...Microcomputer, 2...Solenoid valve as load, 3...Commercial power supply, RY1...Relay as switching means, Tr1, Tr2...Transistors forming a logic circuit, 4...Photocoupler as detection means, 5 ...Alarm buzzer, 01,02...
Output port.

Claims (1)

[Scope of Claims] 1. A switch means provided to turn on/off energization to a load, and first and second input terminals to allow energization to the load and drive the load. and load driving means for operating the switch means under the logical product conditions of first and second command signals given to each of them; a detection means for outputting a signal; first and second output terminals for outputting the first and second command signals in correspondence with the first and second input terminals of the load driving means; and an input terminal for inputting the monitoring signal from the detection means, and the second output terminal is normally supplied with the monitoring signal from the first output terminal to the load driving means in order to control the driving of the load. A second command signal of a predetermined level is outputted so that the switch means is actuated in relation to the command signal, and in this state, the first output terminal is provided with a second command signal which causes the switch means to actuate in accordance with the command signal applied thereto. - Outputs a first command signal that is inactive, and outputs a first command signal that is applied to the first output terminal based on the monitoring signal from the detection means that is input from the input terminal. When it is determined that the switch means does not operate in response to the command signal, the second command signal outputted from the second output terminal is set to a level at which the switch means is inoperative, regarding this as an abnormality. An electrical load drive device comprising a control means.