JPH0660922B2 - Encoder disconnection detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for detecting disconnection of a signal line transmitting an output of an encoder.

[Conventional technology]

Encoders are generally widely known as those used for position control of industrial equipment. For example, a rotary encoder that emits a coded signal corresponding to an angle is used as an angle detector for a joint of an industrial robot.

FIG. 3 is a circuit diagram showing a conventional encoder and processing circuit.

In the figure, (1) is an encoder, (2) is output data that changes to a high level (hereinafter "H") or low level (hereinafter "L"), (3) is output data (2) AN as input
D gate, (4) is an output transistor whose base is connected to the output side of the AND gate (3), the emitter is grounded, the collector is connected to the signal line (5), and the open collector type encoder (1) is It is configured. (6) is an encoder input processing circuit, (7) is a + 12V positive power supply, (8) is an input pull-up resistor connected between the positive power supply (7) and the signal line (5), (9)
Is an input buffer connected to the signal line (5), (10) is the input data, (11) is an encoder output enable signal that allows the acquisition of the specified output data (2), and is output via the output buffer (12). The other input of the AND gate (3).

The conventional encoder and its processing circuit are configured as described above, and in order to capture the output of the encoder (1), the encoder output permission signal (11) is set to "H". With this, AN
D gate (3) is opened and output data (2) is AND gate
It is output from (3).

Now, if the output data (2) is "L", the AND gate (3)
Output becomes "L", the output transistor (4) is turned off, and its output becomes high impedance. Processing circuit (6)
, The signal line (5) has a high impedance, so it is pulled up to + 12V by the input pull-up resistor (8), the input of the input buffer (9) becomes "H", and the input data (10) becomes " H ”. That is, the encoder (1)
When the output data (2) of the above is "L", the input data (10) of the processing circuit (6) becomes "H".

Next, if the output data (2) is "H", AND gate
The output of (3) also becomes "H", the output transistor (4) turns on, and its output becomes low impedance. Processing circuit
At (6), since the signal line (5) has low impedance, the input of the input buffer (9) becomes "L" and the input data (10) becomes "L". That is, when the output data (2) of the encoder (1) is "H", the input data of the processing circuit (6)
(10) becomes "L".

[Problems to be solved by the invention]

In the conventional encoder and its processing circuit as described above,
Since the receiving side detects whether the output of the signal line (5) is "H" or "L", if the signal line (5) is disconnected,
The input data (10) becomes "H", and there is a problem that it cannot be distinguished whether the signal line (5) is broken or the output data (2) of the encoder (1) is "L".

The present invention has been made to solve the above problems, and an object of the present invention is to provide a disconnection detecting device for an encoder in which disconnection of a signal line can be easily detected on the receiving side.

[Means for solving problems]

The disconnection detection device for an encoder according to the present invention receives a disconnection inspection signal and output data as input, and does not invert the level of output data when the disconnection inspection signal is at the first level and inverts it when it is at the second level. An inversion element is provided to supply to the transistor as an output, and disconnection detection means for issuing an abnormal signal is provided if the input level of the signal line connected to the collector of the transistor is not inverted even if the level of the disconnection inspection signal is switched to the receiving side. Be prepared.

[Action]

According to the present invention, the input level of the signal line is inverted when the level of the disconnection inspection signal is normally switched, and the input level of the signal line is not inverted when the level of the disconnection inspection signal is switched when the signal line is disconnected. .

〔Example〕

1 and 2 are diagrams showing an embodiment of the present invention, FIG. 1 is a circuit diagram of an encoder and a processing circuit, and FIG. 2 is a flow chart of a wire breakage detecting operation. (1) to (12) Is the same as the above conventional device.

In FIG. 1, reference numeral (15) is a disconnection inspection signal issued from the processing circuit (6) when the disconnection inspection of the signal line (5) is performed, and it is an output buffer.
It is output to the encoder (1) side via (16). (17) uses the output data (2) and the output of the output buffer (16) as input
Exclusive O that forms an inverting element that outputs to the ND gate (3)
R gate (the output is not inverted with respect to the other input when one input is "L", the output is inverted when one input is "H"), (18) is the input buffer (9) A CPU (central processing unit), (19) connected to the output side of the memory is a memory.

In the disconnection detection device for an encoder configured as described above, the encoder output permission signal (11) is assumed to be "H".

Normally, the disconnection inspection signal (15) is "L", and since this is input to the exclusive OR gate (17) via the output buffer (16), its output is at the same level as the output data (2). Become.
That is, in this case, the circuit is exactly the same as in FIG.
When the output data (2) is "L", the input data (10) is "H", and when the output data (2) is "H", the input data (10) is "L".

Next, the disconnection detection operation of the signal line (5) will be described with reference to FIG. The program of FIG. 2 is stored in the memory (19).

First, in step (21), the encoder output permission signal (11) is set to "H". At this time, since the disconnection inspection signal (15) is "L", if the signal line (5) is normal, the input data (10) is the output data (2) "L" as described above. If it is "H" and the output data (2) is "H", it is "L". Now, assuming that the output data (2) is "H" and the input data (10) is "L", this is recorded as X in the memory (19) in step (22). Next, when the disconnection inspection signal (15) is switched from "L" to "H" in step (23), the output data (2) is inverted by the exclusive OR gate (17) and the AN signal is output.
It is input to the D gate (3). Now, the output data (2) is "H"
Therefore, the input of the AND gate (3) becomes "L" and the input data (10) becomes "H". The input data (10) is recorded as Y at step (24). Next, step (25)
Then, the input data X and the input data Y are compared with each other. If they are equal, it is assumed that there is no disconnection of the signal line (5) or failure of the output transistor (4) at step (26). If signal line (5)
Is disconnected, the input data (10) becomes "L" regardless of the level of the output data (2), so that X = Y and the signal line (5) is disconnected or the output transistor is turned off at step (27).
Suppose there is a failure in (4). That is, an abnormal signal is emitted.

Although the case where the output data (2) is “H” has been described above, the same description can be made for the case of “L”, which can be normal when X ≠ Y and a failure when X = Y. .

〔The invention's effect〕

As described above, in the present invention, the input level of the signal line is inverted when the level of the disconnection inspection signal is normally switched, and the input level of the signal line is inverted when the disconnection inspection signal is switched when the signal line is disconnected. Since the disconnection of the signal line can be easily detected on the receiving side, there is an effect that the safety of using the open collector type encoder can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an encoder and a processing circuit showing an embodiment of an encoder disconnection detecting device according to the present invention, FIG. 2 is a flow chart of disconnection detecting operation, and FIG. 3 is a circuit showing a conventional encoder and processing circuit. It is a figure. In the figure, (1) is an encoder, (2) is output data, (4) is an output transistor, (5) is a signal line, (7) is a power supply, (10) is input data, and (15) is a disconnection inspection signal. , (17) are inverting elements (exclusive O
R gate) and (18) are disconnection detecting means (CPU). The same reference numerals in the drawings denote the same parts.

Claims (1)

[Claims] 1. A first level and a second level in which data to be output from an encoder is supplied to a base of a transistor and is output to a receiving side via a signal line connected to the transistor and connected to a power supply. When the disconnection inspection signal is at the first level, the level of the output data is not inverted, and when the disconnection inspection signal is at the second level, the output is made. Inverting elements for inverting the level of the data and outputting the inverted data to the bases of the transistors are provided, and the first of the disconnection inspection signals is provided on the receiving side.
A disconnection detecting device for an encoder, comprising disconnection detecting means for issuing an abnormal signal when the level of input data from the signal line is not inverted even when the level and the second level are switched.