CONTROLLER OUTPUT CIRCUIT

• US 3,745,546 A
• Filed: 06/07/1971
• Issued: 07/10/1973
• Est. Priority Date: 06/07/1971
• Status: Expired due to Term

• Current Assignee: Allen-Bradley Company (Rockwell Automation, Inc.)
• Original Assignee: Jay M. Erdman, Odo J. Struger
• Inventors: Struger, Odo J., Erdman, Jay M.
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US05/150,487
• Time in Patent Office: 764 Days
• Field of Search: 340/250 317/4A,335C,41 337/79,266,241,242,332,376
• US Class Current: 340/638
• CPC Class Codes: H02H 3/046 Signalling the blowing of a fuse detecting non functioning of a lamp H05B47/20

Abstract

An output drive circuit for a programmable controller includes a triac connected to an a-c power supply in series with a fuse and the controlled external load. The fuse is shunted by a neon indicator lamp and the triac is shunted by a high impedance path including a resistor and capacitor. When the fuse blows and the triac is turned off the the controller, current flows through the neon bulb to indicate the faulty fuse.

Claims

1. In an output drive circuit for a controller which is connectable to a load to supply current thereto, the combination comprising:

an electronic switch having an input terminal connected to the controller and a pair of load current carrying terminals connected to conduct load current to said load when an actuate signal is received from said controller;

a fuse connected in series with said electronic switch to conduct said load current;

high impedance means connected in shunt relation to said electronic switch to conduct a small amount of said load current when said electronic switch is non-conDuctive; and

an indicator lamp connected in shunt relation with said fuse;

wherein the high impedance means conducts sufficient current to illuminate said indicator lamp when said electronic switch is non-conductive and said fuse is open circuited.

2. The output drive circuit of claim 1, which includes a logic gate having an input terminal connected to the controller and an output terminal connected to said electronic switch input terminal, said logic gate being operable to prevent application of the actuate signal to said electronic switch when a disabling signal is received at said gate input terminal from said controller.

3. The output drive circuit of claim 1 wherein said electronic switch is a triac and said high impedance means is a series connected resistor and capacitor connected to said load current carrying terminals.

4. In a controller having a plurality of output drive circuits, each of said output drive circuits containing an electronic switch having a control terminal connected for operation by said controller, and a pair of load current carrying terminals connected to conduct load current to an external load connected to said controller, the improvement in said output drive circuits comprising:

a fuse connected in series with said electronic switch to conduct load current;

high impedance means connected in shunt relation with said electronic switch; and

an indicator lamp connected in shunt relation with said fuse;

wherein a trickle current flows through said high impedance means when said electronic switch is nonconductive, and said trickle current flows through said indicator lamp when said fuse is open circuited to illuminate the same and provide a visual indication when said fuse opens circuit.

5. A circuit as recited in claim 4 in which a logic gate is connected to the control terminal of said electronic switch and said logic gate includes an input terminal connected to receive a disabling signal from said controller.