Connect High/Low Level Alarm Circuit with 6 LM741 Op Amps

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SUMMARY

The discussion focuses on connecting high and low level alarm circuits using six LM741 operational amplifiers. The user encountered difficulties in achieving functionality and sought advice on reliable circuit design. Key issues identified include a design error that could lead to long-term unreliability, particularly concerning the arrangement of U3 and U4, which resembles an ideal diode feeding a peak detector. Additional insights were provided regarding stability issues when driving a coaxial cable directly with the op-amp's output.

PREREQUISITES
  • Understanding of operational amplifier configurations, specifically LM741.
  • Knowledge of alarm circuit design principles.
  • Familiarity with AC signal processing.
  • Basic concepts of circuit reliability and stability.
NEXT STEPS
  • Research the design principles of alarm circuits using operational amplifiers.
  • Study the effects of circuit design errors on long-term reliability.
  • Learn about stability issues related to op-amps driving coaxial cables.
  • Examine the application notes for Bourns potentiometers and their use in op-amp circuits.
USEFUL FOR

Electronics engineers, hobbyists designing alarm systems, and anyone involved in operational amplifier circuit design and troubleshooting.

chrisla
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Hello,
I completed this circuit with 6 op amps LM741. Now I want to connect any high and low level alarm circuit. I have found and tried some solutions but I didn't get it to work. Can you give me some advice how to do it?
 

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chrisla said:
Hello,
I completed this circuit with 6 op amps LM741. Now I want to connect any high and low level alarm circuit. I have found and tried some solutions but I didn't get it to work. Can you give me some advice how to do it?

Welcome to the PF.

What is the circuit supposed to do? You are feeding in a large AC signal -- what do you mean by high and low level alarms?

BTW, there is a design error near the right of the schematic that will cause the circuit to become unreliable in a couple years after construction. Do you know what it is?
 
U3 and U4's function has me scratching my head. I haven't seen that particular arrangement before. It looks like it might be a variation of an ideal diode feeding a peak detector.
 
berkeman I'm curious what will make the circuit unreliable?
 
nevere said:
berkeman I'm curious what will make the circuit unreliable?

See the discussion about potentiometers and opamps starting at post #39 on page three of this fun thread:

https://www.physicsforums.com/showthread.php?t=178516&highlight=bourns&page=3

The thread discussed a number of "Bad Circuit" examples from the textbook "The Art of Electronics" by Horowitz and Hill. Let us know if the explanation in the thread (and the Bourns application note) make sense to you. :smile:
 
Also asking for stability issues using the opamp's output to directly drive a coaxial cable to scope. Needs 10 ohms or so of series resistance. (Unless this is actually a scope probe).
 

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