Relays for AC/DC Auto Start Control Panel

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SUMMARY

This discussion focuses on designing an Auto Start Control panel that activates on a 24 VDC power signal or the loss of 120 VAC power. The user is considering using a 24VDC relay to manage these signals, specifically addressing the challenge of activating the start signal with both 24 VDC and 120 VAC inputs. The proposed solution includes using a rectifier, voltage divider, diode, and capacitor to convert the 120VAC signal into a 24VDC signal, allowing for effective relay operation based on the presence of either signal A (24VDC) or the absence of signal B (converted 120VAC).

PREREQUISITES
  • Understanding of relay operation and configurations
  • Knowledge of AC/DC signal conversion techniques
  • Familiarity with rectifiers and voltage dividers
  • Basic electrical circuit design principles
NEXT STEPS
  • Research relay types that support both AC and DC operation
  • Learn about rectifier circuits for AC to DC conversion
  • Study voltage divider circuits for signal processing
  • Explore practical applications of diodes and capacitors in control panels
USEFUL FOR

Electrical engineers, control panel designers, and technicians involved in automation and power management systems will benefit from this discussion.

littleblackdo
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Are there relays which work with both AC and DC? I am design an Auto Start Control panel which will activate on a 24 VDC power signal OR loss of 120 VAC power. I am using relays to accomplish this and I am not very familiar with them.

I was thinking a 24VDC relay connected to the 24 VDC signal. This relay will activate the signal when relay is deenergized ( I still have to figure out how to accomplish this if the DC signal the relay is monitoring is normally not energized). I am just not sure how to accomplish having the start signal with both a 24 VDC signal and 120 VAC. This is supposed to be designed into a simple control panel. Cannot be very complicated due to time restraints (This is a work project, not school). Should I use a rectifier?
 
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You can use a voltage divider, a diode and capacitor to turn the 120VAC signal to 24VDC. Call that signal B. Signal A is 24VDC present. Then the relay activates when A or NOT B.
 

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