Build Trigger Circuit with Solar Panel & Capacitor

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SUMMARY

This discussion focuses on building a trigger circuit using a solar panel and a 2200 uF capacitor, which charges to a maximum voltage of 1.7V. The proposed solution involves using an LMV431 voltage reference set at 1.25V to control a high-side PNP transistor, allowing the capacitor to discharge through an LED when the voltage reaches the desired threshold. Incorporating hysteresis into the design is recommended to enhance the circuit's switching behavior.

PREREQUISITES
  • Understanding of basic electronic components such as capacitors and diodes.
  • Knowledge of transistor operation, specifically high-side PNP transistors.
  • Familiarity with voltage references, particularly the LMV431.
  • Basic circuit design principles, including hysteresis implementation.
NEXT STEPS
  • Research the specifications and application of the LMV431 voltage reference.
  • Learn about high-side PNP transistor configurations and their applications in circuits.
  • Explore hysteresis in electronic circuits and its effects on switching behavior.
  • Investigate solar panel output characteristics and their integration into trigger circuits.
USEFUL FOR

Electronics enthusiasts, hobbyists building solar-powered devices, and engineers designing trigger circuits for low-voltage applications.

ZPlayer
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Hello,

I have a small solar panel that is connected to a 2200 uF capacitor through a diode and charges it to 1.7V maximum. I would like to create a circuit that will use the voltage across capacitor terminals as a trigger for other events. Suppose that when the capacitor is charged to exactly 1.7V, it triggers some other element and discharges through an LED. Is it possible to build such circuit without any other voltage sources except for the solar panel?

Thanks.
 
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You could use a 1.25V voltage reference with some voltage division, and have that turn on a highside PNP transistor to let current out of the capacitor and into a load. It would be good to have a bit of hysteresis in the circuit as well, depending on how you want it to work as a switch.

LMV431 (1.25V) voltage reference: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=LMV431CZ-ND
 
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