Creating a stable 5V DC supply out of 6 V (RMS) AC

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To create a stable 5V DC supply from 6V RMS AC, a full-wave bridge rectifier and an LM7805 voltage regulator are proposed, but concerns arise regarding the minimum input voltage for the regulator. The circuit requires a sufficiently large capacitor to smooth out voltage ripples, with calculations suggesting a minimum of 4700 µF for a load of less than 1A. Using a higher voltage transformer, such as a 9V or 12V, is recommended to ensure adequate voltage for the regulator after accounting for diode drops and ripple. Additionally, Schottky diodes are suggested for better efficiency, and the importance of including safety components in the circuit design is emphasized. Overall, careful consideration of component specifications and load requirements is crucial for successful implementation.
  • #61
First of all, I would like to thank @Borek who, in post #2, mentioned the DSO138 oscilloscope. The device has really been very helpful.

Next, I have performed the experiment, based on the circuit I had posted here. These are the results from the oscilloscope:

WhatsApp Image 2021-05-17 at 2.22.03 PM.jpeg

Output of full wave rectifier bridge
WhatsApp Image 2021-05-17 at 2.22.03 PM (1).jpeg

After passing the output through the voltage regulator
with necessary filter capacitors

I can see that the average voltage is 4.43 V, the maximum being 4.83 V. 5 V is not reached. Is this an accuracy error of the oscilloscope?
 
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  • #62
Does the first picture look like full wave rectification? Check your diode orientation.
 
  • #63
pbuk said:
Does the first picture look like full wave rectification?
Yeah, I have seen that. Trying to figure out the issue.
 

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