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Hi, I want to make this VA meter project for my 0-30V power supply unit(also project from here). I have a few questions about the VA meter.  http://electronics-lab.com/projects/test/007/index.html is the project.

- The power suplly, can exceed the 30V limit, and to be aroun 31-32V for example. The maximum input voltage for the VA meter is 30V, can this be harmfull for the VA meter?
- One of the VA meter's inputs gets positive power directlly after the bridge rectifier. On the schematic the limits are 14-35V. In order the power suplly transformer has 2x30V windings, after the rectifier I expect voltage value above the 35V maximum?
- Can I use separate 5V power supply only for the VA meters( with common ground with the power supply)

This is for the current moment :)+

Best Regards!

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  • 1 month later...

Hi morpheous87,  with the right tweaking you can get the display to work with much higher voltages.   I set mine up to work up to about 60 V.     It's been many years since I worked with this but here are some of the issues:

1.   The voltage signal to the chip must be less than 5 volts so the voltage divider needs to be changed to ensure your max voltage signal to the chip does not exceed 5v.  The project you referenced was designed for a max of 30v so the voltage divider was designed with that in mind.
2.  because the sense voltage  in 1 above will represent a different value than the original program you need to change the software code to display the correct voltage.
3.  Most 5 and 12 V regulators don't tolerate imput voltages higher than about 30V.   I think I used a LM317HV regulator to get to 12 volts then used a standard  regulator to go from 12 to 5v.

I think sample code was posted several years ago on this forum.


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