how can'i get 5 V AC output 230 V AC: input? for a measurement unit bases on DSP?


closed as too broad by PeterJ, Dmitry Grigoryev, uint128_t, PlasmaHH, Daniel Grillo Apr 27 '16 at 11:29

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    \$\begingroup\$ Use a step down transformer. \$\endgroup\$ – JIm Dearden Apr 26 '16 at 12:11
  • \$\begingroup\$ A potential divider? \$\endgroup\$ – Andy aka Apr 26 '16 at 12:12
  • \$\begingroup\$ You probably don't want 5 V AC which will have peaks of around 7 V DC so think about that side of things and you probably want to add a 20% margin because mains power can be above the nominal by a fair bit. \$\endgroup\$ – PeterJ Apr 26 '16 at 12:18
  • \$\begingroup\$ You might want to consider using a Digital to analog converter to produce the wave. Its safer and probably cheaper. You can get ICs to do the function and some DSPs have inbuilt peripherals. \$\endgroup\$ – Adam Z Apr 26 '16 at 12:21
  • \$\begingroup\$ my objective is to build a prototype that can estimate frequency and phasor from LV and MV. i use dsp technique so i should sampling the ac waveforme thats why i need pt/ct to attenuate the signal ? the question is how i choose PT/CT and the current sensor? \$\endgroup\$ – Ala Ben Hassin Apr 26 '16 at 12:38

Stepping down or up AC voltages is precisely what transformers do.

Alternately, if you only need to measure the voltage, and not draw significant current from it, you could use a voltage divider. A voltage divider would be much cheaper and simpler.

However, keep in mind that there are safety codes that require that the low voltage components are isolated from the mains components. You would not want to accidentally electrocute the user of your device when there's some fault in your device. A transformer may meet these isolation requirements. A voltage divider certainly will not.

  • \$\begingroup\$ thanks . but i need to know how i choose PT/CT and the current-sensor how i know if my choice is achievebal ? because after i nees to sample the waveform \$\endgroup\$ – Ala Ben Hassin Apr 26 '16 at 12:48

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