Electronic – Full wave diode bridge rectifier troubleshooting

bridge-rectifiercircuit-designdiodestroubleshooting

I am trying to make a full wave diode bridge rectifier, as the title suggests. I have a 120-12vac transformer that I'm using to supply the circuit. However, whenever I measure the voltage across the output of the bridge, I am still getting an AC signal. Whats even weirder is that I now get readings across the terminal on both DC and AC settings of my multimeter, and the VDC measurement is ~20V, which seems a bit odd… Anyways, I have no idea what is happening, so any suggestions would be fantastic.

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Best Answer

it's not surprising you are seeing close to 20Vdc at the output. The nominal voltage of your transformer secondary is 12Vac (which could be even higher ~14Vac). Now, the ac voltages you have are RMS. So the capacitor is going to charge up to the peak value of the sine wave, which is 12Vac*sqrt(2) = ~17V for a secondary output of 12Vac. If this were more like 14Vac at the secondary, it would make sense why you are seeing 20Vdc at the output.