PCB Heaven

General Category => Analog discussion => Topic started by: cheerio on October 17, 2011, 17:54:28 PM

Title: rectifier
Post by: cheerio on October 17, 2011, 17:54:28 PM
Here is what my problem is...
I have 12V AC and i need it rectified. I use the circuit that i attached.
I did never mess around with ac before so i probably messed the circuit.
What i do not understand is why i get quite significant negative voltage, the low voltage and the low Freq. of the pules.
 Can anyone help me with this simple circuit please?

I use 1n4148 Diodes and a 100nF foil Capacitor.
Title: Re: rectifier
Post by: kam on October 17, 2011, 18:28:03 PM
for your rectifier you may wanna use 4001 (or 4004 or 4007) diodes instead. Also, the capacitor must be much bigger than this. I recommend you use at least 100uF capacitor electrolytic.

Something important: You have the DC output marked wrong! The positive will be supplied from the top diodes and the negative from bottom. So you may need to connect the probes differently.

After these changes you will get the result you expect

For better smoothing results, you may wanna use a U filter. This uses 2 capacitors and one inductor, like the attached image. The capacitors may be 10uF for C1 and 100uF for C1. As for the inductor, you may use a thick wire air-core or better iron core, with 20 to 40 wounds.
Title: Re: rectifier
Post by: cheerio on October 17, 2011, 18:31:52 PM
 I actually swapped the measure points on the circuit and did not notice it.

i try this later and post the results.

thank you
Title: Re: rectifier
Post by: cheerio on October 19, 2011, 01:55:03 AM
i followed your advice. Just to realize that i measured AC the whole time :(
switched to DC and all works fine :)