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Author Topic: building an AC rectifier  (Read 956 times)
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I want to make sure I am not doing something silly and blow something up smiley if someone can confirm this is correct I would greatly appreciate it. I am mostly worried about the capacitor.

the diodes are 1n4007 and the input is coming from a 12v 1A 12w ac adaptor
https://www.dropbox.com/s/z6ntr9ogph1tkvq/photo.JPG
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Doesn't look right to me. Where is the AC input? It should go to the junction of the diodes with opposite connections. That is the DC comes from the pair of anodes, and pair of cathodes joined and the AC goes in the other pair where an anode and cathode are joined.

Draw us a schematic of what you are trying to make.
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Doesn't look right to me. Where is the AC input? It should go to the junction of the diodes with opposite connections. That is the DC comes from the pair of anodes, and pair of cathodes joined and the AC goes in the other pair where an anode and cathode are joined.

Draw us a schematic of what you are trying to make.
ac input is the black and red wires. Though I think it doesn't matter with AC...?

this is what I am trying to build
https://www.dropbox.com/s/gn5mij3fa0d2v4x/Screenshot%202013-12-08%2014.39.12.png
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ah I think you're right. I am still new to reading schematics, but this seems more correct, maybe?

https://www.dropbox.com/s/xbwbhmbz054pzb4/photo2.JPG
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Hi, your final attempt is correct, the diagram has pos and neg transposed but your protoboard layout is correct.

Note use colours other than red black for AC, make it a general rule Red is positive and Black is Negative or gnd, when you get more and more components involved and more and more wiring, a rule of thumb for colours will help.

The pos and neg signs on the diode diagram show anode and cathode connections to the diode, not the output polarity of the rectifier.

Your proto layout has the connection of the two cathodes as the positive output, the connections of the anode junctions as the negative output, this is correct.

Tom.... smiley
« Last Edit: December 08, 2013, 03:40:50 pm by TomGeorge » Logged

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ah I think you're right. I am still new to reading schematics, but this seems more correct, maybe?

https://www.dropbox.com/s/xbwbhmbz054pzb4/photo2.JPG
Yes looks a lot better to me as well.
Where is the AC coming from?
That is a 35V working capacitor so the maximum RMS AC you should be using is 24V.
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ah I think you're right. I am still new to reading schematics, but this seems more correct, maybe?

https://www.dropbox.com/s/xbwbhmbz054pzb4/photo2.JPG
Yes looks a lot better to me as well.
Where is the AC coming from?
That is a 35V working capacitor so the maximum RMS AC you should be using is 24V.

not sure if you're asking about what I posted in first part but it is a  12v 1A 12w ac adaptor, so there is already a transformer.

I tried it out and it seems to be working correctly I now have a DC voltage.
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Quote
the input is coming from a 12v 1A 12w ac adaptor

Such a device is almost certainly going to be supplying you with DC,  not AC.
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Such a device is almost certainly going to be supplying you with DC,  not AC.
No, I have a few adapters that give out AC and not DC. They are used mainly for audio mixers and the like where you can generate split supplies from the AC.
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Quote
the input is coming from a 12v 1A 12w ac adaptor

Such a device is almost certainly going to be supplying you with DC,  not AC.

nope. definitely AC.
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FYI - you can buy a bridge rectifier that has 4 diodes in one package with 4 terminals.  Building one yourself is a good learning experience, but I can't remember the last time I built built one.

Also, it's a good idea to "derate" you components.    The voltage rating on your 1N4007 is fine, but at 1 Amp, you are pushing it to it's limit.    When you first power-on, you will likely get quit a bit more than 1A of "inrush" current  as the capacitor charges-up.    Your diodes will probably survive, but it's good to have some safety margin.   (I haven't checked the specs, but they probably can withstand more current for a short time.)
« Last Edit: December 09, 2013, 03:13:52 pm by DVDdoug » Logged

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FYI - you can buy a bridge rectifier that has 4 diodes in one package with 4 terminals.  Building one yourself is a good learning experience, but I can't remember the last time I built built one.

Also, it's a good idea to "derate" you components.    The voltage rating on your 1N4007 is fine, but at 1 Amp, you are pushing it to it's limit.    When you first power-on, you will likely get quit a bit more than 1A of "inrush" current  as the capacitor charges-up.    Your diodes will probably survive, but it's good to have some safety margin.   (I haven't checked the specs, but they probably can withstand more current for a short time.)

ahh, wish I would have known that! it was indeed good learning experience though.
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Small signal diodes tend to fail open, higher current diodes tend to fail short. I suspect that the small signal diodes fail short, but then the thin whisker of wire burns like a fuse.

So I tend to derate current about 3 times. Need 1A, I like to pick out a diode rated at least 3A.
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