bridge rectifier chip

[scaesic]

bridge rec's have a + and minus sign on them, but they just have the wave symbol on the other two pins - how do you know which one to connect live to and which to connect neutral to?

i'm planning on using the db305 or db306, but the data sheet has no further info.

[Jake Lessen]

Doesn't matter.....alternating current goes back and forth anyway.  The current flow changes direction 60 times per second.  Hook up the alternating current lines to the pins with the wave symbol next to them, and the plus and minus pins are the "DC*" pins, like the plus and minus on a battery. 

*Not really DC without filtering, but at least the current goes the same way. 

[scaesic]

Doesn't matter.....alternating current goes back and forth anyway.  The current flow changes direction 60 times per second.  Hook up the alternating current lines to the pins with the wave symbol next to them, and the plus and minus pins are the "DC*" pins, like the plus and minus on a battery. 

*Not really DC without filtering, but at least the current goes the same way. 

i could be wrong but i think you've simplified the situation grossly.

the current changes direction in the live line, whereas the neutral acts as a drain wire, and gives a reference point for voltages.

on a diode bridge the "live" and "neutral" wires dictate where the + and - points are at?  am i wrong? it could easily be the case that a chip has some more complex circuitry so that the + and - are always plus and minus, but that is basically what i am asking, because i dont' know.

[Paul Perry (Frostwave)]

A bridge chip is just four diodes arranged in a square.
http://en.wikipedia.org/wiki/Diode_bridge tells all.

[Mark F]

i could be wrong but i think you've simplified the situation grossly

With all due respect, I think you are "overcomplicating" this. Just hook up the AC to the pins with the wavy lines and the outputs will be + and - "pulsating DC" which you then smooth with filter caps etc. I really don't think it's any more complicated than that. I've done it this way countless times as I'm sure many members of this board have. As far as the "chip" is concerned I think it is just four diodes configured in a bridge and manufactured in a monolithic structure. I hope that helps.

[Mark F]

Whoops! Paul beat me to it!

[BrianJ]

I don't think you should connecting "live" and "neutral" directly to a diode bridge.  There should be an transformer of some kind in between.  The two wires of the secondary can be connected either way to the the AC pins of the bridge because there are out of phase and of equal potential.

[km-r]

OT
i remembered someone once asked me to replace a fuse for a tube amp. talkative guy...
He: y'know i wanna buy me a new pair of 6L6, can you bias my amp for me?
Me: no, i cant, but you have to buy a "matched quad of rectifier diodes" for that...
He: REALLY?? can you get me those? i can pay you.

Mehh...

[scaesic]

I don't think you should connecting "live" and "neutral" directly to a diode bridge.  There should be an transformer of some kind in between.  The two wires of the secondary can be connected either way to the the AC pins of the bridge because there are out of phase and of equal potential.

there is a transformer stepping down the voltage, il just hook it up and see what happens.

incidently, i plan to use this power supply to supply +/-20V AND +/-15V.

i get +/-20 out of the smothing caps and hoped to power the power amp with that, then i planned to hook up some 15V regulators and use the output of that to power other parts of the circuit. Anyone see a reason why this might not work?

[petemoore]

  see if you can find 'power supply for effects' IIRC.
  All the details about converting Ac to Dc, the Ac inputting, transforming, Diode Bridgeing [pretty slick how that works BTW, I think I had all that in mind once, notice all four -->l-- diodes point up' {{or 'over', depending on how it's drawn]...
  Then the system lets the *AC keep 'topping off' a capacitor, which holds a *DC charge..very close to DC anyway, throw a regulator on there and you've got very clean VDC.
 

[outoftune]

it's not as simple as hooking up ac to the one's with wavy lines b/c if you do not know how a diode bridge works, then just having one labeled does not tell you anything. i actually had to deal with one of these at work where the datasheet was not clear at all. since i'm still learning i made the mistake of thinking that both of the pins on the wavy side were ac, really it is the diagonal and diagonal to the + sign is the - . follow the link and learn more about diode bridges and it will make more sense.

[scaesic]

it's not as simple as hooking up ac to the one's with wavy lines b/c if you do not know how a diode bridge works, then just having one labeled does not tell you anything. i actually had to deal with one of these at work where the datasheet was not clear at all.

this is exactly what i was having trouble with, the thing is, the diode bridge chip is not the same "pin out" as 4 diodes in a square,
it has the two ac pins on pin 1 and 2 the two dc pins on pin 3 and 4.

also, the data sheet is pretty useless, you'd think it'd have a schematic of the circuit inside for such a simple chip. On the other hand, there COULD be some trickery so that the + and - pins are always the right polarity no matter what the ac polarity is.

[petemoore]

  chips not too expensive.
  connecting it is pretty simple.
  Using the schematic for a tranny/DB/filter caps, you have two 'unmarked' nodes, basically you just connect the 2 secondary connections to the DB where there are no polarity markings, put the cap across the DB output [following polarity]...add a regulator etc., there's your DC output.
  If using a CT tranny to get +/Gnd./- supply, the CT is Vbias/ground, the + is V+ and the - is V-  [add filter caps and regulator].

[Paul Perry (Frostwave)]

Since you already know (from the link I gave) how the four diodes are connected, you only need a multimeter with a diode test function to work out which pin is what.

[outoftune]

Since you already know (from the link I gave) how the four diodes are connected, you only need a multimeter with a diode test function to work out which pin is what.

Yep. Diode test it if in doubt. Also though, as I said, the positive voltage is the pin closest to the + sign. diagonal from that is the -, leaving the other two as AC.

[Mark F]

I don't think you should connecting "live" and "neutral" directly to a diode bridge.  There should be an transformer of some kind in between.  The two wires of the secondary can be connected either way to the the AC pins of the bridge because there are out of phase and of equal potential

OOPS! Again! I just assumed the transformer was there. You know what they say about assume.

[scaesic]

I don't think you should connecting "live" and "neutral" directly to a diode bridge.  There should be an transformer of some kind in between.  The two wires of the secondary can be connected either way to the the AC pins of the bridge because there are out of phase and of equal potential

OOPS! Again! I just assumed the transformer was there. You know what they say about assume.

well, fortunately im not stupid enough to try atatching a diode bridge to the mains direct.

[Mark F]

well, fortunately im not stupid enough to try atatching a diode bridge to the mains direct.

I didn't think so. That's why I assumed the proper stepdown.