Bridge Rectifier help....please?

Kd You can us a rectifier from radio shack , part number 2760268 Your 12 vac connects to the to leads with the sine wave markings , this ill I've you nominally 12 vdc out on the other two pins. Connect the + from the rectifier to the dropping resistor on you led assembly and the negative lead of the rectifier to the ground or - lead on your led assembly. Radio shack part is $1.5 less other places but this is convenient .

This may be of help. The 1 amp bridge rectifiers cost about 50 cents each from www.allelectronics.com

 

http://www.allelectronics.com/...DGE-RECTIFIER/1.html

 

 Radio Shack also has them,they are just more expensive.

 

Here they are circuited in Marx towers

 

http://www.jcstudiosinc.com/MarxTowerLEDs

 

Dale H

You could probably just use a standard small diode inline to do what you need. It will only give you half wave DC, but that should work fine. You may have to decrease your resistor value to get the brightness you want, because with half wave the effective average DC voltage is lower than your input AC voltage by .707 I believe.

 

Rod

You don't need a bridge, a simple diode is all I ever use for this kind of thing, Rod's right.  The resistor value is non-critical, the only limitation is making sure you don't drive them with more than 20ma each.  I normally select the resistor for the light level I desire.

 

Are they wired in series or parallel?  Are they white LEDs or colored?

 

If you haven't already sealed up your 2 LEDs you can connect them back-to-back (in parallel but with opposing polarities).  Each LED (which is effectively a diode itself) acts as the "diode" for the other to block the opposite polarity voltage.  Then just add a resistor.  Photo shows two 3mm white LEDs connected as such plus a 470 ohm resistor (1/2 Watt variety would work fine).  Average current in each LED was ~10mA when powered by 12VAC.

 

 

If all you have are 1000 ohm (1K) resistors, you can put 2 in parallel to "make" a 500 ohm resistor.  Or 3 in parallel to make a 333 ohm resistor.  The current into each LED was ~12mA with a 330 ohm resistor, and ~8mA for a 1000 ohm resistor.

 

Just an alternative to stir up the pot...

 

Parallel.  Warm white.

And, my thanks to all who've provided some suggestions.

 

If I get this thing going, I'll try to post a couple photos in appreciation.  Posting photos...another of my 'Achilles Heels'...for which my wife bails me out repeatedly.

 

KD

 

 

Stan has an excellent suggestion, I forgot all about that, but it works great on plain AC.  For that connection, I'd suggest a 470 ohm resistor, I think they'll be plenty bright.

Well, Stan/John, you're right!...  Works like a charm!  I have a new-found trick for the bag.

 

...and the tavern looks pretty cool, methinks!

 

 

 

 

 

 

 

 

 

Sorry about the glare on the 'beer' sign...looks better than photo portrays.  I used a 680 ohm resistor on the up-light LED's...maybe I'll try another to tone it down a tad.

 

Thanks, again, to all of the suggestions!  The forum is great for this sort of help!

 

Have a TGIF day!

 

KD

 

 

 

 

 

No problem with glare, your images didn't come through.  No glare in what we see, here's a sample.

 

 

 

It appears you tried to paste them directly from your computer, you can't do that.  Use the +Add Attachments link to upload them to the forum.

We used the 'Add Attachments' link.  It's the same ol' problem we've been having for months.  I'm at the shop now....when I get home this evening the wife and I will try....again...to figure out what the problem is.  The file of pictures is on my computer.  They always appear just fine as I construct the reply and add attachments.  Somewhere along the line after pushing 'Submit Reply' they go south to inaccessibility.  It is, indeed, a very frustrating situation since I have much that I would share photographically, but it simply doesn't seem to work.  If I thought the Best Buy Geek Squad could figure it out, I'd have them buzz on over in their funky black&white VW!!

 

Later.

 

Sorry.

 

KD

Post a query in the forum help section, perhaps Rich can assist you in getting photos to show.  All I ever do is use the Add Attachments, but your links look nothing like mine.

 

This is what my link looks like "in the raw".

 

<code>https://ogrforum.com/fileSendAction/fcType/0/fcOid/22970454987118446/filePointer/22970454997393910/fodoid/22970454997393906/imageType/MEDIUM/inlineImage/true/Image%2520Not%2520Found.jpg</code>

 

<code>https://ogrforum.com/sendTempFile/fileUploadProcessOid/48911566/fileUsageType/ATTACHMENT/uniqueOid/22970454996741207/imageType/SMALL/inlineImage/true/IMG_7177.JPG</code>

 

For some reason yours are going into some temp file process.

 

 

John...

 

Thanks for your notations.  My wife has 'played' with the attachments process and I believe the photos now show in the original post (We opened the thread w/o signing in).

 

Still not sure quite what's going on, but maybe we're getting closer.

 

Thx,

 

KD

Looks good, they're showing up now.  Nice job on the building as well.

 

@ dkdkrd. This looks great, you've done an awesome job. Although you can use the two LED's with different polarity and a resistor in series with them and that acts as a rectifier but please note that doing so with reduce the expected lifetime of these LED's because they are designed to work on DC voltage levels. The issue with connecting them like this is that for a very short amount of time when the voltage is rising from 0V, the voltage going to the LED is too low and that forces a larger than recommended amount of current flow through the LED. Now doing so doesn't apparently give any issues but LEDs blow up this way. You can just get four diodes and connect them in a bridge to make a rectifier yourself. 

 

pcb assembly

Actually, using two LED's back-to-back with opposite polarity on AC is an excellent way to protect them, and there's no reduced life involved.  The LED that's not lit is protected from excess reverse voltage by the one that is lit.  This is just as good as a diode in series or across the LED.

 

There is absolutely no issue with "too low a voltage" on an LED forcing excessive current.

 

 

Adding to GRJ's comments, there is nothing untoward about driving LEDs with a non-steady voltage.  A good example of this are the zillions of Christmas LED light strings powered by AC voltage; each LED sees a voltage that varies from 0V to a few volts 60 times per second!

 

Also, the "output" voltage of a bridge rectifier drops to 0V at the same time as the AC "input" voltage.  A bridge rectifier (or four diodes) in and of itself does not address varying voltage.