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Problem with wiring project

Phil Brown

Mar 4, 2015
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I have a project I found on Instructables:
http://www.instructables.com/id/Magnetic-table-lamp/

I'm trying to duplicate this on the breadboard. I wired the circuit board up the way you see in step 5.
After that things get very sad.

I know that on the Bridge I connect the Positive to the ~ and the negative to the other ~. I believe how the bridge is designed is that it doesn't matter which ~ I connect to. But the LED's I'm having a tough time finding where I connect those. One end to 1 of the resistors I get, but the other end doesn't connect to the other resistor does it?



Thanks for the help/
 

KTW

Feb 22, 2015
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Did you see the schematic?

FF0HYYWGWXOE7K7.MEDIUM.jpg
 

Phil Brown

Mar 4, 2015
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Did you see the schematic?

FF0HYYWGWXOE7K7.MEDIUM.jpg

I did and I just am too much of a novice. Although I think what I should do now is connected 2 LEDs to a resistor and then the other end to the capacitor. And then the other 2 LEDs to the last resistor and then to the same resistor.

Close?
 

KTW

Feb 22, 2015
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I'm just as much a novice Phil but what I see are two sets of LEDs, each pair connected to a resistor and then the ends of both those resistors are connected to the negative side of the capacitor.
 

Phil Brown

Mar 4, 2015
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I'm just as much a novice Phil but what I see are two sets of LEDs, each pair connected to a resistor and then the ends of both those resistors are connected to the negative side of the capacitor.

You are correct! I think I have a component sized incorrectly, the LEDs are on but then in 20 minutes burn out.

But hey that's a start.
 

KTW

Feb 22, 2015
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It calls for 1 Watt resistors and you are only using 1/4 Watt.

6.8 uF capacitor.
 
Last edited:

davenn

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Sep 5, 2009
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Hi Phil

Instructables are notorious for poor circuits etc on their site

OK if your LEDs are burning out, up the resistor values somewhat, 39 Ohms seems way too low.
With 12V, I would be using something around 1000 Ohms (1k)

you mite want to have a look here .....
https://www.electronicspoint.com/resources/got-a-question-about-driving-leds.5/
its a resource section on this forum site all about driving LEDs, you may find it very helpful :)

cheers
Dave
 

Phil Brown

Mar 4, 2015
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Hey thanks everyone.

I am measuring 13.9V across the circuit.

Dumb question, why is it negative on my multimeter?

Sorry for all the dumb questions, I will try upping my resistors!
 

davenn

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Dumb question, why is it negative on my multimeter?

1) do you have the red and black probes on the correct places ? red = positive, black = negative
2) do you have the red and black probes in the correct sockets on the multimeter ?


show us a photo of your construction you may have a wiring error if you have the above 2 points correct

Dave
 

KTW

Feb 22, 2015
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The DC supply may be reversed.
I just bought two from Amazon and the negative is on the center of the plug.

I just noticed the LED's you are using don't match either.
 
Last edited:

BobK

Jan 5, 2010
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The circuit is designed for 150mA LEDs. You are using what are probably 20mA LEDs. No wonder they are burning out. And if you change the resistors to make them run at 20mA they will not put out much light. And they are narrow as opposed to wide angle. Really not suitable for this project.

Bob
 

Phil Brown

Mar 4, 2015
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The circuit is designed for 150mA LEDs. You are using what are probably 20mA LEDs. No wonder they are burning out. And if you change the resistors to make them run at 20mA they will not put out much light. And they are narrow as opposed to wide angle. Really not suitable for this project.

Bob

Thanks Bob.

I can't see on the Amazon page where it says how many mA it needs, is this something that is just knowledge you have?

Would this have been a better LED?
http://lighthouseleds.com/10mm-5w-4-chip-led-white-ultra-bright-180-000-mcd.html
 

Gryd3

Jun 25, 2014
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The circuit is designed for 150mA LEDs. You are using what are probably 20mA LEDs. No wonder they are burning out. And if you change the resistors to make them run at 20mA they will not put out much light. And they are narrow as opposed to wide angle. Really not suitable for this project.

Bob
You can make them work... if, you use more LEDs to compensate.
Additionally the narrow angle can be compensated for by aiming them differently, or even taking some sand-paper and scuffing up the plastic lens to give it a 'diffused' or 'frosted' finish. Of course the sandpaper trick will give you a more uniform light, but because of this it will not project quite as well.
 

KTW

Feb 22, 2015
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When making a duplicate circuit you should stick with the items listed or you'll run into problems.
LED's can be searched to find their properties.
If you're baking the same cake just follow the same recipe.
.5 watt led.JPG
 

BobK

Jan 5, 2010
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Yep, that looks like the right one.

Bob
 

Phil Brown

Mar 4, 2015
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Yeah I looked at the recipe and said, "OK lets see what I can get on Amazon with free shipping." I can see where that's a dumb idea and can bite me in the ass.

KTW, mind if I ask what website the picture you attached is from?
 
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