Problem with wiring project

[Phil Brown]

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]

Did you see the schematic?

 

[Phil Brown]

Did you see the schematic?

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]

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]

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.

 

[Phil Brown]

Is it working with 12 volts?

Here's the components list:
http://www.amazon.com/gp/product/B00452YFZU/ref=oh_aui_detailpage_o02_s02?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B0087YQPKU/ref=oh_aui_detailpage_o02_s02?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B00C5NG4LY/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
http://www.amazon.com/gp/product/B004JO2HTA/ref=oh_aui_detailpage_o02_s02?ie=UTF8&psc=1
Capacitor 220 uF 16V I didn't buy this one off Amazon

And maybe the capacitor is where I went wrong?

 

[KTW]

It calls for 1 Watt resistors and you are only using 1/4 Watt.

6.8 uF capacitor.

 

[davenn]

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]

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]

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]

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.

 

[BobK]

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]

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]

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]

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.

 

[BobK]

Yep, that looks like the right one.

Bob

 

[Phil Brown]

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?

 

[KTW]

You can still get free shipping with a paypal account.

http://www.ebay.com/itm/20pcs-8mm-0...t=LH_DefaultDomain_3&var=&hash=item2592abeb22

Just pick the color and quantity.

Enter 0,5W straw hat LEDs into your search engine.