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Help with 24 led light powered by 12 Volt car battery

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In post #51 R3- 1.45k Ohms - Other direction 1.31k Ohms

I will check ALL the pcbs to make sure & replace R3 with the 2.7k as you suggested & get back to you with results..
Thanks
 

I forgot to mention, the 2.7k resistors should be 1% tolerance type.

I referred a link on soldering in post #18. Now I offer another for surface mount components:
YouTube - ‪CuriousInventor's Channel‬‏
Most of the information pertinent to chip resistors is at the beginning but there are some removal tips near the end.
 
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Thanks, I forgot to mention that the link you provided before was great, actually don't want to admit it, but I learned a few things..
You have been extremely helpful.
Wish I waited a while before purchasing the 2.7K resistors..
Just purchased 100 Pcs, all of them 5% :(

Thanks again
 

They'll probably be okay. It's not so much a matter of having them exactly 2.7k as having them all the same. They're cheap enough to use for soldering practice. I soldered badly for years before discovering the magic of flux.
 

KJ6EAD said:
They'll probably be okay. It's not so much a matter of having them exactly 2.7k as having them all the same. They're cheap enough to use for soldering practice. I soldered badly for years before discovering the magic of flux.
Click to expand...

Doesn't resin core make it all that much easier,lol
BTW, I found two pcb's with tons of smd resistors on them, just have to wait till the helping hands with magnifying glass & built in light comes in..

**broken link removed**



Numbers are small ,lol

Also, you never stated watts :) 1/8 , 1/4 , 1/10 , 1/16 does it matter?

Thanks
 
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campus189 said:
Doesn't resin core make it all that much easier? Also, you never stated watts :) 1/8 , 1/4 , 1/10 , 1/16 does it matter?
Click to expand...
That's rosin, not resin, though it's made from pine sap. I made my own flux once just to see how it was. The flux in the solder core isn't adequate for SMD soldering because it boils off before you can complete the joint. The wattage will be ⅛W or ¼W for the size part you're using but won't matter.
 

Ok,

Swaped R-3 with 2.7k Ohm Resistor

Installed the 2.7K & have the following results...

Old results

Pin1-Ground
Pin2-2.1v
Pin3-2.8v
Pin4-5.1v

New results with 2.7k 5% resistor
Pin1-Ground
Pin2-1.4v
Pin3-1.8v
Pin4-3.4v

With 1.5 Ω still connected- 3.3v on one side and 3.0v on other side of resistor.
LEDs are at 3.0v

Hope this helps

---------- Post added at 17:58 ---------- Previous post was at 16:58 ----------

Just for the hell of it, i bypassed the 1.5 Ω resistor & got LED voltage of 3.3v
The PCB on the dc to dc converter heated up bad and the LED PCB heated up.
So I re connected the 1.5 Ω & no problems as far as the two PCBs heating up so far..
 
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3.43V was expected. 3.4V is good enough. :smile: Did you do all 8 converters or just 1? I'd like to know if the output of all is the same. The calculated value for the dropping resistor for the LED board would be 0.625Ω but if you want to try 0.75Ω (2@ 1.5Ω in parallel) and measure the current, you can.

By the way, the pin 2 and pin 3 voltages are irrelevant for our purposes. In the original design, those voltages were developed from the main output to satisfy the USB port requirements. They account for several extra resistors on the board (R5-R8) which you could remove but they're not using much power (215µW) so why bother.
 
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I did just one, I couldn't wait for the helping hands & magnifying glass to come in, but really hard to to see.
I have to use a sewing pin to hold it down to keep it from moving, its so light.
Running at 3.0v has been running 4 hours now, no heating issues at all.
Would I get the 3.1v by using the 2-1.5Ω resistors in parallel?
It's plenty bright enough with no heating, but when the 1.5k Ω was bypassed I got 3.3v on LEDs
Just don't want to heat stuff up,lol
Almost forgot, total draw with dc to dc converter is around 200mA , I like that, small draw :)
Flea bay doesn't have the resistors, ill have to scroll through your posts here to order them.
So should I order both kinds of resistors? Or just the .75 Ohms
1/4W or 1/2W ? (only draws 200mA ) I would think 1/4W would work
When I do all 8, i'll repost values
Thanks again
 
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campus189 said:
Running at 3.0v has been running 4 hours now, no heating issues at all.

Would I get the 3.1v by using the 2-1.5Ω resistors in parallel?

It's plenty bright enough with no heating, but when the 1.5k Ω was bypassed I got 3.3v on LEDs

Almost forgot, total draw with dc to dc converter is around 200mA, I like that, small draw :)

Flea bay doesn't have the resistors, ill have to scroll through your posts here to order them.
So should I order both kinds of resistors? Or just the .75 Ohms
1/4W or 1/2W ? (only draws 200mA ) I would think 1/4W would work
Click to expand...

By 3.0V, do you mean across the LEDs?

I don't know. The LED voltage is not important at this point, the current is. What we're hoping to achieve is a current through the LEDs collectively of 480mA or slightly less. The two 1.5Ω resistors in parallel create a resistance of 0.75Ω. This is just an experimental value to see what LED current we get.

There is no 1.5kΩ resistor here. There was a 1.5Ω resistor with each light.

Is that 200mA measured on the 12V supply side of the system or on the 3.4V side?

You shouldn't be ordering anything yet. The correct resistance value is not yet determined.
 

Oops, lol
Sorry bout that.
Got a crapload of resistors, just not the two posted above.
Figured I could use them down the road anyways :)
 

Ok,

Helping hands came in, getting started now.
Will post results later of all of them with new smd resistor.
 

7 of them are at 3.4v

1 of them is screwed up somehow with a voltage of 7.8v

I can accept losing 1 out of 8

What a pain to replaced them all,lol
 

Good, the voltages are consistent. The only thing I can guess went wrong with the bad one is perhaps a solder bridge to R6.

These have got to be the world's worst white LEDs. They make lots of heat while producing weak light and I haven't even run them up to full current yet.

I have to do one more test on the LEDs tomorrow. Then I'll be able to tell you which resistor is needed for the LED board.
 

Why I went out & purchased a bunch of LEDs to test on Breadboard.
I was hoping to use these, as they have enclosures that look nice.
Thanks again for help.
 

I did some testing with my Ningbo light and it turns out that the Vf of the LEDs is 3.4 when running at 480mA. You should try running one of yours with no resistor (bypassed with wire) on the LED board directly from the 3.4V converter output while measuring the current. If it's more than 480mA, disconnect it immediately. If it's less than or equal to 480mA, let me know what the measurement is.
 

KJ6EAD said:
I did some testing with my Ningbo light and it turns out that the Vf of the LEDs is 3.4 when running at 480mA. You should try running one of yours with no resistor (bypassed with wire) on the LED board directly from the 3.4V converter output while measuring the current. If it's more than 480mA, disconnect it immediately. If it's less than or equal to 480mA, let me know what the measurement is.
Click to expand...

Tested with resistor bypassed 218.5mA Still 3.2v at led
 

you can try 4 series connection of white LED without dropping resistor.
 

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