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LED and wall adapters

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This is where i measured the voltages from...i guess i'm not sure what you mean by measuring 'across' the resistor then?? I assumed the 5.36 value here is measuring across the resistor :? ...sorry i'm a noob, can you tell :p
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airbrush said:
This is where i measured the voltages from...i guess i'm not sure what you mean by measuring 'across' the resistor then?? I assumed the 5.36 value here is measuring across the resistor :? ...sorry i'm a noob, can you tell :p
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It means one meter probe at each end of the resistor, so you measure the voltage actually dropped across the resistor. The same with the LED's, place one meter probe at either side of an LED to measure it's voltage drop.
 
This circuit will work for the green LEDs but the pot will have some slack when the LEDs are off.
 

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okay here are my readings

orange pot min:
2.77 vout
0 at the resistor
1.29 at the LEDs

orange pot max:
11.27 vout
7.43 at the resistor
1.9 at the LEDs


green pot min:
6.02 vout
0.68 at the resistor
2.67 at the LEDs

green pot max:
11.48 vout
4.97 at the resistor
3.18 at the LEDs

...i'd like to use the same circuit as before as i already have them made...just need to swap out the resistors once this is figured out
 
This circuit is for your orange LEDs.
 

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okay thanks...these schematics are slightly different from the originals...an extra 0.1 capacitor in there....is this necessary??

Will the other one work properly by just changing the resistors to the values you have in these new ones without adding the capacitor??? :?
 
All circuits in the datasheet show a capacitor on the output of the regulator to keep it from oscillating if your wiring isn't perfect. Use a ceramic disc capacitor.
 
i mean as compared to the schematics on the previous page....there is another capacitor in there the other didnt have (0.1uF)...is this necessary for this to work properly...or can i just simply changed the resistors
 
airbrush said:
there is another capacitor in there the other didnt have (0.1uF)...is this necessary for this to work properly
The capacitor is cheap, simple and is recommended. Use it on a second circuit if the 1st one without the capacitor blows-up!
 
...will do....need to do a little more shoppin for parts, hopefully i can hit the electronics place after work tomorrow before they close. Thanks again.
 
well...almost

here's a couple pics of it so far...not complete yet.

Still have a problem with the green LEDs for some reason....they are still dimmly on....they others all work fine :?

What do i need to check for these? circuits are made as per the recent schematic.

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I see 10 LEDs but the circuit has only 2. What did you do? Make a bunch of these circuits?

I would take the two green LEDs with their 120 ohm current-limiting resistor, connect them to my variable voltage supply then turn down the voltage until they were off. Then I would set the circuit's minimum voltage to be a little less.

You can reduce the value of the 620 ohm resistor like this:
 

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audioguru said:
I see 10 LEDs but the circuit has only 2. What did you do? Make a bunch of these circuits?

each color is on a seperate dimmer...they are wired in parallel series of 2leds

I would take the two green LEDs with their 120 ohm current-limiting resistor, connect them to my variable voltage supply then turn down the voltage until they were off. Then I would set the circuit's minimum voltage to be a little less.

I'm not sure what you mean by "connect them to my variable voltage supply" ?? I have them hooked up as shown in the schematic...just the greens ones dont dim off when the dimmer is at its minimum

You can reduce the value of the 620 ohm resistor like this:

so basically i just change this resistor until they dim off??
 
Yes, change the resistor until the LEDs are dimmed enough.

Are you connecting LEDs in parallel? You shouldn't because then they would have different brighness levels as your display shows. Also, with LEDs in parallel then they share the current and are half as bright as they should be. Do it this way:
 

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audioguru said:
Yes, change the resistor until the LEDs are dimmed enough.

Are you connecting LEDs in parallel? You shouldn't because then they would have different brighness levels as your display shows. Also, with LEDs in parallel then they share the current and are half as bright as they should be. Do it this way:

yes...that is how i have them...sorry maybe i'm using the wrong phrasing when i said paralleled series....is that not what this arrangement would be called? But yes its strange that these ones behave this way...some are brighter than others...only on the green leds are doing this...the white and oranges are fine...all the same brightness. :?
 
yup the 560 resistors did the trick...not sure why why the green leds have variation in brightness??...oh well...i can live with it..its only when they are very dim.

Here's a shot of the guts, need to tidy up the wiring a bit on the inside, slap the etched glass on front and back, then she's a done deal...woohoo!!


Thanks again for all the help...much appreciated. :D Final assembled pics to follow soon....

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Nice going, its done! :lol:
Some of the green LEDs were made on a warm Friday afternoon and the others were made on a freezing Monday morning. They are all different, unless you purchase "batched" ones from Agilent at Digikey. :lol:
 

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...the final assembled lamp :D

Thanks again for all the help...wouldnt have been possible without it.

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