Need help with light

All about lighting. LED, CFL, Halogen, Other? Questions and info about lighting go here.

Need help with light

Postby anvit2a » 24 Jul 2011, 13:49

Hi

I have been looking alot around to deside what kind of light i'm going to use for my scanner... I have concluded like 4 crees will do the job. They will be so called cool white or natural white which should be the best? there is also the warm white version but that will give me not "clear white" pages so to say right?

I'm trying to figure out what i need to make the light and make the brightness adjustable...

I saw this:
viewtopic.php?f=1&t=706&hilit=cree&start=70#p9672

and this video posted here:
viewtopic.php?f=1&t=706&hilit=cree&start=70#p9687

That i think will work fine for me.. But i really need to ask what i need to do. I will need a buckpack, 4 crees and? What about powersource and all that? I have tried finding solutions on the forum but can't seem to find the complete answer. Maybe it is too much i ask to what exactly to do and buy to get the lightning working? I just want this to be perfect the first time... i don't mind a bit of work just that it will be working really good when done.

Hope you all have a great summer

Best regards
Anders
anvit2a
 

Re: Need help with light

Postby jck57 » 24 Jul 2011, 22:08

anvit2a wrote:Hi

I have been looking alot around to deside what kind of light i'm going to use for my scanner... I have concluded like 4 crees will do the job. They will be so called cool white or natural white which should be the best? there is also the warm white version but that will give me not "clear white" pages so to say right?

I'm trying to figure out what i need to make the light and make the brightness adjustable...

I saw this:
viewtopic.php?f=1&t=706&hilit=cree&start=70#p9672

and this video posted here:
viewtopic.php?f=1&t=706&hilit=cree&start=70#p9687

That i think will work fine for me.. But i really need to ask what i need to do. I will need a buckpack, 4 crees and? What about powersource and all that? I have tried finding solutions on the forum but can't seem to find the complete answer. Maybe it is too much i ask to what exactly to do and buy to get the lightning working? I just want this to be perfect the first time... i don't mind a bit of work just that it will be working really good when done.

Hope you all have a great summer

Best regards
Anders


I recommend going to LED Supply website:
http://www.ledsupply.com/buckpuck.php
Click on BuckPuck Documentation to download the .pdf file. This file graphically illustrates applications and options. You can even buy a kit already set up with a pot to adjust dimming. For a power source you will need a 24vdc power supply of at least 1.0 amp output.
jck57
 
Posts: 353
Joined: 23 Nov 2009, 15:21

Re: Need help with light

Postby tosborn » 25 Jul 2011, 00:22

How did you come up with 24vdc? A Cree Q5 at 1000ma has a forward voltage of 3.7 volts. So 4 Q5's would require 14.8 volts, plus 2 volts for the buckpuck, would equal 16.8 volts. So wouldn't an 18vdc source be plenty?
tosborn
 
Posts: 12
Joined: 29 Mar 2011, 18:49

Re: Need help with light

Postby jck57 » 25 Jul 2011, 09:43

tosborn wrote:How did you come up with 24vdc? A Cree Q5 at 1000ma has a forward voltage of 3.7 volts. So 4 Q5's would require 14.8 volts, plus 2 volts for the buckpuck, would equal 16.8 volts. So wouldn't an 18vdc source be plenty?


I already had the 24vdc supply and I read somewhere in the forums somebody else was using 24v. Going back to find the voltage references I read where Ryan used 4 Q5 Crees powered by a 15vdc supply. I don't understand the theory enough to know what if any differences in light output or problems could arise from using a wide range of voltages. 24v worked fine for me. I used a fixed 800 ohm resistor for dimming. Thanks for the correction.
jck57
 
Posts: 353
Joined: 23 Nov 2009, 15:21

Re: Need help with light

Postby daniel_reetz » 25 Jul 2011, 10:46

Anything above that threshold should be OK. The buckpuck will "buck" the voltage/current down to where it needs to be, so going higher (up to 32V, IIRC) is not a problem, but being at or below the threshold you calculated could potentially cause a problem.
User avatar
daniel_reetz
 
Posts: 2738
Joined: 03 Jun 2009, 13:56

Re: Need help with light

Postby anvit2a » 25 Jul 2011, 16:32

Okay thanks alot of the replies. But i still need some advices :D

I have been looking on these leds which seems to be used alot with these book scanners ?
http://www.ebay.co.uk/itm/Cree-XP-G-R5- ... 4a9c297c00

I'm not yet sure how many i would need... I accually think 3 would be more than enought, but i'm not sure yet.
So i then need a power supply and a "buckpuck" or socalled LED driver right?
It needs to be 700 or 1000 mA ?
And also how many Watts?

If i calc with 3 leds it get that is: 3 * ( 1A * 3,7V) = 11,1 W

I will thne need the LED driver and i really would like to be able to adjust the light. How do i do that then?
I found this led driver;
http://cgi.ebay.com/3w-LED-Driver-MBI66 ... 519a335e33
It is 3w and 700mA.


I was thinking maybe powering everything by a computer power supply also described in the topic:
viewtopic.php?f=1&t=1101

it should be possible to do outputs of 12V, 5V and 3.3V from a power supply.
Any chance i can connect the led driver to the 12V and then put in 3 LEDs?

Thanks for all the help!

Anders
anvit2a
 

Re: Need help with light

Postby Ryan_phx » 25 Jul 2011, 23:36

In my build thread, I've got a picture of my wired light rig. It might help you visualize the setup. I used (at Daniel's suggestion) an old laptop power supply. Really all you have to do is cut off the end where it plugged into the computer. You can also see that there's a switch between the power supply and the BuckPuck. Sorry I can't be more helpful right now, but I'm moving across the country in a few days, and all my stuff is packed.
Ryan_phx
 
Posts: 63
Joined: 29 Dec 2010, 14:51
Location: Sandusky, OH

Re: Need help with light

Postby daniel_reetz » 26 Jul 2011, 12:03

Hey Anders, yes RyanPHX is right.

Generally:
3 LEDs should be enough. The Crees are as good as any. They are what I use.
A used laptop power supply in the 19-24 volt range is a good option. Whatever wattage you calculate, double it for safety.
There are a few different kinds of BuckPuck drivers. You can choose one that is adjustable with a potentiometer.
User avatar
daniel_reetz
 
Posts: 2738
Joined: 03 Jun 2009, 13:56

Re: Need help with light

Postby anvit2a » 29 Jul 2011, 15:18

I'm planning to make a few power supplys for a few diffrent things for my bookscanner.
I need to make at least these;

* Power supply for 3x LED lights, with one "brightness controller"
* Power supply for 2x Canon PowerShot A495 (3V 1,5A ?)
* Power supply for 2x 4.3" LCD screens (12V, maybe 1A ?)
* Power supply 4,5 V and 1A for trigger?

I'm not sure if i need more but i really want this project to learn me how to make and understand a bit more about these things. I wanna do it this way because everything can be power into the circuits by the same DC. I'm planning to use a computer power supply. most of the power supplys should be adjustable with a potentiometer.

The first and maybe the most difficult thing is the LED power supply/driver.
I will be using these leds; Cree XP-G R5 Cool White
It is a 3W led with Min. lumens 139 @ 350mA and a max drive current of 1500mA or a bit more like this:

Forward voltage (@ 350 mA) V   3.0
Forward voltage (@ 700 mA) V   3.2
Forward voltage (@ 1000 mA) V   3.3
MAX 3.75

The max voltage is then 3,7V and the led might be driven at 1000mA.

For this i have been looking at the data from LM317 at page 22;
http://www.national.com/ds/LM/LM117.pdf

And also this "guide"; http://www.instructables.com/id/RGB-Col ... %2b-Spot-/

I really need to get around this and figure out what to order so i won't order anything i don't need (this project has to be as cheap as possible )

If i look at the datasheet at page 22 i have a current limited 6V charger.
I have calculated that R1 (resistor 240 in datasheet) could be 240Ω. (calculated with http://www.reuk.co.uk/LM317-Voltage-Calculator.htm)
and R2 (resistor 1.1K in datasheet) should be 2064Ω which means a potentiometer with 2k Ω.
But how do i fix the current? in the datasheet it is the 100 resistor, 2N2222 and 1* ? I should adjust to 1000mA ? This part i cannot seem to find a way to calculate... (It is not possible to make this adjustable very easy and cheap?) or maybe i should not even adjust the current? This is where i am right now ... i really want to be able to make this so i can adjust the brightness of the leds. I just want to understand the datasheet perfectly to be able to adjust to my own purpose.



and also the princip for Power supply for 2x Canon PowerShot A495 (3V 1,5A). I want to make this part adjustable too. atleast at the voltage. Maybe it is not needed to be able to adjust the current? then i maybe should just use the simple adjustable regulator from page 1 in the datasheet? if i can understand this part i should be able to do the rest myself i think.

another question... what is best to be able to "slowly" adjust the voltage(/brightness?) with a potentiometer? I mean should i use like a R1 at 240Ω and R2 (potentiometer) at 2k Ω? Or is it better with higher values like R1 = 1200Ω and R2 = 10kΩ
Have i got any chance to foresee what the best solution is?


Really hoping someone on here can help me out. I can see there had been used the LM317 for another power supply for cameras with "dummy" battery.

All the best !
Anders
anvit2a
 

Re: Need help with light

Postby anvit2a » 03 Aug 2011, 05:03

What do i want to be able to adjust?

Current or voltage? or both?
anvit2a
 

Next

Return to Lighting

Who is online

Users browsing this forum: No registered users and 1 guest