High CRI LEDs?

[Blarg King]

For all this effort you might consider just using an incandescent light source.

I want it to be able to run off a battery for a decent amount of time.

 

[FireMyLaser]

You can use a switch-mode voltage buck driver to adjust intensity without great heat loss or strobe artifacts. There are many kinds on ebay, but you'll have to solder on your own potentiometers to set the min and max limit.
For a common LED strip for example, you'll need a range of approx 9-12V for 0 to 100% intensity. You can use an old laptop power brick for the power supply (it needs to be over 12v DC).

 

[Spectre Gadget]

PWM might drive up the complexity and cost, especially if you're in a DIY mood. What about simply installing switches that turn off/on individual rows in your light? That way you can adjust the brightness and distribution of light however you want.

As far as power goes, you only need a 12VDC 'wall wart' power supply. I did my kitchen over/under cabinet lighting this way. The strips have a resistor per every 3 or so LEDs to regulate the current for you.

For the battery power... Try an 11.1 VDC LiPo battery after you get the wall power to work. This way you can take a current reading to determine how many mAh you need (capacity).

mA * (hours run time) = mAh of battery capacity

 

[Blarg King]

PWM might drive up the complexity and cost, especially if you're in a DIY mood. What about simply installing switches that turn off/on individual rows in your light?

Yeah I'm avoiding PWM because of complexity and flicker. Having switchable rows might not be a bad idea.

As for power, I have a ton of old 12 volt laptop supplies laying around that I can use for mains power and for battery power I was thinking of using some of those big LiPo packs they use for RC planes as they're inexpensive, have impressive power density, and can handle whatever current I need to pull out of them.

 

[Benm]

I've done a write up on a linear regulator here:

Merghart.com - Opamp based adjustable current source

You can put a LED strip in place of the laser diode and adjust components to meet your needs. If you want to run a lot of leds you should use a different output transistor or mosfet to handle the load. You could use something like a TIP142 darlington power transistor so you can drive 10 amps if you want to.

At such currents you'll need a low-value high current sense resistor. It might be more practical to use 'standard' 1 ohm resistors, 10 or 20 in paralel, for such high output currents... I'm not sure how many leds will fit in your lightbox, but 5 meters of the stuff can draw several amps easily.

 

[Spectre Gadget]

As for power, I have a ton of old 12 volt laptop supplies laying around that I can use for mains power and for battery power I was thinking of using some of those big LiPo packs they use for RC planes as they're inexpensive, have impressive power density, and can handle whatever current I need to pull out of them.

That will work too... nice and cheap! But like Ben said: these things can rack up current quick!

Whatever you do... post some pics when you get it going. We love to see how things come together here!!!

 

[Blarg King]

Im not sure of the timeframe. Im waiting for student loans and stuff to go through before I invest in this project so it might be a few weeks.

I appreciate the schematics but honestly its going a bit over my head. My electronics skills have mostly been small simple projects using basic parts. I'm not really familiar with all the diodes and reference voltages and transistors. Any way of dumbing it down for a electronics newb like me?

 

[Benm]

First thing about the circuit: It's not expensive, even if i source all components locally with the TIP142 high current transistor instead of the BD139 parts costs is under $5.

You can build the circuit exactly as is, only substituting the TIP142 for the BD139 transistor.

For R4: you can put 1 ohm, 1 watt (film, not wrie wound!) resistor there to get a maximum output of 1.2 amps or so. Put 2 in paralel to get 2.4, three for 3.6 amps and so on if your leds require it.

The CA3140 opamp comes in a 8 pin, full sized package and can be readily soldered into common experimenting circuit board. Just get the 'PDIP' sized part, not the 'SOIC'. The latter is the same chip in a smaller surface mount package not really suitable for novice solderers.

 

[WizardG]

For high CRI LEDs I like Bridgelux.

Bridgelux, Inc. LED Lighting