Posted by
Dale Callaham on
URL: http://confocal-microscopy-list.275.s1.nabble.com/LEDs-tp4288043p4291056.html
Hi Caroline,
I just have some ideas. The 2 sources I will give you for UV-LEDs are
surplus sources so their stock changes, but the parts they show today
are cheap enough that you can experiment with it. These links may wrap
so copy and paste the full URL into your browser...
http://www.allelectronics.com/make-a-store/category/340075/LEDs/5mm-Ultraviolet/1.htmlhttp://www.goldmine-elec-products.com/products.asp?dept=1239I would stick to 20mA current (control it, see below) unless you know
other specs. These devices will have a nominal operation current and an
"absolute max" dc current at which point you risk toasting the small
wires inside the device. Buy some visible high output LEDs to experiment
with.... and remember that the UV from these can damage your eye same as
from any other UV source.
LEDs can have different emission patterns and to avoid optics in
addition to the LED you want to find one with a 15 to 30 degree pattern
from the molded LED lens. The one from All Electronics specifies, the
other doesn't. Buying prime LEDs from a regular distributor will always
give you more specs, possibly reliability and consistency, but will cost
more.
A couple of points. LEDs are listed with a Forward Voltage at a
particular forward current : something like Vf = 3.6V @ 20mA (just an
example!). The Forward voltage is NOT something you control - it is a
function of the chip construction/composition; you want either provide a
regulated current (from a "current source" or current regulated power
supply, or ASSUME that Vf value in your circuit and calculate
appropriate resistance in the circuit so that the applied voltage will
deliver that current and no more.
LEDs can be wired in series, adding up all the Vf voltages and choosing
a power supply that will allow for current control or addition of a
current stabilizing "ballast resistor" in series with the LEDs.
If you get into higher power devices there are some interesting devices
that seems like it might be useful to homebrew construction:
The BuckPuck is a simple controller that allows for dimming (output
current control...):
http://ledsupply.com/led-drivers.phphttp://www.leddynamics.com/LuxDrive/datasheets/3021-BuckPuck.pdfI have no connection with these companies.
Dale Callaham
Caroline Bass wrote:
> Since we are on the topic, are there any easy and relatively easy way
> to adapt a stereomicroscope with LEDs? I’d like a dissecting microscope
> to visualize GFP.
>
> Thanks!
>
> Caroline