Wow, this is great! Eager to see some fluorescence data from the brighter led. If you get good fluorescence brightness, I can send you a 385 and or 365nm led to try too!

Hey Jeff, that sounds great, I'm waiting on some disposable UV cuvettes I ordered they should be in monday (I'm tired of cleaning the quartz one's!) If this works like I think it should, then I will go ahead and follow through with the cuvette holder I have been designing on my CAD program, it consists of a solid piece of high density non-compressible black foam.

One is designed for the UV LED and the other for the notch filter (when using a laser.)

Great, ping me when you have some fluorescence data and I'll dig it up!

I had to redesign a few aspects of this circuit, so I posted the new design pics. The LED was running too hot, even with the heat sink, so what I did was ran another 9v battery in series with the first one (which I should have done in the first place to increase current.) then upgraded the resistor to a 3W 1k ohm with an inrush current limiting capacitor at the load terminal.

Now she's running right, still a little warm but that's expected, I got her just under peak voltage at: 3.4v with 200Ma continuos for 2 minutes.

Correction to previous post: I said "in series to increase current." oops, I meant in parallel to increase current. Sorry. Typing too fast.

Here is a breadboard schematic of the circuit;

NOTE* This is a corrected schematic, the previous schematic shows the red lead comming from the anode side of the POT going to the Vin+ pin of the LED driver, that is incorrect, it goes two pins over to the anode pin LED Vout+

Here is my updated LED driver circuit, which can now run any high powered LED up to 3 watts @ 5vdc.

Some specs on the new upgrade:

Prolight 1W driver circuit apr6

5 pf 3Kv inrush current limiting capacitor Buckpuck LED driver (350mA) NPN (TIP31) Power transistor (40V 3A 20W) PWR supply 9v battery 3.4v 200mA at LED

Here is the schematic for the LED driver circuit if anyone is interested.

This is Rev 2.0

I'm posting REV 3.0 because I am incorporating bourns POT which will control the main voltage, while I can utilize the trimmer POT to adjust the voltage by the hundreth's of a volt. Very cool and it works!!

Hi, Dave - i'd love to work with you to design an experiment for comparison of 405nm laser, 405nm LED, and maybe 385nm and 365nm LEDs, with a known simple fluorescence test. Would you be interested in doing that? We could do everything exactly as done in the OTK beta tests, with mineral oil and acrylic cuvettes, but change only the light source. That way we'd only change one variable at a time. Interested? I could send you the LEDs then.

hey Jeff, that sounds like a great plan!

Great, Dave - can you send your address to jeff@publiclab.org so I can mail the LEDs to you?

I was thinking we'd want to be really rigorous and consistent on the setup:

• 4 light types (3 LEDs and 1 laser) in exactly the same positions
• mineral oil negative control
• one sample of motor oil
• a calibration reference

We'd want to be really careful to not change anything except the light type. Does this sound like a good setup? Anything else you can think of to document or standardize to get a clear result?

After this initial test, we could try measuring a motor oil and a diluted crude oil sample, side by side. But let's separate out these tests, and examine one thing at a time, narrowly and well-controlled.

Hey jeff, ok, on the calibration reference, what do you want it to be, an empty cuvette, so we can get a baseline on all 4 light sources?

What do you think of just mineral oil?

That sounds good, will use the mineral oil as our control sample.

very excited!