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Water documentary - building a bandpass filter for viewing fluorescein in plants?


I hope you can help me. I work for a film production company in London called Passion Planet and we are making a documentary series about water. We have a crew travelling to the Amazon rainforest, leaving this Monday 22nd October, and while we’re in the field we are hoping to film an experiment viewing fluorescein dye in a plant. 

I am trying to create a way to illuminate the plant. The excitation peak of the dye is 489 nm, The emission peak is 509 nm.  

So far I have found the following on the RS website: 

1. Blue LED e.g. Cree XPEBLU RS Stock No. (810-7064)   

2. LED driver e.g. Philips 17 W RS Stock No. (722-7902)  

I am hoping to connect the LEDs in series so that they are all powered by the same driver. But I can't see what connectors would be appropriate. Also, it doesn't look like RS stock a driver connector (something like this ?) Do I need one? 

Ideally we'd be able to illuminate the plant from several angles. 

Also, I'm looking to place the LEDs in a spot lens to help illumination but is it still possible to attach a heatsink? 

I don't have any store cupboard equipment so need to buy everything - any advice would be really appreciated. 

Thank you in anticipation, 

Catherine Watling 


October 17, 2018 13:50

Hello Catherine,

Exciting and interesting project, but I think your timescales may be just too tight.
Looking at the LED it is a SMD, so you need to provide the PCB to mount it on and the heat sinking. I could not find any self contained modules with this LED for simple use.
The LED has a forward voltage drop of 3.1V(@1A) so at 0.7A you need to design to get rid of approximately 2.2W. I haven't tried to size the heat sink but there is a detailed document

As for wiring the LEDs these are in series and at 3.1V/LED the driver should be able to drive 7 as it has up to 24.6V available but I haven't looked into temperature effects.

I don't think you need special connectors and think it is just free wires for in and out, but need RS to confirm that.

Looking for any suitable housed LED's as said I could not find any, but did find some laser modules which may be an alternative? These tend to come in a format that just needs bolting to a heatsink and use discrete wires so no PCB design, but you then need to look at the output optics, but perhaps just a fibre optic is all that is required?

I shall look again to see if I can find a housed LED, but hope the above may help or trigger some thoughts from others.

Just one other thought is could one of the compact spectrometers provide an alternative ready to use solution such as

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