White light sources

The components for the light sources described in this section were bought with research funding awarded to P. J. Aphalo and built by P. J. Aphalo.

We have available for use for gas-exchange two custom made light sources assembled with high-power (10W) COB LEDs (type Optisolis NFCWL036B-V3, Nichia) with an emission spectrum very similar to that of the light sources in the chambers. (There is a difference in the contribution of the peaks at 405 nm and 425 nm.)

COB LED with reflector and diffuser

COB LED without reflector and diffuser

Sources for specific wavelengths

We are testing prototypes of three small LED luminaires emitting UV radiation at 365 nm and 385 nm (PowerBar V3 from Lumitronix, with 12 LEDs of types NVSU233B U365 and NVSU119C U385 from Nichia, respectively), and emitting FR light at 730 nm (Lumitronix PowerBar V3, using LEDs OSLON SSL 150 type GF CSHPM2.24-2T4T from Osram). The prototypes are one for each wavelength and if funding becomes available, more could be assembled.

UVA and FR sources PowerBar V3 modules

We have a large selection of single colour high power (3W) SMD LEDs spanning wavelengths from 365 nm to 940 nm (from various manufacturers including LED Engin, Epileds, Brightlux, and CREE). We also have modern high power SMD LEDs emitting at 280 nm, 305 nm, 325 nm, 340 nm (types DUV280-SD356L, DUV310-SD356L, DUV325-SD356L, DUV340-SD356L, Roithner-Laser, Vienna, Austria) and 345 nm (type MTSM340UV-F5120, MarkTech, USA).

High power UVA (325 nm) LED

Assortment of LEDs spanning wavelengths 275 nm to 940 nm.

We have LED arrays with multiple channels. We have used for many years (from before blue + red LED light sources became available from LI-COR) custom-built red-green-blue (RGB) light sources for gas-exchange measurements to study stomatal responses. Some were built from commercial RGB LED arrays (from Norlux, USA) and others from separate red, green and blue arrays to allow a choice of wavelengths. More recently, with progress in LED technology we have had custom arrays assembled in China according to our own design. We have five channel arrays (five wavelengths, 5 \(\times\) 10 W) and 12-channels arrays (12 \(\times\) 10 W).

Custom assembled LED array with 12 channels

Custom assembled LED array with 12 channels

A two-channel controller for these additional light sources, capable of both constant current dimming and pulsing is currently being assembled. It integrates loggers to record the current flowing through each channel. It can function either autonomously or tethered to a computer. Programming and data retrieval is done through USB or if connected through a YoctoHub through a network connection. Output current 0 to 1050 mA, output voltage 2 V to 48 V. Input voltage 9 V to 60 V DC, at least 4 V higher than output voltage. Efficiency up to 96%.

Intelligent LED controller (bare circuit)