I am performing an imaging experiment in which LED stability is critical. I use 2-3 red LEDs to illuminate a surface while imaging that surface. In each LED circuit, I use a constant-voltage laboratory power supply (typically 11 V / 0.05-0.10 A) and a buckpuck LED driver to achieve constant current. The buckpuck's output current is adjustable using a 5k potentiometer between the REF and CTRL pins (higher resistance = higher current output = brighter LED). The circuit diagram is illustrated below.
The LED itself is attached to a heat sink to avoid overheating. Despite this, I am still having issues with LED instability. Does anybody have any suggestions to make the LED brightness more stable?
Here are the specific components I am using:
- Power Supply: TENMA 72-7245 Dual Output Power Supply
- LED Driver: LuxDrive 1000mA Buckpuck 3021-D-E-1000
- LED: Osram LRW5SN Platinum Dragon Red 625nm LED
- Potentiometer: Bourns 3590 Precision Potentiometer, 5k 2W 10-turn linear wirewound
Any help is much appreciated! Thank you.
EDIT: Thank you for the feedback so far. Ideally, I would like to avoid large changes to the circuit design if at all possible. Given that, would the following things help reduce high-frequency noise at all?
- Grounding. I'm not really sure how to properly ground this circuit, or if it needs it.
- Decoupling capacitors. Could a capacitor between Vin +/-, LED +/-, or CTRL/REF reduce high frequency fluctuations?