Run a Lumen Subsea Light WITHOUT PWM?

Blue Robotics Products Lights
1

Hi!
I want to supply the LED of the “Lumen” directly, and not over the PWM-logic.
Does anybody know, how this could work?
Is there a circuit diagram of the internal board available?
Regards
Stefan

2

Found the “Lumen Schematic pdf”…
Thank You!

3

Hi Stefan,
The PWM logic runs on 3 to 48 volts so you can just tie the logic to the positive and the light will stay on.

1 Like
4

Hi gcelec, thank you for response,
Of course you’re right!
Anyway, I’ve only 2 wires down to my rov for lighting… no network, no battery, ect… → 2 wires only…

This is the reason, why I want to run the LED directly. Regulating the voltage should then dim the intensity of the light. I need to regulate the light for special environments - this is a must…

My question is - to bypass the PWM control - on which points would you connect the “plus” and “minus” in the pdf-schematic? LED+ and LED-? (right, top corner of page 1)

What is the maximum Voltage, I can supply the LED directly?
I would run them in water only - never in air…

I’m not an electronic engineer :-/ …sorry…

Thank You!
Stefan

5

As gcelec stated, the maximum voltage you can supply is 48V. Unfortunately, I don’t think you’re going to see a significant change in brightness by adjusting the overall input voltage to the light - the internal regulator means this difference is compensated for? With only 2 wires, you may need to add additional hardware on the subsea side to generate your pwm signal?

6

Thank You guys and a very happy and sucessful 2023!
I understand.
We’ll solder out the the 10uH coil before the “plus” and connect the “plus” directly.
Then we’re free from the PWM-Logic and can regulate the the voltage, with a direct influence in the brightness of the LED.
Thank You and anyway - GREAT PRODUCT…very, very well done!!
Stefan

7

Hi @Nubu,

The Lumen PCB includes a constant-current LED driver, along with some circuitry to ensure a stable signal, and a temperature sensor and corresponding code that reduces the output if the LED starts overheating. I wouldn’t recommend modifying the PCB to run without the built in protections, and doing so would be at your own risk.

The LED is receives its power from the LED+ and LED- connections, although the PCB supplies power to the LED via the SW pin of the A6211 chip.

While the Lumen PCB accepts up to a 48V input, the LED itself (as installed) is configured to run on a 6V supply.

That inductor helps to smooth the supply to the LED - I don’t expect there would be a significant benefit to removing it, and leaving it in may help reduce voltage spikes from your input PWM signal. Again though, you can do modifications if you want to, we just can’t guarantee they’ll work and that they won’t damage the product.