[PSUBS-MAILIST] PWM LED driver for Cliff's enclosure

Sat Apr 22 10:50:22 EDT 2017

I have not ever wanted to dim my light, perhaps I have not been in the right environment.  I am not sure that should be a concern, I mean to keep it simple.Hank 

    On Saturday, April 22, 2017 7:32 AM, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 I'm still planning on making a second set of lights and so will machine the enclosure. My first set is 5K, but the next one is 10K. Now having said that I already have the driver for it, but am happy to test the proposed one. Ah, and my existing driver lacks dimming so this would also be a plus.
Best,
Alec
On Sat, Apr 22, 2017 at 8:29 AM, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

River, thanks for picking up the ball on the LED driver PCB for the Psub 10k light.  I support everthing you have said but do agree with Alan on the supply voltage range.  A lot of the PSub community use a 36VDC main bus to drive the Minn Kota 101's for thursters.  The expected voltage range for three 12V batteries in series is on the order of 30-40 volts so 36V max on the LT3478 is not going to work.  See specification of this supply voltage in the 10K LED project speciation page I sent you.  Also, you will need to change the pin out in the Psub spec. as well as the part number for the Subconn connector to be able to have diming via a 0-5 VDC analog control signal.
For simplicity and KISS, I think we should abandon the optional side mount on the enclosure drawings I developed and just focus on the rear entry for the bulkhead connector.  Due to the delay in getting a viable driver for the 10K LED project, a lot of folks have gone their own way on external lights.  We are going to have to get someone that still needs external lights to machine the prototype enclosure.   I am willing to test the prototype light in my test chamber.

Cliff
On Sat, Apr 22, 2017 at 12:03 AM, River Dolfi via Personal_Submersibles <personal_submersibles at psubs. org> wrote:

Hey everyone,
I've managed to convince a professor at the University to let me tackle developing a high power LED driver for psubs purposes for a grade. I'm just curious which features everyone would like in an LED driver. I am designing a driver for the Bridgelux Vero 29 LED array and will hopefully package it into a form factor so that all of the electronics fit into the enclosures Cliff designed and presented at the last convention. 

So far I plan on using a small microcontroller (probably an ATTiny for those who are interested) to generate a PWM signal that will switch a MOSFET, to control the amount of power delivered from an off the shelf constant current LED driver chip. The chip I found, the LT3478, seems to be ideal for PSUBS purposes, as it contains it's own converter that will accepts anything between 5 and 36 volts. 

I'm also probably going to incorporate a temperature sensor that will shut the light down if it gets too hot (running the light for too long out of the water) and killing the electronics/melting the lens. The microcontroller will accept a 0-5 volt analog signal from either a potentiometer or a PLC in order to convert that to a PWM signall to dim the lights.

Are there any major features that I'm missing? It seems that PWM dimming and application specific temperature control are the big ones. Curious to get input from those that are running LED rigs right now.

-- 
-River J. Dolfi
412-997-2526rdolfi7 at gmail.comrwd5301@psu.edu
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