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

Sat Apr 22 16:40:34 EDT 2017

On the dimming subject again,
I mentioned previously that on the data sheet I posted a link to
http://www.farnell.com/datasheets/2160797.pdf?_ga=1.31757435.455949694.1492842236
it has a PWM dimming control circuit.
This circuit goes on your output lead to the LED & has 3 components, you can
add a capacitor if you feel it's needed. I believe it could be retro fitted to The
driver units Alec bought. I will give it a go some time.
Alan

Sent from my iPad

> On 23/04/2017, at 8:19 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> River,
> with regard to dimming, I think it's a good option. Below are comments
> on a dive light manufacturers web site...
> For primary lights, the more power the better, but since bright lights can cause a white-out like having your brights on in the fog, they should have the vast majority of their output in the center beam. This is doubly true for night diving in poor visibility water where higher power can reduce your visibility.
>    Another comment I saw was that for close up photography you may need to
> back off the power.
>    I am going to use an identical light as my navigation & surface spot lights, so with
> PWM I can set the light output low for them & have the option of interchanging 
> drivers & lights. Also maybe thermal control of the light would be set up on the pwm circuit. The dimming function in this instance would be important on any lights
> that are out of the water as they heat up really fast. It may be that from experience
> you learn to set these above water lights at a certain intensity on the pwm dimming
> that they can handle.
> Alan
> 
> 
> 
> Sent from my iPad
> 
>> On 23/04/2017, at 12:29 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
>>> 
>>> 412-997-2526
>>> rdolfi7 at gmail.com
>>> rwd5301 at psu.edu
>>> 
>>> _______________________________________________
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>>> Personal_Submersibles at psubs.org
>>> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>> 
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