Some VERY interesting LED modules

[noel shelley]

On noel shelley Said:

[…] One thought is to use the heatsink membrane between the LED unit and heatsink. […]

I have never understood why, Noel … but please note that the use of such membranes is explicitly rejected in the data-sheet.

MichaelG.

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Ref. [repeated for convenience]
https://docs.rs-online.com/3995/0900766b8161ece2.pdf

 

[Michael Gilligan]

On Michael Gilligan Said:

 

 

EUREKA !

THE APPLICATION NOTE :

**LINK**

https://www.mouser.jp/pdfdocs/PLWS3000-Series-Orion-Beam-Forming-Module-Application-Note.pdf

MichaelG.

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Edit: __ It’s well-presented, and very informative.

Edited By Michael Gilligan on 17/01/2023 07:56:16

Quoted wiith apologies to Les & Robert for my not having properly studied this ^^^

RTFM would seem to be the order of the day !

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

I have never understood why, Noel … but please note that the use of such membranes is explicitly rejected in the data-sheet

MY ERROR ^^^ 

It is Thermal Pastes that are explicitly rejected

MichaelG.

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[noel shelleyParticipant @noelshelley55608]

Thank you Michael, It was because I had studied the data sheets that I am intent on using membrane rather than the paste I have tubes of ! The machined faces of both the heatsink and the LED unit are a very close fit but in an effort to avoid the risk of my lovely LEDs producing strange smelling smoke I would rather be safe. The 3 holding screws will ensure a good contact but a small dob in the middle would do little harm – the risk of paste creep is in the context of a LARGE DOB I fancy ? Time will tell. Noel.

PS what is RTFM ?

[Michael GilliganParticipant @michaelgilligan61133]

Read The Flippin Manual

🙂

MichaelG.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

I used one for a stroboscope with good results. It was a one-off application so I just lashed up a circuit.

Due to low duty cycle minimal heatsinking was required.

Robert.

Could you provide more detail please Robert?  I’ve been dithering about using one or more of these lights in an attempt to improve on my early high-speed photographic experiments, for which a high speed flash is needed.

I used a camera, flash, Arduino, and microphone to catch events like this airgun pellet destroying some water filled plastic tumblers – can you see the pellet:

Here’s the setup:

Operation: The room is darkened.  Starting the Arduino opens the camera’s shutter in ‘B’ mode.   Firing the pistol is picked up by a microphone connected to the Arduino, which having heard the pistol fires the flash, closes the shutter and puts the lights back on.  The exact timing can be varied by the Arduino, and with luck and judgement the flash catches the event at the right moment.

The method is limited mainly by the flash unit.  The photo flash unit I used controls brightness by reducing the time power is applied to it’s Xenon tube: from memory a few milliseconds.  Faster the better, but a bigger problem is the reduced light output from the flash makes it difficult to get good photos.   I need a faster, brighter flash.  The problem shows up attempting to photograph bursting balloons – the bits fly just too far too quickly for my apparatus:

Plessey’s application note suggests their device could be pulsed fast and maybe with way over-the-top amps.   The app note quotes 400A for 8 to 20uS, though that may be the thyristors not the LEDs!   However, as it’s heat that destroys devices, might work.  I wonder how hard the LEDs could be driven by one very short high amperage pulse and live to do it again!

From your stroboscope experience are these LEDs an viable alternative to a Xenon flash?  And what sort of power supply would I need – I’m thinking fat capacitor with a fast switching transistor, but that feels too simple.  Grateful for anything else that might help, even if it’s bad news like that won’t work!

Ta,

Dave

 

[Michael GilliganParticipant @michaelgilligan61133]

This may be of general interest:

https://www.qats.com/cms/wp-content/uploads/2013/09/Qpedia_Jan08_Cooling-High-Power-LEDs.pdf

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Did some swotting on my ‘would Michael’s LEDs make a good photoflash’ question and the answer is discouraging.   Not only do LEDs need to be kept cool – heatsinking is important – but they are rapidly damaged by not much excess current, causing their ability to produce light to drop.    Not good, because I need a lot of light, ideally many times to keep the cost down.

Many devices can be overloaded savagely provided it’s only done in short bursts.   The early cavity magnetron used in WW2 radar sets was only good for a few hundred watts continuous.  Despite that, the radar output pulses measured in megawatts!  The trick was to allow enough time between high-power pulses for the device to cool down to a safe average temperature.   Operated that way, a 500W magnetron would pulse megawatts for a few hundred hours before trouble started.   They were regularly replaced during routine maintenance or immediately if the output started to drop.

Woe, woe and thrice woe from my point of view, LEDs aren’t suitable for this type of gross overload.

LED lighting has burgeoned in photography since I last looked, but mainly as a replacement for conventional lighting.  One reason is they run a lot cooler than filament lamps, another that LED light can be controlled artistically in various ways.   However, although LED photoflash units exist, Xenon tubes are way ahead of LEDs whenever a fast pulse of very bright light is needed.

Though not a contender for what I need because they take too long to ignite, looks like Magnesium flash bulbs have gone the way of the Dodo.

Back to the drawing board.   Unless someone knows different!

🙁

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Don’t despair, Dave … just avoid massive overloading

You will find that many applications [automotive, etc.] over-run LEDs in a rapidly pulsed mode.

Unfortunately however, the major benefit is the increased apparent brightness to the human eye, rather than the actual quantity of light emitted.

MichaelG.

[Mark EasingwoodParticipant @markeasingwood33578]

Dave, I have no knowledge of electronics, and can’t help with your LED’s, but I have had some experience with triggering off camera flashes.

I bought a trigger kit from Hi-Viz in the USA back in about 2011, then decided my soldering skills were not good enough so it was left on a shelf. Then about 6 year back I had a few days at home due to a work related left hand injury. I decided to solder some electronic items, including assembling the trigger device, as self prescribed hand physio, a bit of a challenge with bandaged fingers!

I then went on to build a triple solenoid water drop device and controller, drawn up in KiCad and built on strip board. I took some pictures using this equipment, but then it got packed away before I fully utilised it’s potential. I think I also had a reliability issue, bad connection, or my dodgy soldering.

I think the trigger unit has been upgraded since 2011. Lots of info on this site Hi-Viz. Either sound or movement can be used as a trigger.

Low output settings of 1/64th or 1/128th (if available) = shorter flash times, so multiple units on low power may be better than just one on a higher setting. The Inverse Square Law applies to lighting, so if you move the light closer to the subject you get a lot more light on the subject, but a lot less spread of light.

Flash Durations

The Nikon SB24/25/26 flash units have a stroboscopic setting built in, and although very old in photography terms, are good units if you can find them on ebay etc. They also have a choice of sockets for cable connections, unlike most modern flash units which only have the-hot shoe or wireless. A hot-shoe connection block, with jack plug socket should be available.

This is a useful (old) book if you have any of the above units.

The SB 26 and the LumoPro LP160 have a built in slave light, so can be easily triggered by any nearby flash, (others may be available). “Pocket Wizards” were the modern wireless way to trigger a flash unit or units, but other cheaper makes are now available, from Godox and others.

Using an Opto-Isolator to connect a non-genuine/unknown flash unit, is a good idea due to the high voltages used on some older flash units, which could fry the innards of your expensive digital camera, (mechanical cameras didn’t have delicate electronics to fry).

Flash Voltages

I have some PDF files of the above circuits, I can PM them if you are interested, although they are 6 years old, and some are copyrighted.

Mark.

[Author]

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