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Use of flash in regards to vibration
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mawyatt



Joined: 22 Aug 2013
Posts: 2035
Location: Clearwater

PostPosted: Thu Jan 03, 2019 12:11 pm    Post subject: Reply with quote

iconoclastica wrote:
With what frequency can you fire these speedlights without them overheating?


Felix,

Think this has a lot to do with the speed light, power output and batteries. I had a YN622 melt the plastic lens and the batteries (Enloops) got so hot you couldn't hold them.

Lou's use of an external battery helps in two ways, one is the larger battery capacity and the other is removing a major source of heat from the speed light.

Best,
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mawyatt



Joined: 22 Aug 2013
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Location: Clearwater

PostPosted: Thu Jan 03, 2019 12:20 pm    Post subject: Reply with quote

iconoclastica wrote:
Quote:
Even with the external battery pack, you still have to deal with batteries


This one is easily overcome by soldering an external power supply to the battery connectors. I have a 5.8V 3W leftover PS connected to a unit with the flashtube wired outside the unit. Can't test the heat though, for the recharging time is about 10seconds and there's no manual power setting possible.

At least it needs a faster supply.


Please consider that the speed light draws a very large initial current from the batteries to recharge the energy storage capacitors, and a separate power supply would need to be able to supply this large current or you'll experience very long refresh times like you've seen.

If you are going to all the trouble to configure a separate high power power supply, why not just use a strobe since a separate power supply kind of negates the speed light advantages of small size and portability.

Speedlights nor strobes were never designed for the abuse we put them thru with our stacking macro use, and both actually do well considering. As mentioned I've had speed lights melt but also strobes actually explode Shocked during long stacking sessions, had 3 Neewer do this!!

For my studio use the strobes I've found (Adorama Studio 300 or Godox SK300II) have worked flawlessly under this abuse, so I can't complain.

Best,
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iconoclastica



Joined: 25 Jun 2016
Posts: 215
Location: Wageningen, Gelderland

PostPosted: Thu Jan 03, 2019 12:35 pm    Post subject: Reply with quote

Quote:
why not just use a strobe since a separate power supply kind of negates the speed light advantages of small size and portability[/code]


There's two arguments for that, both non-technical:
    - The speedlight + PS was made from scrap parts, whereas the strobe I was looking at just now costs 780 pounds;
    - I work in studio only, so size and portability are - for me - not prime considerations.

Am I mistaken to think that a 15W PS would charge the speedlight 5x faster than the present 3W PS?
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mawyatt



Joined: 22 Aug 2013
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PostPosted: Thu Jan 03, 2019 1:17 pm    Post subject: Reply with quote

iconoclastica wrote:
Quote:
why not just use a strobe since a separate power supply kind of negates the speed light advantages of small size and portability[/code]


There's two arguments for that, both non-technical:
    - The speedlight + PS was made from scrap parts, whereas the strobe I was looking at just now costs 780 pounds;
    - I work in studio only, so size and portability are - for me - not prime considerations.

Am I mistaken to think that a 15W PS would charge the speedlight 5x faster than the present 3W PS?


The strobes I mentioned are about $109 US. The Adorama and Godox are the same I believe (I only have the Adorama), but the Adorama comes with a Bowens mount reflector, whereas the Godox does not (requires a separate purchase).

I recall that the initial current draw for a quality speed light can exceed 10 amps from the batteries. To be safe I would think a power supply would need to be able to supply this peak current for maybe ~1 second, then slowly taper off.

If you consider the energy supplied by the flash as FE, the battery voltage VB, the battery current I and the overall average recharge efficiency as Eff (energy out/energy in), then a very crude estimate of the recharge time is:

Time to recharge = FE/(VB*I*Eff)

So for FE =60WS, V =6 volts, I = 10 amps, Eff = 25%

Time = 60/(6*10*0.25) or 4 seconds.

Of course this assumes full 60WS recharge, battery with no internal resistance (no voltage drop), constant 10 amp recharge current and 25% overall efficiency.

First off the current isn't constant (probably a tapering off exponential decay), the battery has a internal resistance or voltage drop and so on. So a very very crude estimate indeed, but an estimate nonetheless.

Best,
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iconoclastica



Joined: 25 Jun 2016
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Location: Wageningen, Gelderland

PostPosted: Thu Jan 03, 2019 2:32 pm    Post subject: Reply with quote

Ah, I see. One of those times that the translation of the English got me Crying or Very sad

Thanks for the calculations. Sofar, I see no smoke coming out, which is always a good sign, but before upscaling I'll find someting to limit the current.
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dy5



Joined: 07 Feb 2010
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Location: College Park, MD

PostPosted: Thu Jan 03, 2019 4:28 pm    Post subject: Reply with quote

Looking around for information on flash durations relative to power, these two articles were among the most useful.

One showing how strobes and speed lights differ.

Another with some very interesting test data.
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mawyatt



Joined: 22 Aug 2013
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PostPosted: Fri Jan 04, 2019 7:59 pm    Post subject: Reply with quote

I just borrowed a LeCroy Oscilloscope and made some quick strobe/speedlight measurements. I'll post these on a different thread so as not to clutter up this thread.

Best,
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iconoclastica



Joined: 25 Jun 2016
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PostPosted: Fri Jan 11, 2019 1:52 pm    Post subject: Reply with quote

Today I took one of my Metz Mecablitzes 48 apart for conversion. This one had its lcd display obscured and unreadable, and the hinge pin of the battery compartment door broken. With Metzes, the hinge pins always break, it seems. I had seen earlier that there are no wires from the battery compartment to the electronics, instead the lips of the batter contacts are soldered directly onto the pcb and well hidden by that same pcb. So, no easy bypass was possible to make an external power socket.

Instead I tried to fit pseudo-batteries, but their negative end are not smooth metal but open, and at the first try what remained of the battery door's hinge and lock broke of, rendering the door now completely useless. Then I tried spades onto the first and last battery contact. Bending the contacts upward, one broke off, so there was nothing to it than completely removing the battery compartment forever and solder my wires to the pcb instead. Metz are not sturdy built flashes.

Now I have the contact wires coming through the battery compartment door, now permanently taped into position. The wires are connected to a 6V 12Ah sealed lead acid battery. The recharge is so fast that I even can't see the ready-indicator flicker, even after multple full outputs. I will have to watch the temperature now.

Batteries of this type can be left to the charger continuously. In fact, this setup is mobile too, but when going into the field, I think I'd prefer a battery with less capacity than 12 Ah (=1900 gram).

I think I would like a modelling light too. I am thinking of a led that swings away like the top part of a condenser. And a trigger-splitter, to flash in silent mode.
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Saul



Joined: 31 Jan 2011
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PostPosted: Fri Jan 11, 2019 2:50 pm    Post subject: Reply with quote

iconoclastica wrote:
...The wires are connected to a 6V 12Ah sealed lead acid battery. The recharge is so fast that I even can't see the ready-indicator flicker, even after multple full outputs. I will have to watch the temperature now.

Batteries of this type can be left to the charger continuously. In fact, this setup is mobile too, but when going into the field, I think I'd prefer a battery with less capacity than 12 Ah (=1900 gram).

I think I would like a modelling light too. I am thinking of a led that swings away like the top part of a condenser. And a trigger-splitter, to flash in silent mode.


For the field setup before I used this, now - this. Same effect, smaller size, fits to the pocket

For the studio setup - 6v switching power supply
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iconoclastica



Joined: 25 Jun 2016
Posts: 215
Location: Wageningen, Gelderland

PostPosted: Sat Jan 12, 2019 11:34 am    Post subject: Reply with quote

Yes, that's the same idea. I made identical battery dummies some time ago, possibly after seeing your picture. I don't recall what it was I would make them for, only that it didn't work that well in that project. It's a non-destructive approach that I much prefer and would have followed, if only I had not been so quick to break parts off Embarassed

Today I moved to the second Metz, or the first one got stuck into its mode and without display I couldn't make out what it thought it was doing, nor change it. Got worse while trying to fix it, so at the second attempt I used battery dummies. Need to find a way to keep them more firmly in place though.

Modern rechargeables ae much more weight efficient, but in my experience don't equal lead in reliabilty and longevity. But there's many a way to Rome.
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