Luna Pro battery adapter $$$$

BrianShaw · Feb 10, 2014

Isn''t that basically how the Gossen adapter is constructed (option 3)? And how different is his device from Gossen's in terms of contact surfaces? Since that paper offers virtually every option available except legalizing and resuming production mercury cells... then what did you reject? I'm not challenging you; I'm truly confused.

BTW... I always thought spinning hte batteries in the TV remote had something to do with heat and/or assertion of human superiority and dominance over electronic devices.

miha · Feb 10, 2014

Tom1956 said:
This was one of the ideas I rejected. Introduced too many contact surfaces and does nothing for the voltage output curve problem. The current draw of the meter is so low that extra contact surfaces introduced an intermittency problem. Think of the AAA's in your TV remote. How many times have you bought new batteries only to discover all you had to do was take thm off and wipe them off, or even revolve them in their compartment with your thumb? All this gimmick does ia suck the contents out of an egg and replacing them with something else so it would still look like an egg.
To sum up the problem the best course of action outside of regulation is to proceed with your favorite idea and test and/or replace the silver batteries regularly with a digital voltmeter, before your reach the end of the curve plateau. BTW--Family Dollar is now selling 357 silvers a lot cheaper than the drug stores or Wallyworld.

I purchased his adapter in February 2009 for my Leicaflex. And to be frank I think the camera's meter still runs on the very first battery. I might have changed it once in five years but I really can't say for sure.

From the link:

Only Silver-oxide cells can be used because they have a
constant output voltage like mercury cells.

E. von Hoegh · Feb 10, 2014

Tom1956 said:
At that time I never knew of this board or what I was to later learn from my exposure to you folks. But allow me to once again give honorable mention to E von Hoegh's wein and Nikkormat idea about leaving air holes covered. Because I do know that if if duty time capacity of the battery per meter-reading meets his standard on a Nikkormat, then certainly it will work on the Luna Pro with its lower corrent draw. Though I cannot speak for its voltage curve.
Besides it is moot anyway because the inventor this little regulator only had several prototypes made before dropping the project due to marriage, and asked me to not pass on his name. Even sent me a photo of him and his bride. I remember it being a case of love is surely blind. But my best to him.

Indeed it does. For going on three years... that's right, the cell I put in the 'mat was still good the last I used the camera's meter about two months ago. I put the cell in in April 2011, with three of the four holes covered. I use standard hearing aid cells. If and when the mercury cells in the Gossen ever die, I'll let you know how they work in a LunaSix.

E. von Hoegh · Feb 10, 2014

BrianShaw said:
... but since EvH died before the zinc-air cell was first produced, he should be credited with thinking of the idea first.

What do you mean, I died?

Tom1956 · Feb 10, 2014

Who am I to talk you out of being happy when you're happy? All in all the best idea for the average joe is to put 357's in there with a paper ring to fill out the diameter, and a little wad of aluminum foil on top of the sandwich before screwing on the cap, and re-rating your film speed for the higher voltage. But most importantly, keeping a vigilant check on your battery voltage with a DVM to avoid the slow falloff. Silvers are the closest to mercury on discharge curve, but still far from it. Past the 50% lifetime, you're playing with fire.

miha · Feb 10, 2014

His graph says otherwise. Can you share your reference with us?
http://shrani.si/f/2S/L0/25Af72bc/battery.png

BrianShaw · Feb 10, 2014

Tom - not intending to be pedantic, but... past 50% lifetime of a silver cell?? In the service life table presented in the aforementioned paper archived by Butkus the silver cell life ranged from 0 to .65, with the drop off starting at .5

That isn't 50% life when the voltage falloff starts..

If I read the table correctly it shows ZincAir to have a longer service life than silver, but a very similar voltage falloff. Am I not reading this table correctly?

Tom1956 · Feb 10, 2014

Brian. one of the things that I remember troubling me most in my research was the number of voltage curves that were in conflict with each other. It was mind boggling. Some made the silver to look like God's answer to mercury, and others were not so bright and cheery. So to be honest, I made my decision, perhaps completely arbitrary; to go with the battery manufacturer's own curve (posted somewhere above). The manufacturer's curve was almost disappointing. So I took this as their honesty, and ran with it. When a manufacturer paints a less rosy picture of their own product than all these other 3rd party curves, you (I) tend to admire and appreciate their frankness and take it to heart.

miha · Feb 10, 2014

A likely candidate for an adapter would be the one in the link: http://www.houseofbatteries.com/documents/357303H.pdf

Dan Fromm · Feb 10, 2014

E. von Hoegh said:
What do you mean, I died?

Kingslake says you died in 1915. See http://books.google.com/books?id=OJ...YQ6AEwAA#v=onepage&q="emil von hoegh"&f=false

You're a ghost, or perhaps a doornail that can type. Or an imposter. Since we're on the Internet, you could be a dog named after the man.

Chan Tran · Feb 10, 2014

My solution is simply not using any meter (or built in meter of a camera) that requires a precise voltage to work correctly. There are many meters that would read exactly the same for a range of battery voltage and simply quit working if the battery voltage is too low instead of giving a different reading.

Xmas · Feb 10, 2014

Tom1956 said:
Who am I to talk you out of being happy when you're happy? All in all the best idea for the average joe is to put 357's in there with a paper ring to fill out the diameter, and a little wad of aluminum foil on top of the sandwich before screwing on the cap, and re-rating your film speed for the higher voltage. But most importantly, keeping a vigilant check on your battery voltage with a DVM to avoid the slow falloff. Silvers are the closest to mercury on discharge curve, but still far from it. Past the 50% lifetime, you're playing with fire.

That is not recommendated merely web bullsh1t the galvanometer circuit is trimmed to be linear top and bottom of scale with a mercury cell of 1.3 volts with a cell of 1.5 volts it won't be linear.
You need two Shockety diodes or recalibration.

As well...

The voltage against life time of silver cells are dependent on current draw, duty cycle and cell type ie construction. The mercury cells we used in 75 for a high current would only give 1.3 volts with low current light duty, so the sag at 50% you quote for silver won't necessarily repeat at light duty low current... it is for a specific type and current draw, temperature etc.

Our application in 75 was different BTW AA batteries low duty high peaks switching mode voltage regulation, mercury cells we tested failed immediately...

The Schockey diode is ok with fresh batteries discard early cept if you are a pro with E6 and shoot every day - carry a back up meter and test voltage with resistor and multi meter.

Note the last (magnum) pro I asked did he not have a backup was not willing to answer... his lips moved...

Mercury cells were nearly as annoying during a shoot you pushed the rocker and got no reading when you illuminated the scale... was it too dark or had the cell failed or bad contact... you needed spare batteries and cotton handkerchief... or backup meter.

Tom1956 · Feb 10, 2014

Xmas said:
That is not recommendated merely web bullsh1t the galvanometer circuit is trimmed to be linear top and bottom of scale with a mercury cell of 1.3 volts with a cell of 1.5 volts it won't be linear.
You need two Shockety diodes or recalibration.

As well...

The voltage against life time of silver cells are dependent on current draw, duty cycle and cell type ie construction. The mercury cells we used in 75 for a high current would only give 1.3 volts with low current light duty, so the sag at 50% you quote for silver won't necessarily repeat at light duty low current... it is for a specific type and current draw, temperature etc.

Our application in 75 was different BTW AA batteries low duty high peaks switching mode voltage regulation, mercury cells we tested failed immediately...

The Schockey diode is ok with fresh batteries discard early cept if you are a pro with E6 and shoot every day - carry a back up meter and test voltage with resistor and multi meter.

Note the last (magnum) pro I asked did he not have a backup was not willing to answer... his lips moved...

Mercury cells were nearly as annoying during a shoot you pushed the rocker and got no reading when you illuminated the scale... was it too dark or had the cell failed or bad contact... you needed spare batteries and cotton handkerchief... or backup meter.

I read you post and agree with it. But then I did not have the APUG site and you smart people at the time to provide other alternatives. I proceeded with the info available and procured 2 copies of the prottpe regular and installed them into 2 luna-pros--mine and a buddy's. Both were successful and not 2 guys own voltage regulated luna pros. Truly voltage regulated, accurate to 1/3 stop.

pstake · Feb 10, 2014

Chan Tran said:
My solution is simply not using any meter (or built in meter of a camera) that requires a precise voltage to work correctly. There are many meters that would read exactly the same for a range of battery voltage and simply quit working if the battery voltage is too low instead of giving a different reading.

Ya but then we'd have nothing to talk about on this thread.

Plus, I really like using the Luna Pro. So simple and versatile and pocketable.

Tom1956 · Feb 10, 2014

pstake said:
Ya but then we'd have nothing to talk about on this thread.

Plus, I really like using the Luna Pro. So simple and versatile and pocketable.

Speaking as the authorative sounding thread hog, if I had the whole thing to do over, I'd have probably settled on EvH's Nikkormat trick, and rotated the batteries regularly so the bottom one didn't get air starved.

AgX · Feb 11, 2014

Shokety and Shockey diodes? The cause for the confusion:

There are Schottky diodes.

And there is a Shockley diode-equation

Xmas · Feb 11, 2014

AgX said:
Shokety and Shockey diodes? The cause for the confusion:

There are Schottky diodes.

And there is a Shockley diode-equation

Hi

Thanks for correction, alas spellun is not my forte, tend to lapse into phonetics, especially Ge derivations...

But I forgot to say if you fit two Schottky diodes and and two fresh silver calls to your Lunasix.

And slide the test switch across you should get shade over (past) good battery datum, in service it should drop to dead centre of datum and eventually drop considerable when exhausted, if is is off the test datum replace both the cells for paid work. This was necessary for mercury cells, as one would fail rather then two,... dont ask how I know this...

If you have a meter without a battery test voltage datum you will need a resistor and multimeter to test silver cells.

Noel

pstake · Feb 11, 2014

Xmas said:
Hi

Thanks for correction, alas spellun is not my forte, tend to lapse into phonetics, especially Ge derivations...

But I forgot to say if you fit two Schottky diodes and and two fresh silver calls to your Lunasix.

And slide the test switch across you should get shade over (past) good battery datum, in service it should drop to dead centre of datum and eventually drop considerable when exhausted, if is is off the test datum replace both the cells for paid work. This was necessary for mercury cells, as one would fail rather then two,... dont ask how I know this...

If you have a meter without a battery test voltage datum you will need a resistor and multimeter to test silver cells.

Noel

Is it possible to adapt a Luna Pro to be voltage independent? a la Chan Tran's comment.

This isn't exactly related to what you wrote, I don't think, but it seems like the kind of question you or AgX could answer.

AgX · Feb 11, 2014

Then one would need to install a (even small) circuit into the casing. However, opening that and alike Gossen meters may lead to damage of the foil cover of the underside. Basically this is a cosmetic issue, but should be taken into acount. (I once opened Profisix without any damage though.)

Xmas · Feb 11, 2014

pstake said:
Is it possible to adapt a Luna Pro to be voltage independent? a la Chan Tran's comment.

This isn't exactly related to what you wrote, I don't think, but it seems like the kind of question you or AgX could answer.

Yes

The simplest way for any light meter device is to buy one or two reworked cell cases (with diodes fitted), load (them) with silver cells and you are done AgX and I both posted a link to a source earlier.
Or print this PDF and get any wire person to make you several reworked casings.
As AgX suggests one needs to be careful with some meters to avoid cosmetic damage
Note some meters don't need adaption, eg spotmatics
But read the PDF carefully.

Noel

E. von Hoegh · Feb 11, 2014

Xmas said:
Hi

Thanks for correction, alas spellun is not my forte, tend to lapse into phonetics, especially Ge derivations...

But I forgot to say if you fit two Schottky diodes and and two fresh silver calls to your Lunasix.

And slide the test switch across you should get shade over (past) good battery datum, in service it should drop to dead centre of datum and eventually drop considerable when exhausted, if is is off the test datum replace both the cells for paid work. This was necessary for mercury cells, as one would fail rather then two,... dont ask how I know this...

If you have a meter without a battery test voltage datum you will need a resistor and multimeter to test silver cells.

Noel

Correct. Open circuit - that is no drain - voltage won't tell you enough - depending on the chemistry some cells will give their rated voltage even though the internal resistance has risen to the point where the cell won't deliver enough current (microamperes) to operate the meter properly. There is more than enough room in most meters to install a voltage regulating circuit, which must be arranged so there is no drain on the cell/battery when the meter is not in use.
I just use the air cells, there is no "air starvation" issue in my FTN finder so there won't be in a Gossen.

E. von Hoegh · Feb 11, 2014

Xmas said:
Yes

The simplest way for any light meter device is to buy one or two reworked cell cases (with diodes fitted), load (them) with silver cells and you are done AgX and I both posted a link to a source earlier.
Or print this PDF and get any wire person to make you several reworked casings.
As AgX suggests one needs to be careful with some meters to avoid cosmetic damage
Note some meters don't need adaption, eg spotmatics
But read the PDF carefully.

Noel

This is because they use one type or other of bridge circuit and are far less sensitive to the voltage supplied.

pstake · Feb 11, 2014

Xmas said:
Yes

The simplest way for any light meter device is to buy one or two reworked cell cases (with diodes fitted), load (them) with silver cells and you are done AgX and I both posted a link to a source earlier.

Noel

This is what I have. Mine has two diodes fitted by someone who knows about such things. It also has few other modifications to make it easier to read in low light (silver EV scale instead of black, in a black body, plain black outer ring on the dial to replace the original which cracked)

I was only wondering about the voltage-independence because of all the talk about silver-oxide batteries delivering lower voltage once drained to 65 percent. Seems like a circuit installed would render this moot.

But I'm leaving it alone until i start having problems, and then I'll consult someone wiser than myself or just buy new batteries.

BrianShaw · Feb 11, 2014

pstake said:
This is what I have. Mine has two diodes fitted by someone who knows about such things. It also has few other modifications to make it easier to read in low light (silver EV scale instead of black, in a black body, plain black outer ring on the dial to replace the original which cracked)

I was only wondering about the voltage-independence because of all the talk about silver-oxide batteries delivering lower voltage once drained to 65 percent. Seems like a circuit installed would render this moot.

But I'm leaving it alone until i start having problems, and then I'll consult someone wiser than myself or just buy new batteries.

After about a decade of using a Gossen adapter I have yet to experience a problem. I suppose if one is sufficiently concerned they can avoid the whole issue by getting a spotmatic, or selenium cell meter.

AgX · Feb 11, 2014

But the question remains:
Is there a practical alternative to "just" inserting a diode into the circuit as de Gruijter unfolds in his treatise?

A voltage regulator that nevertheless will work with those small differences in cell voltages?

Luna Pro battery adapter $$$$

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