Run-Time Plot - Mr Bulk's LGI

Run-Time Plot - Mr Bulk\'s LGI

This runtime plot is for a 3xAA Brinkmann Legend modified by Mr. Bulk with a direct drive LS. At the end of six hours it was still putting out enough light to see your feet with.

Eequipment used is a photocell and a Radio Shack 22-805 multimeter with a PC interface that is using ScopeView softwasre (v 1.08)

The vertical axis is in MA and the horizontal axis is 15 minutes per division.

Be aware that your actual battery milage may vary from that indicated by this tuntime plot.

Re: Run-Time Plot - Mr Bulk\'s LGI

Roy,

Have you tried it in NiMH?

Alan

Re: Run-Time Plot - Mr Bulk\'s LGI

Mr Bulk advises against useing anything other than alkaline batteries.

All my runtime plots are currently using Everactive Alkaline batteries. Li AA batteries will come later. I don't use rechargble batteries in my flashlights..they die too quickly and unexpectedly (my opinion only).

Re: Run-Time Plot - Mr Bulk\'s LGI

Cool! Kinda looks like a long, slowly decreasing wave (except for that dastardly drop right at 2 hours), but then after that it goes into a "dusk mode", a sufficiently bright output falling into the output range of most "regular" multi-Nichia lights such as the Opalec NewBeam (which produces 41 lux according to QuickBeam's charts at http://thelightsite.cruxial.com/reviews/lux_charts.htm ) for many additional hours.

Thanks Roy, for this most useful comparative resource.

Re: Run-Time Plot - Mr Bulk\'s LGI

Thanks Roy, for all the informative run-time plots you've done.

When I last asked Mr Bulk about rechargable batteries for the LGI, he said it's ok to use them if you give them time to cool off after a recharge.

Charlie,
Any comments?

Re: Run-Time Plot - Mr Bulk\'s LGI

Roy:

I'm confused by your graph. The average current for the first two hours is approximately 2.25 mA according to the graph or 4.50 mAh.

The capacity of an alkaline is supposed be 2900 mAh at low current and less at higher currents. Your graph therefore doesn't appear to be showing mislabeled Ah. On the other hand, the mAh drain over two hours would considerably exceed 4.50 mAh.

I don't quarrel with the slope of your curve (be it brightness, current, or voltage) but wonder what the horizontal axis measurement unit really is?

Re: Run-Time Plot - Mr Bulk\'s LGI

I'm not measuring the output of the battery, but am measuring the output of the photocell. The horizontal axis is TIME, in this case, 15 minutes per division. The vertical axis is the MA output of the photocell.

Re: Run-Time Plot - Mr Bulk\'s LGI

Originally posted by LedCrazd:
Thanks Roy, for all the informative run-time plots you've done.

When I last asked Mr Bulk about rechargable batteries for the LGI, he said it's ok to use them if you give them time to cool off after a recharge.

Charlie,
Any comments?

Click to expand...

<font size="2" face="Verdana, Arial">I almost always run NiMh's in my Brink 3AA. That's the reason I chose the 3AA body (3.6v)

I definitly let the batteries sit overnight (after being charged) before using them. They work great!!

Re: Run-Time Plot - Mr Bulk\'s LGI

LedCrazd,

What Slick said.

Re: Run-Time Plot - Mr Bulk\'s LGI

Roy:

Do you know if the current output of a photocell is directly proportional to the light input? I wonder if the current output is non-linear the same way that light output from filament or LED lights in non-linear to current.

Re: Run-Time Plot - Mr Bulk\'s LGI

Originally posted by lemlux:
Roy:

Do you know if the current output of a photocell is directly proportional to the light input? I wonder if the current output is non-linear the same way that light output from filament or LED lights in non-linear to current.

Click to expand...

<font size="2" face="Verdana, Arial">Let me answer this for Roy. A silicon solar cell [what is being used here as the sensor] without additional filtering responds to a range of wavelengths greater than that of the human eye. It also has relative sensitivity as a function of wavelength very different than the human eye and in fact is most sensitive in the infrared portion of the spectrum. Regarding linearity, if you do not change the relative mix of wavelengths of your measured radiation, then current output is very linear with the intensity of the incident radiation through at least several orders of magnitude. Since the spectrum of a white LED shifts only slightly with current and temperature, The Roy's graphs are likely a very good measure of the relative intensity vs time for the light being tested. Because different white LEDs can have significantly different spectra, absolute intensity comparisons between different LEDs using uncorrected silicon solar cells as a sensor will not be very accurate. Absolute intensity comparisons between LEDs and incandescent lamps will be wildly inaccurate. Relative intensity measurements of a given incandescent lamp as a function of battery discharge will also be meaningless because the spectrum of an incandescent shifts so much with voltage.

Re: Run-Time Plot - Mr Bulk\'s LGI

There is some relationship between light output of the LED and the current measured from the photocell, but I have no idea what it is. I should think that to make the correlation, you would need a NBS calibrated light source to measure. I seem to remember that back in the days of light meters and 35mm cameras, the cheaper light meters that used photocells, had logarithmic scales.

ADDED:

Doug S.....thanks for a good explanation. You got there as I as composing my reply!

Re: Run-Time Plot - Mr Bulk\'s LGI

Lambda's plots (and hopefully soon mine) will be corrected for spectral response as the digital meter with PC output (I ordered one from Web-Tronics.com last night) will be fed off the Meterman LM631 (this is what Lambda is doing).

The 631 is a true illuminance meter with spectral weighting filter. And if you measure lux at one meter that will provide candela.

I'm thinking of a black-flocked tube into which I can mount the meter at one end and the flashlight at the other. That will allow measurement of the peak portion of the beam and watch it decay...I wonder what the batttery life of the 631 and multimeter's batteries are???

Cheers,

Richard

Re: Run-Time Plot - Mr Bulk\'s LGI

Before I get beat to death over my inabality to accurately measure light, remember, I'm only measuring how long (TIME) a flashlight produces light!

I only have about $50.00 invested in my set-up! A $40.00 multimeter with a PC interface and a photocell from a $10 solar power demo kit! As much as I'd like to have a calibrated logging candlepower meter, my retirement check won't alow that and flashlights at the same time!

ADDED:

Right now I'm doing a runtime plot on an ARC AAA with a IR led....no visable light! Bet my photocell ain't gonna work to well on my UV AAA!

Re: Run-Time Plot - Mr Bulk\'s LGI

Originally posted by Roy:
Before I get beat to death over my inabality to accurately measure light, remember, I'm only measuring how long (TIME) a flashlight produces light! :ADDED:

Right now I'm doing a runtime plot on an ARC AAA with a IR led....no visable light! Bet my photocell ain't gonna work to well on my UV AAA!

Click to expand...

<font size="2" face="Verdana, Arial">Or more accurately stated, how long it produces what it produces. I predict that your IR ARC AAA will have a significantly higher mA reading than your white ARC AAA.

Re: Run-Time Plot - Mr Bulk\'s LGI

Doug S. Roy, and rlhess:

Thanks for your edifying discussion.

Re: Run-Time Plot - Mr Bulk\'s LGI

You're welcome!

Re: Run-Time Plot - Mr Bulk\'s LGI

Moved to reviews. Follow via the link up by your name.