I suspect my Q8 doesn't output all 5000 lumens - Fixed

[Pete7874]

@ImA4Wheelr

Unfortunately the pics in this thread are temporarily down.

It’s due to the whole photobucket fiasco.

If you are using Firefox browser, just install the “Photobucket Hotlink Fix” add-on and you will be able to see the images.

https://addons.mozilla.org/en-US/firefox/addon/photobucket-fix/

[ImA4Wheelr]

^

Awesome. Thanks Pete7874

[Sidney_Stratton]

So I’m testing thermal stepdown. I may have found the problem. At the 1 min 30 sec mark the light stepped down. 29.2º to 34.6º C (∆ 1.4º) with a slight drain of 0.1 volts.
So I must have screwed up the thermal configuration in Narsil settings. I hadn’t noticed the stepdown when testing outside against the building some 20 meters (≈ 30 yds). I’m sure I had it configured correctly as the program confirmed with 2 blinks. Would have the tailcap quarter turned for some extended period (say a week) reset to a default 90 sec timer? Or maybe I entered 1 click too early when disabling the blinky mode?

This stepdown would be the most probable cause of my primary query “I suspect my Q8 doesn’t output all 5000 lumens”

[Sidney_Stratton]

ImA4Wheelr:

This thread shows how to build an external shunt to that you can measure high levels of current using the voltage reading on you DMM.

I’ve built shunts for my power supplies. Using Simpson’s Moving Magnet. Don’t recall their F.S. (Full Scale) Voltage but quite low. However, I was passing some 20 volts across the shunt as a threshold to calibrate the meter. Wonder if such could give reliable results at say 3 volts?
At the lower end the shunt behaves erratically as any and all small discrepancy in contact resistance skews the readings.

[contactcr]

@Zulumoose

There are apparently various light measuring apps for cell phones, which, although likely fairly inaccurate, would still be perfect for comparative testing.
When used with ceiling bounce it could give you at least an objective measure of comparison to your other lights, and a way to check how much your meter setup is affecting output, and whether any changes you make are having a beneficial effect.

DO THIS.

Read Me on how to set up:
https://github.com/zakwilson/ceilingbounce/blob/master/README.md

Main site:
https://github.com/zakwilson/ceilingbounce

Top off batteries and calibrate it with your 1200lm light (especially if it’s a constant current driver).

Costs you nothing and now you have a setup that (in my experience) is surprisingly close to much more expensive measuring equipment.

[Sidney_Stratton]

And as I explored the low level, I exasperated the results with a multimeter current test. Boy did I skew off the handle.

Was quite convinced something folly.

Thank you all, and for your patience.

[Sidney_Stratton]

contactor

Your link to a ‘work in progress’ will be tried out. Great opportunity to try something from GitHub.

Thanks!

[WalkIntoTheLight]

Use the Narsil cheat-sheet, and perform a factory reset of your light. It sounds like you’ve messed it up. The default settings are a 3-minute timed step-down for thermal protection. Measure your brightness within 3 minutes.

[ImA4Wheelr]

@Sidney Stratton

ImA4Wheelr:

This thread shows how to build an external shunt to that you can measure high levels of current using the voltage reading on you DMM.

I’ve built shunts for my power supplies. Using Simpson’s Moving Magnet. Don’t recall their F.S. (Full Scale) Voltage but quite low. However, I was passing some 20 volts across the shunt as a threshold to calibrate the meter. Wonder if such could give reliable results at say 3 volts? At the lower end the shunt behaves erratically as any and all small discrepancy in contact resistance skews the readings.

I wish I knew the answer to your question. If you trust your 5 amp power supply's meter, I would think that you could use it to calibrate an external shunt to a reasonable degree of accuracy. Obviously, it would be better to calibrate the shunt at a current and voltage closer to what you want to measure, but we all have to make due with what we have.

To get consistent readings, I like to use bare wire (no insulation with a fan blowing air across the shunt to keep it as close to room temperature as possible.