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PL-7W Camping lantern

PL-7W Camping lantern

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This is one of the later fluorescent camping lanterns. Takes 4x R20 cells, as usual, the real power into the ballast is about 2.3W, so the lamp get about 2W, of pulsed DC current (so actually ~57% of full power for single polarity).
But what surprised me a bit in a good way is the cathode side filament is actually heated from the ballast, and the voltages are designed so, it does not start before the filament heats up.
The consequence is, when the batteries get weaker, the OCV reduces, so the cathode has to heat up to higher temperature. And with too weak batteries, it does not ignite the discharge at all.
That behavior should ensure, the lamp either ignites with properly heated cathode, or (below 4.5V) does not ignite at all - so no cold cathode operation at all...
That is quite promising for the lamp life expectations (it shouldn't get killed by a weak battery so easily).
The power quite well matches the used battery size - with 2hour/ignition it should last about 11 hours of burn time with R20 (regular carbon-Zinc), about 20 hours on LR20 (alkalines).
But the mechanical construction is rather flimsy (switch - sliding contacts on PCB copper without any reinforcement, battery contacts just some flat steel bands, all the contacts do not look that much reliable)

Johnlite.JPG Energizer.jpg PocketF4T5BLB.jpg CampingLantern.jpg

Light Information

Light Information

Manufacturer:Unknown
Lamp
Lamp Type:PL-7W
Shape/Finish:T4 U-bent
Fixture
Ballast Type:Rapid start, rectifying lamp inverter
Electrical
Wattage:2.3W
Voltage:6V nominal; that means 4.5..6V ignition, steady operation down to 3V
Optical
Color Temperature:Daylight
Physical/Production
Factory Location:China?
Application/Use:Camping (outdoor) lantern

File information

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Filename:CampingLantern.jpg
Album name:Medved / Battery powered
Keywords:Lanterns
File Size:409 KB
Date added:Jan 11, 2015
Dimensions:2050 x 1596 pixels
Displayed:178 times
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SuperSix
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ATL P42STUFF supersix94
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Jan 11, 2015 at 01:27 PM Author: SuperSix
I'm surprised! Looks like a pretty good quality lantern. Most of the ones I've seen have been lamp killers!

Atlas Lamps - Seeing Is Believing!

http://www.youtube.com/user/P42STUFF

Medved
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Jan 11, 2015 at 01:43 PM Author: Medved
Just a note: On the top right you may see different sections of a DC discharge:
Cathode glow, dark band and anode column, they are quite well visible there...

@SuperSix: Electrically yes, but the mechanical design could be better (you may see even the groove from the switch contact spring, I doubt the copper will last there...). It is rather shame, it won't cost that much more...
But I haven't seen that many battery lanterns, probably this still belongs to the better ones...

No more selfballasted c***

themaritimegirl
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Florence


themaritimegirl themaritimegirl themaritimegirl
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Jan 11, 2015 at 01:48 PM Author: themaritimegirl
Surprising and remarkable ballast design for a modern-day unit. I assume the cathode is heated via a low-voltage winding on the transformer?

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SuperSix
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ATL P42STUFF supersix94
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Jan 11, 2015 at 01:53 PM Author: SuperSix
Yes, I can see the dark space quite well in the photo.

Most of the battery lanterns I've seen are quite flimsy in design, but the circuits are usually pretty poor too.

What's the trimpot for that I can see on the board?

Atlas Lamps - Seeing Is Believing!

http://www.youtube.com/user/P42STUFF

Medved
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Jan 11, 2015 at 01:54 PM Author: Medved
@TheMaritimeMan:
Yes. As you may expect from me, the schematic is already drawn on a piece of paper and components measured as far as the circuit allows. Just now I'm trying to figure out, how to redraw the schematic to a more presentable form, to be posted here...

@SuperSix:
Adjusting the desired power level, as this circuit is quite sensitive to transistor parameters and these tend vary quite a lot over the production.

No more selfballasted c***

Medved
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Jan 11, 2015 at 05:12 PM Author: Medved
As promised, the reverse engineered schematic is published here...

No more selfballasted c***

rjluna2
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Robert


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Jan 11, 2015 at 06:03 PM Author: rjluna2
I see that you used the term R20 for size "D" battery.

http://en.wikipedia.org/wiki/D_battery

Yes, the pot is used to adjust due to the hfe variation of the silicon die of the transistor.

Pretty, please no more Chinese failure.

Medved
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Jan 26, 2015 at 03:36 PM Author: Medved
By the way I just have tried to insert there a regular PL-7W (/830 color) tube in order to check, how difficult would be to find a replacement tube. I was expecting the regular tube would have very low efficacy, as the reduced power won't warm it up to the temperature the PL's normally operate (the U-tubes are sold for about double or triple the price of the regular PL tubes, so I have expected those being optimized for the battery lantern use, so with colder operation at the fraction of the rated power).
Well, when tested with a CdS on an Ohm meter, the standard tube gives off about 30% more light, a difference just corresponding to the rare earth vs halophosphate phosphor chemistry. So no difference in the discharge UV output efficiency...
Interestingly, the new Philips start way faster, it even prematurely cold starts. But as the filament heats up really quickly even with flat batteries, so I'm not that much worried about the lamp, mainly if it is practically one of the most common lamp type, nothing special...
I will now look for some /840 or /865, that color would suit such lantern better...

No more selfballasted c***

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