Greetings all profound and sagacious makers and users of CS,
LAMPS
Reading the posts leads me to believe that people are having a hard
time finding 0.40 ma. lamps (bulbs). All 0.40ma lamps are rated for 28.8
volt use. The best places to look for them are places that have 28 volt
systems. Electronic stores carry stuff for electronic circuits which are
usually 6 or 12 volt. Since we want 28 volt things we should look at
places using 28 volts. Users of 28 volt systems are airplanes, boats,
big rig trucks (18 wheelers),telephone equipment. Try going to the
little airfields, marinas,truck stops,and telephone suppliers. I live in
a small town and even the little auto parts store had big truck bulbs.
Here is a list of lamp numbers to ask about, of the maintenance shop
people(airfields,marinas,truck stops), if they have them.
All these lamps are rated 28 volt (28.8) at 0.04 A (40ma) and most
are bulb type
T1 3/4 (thats the shape of the glass bulb). If not, I will indicate
the bulb type .
# Base Bulb
28PSB5 slide T2
85 wedge
327 mig.flange
334 mig.screw
385 mig.flange
387 mig.flange
388 mig.groved
1764 wires
1819 min.bayonet T3 1/4
2187 wires
7327 bi-pin
7387 bi-pin
7632 bi-pin
8623 thr.knurled T1 1/4
8627 wires T1 1/4
Hope this will help a little bit with finding lamps.
Quite a few of these are military lamps also, so ask your friends at
the mil. bases.
BATTERIES
A lot of you use batteries for making your CS, so a short
presentation on batteries might be helpful.
To facilitate this end, some data is needed first, so let me make a
list of small battery and small lamp data to start with.
NEMA # Eveready # Design ma/hrs Energy in A/HR
1.5 VOLT D CELLS
13F 950 2...@360hr 7.2 A/H
13C 1150 [email protected] 5.925
13D 1250 6...@139hr 8.34
9 VOLT MINI BATTERIES
1611 206 1...@40hr 0.48 A/H
1600 226 1...@61hr 0.732
1603 276 2...@350hr 7.00
1604 216 9...@50hr 0.45
9 VOLT MINI ALKALINE
1604A 522 1...@33hr 0.594 A/H
SMALL LAMPS (FLASHLIGHT),Current Densities
TWO CELL
PR 2 2.4V 0.5A 80% of 3V
PR 4 2.3V 0.27A 76% of 3V
PR 6 2.5V 0.3A 83% of 3V
K 2 2.4V 0.7A 80% of 3V Quartz filament
THREE CELL
PR 3 3.6V 0.5A 80% of 4.5V
PR 7 3.7V 0.3A 82% of 4.4V
K 3 3.6V 0.75A 80% of 4.5V Quartz filament
FOUR CELL
PR 12 5.95V 0.5A 99% of 6V
PR 13 4.75V 0.5A 80% of 6V
FIVE CELL
PR 18 7.2V 0.55A 96% of 7.5V
As we can see some of the small lamps were designed to be used at the
rated battery voltage and some were designed to be used at 80% of the
battery voltage. This has to do with current density of the filament
material. Most of these lamps are carbon filaments and the K lamps are
fused quartz glass filaments (with metal atoms added to the glass).
Every material that conducts electricity has a current density limit, as
the current increases the material heats up until it can not handle any
more current with out vaporizing (burns out). Some of the lamps were
operated close to their current density limits so as to be as bright as
possible. The problem with that was they had short life spans before
burn out. By derating by 80% they were as bright but would last a long
time. With a fresh battery they were brighter for a short time and as
the battery voltage dropped they were as bright as the lamps operating
at max current density. Please note that the normal currents for the
carbon filaments is about 0.3 to 0.5 Amps (300ma to 500ma). The quartz
lamps will operate at filament temperatures as high 2000f Degrees and
the glass bulb will get up to 300 to 500 degrees. Thats why its
important not to touch the glass with your fingers, also skin oils will
set up a thermal stress in the glass and it may break. Note that the
quartz lamps have high currents ( 0.7A ,700ma) because the glass
filaments will with stand a higher temperature than the carbon filaments
with out vaporizing. Of course this high current means that the
batteries won`t last long. When camping I take a flashlight with a
quartz lamp if searching for someone and a long lasting flashlight with
derated carbon lamps for general tasks and trail walking.
Lets look at the battery data and see what we can learn from it.
Batteries are designed to give a certain current at a given number of
hours. This data is used by engineers when selecting batteries for their
pet projects and designs. The battery manufacturer prepares the chemical
mixture in the battery to meet the design requirement. Of course a
battery will produce more current for a short time (a short circuit or
over load) but the chemical reaction can not keep up and the battery
will go dead in short order. If the battery is left alone for awhile it
seems to rejuvenate itself and will work for a short time again.
However, again, that old current density thing pops up because the
current density of the chemical mixture in the battery was exceded and
the mixture changed its composition,rendering it less able to produce
electricity. We see that the #276 9 volt battery has the capability of
providing 7 A/H of energy , but only at 20ma over a 350 hour time
period. If energy is removed at a higher rate battery life will be
shortened and you will not get 7 A/H of energy out of it. Now pretend
your in the store and see the high priced alkaline battery (# 522) next
to the lower priced zinc-carbon (# 276)battery. Think your getting your
monies worth? Look at the energy available ,0.594 A/H as compared to 7
A/H,almost thirteen times more energy if you buy the # 276 battery. So
what good is an alkaline battery for anyway? The alkaline battery is
engineered to provide a constant steady voltage over its life time.
Really nessesary for some electronic machines like tape recorders,CD
players ,pocket computer games, etc. Its a trade off of stable voltage
versus energy content.
Looking at the D cells its pretty obvious the # 1150 is the only one
you would want in a flashlight, and even it is being overloaded unless
you use a PR 6 or PR 7 lamp. With the other lamps you use it for short
times with rest periods for the chemical mixture to recover. With the 9
volt batteries the # 276 is the choice if your going up to 20ma or over
on current. Even if your a low current person the # 276 would be your
best buy energy wise. Watch out for the cheapy and special sale
batteries, look at the number and see what your getting.
Enjoy making your CS. If this was a boring post at least you had
something to read at 3am if you couldn`t sleep-ha.
Bless you all Bob Lee
--
oozing on the muggy shore of the gulf coast
[email protected]
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