My mother bought this at a supermarket. It's a "nightlight" that plugs
directly against a wall outlet.
It has no country markings, just "1W", "AC220", "50/60Hz and "CE".
The "CE" is probably bogus. It is probably of Chinese origin.
http://users.forthnet.gr/ath/jgal/nitelite1.jpg
I opened it and it contains a small low pressure mercury lamp, which
contains 3 electrodes on each end. I suspect the third electrode is an
auxiliary one, to initiate the discharge. You can discern the switch and the
integrated circuit which plugs directly on the wall outlet.
http://users.forthnet.gr/ath/jgal/nitelite2.jpg
It's also problematic: Although it starts nicely and its glow looks like
that of a miniature fluorescent the first 3-4 seconds, after 4-5 seconds,
the auxiliary electrodes kick in again and it produces a purple glow around
the electrodes which flickers on and off, similar to the starting argon glow
on the discharge tube of a high pressure lamp.
This leads me to believe that the circuitry is all faulty. It's probably
supposed to be cutting off the current to the auxiliary electrodes, but
instead the current through them continues, causing auxiliary discharges
which keep going and going, causing argon flicker.
Here's a picture of it being lit:
http://users.forthnet.gr/ath/jgal/nitelite3.jpg
The auxiliary discharges don't show on this pic.
I was wondering how safe this thingy is. My impression is that leaving this
thing unattended through the night, one risks the danger of fire. Opinions?
I received two e-mails from a Bart Lederman who says he can
read but not post to this group. He sent me some information
about this topic that I have appended below. Bert's e-mail
is lederman at pirulo dot zko dot dec dot com if you would
like to respond to him via e-mail. This is the second of his
two messages and contains all the technical info from the
first plus some additions.
Note that the diagrams will look very strange unless you use
a fixed width font.
***Begin included text***
I tried posting something from my new location, but in case
it doesn't get out to the community I'm taking the liberty
of sending you a copy. It has some changes from what I sent
you before, now that I've found some of my old materials.
Bart.
--------------------------------------------------
I sent some mail to Victor Roberts to pass on to the
group
yesterday, working from memory.
Last night I dug through my 'stuff' and found some
lamps,
one test jig, some notes, a catalog from 1988; but for some
reason, not the original spec. sheet with their circuit
diagrams. Since I'm also missing the BLB lamp, I'm sure I
still
have some more data somewhere and will keep looking for it.
What I have now indicates I need to update some of the
information I sent out yesterday.
Quite some time ago, JKL Lamps used to sell short cold
cathode lamps which look like the ones in the "Chinese
Nightlight" being discussed. They had one large electrode
at
each end, plus a smaller starter electrode at each end.
I believe they were intended to run on D.C. There were
several models, the smallest of which is about 65 mm long
overall and 6.5 mm in diameter (except for the 'black
light'
model which had a filter over it increasing it's diameter
to
9mm). Turn on voltage is rated at 340 V (not sure if that's
with or without the use of the starting electrode, but I
think
it's without). Maintaining voltage is 185 V, recommended
current is 4 mA, maximum current is 10 mA.
The circuit I have in my notes, which is also still
wired
up in a test jig is: [you will need a monospaced font like
Courier]
----------------------------
| | |
| ----------- | |
| | | | |
| | | | |
| / --- |
C1 | \ | | /
|| | / R1 | L | \
----||-----------| \ | A | / R2
|| | / | M | \
| \ | P | /
--- | | | \
/\ | | | |
120 / \ | | | |
VAX ---- | --- |
| | | | |
| | | ------
| | |
R3 | | |
--\/\/\/-------------------------------
This is very much like the diagram someone else posted,
except with a diode instead of an SCR. R1 and R2 are the
ballasts for the starter electrodes, and I have 47k
resistors
in my test jig. My notes show values up to 220k. R3 is 1500
ohms, and C1 is 1 microFarad (I'm using a non-polarized
film
capacitor). This arraingement works something like a
voltage
doubler, with the capacitor being chared on one half cycle,
and
then it's in series with the line voltage to trigger the
lamp.
With good quality components, it should run a long time.
I haven't spent much time looking at the other circuit
diagram to figure out what the SCR gains you.
It's also possible to run the lamp with only one
starter
electrode: both electrodes at the 'positive end' (on my
lamps,
that's where the evacuation tube is) are connected
together.
Ballast Starter
+
----/\/\/\/\/\/---------/\/\/\/\--
|| |
|| |
|| |
--- |
| | |
| L | |
| A | |
| M | |
| P | |
| | |
| | |
| | |
--- |
| | |
| ------------
|
|
---------------------
-
I did some experimentation and decided I could come up
with
something more efficient. So I did a variation on the
classic
"half wave" voltage doubler:
-----------------------------
| | || |
| | || |
--- | || |
/\ | || |
/ \ | + --- |
C1 ---- ----- | | /
|| | ----- | L | \
----||-----------| | C2 | A | / R1
|| | | | M | \
| | | P | /
--- | | | \
/\ | | | |
120 / \ | | | |
VAX ---- | --- |
| | | | |
| | | -------
| | |
| | |
---------------------------------------
The "trick" here is that while C2 has a relatively
large
value to smooth the output, C1 has a much smaller value
than
would normally be used in a power supply. Before the lamp
fires
the circuit will charge C2 up to 300 volts, which could be
enough to fire the lamps I was using without having to use
the
trigger electrode. After the lamp begins to conduct, C1
acts as
the ballast. I'm working from memory and some notes here,
and
haven't found this test jig yet (if I still have it), but I
think it was possible to eliminate R1 altogether. If not,
my
notes indicate that something like 220k should work. If I
can't find my old jig I may try rigging up a new one this
weekend.
With no resistors, there are no resistive losses
(except
for a little in the diodes, but that will be small), and
the
ballast is reactive. Power factor isn't going to be 1.0,
but
since most loads are inductive I don't think the power
company
will complain about a capacitive load (insert "smiley"
here).
As I recall, I used a 1 micro-Farad non-polarized film
capacitor for C1. I don't remember the value of C2, but it
shouldn't have to be too large (perhaps around 10
micro-Farads). It's mostly to reduce fliker.
Again, use good components and you shouldn't have to
worry
about the unit bursting into flames when unattended.
It's unfortunate that JKL stopped importing these
lamps,
but apparently there wasn't a demand for them in the 1980s.
I
think it's unfortunate because I can think of several
applications for a small flourescent lamp that can run
directly
off of 120 VAC using just diodes and capacitors (and maybe
a
resistor) and not requiring any transformers, coils, or
other
wound components, and no semiconductors other than diodes.
The
lamps were available in a number of colors (some just with
the
phosphor, some also had a colored envalope), and even a
'black
light' version. I could see quite a bit of use for a short
wave
germicidal lamp as well. I don't know if JKL would be
interested in re-introducing this product line, but it
might be
worth talking to them. Perhaps they still have the original
circuit diagrams if I can'f find my copy.
Bart.
*** End Included Text***
--
Vic Roberts
http://www.RobertsResearchInc.com
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