Electronic Ballast for Fluorescent Light [Hack] ?

[C. Nick Kruzer]

I have two identical electronic ballasts that will each power a 20 Watt
tubular fluorescent light bulb.

Will the two 20W ballasts drive a single 40W tubular fluorescent light
bulb if the two ballasts are connected (parallel) to the 40 Watt
fluorescent bulb?

insula

(The 20W bulbs are removed from the two circuits before connecting the
ballast circuits to the 40W bulb.)

 

[Paul Carpenter]

In article <21601-4848AB73-1020@storefull-3256.bay.webtv.net>,
insula@webtv.net says...

I have two identical electronic ballasts that will each power a 20 Watt
tubular fluorescent light bulb.

Will the two 20W ballasts drive a single 40W tubular fluorescent light
bulb if the two ballasts are connected (parallel) to the 40 Watt
fluorescent bulb?

insula

(The 20W bulbs are removed from the two circuits before connecting the
ballast circuits to the 40W bulb.)

WHY?

Check what the electronic ballast says for its power ratings (of
tubes it can drive). Anyway the correct ballast will be peanuts in
cost, a whole new fitting would be cheap as well.

Leaving alone the synchronisation of the outputs of the ballasts, you
have fundamental problems.

Electronic Ballasts (normally with integral starters) provide a means
of getting the correct voltage for the LENGTH of the tube -the 40W
tube will be almost double the LENGTH of a 20W tube. Tube wattage is
proportional to the LENGTH of the tube. Compact fluorescent tubes
get higher wattage in smaller space by compacting the length using
bends and spirals.

Two 20W in parallel will give INCORRECT operating voltage.

Electronic Ballast/starters apply a lower voltage but higher current
through the slectrodes to HEAT the electrodes for 1 - 2 seconds to
enable the START of the plasma discharge with the HIGH strike volatge.
Typical start voltages are around 20-30V, strike voltages are 100V and
greater (says he having had voltage frequency burns from 600V 40KHz
strike voltages).

TWO 20W ballasts in parallel WILL shorten the life of the tube electrodes
by applying too much heating current, hence releasing mercury inside the
tube from the electrodes.

Similar voltages and issues are seen for LCD backlights (except LED
backlights).

--
Paul Carpenter | paul@pcserviceselectronics.co.uk
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[C. Nick Kruzer]

C. Nick Kruzer (me) asked:

drive a single
40W tubular fluorescent light bulb?

Petrus answered:

No...ballasts produce high frequency AC
voltage...not synchronized, they will blow...

Tom agrees and responds:

I wouldn't do that. The THD...could present a
dangerous situation.

Paul C. writes:

WHY?

I'm trying to save money on a set-up for growing plants indoors under
artificial light. I'm growing vegetables which requires a good amount
electricity (wattage) for light. Lights made for growing plants are
expensive, I think because farmers of illicit indoor marijuana gardens
use them. I'm looking for ways to cut costs. I'm sick and tired of
paying three dollars a pound for tomatoes at the supermarket. I live in
a city apartment and can't grow anything outdoors. No direct sunlight
from windows...have to use lamplight. I get a discount on electric
power. Even if I break even in costs with tomato prices in supermarket I
figure I'm ahead..I will also get the pleasure of watching plants grow,
will eat organic grown, will have fun putting the fixtures together and
will have a conversation piece for guests to admire...

The two 20 watt ballasts I have are from screw-in compact fluorescent
lights with the bulbs removed. I can get these for about a buck apiece.
I have already tried one to power a small, linear, tubular fluorescent
light bulb, and it works. I matched the wattage ratings of the
fluorescent grow bulb with the compact fixture wattage from label on
fixture package. I attached wires from ballast to pins on the
fluorescent light tube with molex type connectors salvaged from old junk
computer parts. They fit perfectly. I'm looking for ways to power larger
tubes, that's why I asked about the two 20W ballasts for a 40 Watt tube.

Check what the electronic ballast says for its
power ratings (of tubes it can drive). Anyway
the correct ballast will be peanuts in cost, a
whole new fitting would be cheap as well.

Looks like that's what I'll be doing.

Leaving alone the synchronisation of the
outputs of the ballasts, you have fundamental
problems.

I'm glad I asked. I knew the electronics involved high frequency, but
didn't know much about the technology and applications..

Tube wattage is proportional to the LENGTH of
the tube. Compact fluorescent tubes get higher
wattage in smaller space by compacting the
length using bends and spirals.

That's good to know. It makes sense to me knowing what I know about high
voltage.

Electronic Ballast/starters apply a lower voltage
but higher current through the slectrodes to
HEAT the electrodes for 1 - 2 seconds to
enable the START of the plasma discharge with
the HIGH strike volatge. Typical start voltages
are around 20-30V, strike voltages are 100V
and greater (says he having had voltage
frequency burns from 600V 40KHz strike
voltages).

That certainly would be the incorrect start voltage for the larger tube.

TWO 20W ballasts in parallel WILL shorten the
life of the tube electrodes by applying too much
heating current, hence releasing mercury inside
the tube from the electrodes.

Mercury!!...I don't want to become the "Mad Hatter"!

Such great answers to my question from everyone... You have my
gratitude.

Here is something I found when reading about using plant grow lights. It
is what initiated my inquiry, starting this thread. It involves rewiring
a two bulb fixture to run only one bulb, resulting in a greater
intensity of light. The author (Zink) advises that the "overdrive"
process shortens the life of the fluorescent tube. I found the
information while reading a Gardening forum.

http://community-2.webtv.net/crispmint/HomeGarden/page2.html

http://www.geocities.com/overdrive_lights/

insula