Dimmers for marine lighting

[Randy McHugh]

I was checking out lighting controls and dimmers for lights and was amazed
at the cost of them. I want to design my own to do the things I want, as
well as controlling my powerheads, pump, float control and options for Kalk
dosing, and autofeeding. I think designing a microcontroller system to
control these would be fairly easy. Instead of paying $3,000.00 for
seperate items, I could probably build them all in one box for $300.00.
My problem is, do the dimmers for florescents just flicker the bulbs from
on to off (after the ballast) at a given frequency to give the "appearance"
of lower light. I believe they do but I need confirmation. If so it should
be easy to do.
Also, if I do design this, would any of you be interested in the plans. I,
of course, won't be held liable for anyone KILLING themselves and I would
have to check with my lawyer to make sure I can't be held liable. If all
goes well there may be some pis_ed off companies that sell these products.
Oh well, I never said I was well liked :-)

[Shawn Turner]

Randy McHugh wrote
<snip>

>My problem is, do the dimmers for florescents just flicker the bulbs from
>on to off (after the ballast) at a given frequency to give the "appearance"
>of lower light. I believe they do but I need confirmation. If so it should
>be easy to do.

Uh, no.

Trying to dim a standard ballast is Dangerous (fire
hazard) and Fruitless (the ballast will not like the dim-
ming apparatus and will either self destruct or
destroy the dimmer---Fire hazard.)

A dimming flourescent ballast is a special type of
ballast. It is Not a standard ballast that has had a
diac-triac-potentiometer lamp dimmer added to it.

It is possible to make a dimming ballast yourself.
I recommend against trying to.
I have not looked at www.irf.com for a year or so
but they had some design info. (International
Rectifier) www.sylvania.com news:sci.engr.lighting
www.teccor.com are also interesting
I'd suggest buying the ballasts at your local building
supply store.

Everything else seems feasible.

Anyhow, wouldn't metal halide be a better choice
for a marine setup? (the ballasts for metal halide
use the same principles as the flourescents)
Now that would be a truely interesting project:
a dimming ballast for metal halide--or any other
type of HID lamp.

Shawn T
my EAddr does not
contain animal noises.

[pti...@yahoo.com]

"Randy McHugh" <rmc...@opd.com> wrote:
> My problem is, do the dimmers for florescents just flicker the bulbs from
> on to off (after the ballast) at a given frequency to give the "appearance"
> of lower light. I believe they do but I need confirmation. If so it should
> be easy to do.

Nope, is it not a PWM type system or a TRIAC based dimming scheme like you
have for normal incandescent dimmers.

Instead dimming of fluorescent lamps is done by reducing the current going
through the lamps to reduce the light but also maintaining full (or something
close to it) heating power to the cathodes (on each end of the lamp that are
used to preheat and start the lamps) to keep the lamp from extinguishing
itself under these low current levels.

Dimming electronic fluorescent ballasts are fairly easy to find now and not
very expensive. You can often control them via a control line which typically
is you provide 0-10V dc on the control line to set the level of dimming. Seems
like it would be easier for your project to just buy the dimming ballast and
simply provide for the control signal from you "control" box.

Patrick Timlin --- http://www.geocities.com/CapeCanaveral/4742/
pti...@yahoo.com

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[Randy McHugh]

Thanks for the information, you are right, controlling the dimmer from a
black box would be easier.