Cheap Fluorescent Dimming Ballast - The Planted Tank Forum
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post #1 of 18 (permalink) Old 01-28-2010, 10:54 PM Thread Starter
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Cheap Fluorescent Dimming Ballast

I just purchased an "Easylite" three-bulb fluorescent dimming ballast to play with.

It dims from 10-120%. The few bulbs it's specified to work with aren't much use to aquarists; but given the wide dimming range and other specs, it may actually work with a wide variety of bulbs.

At $20.50 shipped, I'm willing to experiment.

If anyone else feels like experimenting, there are more available. I'm not sure if links to a certain auction site are disallowed only on "Swap n Shop" or forum-wide, so I'm not posting a link; but you have all the information you need to find it. The auction expires in 15 days.

I'll post results once I've received the ballast and had time to play with it. I can also post the hookup diagrams referenced in the auction if there is interest.
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post #2 of 18 (permalink) Old 01-30-2010, 02:38 AM Thread Starter
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I got it.

The specs say "For indoor use with rapid start lamps F32T8/32 watts - F40T12/40 watts - F40T12/34 watts".

What I'm hoping to do is exploit its 10-120% dimming capability to drive a broader variety of T8, T5, and possibly some T5HO; and still retain a useful range of dimming/light output.

Unfortunately all I have to test it with right now are 3x F15T8, but that's a start.

I wired it up first omitting the dimming function, which by default sets it to 100% power.

The first thing I noticed is that this ballast ramps up the power slowly. It takes a few seconds to reach the set power level. That's actually kind of nice for aquarium use, it might not startle the fish as much when the lights go on.

I then compared the light output from one bulb to a reference, the same bulb in a tank next to it. The bulb driven by this ballast looked somewhat dimmer.

I don't have a PAR meter, but I do have a wattmeter. The ballast was drawing 40W. The three bulbs combined are rated 45W. Assuming 85% efficiency, I can estimate the bulbs were receiving about 34W. A bit disappointing, but not surprising; after all, this ballast was not designed for these bulbs.

Then I wired up the dimming function, which required a 3-pin 0.1" connector, and a potentiometer. It works great! Power on the wattmeter varied from 11W-45W.

At max (120%/45W), the light output per bulb was almost indistinguishable by eye from the reference bulb, with an estimated 38.25W to the bulbs.

At min (10%/11W), the light output was quite dim, but not 10% to the eye. That's understandable since the eye has a logarithmic response to light, with more sensitivity at low light levels.

At all times throughout these tests, the ballast never produced more than a small amount of heat. (That's why I'm assuming at least 85% efficiency.)

So far this is very promising. I'll leave it running for an extended period at full (120%) power and look for any signs of trouble (heat buildup, bulb blackening, etc).

And I'll try to get my hands on some T5HO bulbs for further tests. If it successfully drives those at anywhere near full rated power, that will yield a massively adjustable lighting system on the cheap.
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post #3 of 18 (permalink) Old 01-30-2010, 02:48 AM
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Very interesting. I have been interested in something dimmable but,, dimmable T5HO ballests are expensive. I was assuming I'd have to bite the bullet and invest money and time into DIY LEDs. I want to see what develops with this.
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post #4 of 18 (permalink) Old 01-30-2010, 02:52 AM
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I would be careful using the wrong type bulbs with the ballast. You could damage the ballast or bulbs and possibly both.


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post #5 of 18 (permalink) Old 01-31-2010, 12:39 AM Thread Starter
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First, a request:

Does anyone have 3x F39T5HO bulbs that are no longer useful to you, but that still light, that you are willing to donate to this experiment? I will pay shipping/packaging costs.

Ok, now for the latest results.

The ballast did finally warm up. Using an IR thermometer, I waited for it to reach peak temperature, and measured:

129F @ hottest point on case
111F @ center of case

Is this too hot? I don't have that spec for this ballast, so I looked up other guidelines:

* Underwriters' Laboratories sets an absolute maximum safe case temperature of 194F.
* Several electronic ballast datasheets from various manufacturers state max operating temperatures ranging from 122F-140F. These do not specify where on the case to measure, so it probably means average case temperature (which corresponds best to my center of case measurement).
* The only ballast datasheet that specified a max temperature for a specific point on the case said 176F.

While the ballast is producing extra heat as a result of me using it out-of-spec, it is not overheating, at least not by any measure I can find.

I then remembered I have some more bulbs to test! I braved my attic (it's a scary place), and returned with 3x 25W 4' T12 shop lights, and hooked them up. The ballast also drives them nicely throughout the full dimming range:

20W @ 10%, 77W @ 120%

I cranked it up to 120%, waited for the temperature to peak, and measured:

126F @ hottest point on case
109F @ center of case

Even though we're now pulling 77W instead of 45W, the case temperature went down a few degrees. No surprise there; since these bulbs are closer to what it's intended to drive, it's operating more efficiently.

Thinking of nothing else to try, I then opened up the ballast to see what I could learn.

It was easy to open. The circuit is not potted (sealed in plastic). It could be serviced, perhaps even modified to better suit a particular bulb.

There is a separate output transformer for each bulb, and room for a fourth. Since it drives each bulb individually, it's not limited to three bulbs. I have verified it works fine with one or two bulbs. Nice!

The heat is being produced by 4x MOSFET transistors and the output transformers. The most efficient heat transfer is through the back of the ballast case. For my prior tests, I had this ballast on its back directly on a wooden table. I've since elevated it, and the center-point temperature dropped 4F. It should operate even cooler if it were bolted to a metal surface, or fan-cooled.

I had conflicting info whether this ballast was a rapid-start or programmed-start design. After examining the circuitry, I'm fairly sure it's rapid-start. This is important.

Before I continue, here's a quote from Wikipedia regarding different starting methods which will put the significance of starting method into perspective:

Quote:
Instant start
An instant start ballast starts lamps without heating the cathodes at all by using high voltage (around 600 V). It is the most energy efficient type, but gives the least number of starts from a lamp as emissive oxides are blasted from the cold cathode surfaces each time the lamp is started. This is the best type for installations where lamps are not turned on and off very often.

Rapid start
A rapid start ballast applies voltage and heats the cathodes simultaneously. Provides superior lamp life and more cycle life, but uses slightly more energy as the cathodes in each end of the lamp continue to consume heating power as the lamp operates. A dimming circuit can be used with a dimming ballast, which maintains the heating current while allowing lamp current to be controlled.

Programmed start
A programmed-start ballast is a more advanced version of rapid start. This ballast applies power to the filaments first, then after a short delay to allow the cathodes to preheat, applies voltage to the lamps to strike an arc. This ballast gives the best life and most starts from lamps, and so is preferred for applications with very frequent power cycling such as vision examination rooms and restrooms with a motion detector switch.
All T5HO bulbs seem to be meant for use with programmed-start ballasts, not rapid-start ballasts like this one. Using a T5HO on this ballast will shorten its life each time you start it up.

However, there are some mitigating factors.

First, an aquarium light is usually started only once a day. Problems from cathode degradation might not appear for some time. The phosphors might degrade, rendering the bulb useless due to reduction in brightness or spectrum shift, long before the cathodes die.

Second, because of the way the dimming circuit ramps the power up from 0% on startup, this ballast is actually gentler than a typical rapid-start. Practically, it can be considered somewhere between a rapid-start and programmed-start.

In short, it may provide a useful life from a T5HO, but the only way to know for sure is to test.

I am prepared to do such a test. I have X10 home automation under computer control, which will allow me to do an accelerated lifetime test by cycling the ballast on/off 1,000 times, and see what happens to the bulbs.

Thus my request at the top of the post for 3x used F39T5HO bulbs. It's a brutal test even on a perfectly matched ballast, and it would be an awful shame to do that to a set of new bulbs.

Quote:
Originally Posted by hbosman View Post
Very interesting. I have been interested in something dimmable but,, dimmable T5HO ballests are expensive. I was assuming I'd have to bite the bullet and invest money and time into DIY LEDs. I want to see what develops with this.
Seems our thoughts are the same on this.

My "dream light": The bulk of the light produced by dimmable fluorescents, with range covering any needed lighting intensity. Supplemented by a few red, green, and blue LEDs; allowing fine tuning of spectrum to please the eye, or moonlight operation.

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Originally Posted by Firestarter View Post
I would be careful using the wrong type bulbs with the ballast. You could damage the ballast or bulbs and possibly both.
I'm glad you said that. It's a risk/reward situation. I understand that and am willing to risk this ballast and maybe a few bulbs to possibly achieve the reward of a very nice light. I posted this in DIY instead of lighting because the DIY crowd generally understands this too.

I'll also say that I'm not the first to use strange ballast/bulb combinations. They have been used with success in ODNO configurations.
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post #6 of 18 (permalink) Old 01-31-2010, 01:20 AM
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Interested to see how this goes. Just hope you don't run them when not around.


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post #7 of 18 (permalink) Old 01-31-2010, 05:45 PM
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Great thread DarkCobra! Nice detailed writeup, thank you for trying something new and sharing with us!

When I initially saw your OP, I wondered about the "control circuit". How expensive will that be (if you don't have X-10 set up already)? I believe that same company specializes in control circuits and equipment. It would be too bad if the affordable ballast could only be dimmed with very expensive controls.

Not sure about the ballast temperature. Some ballasts run pretty hot. As you said, raising up the ballast for better circulation, or even a little fan can improve things. If the ballast runs hotter than spec it might just fail prematurely, whether that is after one or many years, who knows.

I wouldn't worry too much about the instant/rapid/programmed start ballast characteristics. I have been using Fulhams Workhorse ballasts for years with T5 bulbs, and they are classified as "instant start" and still are recommended and work well with T5 bulbs. It might be an issue where the light is turned on and off constantly (like a bathroom) but not for aquariums.

What is the total wattage you can drive with this ballast?

Can't help with the 3ft bulbs unfortunately... hope you will find them. Testing 4ft bulbs would be even more interesting to those with 4ft and larger tanks.


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post #8 of 18 (permalink) Old 01-31-2010, 05:57 PM
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Quote:
Originally Posted by hbosman View Post
Very interesting. I have been interested in something dimmable but,, dimmable T5HO ballests are expensive. I was assuming I'd have to bite the bullet and invest money and time into DIY LEDs. I want to see what develops with this.
they make LED flood lights now. it's like $60-$100 each but will last 20 years. And I think they are dimmable.


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post #9 of 18 (permalink) Old 01-31-2010, 07:38 PM Thread Starter
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Quote:
Originally Posted by Wasserpest View Post
When I initially saw your OP, I wondered about the "control circuit". How expensive will that be (if you don't have X-10 set up already)? I believe that same company specializes in control circuits and equipment. It would be too bad if the affordable ballast could only be dimmed with very expensive controls.
You don't need X10, manual dimming is cheap and easy. The ballast has a 3 pin male locking polarized header, with 0.1" spacing:

1 - 17V
2 - Ground
3 - Control

All you have to do is give it a 0-17V signal on the control pin to dim from 10% to 120%.

I'm currently doing that with a 1k trimmer, which costs well under $1. That lets me set the dimming by turning a dial. The female connector was scavenged from an old motherboard connector for the "Turbo" button on an old computer. It's neither locking nor polarized, so you have to be careful not to tug on it or plug it in the wrong way, but it fits fine. The proper connector should be easy enough to find for cheap, I know I've seen them before but I haven't yet looked them up.

More sophisticated control schemes are possible. Your imagination's the limit, as long as you can produce the 0-17V signal.

Quote:
Originally Posted by Wasserpest View Post
I wouldn't worry too much about the instant/rapid/programmed start ballast characteristics. I have been using Fulhams Workhorse ballasts for years with T5 bulbs, and they are classified as "instant start" and still are recommended and work well with T5 bulbs. It might be an issue where the light is turned on and off constantly (like a bathroom) but not for aquariums.
If I were keeping this to myself, at this point I'd get three F39T5HO Giesemanns and go for it.

But since I'm sharing in the hope others can also benefit, I'm doing as much "guinea pig" work as possible before the auction ends.

X10 will be used to rapidly cycle the ballast on/off, to see if it will destroy a T5HO in less than the number of on/off cycles you would reasonably expect from the bulb in aquarium use. (But I won't purposely do that to a new set of Giesemanns!)

It also still remains to be seen whether this ballast will light a T5HO at or near the rated power. I think it will, but you never know.

Quote:
Originally Posted by Wasserpest View Post
What is the total wattage you can drive with this ballast?
3x 40W bulbs=120W. At 120% dimming (20% overdrive), 144W.

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Originally Posted by Wasserpest View Post
Can't help with the 3ft bulbs unfortunately... hope you will find them. Testing 4ft bulbs would be even more interesting to those with 4ft and larger tanks.
I'm driving 4ft T8 right now.

4ft T5 should also be no problem.

4ft T5HOs are 162W, over the designed wattage. It may drive those but not at full brightness, or it may burn itself out trying. Exceeding the ballast's wattage is not on my testing agenda.
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post #10 of 18 (permalink) Old 01-31-2010, 07:52 PM
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Manually turning the brightness up every morning and down every evening will not be fun. I am assuming this is why the dimming capability is desired... not to preset the bulbs at a certain level (of course that could be done too).

So the question remains, is there a cheap way to get the 0-17V signal that is sent to the ballast via a timer.

How do the bulbs react if you have the pot set to "0", plug in the ballast, and then turn the pot up? Do they start with a smooth glow all the way up to full brightness?

So the ballast should easily drive two 4ft 54W T5HO bulbs. That is what I would be interested in... to see approximately how many watts the ballast pushes through two of them.


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post #11 of 18 (permalink) Old 01-31-2010, 08:47 PM Thread Starter
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Manually turning the brightness up every morning and down every evening will not be fun. I am assuming this is why the dimming capability is desired... not to preset the bulbs at a certain level (of course that could be done too).
I'm going to assume you want a blast of light for a few hours in the middle of your photoperiod, and that you want to work primarily with mechanical timers.

The simplest control scheme I can think of uses two timers, a relay, and two trimmers.

Timer #1 - Sets the photoperiod. Connected directly to the AC input of the ballast.

Timer #2 - Sets the light blast period, which must fall fully within the photoperiod. Connected to the coil of the relay.

Relay - SPDT, 120v coil. Amp rating unimportant. It has two switched inputs, each of which is connected to the 2nd (center) pin of a trimmer. The output is connected to the control pin of the ballast. Coil connected as above.

Trimmers - First pin is connected to ballast's 17v pin, third pin connected to ballast's ground pin, second pin connected as above.

A few assorted parts - you might need a case, AC cord, connectors, perfboard.

That's it. You can set the light output for either mode individually via the trimmers, and the timing via the timers. Additional ballasts can be added to this control system with no additional components.

All can be had for $20, or less if you shop smart or scavenge some parts. Anyone who can use a soldering iron can do this. If someone's really uncomfortable doing this, I can be persuaded to built it for them.

Quote:
Originally Posted by Wasserpest View Post
How do the bulbs react if you have the pot set to "0", plug in the ballast, and then turn the pot up? Do they start with a smooth glow all the way up to full brightness?
The ballast always starts at 10% on power-up. It then smoothly ramps up to whatever the pot is set to, 10-120%. Turning the pot down while in operation smoothly ramps it down. You cannot shut the ballast completely down via the pot.

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Originally Posted by Wasserpest View Post
So the ballast should easily drive two 4ft 54W T5HO bulbs. That is what I would be interested in... to see approximately how many watts the ballast pushes through two of them.
This ballast drives each bulb individually through a separate channel. Although you're not exceeding the rating of the ballast as a whole, you are exceeding the rating of the two connected channels.

The possibilities, in decreasing order of probability:

1) The ballast limits the current and drives the bulbs at ~40W each.
2) The ballast attempts to drive the bulbs at full rating. In the process, it saturates the output transformers, which makes them appear as a short circuit. This leads to a blown fuse, or massive overheating which will destroy the ballast in short order.
3) The ballast successfully drives the bulbs at full power.
4) ???

Again, I have no personal interest in testing this ballast in excess of its spec.

But if you send the bulbs, I'll do the test. I should be able to detect fault conditions before any permanent damage is done to the ballast.

EDIT: Disregard above paragraph. I'm pretty sure it won't work with F54T5HO. New test results coming soon.

Last edited by DarkCobra; 02-01-2010 at 12:12 AM.
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post #12 of 18 (permalink) Old 02-01-2010, 01:42 AM Thread Starter
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It's been a crazy day.

My CO2 system developed a serious leak, and I spent a few hours hunting down parts to improvise a repair. Through the grace of God, a few hose clamps, and some rubber cement, I now have a leak free system.

I had just enough time to pop into Petco before it closed, and purchased three horrendously overpriced F39T5HO bulbs. I get them home to find one's apparently been opened before, and is broken.

All three are going back tomorrow. But tonight, I test with two of them.

With two bulbs attached, I got power draw of:

22W @ 10%
59W @ 120%

Wow.. It's having trouble with these. These bulbs should draw 78W combined, not counting losses in the ballast. Assuming 15% losses, each bulb is getting only 25W. Also, arc instability showed up at the bottom of the dimming range; the bulbs showed a ripple effect.

It's apparent that these bulbs need a higher voltage to operate throughout their full range, which this ballast is not providing.

Now if 60% of maximum rated light output fits within your light budget, or if you could add another bulb to compensate, this ballast could still work as-is.

But I'm not satisfied with that. I popped the case back open, examined the circuit for a while, and found something interesting.

This ballast adjusts its output solely by altering its operating frequency. Lower frequency = more output, higher frequency = less output. And there are two trimmers on the board, helpfully labelled "HF" and "LF", which set the bounds of its operation.

By adjusting HF, I was able to boost the low-end power so the arc instability didn't appear when the dimming control was at 10%. And by adjusting LF, I was able to brighten the lights considerably, reaching 80W at 120%.

I went no higher, because at that point the frequency had dropped low enough to be audible. With the case still off, I could hear a faint, high-pitched whine a few feet from the ballast; maybe 14-15khz.

As a nearly 40 male, my high-frequency hearing isn't so good. It's better if you're female or younger. So I called my girlfriend in. I'm a gentleman and won't say how old she is.

She said "eww!" the instant she walked in the room. She can definitely hear it better than me! I then adjusted it until she could no longer hear it. At that point it was drawing 70W. Still not the bulbs' full potential, but close enough for me.

I'm sure the sound would still be audible by people younger than us, although putting the case back together and installing the ballast in a proper fixture would muffle it significantly.

These adjustments could also benefit other bulbs - the previous ones I tried were all slightly underdriven.

But F54T5HO is probably not an option, at least not without limited output power or the ballast whining intolerably.

I'll continue to run the ballast at 70W for a while. And I'm still looking for used F39T5HO bulbs for the accelerated longevity test.
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post #13 of 18 (permalink) Old 02-01-2010, 04:42 AM
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Wow... you sure like adventure. I'd be too scared to open a ballast, unless I know it's dead for good. Like the one I drowned recently.

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I'm going to assume you want a blast of light for a few hours in the middle of your photoperiod, and that you want to work primarily with mechanical timers.
Actually I was pondering the morning/evening slow ramp up. You know, over 10 minutes (or whatever period suits you) go from 10% to 100%. And maybe do a 120 for a few hours in the middle.

Looks like the ballast doesn't like T5 bulbs...


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post #14 of 18 (permalink) Old 02-01-2010, 05:28 PM Thread Starter
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The ballast has now been driving 2x F39T5HO bulbs for about 12 hours, at an estimated 29W across each bulb (underdriven by 25%).

No problems at all. Since I'm running only two bulbs for this test instead of three, and the ballast case is still open, I'm not posting exact heat measurements for this test; they'd be useless for comparison again the others. But I can say the ballast is not producing unusual amounts of heat.

This bulb in particular is the one I'm most interested in, and I can live with underdriving it slightly; so for me at least, this ballast is a success!

Since there's still no bites on my request for used bulbs for accelerated longevity testing, I'm at a loss for further useful tests. So...

TO SUM UP:

This ballast can drive 1-3 bulbs, at up to 40W per bulb. It has shown considerable ability to drive bulbs other than the few it was designed for.

Cooling and ventilation are always important for any ballast; but since this ballast produces extra heat while driving certain bulbs, it's particularly important here.

All bulbs are underdriven to some degree, depending primarily on bulb type. In general:

T12s are underdriven slightly.
T8s are underdriven a bit more.
T5HOs are underdriven by a large amount.

Underdrive can be partially compensated for by adjusting the dimmer to 120%. Further compensation is possible by removing four rivets and adjusting two internal controls.

F39T5HOs exceed compensation limits, although they can still be driven at ~75% of rated power. I suspect smaller T5HOs will work at full power.

At the time of this post, these ballasts are still available in any quantity up to at least 10, and the auction expires in 12 days.

I'll continue to monitor this thread, answer questions to the best of my ability, and post if I find anything else out.


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Actually I was pondering the morning/evening slow ramp up. You know, over 10 minutes (or whatever period suits you) go from 10% to 100%. And maybe do a 120 for a few hours in the middle.
Aha. Extending the ramp up/down time can be done easily.

But I also neglected the evening ramp-down in my prior example. To do everything you suggest, you'd need five events:

1) Turn on and ramp from 10-100%.
2) Ramp from 100-120%.
3) Ramp from 120-100%.
4) Ramp down to 10%.
5) Turn off.

Since two timers only provide four events, you'd need a third timer, and a slightly more complex control circuit. It could be done, but we're really getting into computer/microcontroller territory.

Ramping over 10 minutes you'd also find the ramp to be highly non-linear; because both the bulb's and eye's response to different power levels is non-linear. That could be compensated for but that's definitely computer/microcontroller stuff.
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post #15 of 18 (permalink) Old 02-01-2010, 09:06 PM
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Quote:
Originally Posted by DarkCobra View Post
Since two timers only provide four events, you'd need a third timer, and a slightly more complex control circuit. It could be done, but we're really getting into computer/microcontroller territory.

Ramping over 10 minutes you'd also find the ramp to be highly non-linear; because both the bulb's and eye's response to different power levels is non-linear. That could be compensated for but that's definitely computer/microcontroller stuff.
Exactly, that's what I was getting to. It seems like for an electronically inexperienced person, just purchasing the ballast will not help much towards the wonderful gradual on and off that we are all yearning for. While the ballast has the dimming capability, the question is how much a controller for this would cost, and whether it is available at all.

For an electronically versed DIYer it wouldn't be a big problem to figure out some circuit with capacitors to do the gradual up'n'down.


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