Can this be done, Electrical Question - The Planted Tank Forum
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post #1 of 19 (permalink) Old 12-27-2009, 06:03 PM Thread Starter
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Can this be done, Electrical Question

My question revolves around a two tube T5HO fixture. I'm wondering if it is possible to modify the wiring so that each bulb can be switched individually? Knowing that there is only one ballast are these wired such that both bulbs must be on at the same time? Really I don't even necessarily need switches because I could just use two separate timers.
Is this possible?

I'm looking at one of these three fixtures:

Aquatic Life Dual-Lamp T5 HO Light w/two 24 watt bulbs


Catalina Aquarium SOLAR T5 HO w/two 24 watt bulbs


Fishneedit T5 HO Light w/two 24 watt bulbs


TIA
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post #2 of 19 (permalink) Old 12-27-2009, 06:15 PM
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It might be possible, but not necessarily a good idea.

SOME ballasts need both bulbs on at the same time to function. With newer electronic ballasts this usually isn't an issue. Easy to test by taking out one of the bulbs and seeing if it still works with one.

If you have only one ballast you would need to interrupt one of the bulb leads with a switch. You can't do that with a regular timer though. If you are really handy with electrics/electronics you can modify a timer to work as a switch rather than an outlet.

Unless you know exactly what you are doing I wouldn't recommend it though. Look for a fixture with two separate ballasts instead... not sure if there is any.


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post #3 of 19 (permalink) Old 12-27-2009, 07:22 PM Thread Starter
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Hypothetically speaking, because I don’t have a 2 tube T5 fixture to tear into yet, wouldn’t it make a difference if the bulbs were wired in series or parallel? It they are wired in series and you take a bulb out then the other bulb should not light because the electricity needs to flow through both bulbs. If they are wired in parallel and you take a bulb out and the other stays lit then would it be possible to just add a switch to the power lead to that bulb? This way I could plug the light into a timer and it would turn the one bulb on and off by my settings, if I wanted the second bulb on I could switch it on and off as I choose.
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post #4 of 19 (permalink) Old 12-27-2009, 07:50 PM
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most Florescent bulbs use a very high Voltage output to fire.
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post #5 of 19 (permalink) Old 12-27-2009, 08:39 PM
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the biggest concern would be the fact that you are switching the high voltage and making sure you have it insulated correctly and if you don't Ouch or worse and the you add in wet conditions and you come up with what the UL people have nightmares about.

i would not modify it

anyway you will need to know what the voltage is after the ballest then based on that you can decide what kind of switch to use and insulation to use. Since i am sure that the line voltage that is curreently being switched this would be switching the HV. HV switches can be expensice and are a speciality item not radio shack or Home Depot more like Mouser http://www.mouser.com/ plus the air gap for the voltge needs to be maintained or arcing will occure.

Again I would not modify it.


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post #6 of 19 (permalink) Old 12-28-2009, 12:21 AM
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Seems T5HO's are not a "simple" turn the bulb on. Check out

http://www.prolighting.com/trabt5ba.html

This would preclude simply putting a switch on the bulb leads. I don't know the exact voltages/frequencies involved, but a "normal" switch would not work on anything above 600v.


If there is room in the fixture, add another ballast.

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post #7 of 19 (permalink) Old 12-28-2009, 01:39 AM
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Quote:
Originally Posted by smp View Post
... a "normal" switch would not work on anything above 600v... .
This is the correct answer and trying to switch a fluorescent bulb between the ballast and the bulb is not safe and could easily cause a fire.

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post #8 of 19 (permalink) Old 12-28-2009, 02:40 AM
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T5HO bulbs are driven not just at high voltage, but also at a much higher frequency than normal household 60 Hz. As you get to high frequencies you have more problems with inductance and capacitance effects, which can prevent an ordinary switch from ever turning off the current, instead allowing an arc to continue across the contacts, which could cause a fire. Switching that type of power isn't something we should ever try to do.

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post #9 of 19 (permalink) Old 12-28-2009, 03:15 AM
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After reading all of the above. it sounds like a "BAD" idea. I am very "electrically" inclined, and I wouldn't try it.

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post #10 of 19 (permalink) Old 12-28-2009, 04:53 AM
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Quote:
Originally Posted by AquaDean View Post
My question revolves around a two tube T5HO fixture. I'm wondering if it is possible to modify the wiring so that each bulb can be switched individually? Knowing that there is only one ballast are these wired such that both bulbs must be on at the same time? Really I don't even necessarily need switches because I could just use two separate timers.
Is this possible?

I'm looking at one of these three fixtures:

Aquatic Life Dual-Lamp T5 HO Light w/two 24 watt bulbs


Catalina Aquarium SOLAR T5 HO w/two 24 watt bulbs


Fishneedit T5 HO Light w/two 24 watt bulbs


TIA
Dig for some info. If the ballast specs say it can run one bulb, I would expect they can, u could get another ballast and wire it to the other bulb. Then u could use a household timer on each. I have no doubt u could put a switch in the line and turn one bulb off if the ballast can run them parallel. I just don't know how u would insert what kind of timer, Unless u had the regular timer run a solenoid to do the switching. The "high voltage" doesn't seem scary for a number of reasons. Small amps involved, for one. The wires aren't big and the insulation isn't thick. If it is, let me know.
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post #11 of 19 (permalink) Old 12-28-2009, 02:46 PM
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Quote:
Originally Posted by MoonFish View Post
Dig for some info. If the ballast specs say it can run one bulb, I would expect they can, u could get another ballast and wire it to the other bulb. Then u could use a household timer on each. I have no doubt u could put a switch in the line and turn one bulb off if the ballast can run them parallel. I just don't know how u would insert what kind of timer, Unless u had the regular timer run a solenoid to do the switching. The "high voltage" doesn't seem scary for a number of reasons. Small amps involved, for one. The wires aren't big and the insulation isn't thick. If it is, let me know.
Higher voltage isn't "scary," it has a greater ability to arc, one of the most common causes of household fires.

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post #12 of 19 (permalink) Old 12-29-2009, 01:46 AM Thread Starter
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Well I dug deep today and talked with a couple electronic wiz's as well as a couple of the Aquarium light companies. Exactly what I wanted to do cannot be done as I wanted. To make it work as some of you have said you would need to add a second ballast and have each ballast fire a single tube. This would not be that difficult to do as you could use an external ballast and just run a cord up to the light fixture. It would of course void any warranty that came with the light. So decisions decisions, I'll probably just buy a light and live with it for a while and see how it goes. Or maybe get one and tear into it to see just what I can do. We'll see
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post #13 of 19 (permalink) Old 12-29-2009, 01:17 PM
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Or look at two 1 tube T5ho lights. This is going to give you better light coverage anyway...

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post #14 of 19 (permalink) Old 12-29-2009, 01:56 PM
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Just buy two fixtures or one with independent ballasts. Don't kill yourself or burn your house down trying to save a buck.
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post #15 of 19 (permalink) Old 12-30-2009, 03:51 AM
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I do all sorts of electrical experiments and I would definetly not do anything like that. I would run a two ballast system with two switches.


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