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Discussion Starter · #1 ·
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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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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Discussion Starter · #3 ·
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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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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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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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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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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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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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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Discussion Starter · #12 ·
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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Discussion Starter · #17 ·
This is way too easy. . . problem solved by just undoing four screws and taking a quick look. Almost doesn’t merit DIY but I’ll fill everyone in on the details anyway. Backing up just a bit, I received the Fishneedit two bulb T5HO light today. It’s nice sleek and brighter than bright, but I’ll discuss its merits in more detail in my tank thread.



Took it out of the package, plugged it in and switched it on. Both bulbs lit of course so I took one of the end caps off the fixture and unplugged the two pin connector going to one of the bulbs. The other bulb stayed lit, this was good so far. But I noticed that there were nine wires coming out of the power cord, four each for each T5 tube and a shared ground. I needed to see how they were wired to the ballast so took the four screws holding the metal cover on the ballast out and problem solved, I can do exactly what I wanted to do.




There are two (2) ballasts in the case one for each tube they share the white and black wires from the plug with the white one being switched. The ground wire from the plug just went to the case so this made the whole idea of having each tube switched or on separate timers really easy.



Simply remove the existing switch, install a second cord grip and cord through that hole, wire each ballast to it’s own cord, and plug the two cords into separate timers. Way too easy! Now I’m wondering if all HOT5 tubes are each wired to their own ballasts this would make for easy customization of your lighting. One step closer to getting this tank rolling.
 

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Discussion Starter · #19 ·
Just wanted to share a couple pictures of the finishing steps.
Took the switch and terminal block out, installed the new cord grip, cut a small piece of sheet metal to take up the excess space in the switch hole. The cord grip holds it it place perfectly, colored it black with a Sharpie, no one would ever know there used to be a switch there. Re-fastened the ground wires to the case, wired the correct pairs of wire together and it was all ready to tuck back in the case and put the cover back on.



Here is the finished product, each cord controls one tube, so now I can control the two tubes separately by plugging into separate timers.



On to the next project whatever it might be. . .
 
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