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Radio transformer makes a perfect 1.5W fluorescent lamp ballast

Radio transformer makes a perfect 1.5W fluorescent lamp ballast

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I pulled this power transformer out of a cheap chinese radio I bought several years ago and never used. It takes 120 VAC down to 8 VAC. The primary side makes an excellent choke for a 1.5 watt fluorescent lamp. Current is 0.09A, which is still overdriven, but any less wouldn't provide enough preheat current. Likewise, this makes an excellent low-power F4T5 ballast, too.

There's one terminal caveat, though - I have to short the secondary side to get that much current on the primary (otherwise primary current is only 0.04A or so), and as a result power factor is nearly 1.0, and the transformer dissipates nearly 10 watts of power, causing it to eventually become unusably hot.

Two_F8T5s_and_one_F6T5_running_in_series_on_30-40_preheat_ballast.JPG IMG_1802.JPG IMG_1795.JPG F6T5_and_F8T5_running_in_series_on_incandescent_ballast_on_120V.JPG

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Filename:IMG_1795.JPG
Album name:themaritimegirl / Experiments, Projects, & Mods
Keywords:Gear
File Size:245 KB
Date added:Jul 23, 2014
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DetroitTwoStroke
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Jul 23, 2014 at 07:13 PM Author: DetroitTwoStroke
Maybe you could put it in a can of oil, so it is like a mini utility transformer!

Pride and quality workmanship should lie behind manufacturing, not greed.

themaritimegirl
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Jul 23, 2014 at 07:59 PM Author: themaritimegirl

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ace100w120v
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Jul 23, 2014 at 08:15 PM Author: ace100w120v
What about a little computer fan to keep it cool?
themaritimegirl
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Jul 23, 2014 at 08:27 PM Author: themaritimegirl
That could work, although I would still fear that heat within the windings would cause it to melt down and short out. I guess the true end-all solution would be simply an appropriately designed transformer/ballast.

I just thought of something, I wonder how well my autotransformer ballasts would work as a choke - just connect either the primary or secondary side in series with the lamp...

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themaritimegirl
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Jul 23, 2014 at 09:03 PM Author: themaritimegirl
I'm amused as heck right now. I'm currently watching an F4T5 lamp run beautifully from my Advance L-140F-TP. I'm treating the primary side as a choke and leaving the secondary side open. I'll show it in tomorrow's photo. What a way to mess with a lighting enthusiast's head, to show a 4 watt lamp running perfectly from a 40 watt preheat ballast.

I would hypothesize that when using a transformer as a choke, leaving the secondary side open allows the primary side to exhibit it's true impedance - that is, the current it would allow if it were separated from the rest of the ballast and treated like an actual inductor. When you place a load on the secondary side, though, such as the shorting I had to do in this picture, that changes the magnetic flux on the primary side and lowers its impedance, thus increasing current.

Now imagine a redneck dimmable ballast! Have your lamp running on the primary side and a potentiometer on the secondary side.

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rjluna2
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Robert


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Jul 24, 2014 at 05:05 AM Author: rjluna2
Sounds like you had your studies on magnetic circuit that I only had one semester on Circuit I at my local university some time ago.

I still haven't figured out the parameters on henries yet

Pretty, please no more Chinese failure.

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Jul 24, 2014 at 10:10 AM Author: themaritimegirl
Well, I'm just guessing the situation above. Magnetic flux may be the totally wrong term, but for sure a load on the secondary seems to influence the apparent impedance of the primary.

I've learned in school so far how to calculate the impedance of a capacitor or inductor knowing its capacitance or inductance, and the AC frequency.

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Jul 24, 2014 at 12:58 PM Author: rjluna2
That part I do know about that

Pretty, please no more Chinese failure.

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Jul 24, 2014 at 04:08 PM Author: Prismatic
I call this: Learning by doing.

Prismatic@YouTube:

http://www.youtube.com/slprismatic

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Jul 24, 2014 at 08:03 PM Author: rjluna2

Pretty, please no more Chinese failure.

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Jul 24, 2014 at 10:27 PM Author: arcblue
Usually when the ballast is bigger than the lamp, fixture design is compromised. This would make an odd nightlight, not to mention an unsafe one, but....I'm not too fond of the capacitor-resistor ballasts either. I wish I could still find the true preheat fluorescent nightlights...those were pretty cool.

I'm lampin...

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Jul 24, 2014 at 10:32 PM Author: themaritimegirl
Yeah, those preheat fluorescent nightlights are awesome. Many years ago I had an awesome night light - it was only a capacitive ballast, but it had a fluorescent lamp on one side and a miniature incandescent lamp on the other side which could be switched independently. I don't know what the point was since they were about the same brightness, but it was so cool. One day I took apart, never got it back together, and threw it away. I've never seen another since.

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My idol is Mylene Farmer, deal with it.


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Dec 22, 2014 at 05:47 AM Author: vytautas_lamps
Have ever tried to turn on 2 40 watt t12 tubes on one f80t12 ballast with Homemade starting compencator? go to my channel and you will see how I made my own starting compensator

New lighting technologies is a pity fest everywhere you look. From LEDs that last only for two months, to a never-ending global starvation of t8 fluorescent tubes.
We shall reinforce ourselves with good old full mercury t12s and HIDs made to surpass one's life, and give them all the middle finger ;

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Dec 22, 2014 at 02:16 PM Author: themaritimegirl
I'm in North America, where we don't have F80T12 lamps (sadly). We can do it with an F96T12 ballast, though, without the need for preheating or a starting compensator since it's an instant start ballast.

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Dec 22, 2014 at 02:33 PM Author: Medved
When shorting the secondary, you have made just a resistor (with small series inductance) out of the transformer, nothing else. So you would be better with just a ~15W incandescent...

Shorting the secondary means (now assume for a moment the coil is made of an ideal conductor with no resistance at all), you have forced zero induced voltage. As the induced voltage (Faraday's law) is proportional to the rate of change of the magnetic flux, no voltage means no changes in magnetic flux. And no changes in magnetic flux with an AC system simply means no flux at all.
So at the end, the magnetic field is pushed away from the coil, so it has to go through all the wide space around the primary. But that still means the current is flowing through the secondary, it is this current, which is pushing the flux out of the secondary coil.
In the reality you do have certain resistance of the secondary wiring, so the current would cause some voltage drop on that, so this voltage is then allowing some of the flux there.

No more selfballasted c***

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