Help upgrading CFL circuit? Want to drive cfl's up to 25w.

[Clarkdale44]

Hello

I have this circuit which i built, it can drive cfl's up to 15w, do u think it can be modified so that it can drive cfl's up to 25w?
I have used D313 fot his project as the D882 didn't gave me the results i needed.
Right now i am using 12v battery, do u think the transformer i made for this circuit can be used for the famous Jeanna's light (Joule's Thief). If yes then how it would connect on the circuit? I will be making two or three more transformers like this.


Regards!

 

[dr pepper]

A 2n3055 or tip3055 transistor in conjunction with a trans from a dead pc power supply should easily give more power, adding turns to the secondary will give you more power, but there is a limit before the transformer saturates.

 

[Clarkdale44]

A 2n3055 or tip3055 transistor in conjunction with a trans from a dead pc power supply should easily give more power, adding turns to the secondary will give you more power, but there is a limit before the transformer saturates.

Well i tried adding more turns to the secondary about 100 more, it ran at first, there was no difference in power or brightness but then my transformer started giving strange noises and sparks in its coil. Since then its not running anymore, all that is happening is the transistor is getting extremely hot that may even melt lead, you know what i mean its way too hot within 5 seconds after i connect the power.

And what do u mean by "trans" is it transistor or transformer?

 

[dr pepper]

Sorry, lingo, trans = transformer, tranny=transistor.

If the transformer and tranny get hot straight away then most likely the transformer is saturating, the transformer can only take so much magnetism, over this the primary will become a short circuit and things get mad hot.
More turns on the primary will reduce this.
Putting stuff together without design is hit and miss, you'll need to make a few prototypes before it works.

Most cfl inverter circuit I have seen run the cfl tube as a cold cathode, there are heaters each end of a cfl tube which glow when power is first applied to a cfl, this helps to start the arc, inverter driver projects generate a very high voltage forcing the gas in the tube to ionize without the heat so only one wire at each end of the tube is connected, or both wires each end joined as one, this is ok but you must make sure the layers of windings in your trans, sorry transformer are well insulated, put a layer of tape between each layer of winding.

Its not a good idea to use old cfl tubes from ones that dont work anymore, when they are at the end of their life they are only good as a source of components, not the tube.

 

[Clarkdale44]

Sorry, lingo, trans = transformer, tranny=transistor.

If the transformer and tranny get hot straight away then most likely the transformer is saturating, the transformer can only take so much magnetism, over this the primary will become a short circuit and things get mad hot.
More turns on the primary will reduce this.
Putting stuff together without design is hit and miss, you'll need to make a few prototypes before it works.

Most cfl inverter circuit I have seen run the cfl tube as a cold cathode, there are heaters each end of a cfl tube which glow when power is first applied to a cfl, this helps to start the arc, inverter driver projects generate a very high voltage forcing the gas in the tube to ionize without the heat so only one wire at each end of the tube is connected, or both wires each end joined as one, this is ok but you must make sure the layers of windings in your trans, sorry transformer are well insulated, put a layer of tape between each layer of winding.

Its not a good idea to use old cfl tubes from ones that don't work anymore, when they are at the end of their life they are only good as a source of components, not the tube.

You mean those starters with small bulb thingy with a polyester capacitor? they are connected in series with the fluorescent tube. They were used with old magnetic choke, used to light up big fluorescent tubes. Didn't thought of that, will try.

Thanks for the tip about the trans, i will keep that in mind. What i am gonna do next is dismantle the trans and rewind it again, glad i was testing it on breadboard so i don't need to unsolder anything.

Do u know any other way to find whether the winding is short or not. I have seen many electrician do this with motors using an ac bulb, if it glows then its short if its dim then its fine, not sure. I have no idea how they do it.

 

[dr pepper]

Not quite but nearly, cfl's use a similarish method to start the tube, the supply goes to one wire at each end of the tube, the other 2 go to a cap, when the tube is first powered the cap conducts, lighting the filaments making the tube strike.

Shorted windings are tricky to find, even for the experinced, you can use a circuit that 'rings' the coil with short impulses and then counts the number of rings, shorted turns tend to reduce the number of rings, but even then its only a rough guide, and you'd really to to test a known good coil to know what to expect.
Shorted turns if only one or 2 might not stop a trans from working, but it would increase primary current and have the tendancy to overheat.

 

[Clarkdale44]

Can you tell me what should be the primary and secondary gauge margins? I mean if i were to use 30 awg wire for the primary what gauge of wire i should use for the secondary?

 

[killivolt]

Sorry, lingo, trans = transformer, tranny=transistor.

Must be American vs English Translation I would have thought this way. I've never seen Transistor abbreviated before.

Trans = Tranny = Transformer

 

[audioguru]

A tranny is a transmission on a car.

 

[Nigel Goodwin]

Must be American vs English Translation I would have thought this way. I've never seen Transistor abbreviated before.

Trans = Tranny = Transformer

More an age thing perhaps? - back in my day a 'tranny' was a transformer (and still is ), but as youngsters came through they had started using it for transistor.

 

[dr pepper]

I used to read the beano comic, one of my my favorite story titles was 'dannys tranny', about a kid with a magical transistor radio.

 

[dr pepper]

Size of wire depends on the current, there are all kinds of theories on this, I go by current density, 5a per mm2 is considered a sensible max.
Work out the mm2 area of the copper wire and then divide it by the max current, which by the way on a circuit like yours could be double what a meter reads, as meters read average or rms not peak, if unsure just double the reading.
To measure enamelled copper wire first burn the insulation using a flame, then you can use calipers to get the dia.

Having said all this for your app 0.5mm should probably do the trick at a educated guess.

 

[Clarkdale44]

ok thanks very much

 

[Clarkdale44]

Hello



I am trying to build this circuit and was able to make a working prototype on breadboard. Just as i was about to make it permanent on pcb, i thought i should check it one last time and then this happened. Just as i turned it on my transformer started giving weird noises and CFL went down from bright to low and then completely off at the same time my transistor was damn hot. I have no idea why it happened, i mean i have already tested it before for 30 minutes and it was running fine and everything was cool, i have big heatsink installed on the transistor. Still when it was working during that 30 minutes, heatsink was safe to touch, but now it might even melt solder.

I tried different transistor, capacitor, resistor but the transistor is still getting hot.

Just to let to know, when i was packing it all up, i saw one of the high voltage wire was touching the heatsink of the transistor, do u think this has anything to do with this?

Also i used D313 transistor.

Regards!

 

[DerStrom8]

Hi Clarkdale44 ,

Please try to keep posts on the same topic within a single thread. I've moved your latest post to this one.

Regards,
Matt

 

[Clarkdale44]

Alright i will keep that in mind next time.

 

[tunedwolf]

I have always known Tranny as meaning a Transformer, also common, depending on conversation topic, a cheap portable broadcast radio receiver. I have always called or referred to a Transistor as just that, a Transistor

What is the transformer in the circuit? A wound Pot Core? Striking up a 25W tube with this circuit is one thing, which is possible if the output voltage is high enough, having it running at anything like full brightness without either burning out the cathodes or the driver itself is another matter. Adding more turns to the secondary will not only increase your output voltage, it will also increase your feedback voltage. At some point your driver transistor is going to become uncomfortable with that unless you take some precautions with your design. For a simple non regulated circuit like this, a choke in your secondary to limit tube current wouldn't be a bad thing either for example. The transformer breaking down is not unheard of if wound incorrectly or poorly. Because of the high voltages between layers of windings, you may need to place a layer of insulation every few layers, not only that, you need to be very careful when winding that you do not damage the wire insulation (I'm assuming bare enamel wire here) or allow any turns from your current layer to slip down into the middle the previous layers as well as perhaps stacking the successive layers towards the middle of the former such that you increase the distance between the higher and lower voltages at each end of the layers of windings. Also beware of operating the circuit, even momentarily, without any load on the secondary. Even a single "oops" moment with the tube connections may well be enough to fry your driver transistor due to the excessive secondary voltages produced when the circuit is run without a load.

Personally, I would be looking for a better circuit for the application

 

[Clarkdale44]

I have always known Tranny as meaning a Transformer, also common, depending on conversation topic, a cheap portable broadcast radio receiver. I have always called or referred to a Transistor as just that, a Transistor

What is the transformer in the circuit? A wound Pot Core? Striking up a 25W tube with this circuit is one thing, which is possible if the output voltage is high enough, having it running at anything like full brightness without either burning out the cathodes or the driver itself is another matter. Adding more turns to the secondary will not only increase your output voltage, it will also increase your feedback voltage. At some point your driver transistor is going to become uncomfortable with that unless you take some precautions with your design. For a simple non regulated circuit like this, a choke in your secondary to limit tube current wouldn't be a bad thing either for example. The transformer breaking down is not unheard of if wound incorrectly or poorly. Because of the high voltages between layers of windings, you may need to place a layer of insulation every few layers, not only that, you need to be very careful when winding that you do not damage the wire insulation (I'm assuming bare enamel wire here) or allow any turns from your current layer to slip down into the middle the previous layers as well as perhaps stacking the successive layers towards the middle of the former such that you increase the distance between the higher and lower voltages at each end of the layers of windings. Also beware of operating the circuit, even momentarily, without any load on the secondary. Even a single "oops" moment with the tube connections may well be enough to fry your driver transistor due to the excessive secondary voltages produced when the circuit is run without a load.

Personally, I would be looking for a better circuit for the application

Well, i understand what you are trying to say, it is not my circuit to begin with, i just followed though a tutorial to build it, also i wanted to build something that was easy. I tried adding more turns to the secondary but it was a failed attempt. My transformer shorted within few seconds. Since then whenever i try to connect power my transistor getting hot.
Well then i asked many people, they said my transformer is saturating due to a short in the winding. Then yesterday night i dismantled and winded it again. It worked again, but as i was getting happy and starting to make it permanent i thought i should check it again and then this thing happened. Transformer started giving strange noises and then cfl gone from bright to low and completely off and at the same time transistor was again burning hot. I had no idea why it happened again? It was running great minutes ago and tested running it for 30 minutes, i have big heatsink installed on the transistor. Still when it was working, heatsink was safe to touch, but now it might even melt solder.

I tried different transistor, capacitor, resistor but the transistor is still getting hot.

Just to let to know, when i was packing it all up, i saw one of the high voltage wire was touching the heatsink of the transistor, do u think this has anything to do with the issue?

 

[tunedwolf]

The likely failure modes here, assuming that you have wound the transformer with the correct phase relationships for each winding and also wired the correct ends of each winding to your driver circuit, is either excessive voltage on the base of your driver transistor, excessive tube current or lack of resonance. A better transformer will help, but it is a poor circuit to begin with. One major issue with this circuit is load dependent resonance, this will vary lamp to lamp to a large degree and will affect everything from initially striking the lamp to keeping it lit as well as the current drawn. Dimension the components and transformer correctly for the lamp being driven and the circuit will resonate, the current drawn will drop after the lamp strikes up and the transistor and transformer will run reasonably cool. Get it wrong and the circuit will not resonate properly, if at all, excessive current will flow in the primary, leading to heating of both the transistor and the transformer winding and the lamp will either not strike at all, or may initially strike then run really dim as the circuit struggles to achieve resonance. Another thing to be aware of here too, is generation of stray radio waves, this circuit is likely to cause major radio interference locally.

My advice here is to look for a better circuit, perhaps something using a more traditional push/ pull transistor arrangement and a much more forgiving transformer design

You haven't stated in your profile where you are in the world, but there are inexpensive drivers from the far east available on ebay, amongst other places, that come fully assembled and are reasonably reliable, maybe that would be a better route for your project? All you have to do is add your tube and a power source

 

[Clarkdale44]

The likely failure modes here, assuming that you have wound the transformer with the correct phase relationships for each winding and also wired the correct ends of each winding to your driver circuit, is either excessive voltage on the base of your driver transistor, excessive tube current or lack of resonance. A better transformer will help, but it is a poor circuit to begin with. One major issue with this circuit is load dependent resonance, this will vary lamp to lamp to a large degree and will affect everything from initially striking the lamp to keeping it lit as well as the current drawn. Dimension the components and transformer correctly for the lamp being driven and the circuit will resonate, the current drawn will drop after the lamp strikes up and the transistor and transformer will run reasonably cool. Get it wrong and the circuit will not resonate properly, if at all, excessive current will flow in the primary, leading to heating of both the transistor and the transformer winding and the lamp will either not strike at all, or may initially strike then run really dim as the circuit struggles to achieve resonance. Another thing to be aware of here too, is generation of stray radio waves, this circuit is likely to cause major radio interference locally.

My advice here is to look for a better circuit, perhaps something using a more traditional push/ pull transistor arrangement and a much more forgiving transformer design

You haven't stated in your profile where you are in the world, but there are inexpensive drivers from the far east available on ebay, amongst other places, that come fully assembled and are reasonably reliable, maybe that would be a better route for your project? All you have to do is add your tube and a power source

Well, i admit the circuit is quite poor, also i know i can just buy it off ebay but what's the fun in that? The only reason i made this because its easy and fun.

Anyway, i rewinded the transformer, the third attempt, and it is working again. I guess in the end transformer was shorted due to HV secondary was touching transistor heatsink. This time i made sure that there is proper insulation between each and every layer not just the secondary. I am gonna put everything back together in pcb today. Breadboard testing was successful and cfl was able to light up about 60% bright. Gonna need a bigger heatsink though. Also it can drive cfl's up to 20w.

Thanks for all the help...