electronic inverter help

[deerslayer660]

    http://members.misty.com/don/flvdc.html    heer is the ckt

      pleaase help in the Low power fluorescent lamp inverter 1: i am having trouble finding a part

#  for transformer core and a place to order these the transformers i have wound i had to wined on old cores that were steel core and can only get maybe 1 out of 8 to work. when working

this inverter works great driving a  F8t5 12" fluorescent to full bright at only 400ma witch is enough  light to light a room 12' x 15'  i will need maybe 20 of these lights when im finished

so i  need a supply of cores that work everytime i wined one   thanks george

[deerslayer660]

   I schoud have noted that this is the secound ckt down on the page not the first

thanks again george

[Psycogeek]

i am not positive, but if it was a 110 on the high side, then it would be about a 5v on the low side, because it is center tapped, mabey a 6v -6v or 12v center tap would work.

then a adjustment of r2 for any differences.

this is all out of my league, but that is how i would Wang it out :-)

[Psycogeek]

and if you wanted more high side, and mabey a smaller transformer

a 3v -3v centertapped 6v transformer would give more voltage to the output.

oops (again)

i am in the US, so the other side of most of our transformers start at 110-120

the "turns" are reletive to the "ratio" of voltage decrease or increase on the other side.  and he only estimated them anyways.

[Psycogeek]

see also

http://www.fieldlines.com/story/2005/1/31/234116/315

looks at least as well explained.

[deerslayer660]

   psycogeek i think your looking at the first and not secound ckt down on page it will give transformer detais  george

[deerslayer660]

  also the rod transformer from the previous posts is a power waster almost 3 amps draw and overdriving the 12" blub  along with a lot of the other ckts that are easy to find transformers for ckt 1 says it needs a 2 amp supply im tring to conserve

thats the whole gole here im sure someone here smarter than me can solve this prob  george

[commanda]

I have used this basic circuit to light the backlight on lcd displays. The transformer I used was an audio coupling transformer out of an old transistor radio. Radio shack would probably have them. Little red or blue things. need to run them at about 10 KHz to work. The iron cores drop off rapidly much above this.

Start dumpster diving for old computer power supplies. They usually have either 1 or 2 ferrite cored transformers in the size range you're after. Soak them in paint stripper overnight to get apart.

When winding your coils, watch the phasing of that centre-tapped primary. The centre-tap must be the end of one winding, and the start of the other winding. Joining 2 starts together won't work.

Also, this circuit typically won't work with low-gain transistors.

Ferrite rods out of transistor radios will also work in this application.

Amanda

[deerslayer660]

   thanks for replie amanda i had allready salvaged a few ferrite core transformers

from puter power supplies broke all tring to get appart you tought me a new trick i will try next time. also knew about high gain trans. been ueing salvaged from output

side of old cb radios to test. nte186a is what i bought and think will be best to

ues reliabley. after more testing i find the best way to wind these is to wind feedback and pri side by side first 28t each than 300t secoundary. scotch tape in between layers.  secoundary to be a couple wire sizes smaller than feedback and primary. i have now sucessfully wound this on 4 differnt size cores 58" x 34"  

up to 2" x 1 34" witch drives a 15w tube to full bright. im sitting here winding i

58" x 38" with all #36 wire to see what happens. forgot to say these are all steel lamitated no need for ferrite except for maybe efishancy.  also i would like to try

this  can you look at another schmatic for me i cant figure out value of ris 1 and conection of q3 makes no sence to me  ckt is here  http://www.edn.com/archives/1994/033194/07di4.htm   thanks george

[deerslayer660]

 don't know hapened schould have been 5/8" x3/4" to 2" x 1 3/4"  also 5/8" x 3/8"  george

[commanda]

If using laminated iron cores, you'll want to drop your frequency. Do you have an oscillocope? Very useful tool. To lower the frequency, increase the size of the cap on the '555.

The circuit on EDN. R1 is 0.62 ohm, so when the circuit current rises to 1 amp, the transistor connected to it will turn on. This removes gate drive from the scr, and also base drive from the first transistor. This removes the anode supply from the scr, so it resets, and also removes gate drive from the output fet, so the current through the coil switches off. Once this current stops, the voltage across R1 switches off and the whole process starts over. Note for this circuit the output device must be a fet; The value of R1 determines the overall circuit current drain, and it's a resonant circuit. The frequency determined by the inductor, the capacitor on the transformer's secondary, and the tube.

Overall, a pretty neat circuit.

Amanda

[deerslayer660]

    thanks amanda i thought r1 was .62 ohm but i cant get a very clear pic of the ckt

 the number on the scr 2n5027 crosses to a nte 123ap q1 and q2 2n3904 also cross nte 123ap   i have a bag full of 2n4401 cross nte123ap think i will be ok useing these?

 from print q3 will be base  and emitter going on ground correct the guy that drew

that schould have showed that as transistor not a scr just to save confussion. one last question do you think bk changing th cap that i could get it to work with a stel lam core transformr? got a good guess what valu to use? also have to change r1?

 yes i have a scope but it's packed away with some more of my old test equ  i used to be in the communation biz in the 80s till early 90s doing tellefany tv vcr repair

satv and closed curcit tv. early 90s everything started becoming throughaway and harder to make a living so i switched to hvac. any way im just playing around now with these lights till fishing season gets going good so i dont feel like seting up a full bench  thanks george

[commanda]

Your cross-reference list must be wrong, or you're reading the number on the scr wrong. No way can the 2 npn transistors cross-reference to the same device as the scr crosses to. Pretty well any common npn transistor should do for the 2 transistors. Here in Australia, that would be BC548.

Amanda

[deerslayer660]

  amanda can you look back at the curcuit and see if scr number there is 2n5027?

im having a hard time seeing numbers clear.  and the person who wrote directions  

refers to the colector of q3 going to the gate of q4 and emiter of q1? also you got a number of a scr to use in this circuit? thanks again for all your help  george

[commanda]

First, your directions are wrong; that should read "base of Q1".

Second, I just went & looked up my farnell catalogue for unijunction transistors, and found a 2N6027. I think this is the device specified on your circuit.

Amanda

[Nando]

George:

Where are you located ?.

I see that you want a 12 volts !2 " lamps for about 8-10 watts.

Home Depot has those lamps for about 8 or 9 Dollars each that have about 6 to 8000 hours life.

They use a single transistor converter at around 20 KHZ rate.

The info for the circuits that they have supplied in this thread have a common problem and it is the starting current and the operating frequency stability that give a reduced lamp life.

What is your electronic knowledge, as well, the mechanical and electrical principles to wind the wanted transformers -- you want 20 of them ?.

One basic problem is the voltage isolation between layers.

I can calculate the transformer for you with starting filament windings and lamp resonance for long lamp life, a POT core may be the easiest core to use, size around 18 mm diameter( less is ok).

Regards

Nando