Help understand circuit

[ffp]

Well, i think i'll have to take all components of to verify windings and pins... I'll post the resuslts. But i tought every 5 pin transformers were the same. I found other links with the same shocker and they always use this connection. They doesn't even follow a schematics, just solder the components this way and it's done.

 

[ffp]

I think i found the problem. Using the ohmeter on the transformer i could get ~3Ω from the two pins winding and ~300Ω from the outter two pins of the 3 pins winding. But i couldn't get any resistance between the midle pin from the 3pin side and any other pin!

Why is that? And how can i fix it? Seems that the transformer isn't working...

 

[ccurtis]

I think i found the problem. Using the ohmeter on the transformer i could get ~3Ω from the two pins winding and ~300Ω from the outter two pins of the 3 pins winding. But i couldn't get any resistance between the midle pin from the 3pin side and any other pin!

Why is that? And how can i fix it? Seems that the transformer isn't working...

First of all, by no means are all transformers the same. It is easily conceivable that two transformers from two different disposable cameras are different, even. Something I don't understand, though. When you say you get 3 ohms from the "two pins winding", what does that mean? Does that mean the between the two pins on the side of the transformer that only has two pins (as opposed to the side of the transformer that has three pins), or do you mean between the two left-most pins of the side of the transformer that has three pins on one side, where the primary winding is supposed to be on that guy's transformer?

As far as the open pin goes, that is not good. Take a good look at the transformer to see if there is a wire leading from inside the transformer that is broken and not connected to a pin, or maybe connected to the pin but broken somewhere in-between the pin and the body of the transformer. If you can't see anything then your transformer is different, having an unused pin. It is then, practically, a four pin transformer and it would very difficult to "fix" to get a tap for the fifth pin.

 

[ffp]

I mean the first. The two pins from the side where there are only two pins have 3 ohms. My transformer have 5 pins and i can see the windings coming from its core to the pins. Including the middle pin (from the 3 pins side, which isn't working) i can also see the wire and it looks like all the others, attached to the pin.

I don't know whats wrong and i really hope that i don't need to get another transformer...

 

[ccurtis]

I mean the first. The two pins from the side where there are only two pins have 3 ohms. My transformer have 5 pins and i can see the windings coming from its core to the pins. Including the middle pin (from the 3 pins side, which isn't working) i can also see the wire and it looks like all the others, attached to the pin.

I don't know whats wrong and i really hope that i don't need to get another transformer...

I see. Since you measured 300 ohms resistance between the two outer pins on the side of the transformer that has three pins, then your transformer is different from that guy's transformer, in any case, because those two pins on that guy's transformer are not associated with the same winding. It would seem to me then that you connected the transformer incorrectly thinking it was the same as the one in that guy's photo. Therefore, you could have burned up a winding inside the transformer from too much current. From what you measured so far, it appears that your transformer possibly could have worked in this project. Unfortunately, I think you have to get another transformer. If you had looked very closely, you should have seen the thicker wires wired to different pins on your transformer compared to that guy's transformer.

 

[ffp]

Yeah, you're right. But a burned wire shouldn't at least show some resistence? Or maybe a short circuit? I don't understand why i can't measure any resistence.

 

[ccurtis]

Yeah, you're right. But a burned wire shouldn't at least show some resistence? Or maybe a short circuit? I don't understand why i can't measure any resistence.

The wire probably burned completely through so as to leave a small break in the wire, leaving an open circuit. If the wire is very thin it does not take a huge current to do that. A fresh AA battery can deliver a flash current of 10 Amps which is enough to fuse a 30 gauge wire almost instantly. The wire also got hot in the process and likely did damage to the insulation of nearby wires inside the transformer. Since you see a wire connected on the outside but it makes no continuity to anywhere, it is either at a very high resistance, or open altogether. You can be sure of that.

Depending on exactly how everything was wired, you should consider that the transistor and/or diode is also damaged. But as the saying goes, if at first you don't succeed, try, try again.

 

[ccurtis]

I simulated the circuit in CircuitMaker for you. The added resistors simulate the winding resistances. You have to modify the spice values for the default transformer as I indicated in the text next to the schematic. Right click on the transformer, edit device data then change the default coil inductances. Have fun!

 

[ffp]

That's weird, because they say that the diode and transistor are heat sensitive and would burn faster than anything else, and my transistor and diode seems to work. Could the transfromer be damaged by soldering?
Anyway, i'll manage to get another one and do it right...

EDIT: Now i saw the circuitmaker. Thank you, this will help me understand the circuit. I'll try to simulate one myself. And i thought the voltage would be continuous...

 

[ccurtis]

That's weird, because they say that the diode and transistor are heat sensitive and would burn faster than anything else, and my transistor and diode seems to work. Could the transfromer be damaged by soldering?
Anyway, i'll manage to get another one and do it right...

Soldering temperature doesn't come close to melting copper wire, but it can damage semiconductor devices and wire insulation of transformers if applied too long to the pins/terminals of those parts. An open wire inside a transformer is very unlikely to be caused by soldering temperature.

 

[ffp]

So, it must be caused by electric current...
I simulated the same circuit you did with same values and same components, even diode and transistor, but couldn't get the same results.
Also, do the diode and transistors must be this one you used or anyone should work? The transformation relation is ajusted by the windings mH, right? And why you didn't put resistance to all windings?

 

[ffp]

Here's what i got:



Transformer indutance are like your picture: .2, 60 and .1 mH

 

[ccurtis]

You need to simulate for a longer period of time, for at least one thing. The circuit takes milliseconds just to get started and stabilize and you only simulated for 5 uS. You can try other transistors and diodes. I chose those because they are high voltage devices. I'm not sure if the simulator cares about that, but it matters in the real world.

 

[ffp]

Simulating for a loner time i got -900V too, but it takes almost 150ms to get there.In the start it stays at -70V for a while. But in real life any transistor would do? I'll get another tranformer tomorrow and i'll post the results.

 

[ffp]

I got another transformer. This time i can measure the resistence between pins. Pin 1-2 ~3ohms, pin 3-4 ~300 ohms and 4-5 ~1 ohm. I made a image in autocad for what i plan to do with the components. Crossing lines were made doted or slashed for better visualization.



Tell me if something is wrong, before i burn another transformer

 

[ccurtis]

It looks okay. Did you check the transistor and diode with an ohmmeter for shorts?

If all is wired okay and parts are good and if it still doesn't work, then swap the connections to pins 1 and 2 on the transformer (move wires connected to pin 2 to pin 1 and wires connected to pin 2 to pin 1). Keeping fingers crossed.

BTW, what part numbers are your transistor and diode and where did you get them?

 

[ffp]

It finally worked!! Got 330V output instead of 450V and had to change primary connections, but it's ok. Now i must find some way to build a nice case for it...

Thank you very much!!

 

[ccurtis]

Good job. I'm happy to see your perseverance paid off. You could try tweaking the value of the 220 ohm resistor and/or the value of the capacitor to increase the voltage. The capacitor appears to be selected to resonate with the transformer and the resistor dictates the operating frequency to some extent and your transformer is different from that guy's transformer. Trying a different transistor with different gain will also affect the frequency and output voltage.

 

[ffp]

Thanks. How can i know how much input voltage the components can handle? I think it's easier to make a case for a 9V battery, but i'm afraid to burn something.

 

[ccurtis]

Thanks. How can i know how much input voltage the components can handle? I think it's easier to make a case for a 9V battery, but i'm afraid to burn something.

It can difficult to determine analytically because of the several variables involved, not all of them easily known. I don't think you have to worry about burning up the transformer but the transistor and diode are vulnerable to overvoltage stresses in this circuit. Simulation can be useful to help with determining the voltages that exist across the various nodes in the circuit to aid with semiconductor selection. The datasheets for the devices provide maximum voltage ratings.