Tiny inverter and transformer inside of a disposable camera

[LalalaIhaveachair]

Hey everyone, I have nothing but a year of conceptual physics under my belt so I apologize in advance for the horrendous errors I make.


I have a project I'm taking on, in which I'd ultimately have a 1-2cm spark gap, powered by one or two AA batteries. I'd want the device to be handheld (I'm already moderately aware of the safety implications).

I obviously need an inverter, and a transformer (if not a few lined up in series). Do you guys know of any tiny inverters and transformers? I know that they're present in disposable cameras, and I've taken a few apart today, but I'm not sure if they're what I want/what will work. If you know where I could buy these online/in the real world, please reply or message.

These things would have to be pinky-fingernail sized at most.


Thank you,

lalalaIhaveachair

 

[DerStrom8]

Hi, lala. Welcome to ETO
The transformer inside a disposable camera is no where near enough to jump a 1-2cm gap. Using a basic rule of thumb (1kv/1mm, or 10kv/1cm), that would require 10-20 thousand volts. The transformer inside the camera is usually about 300 volts on the output. To get 20kv from two AA batteries, you would need a transformer with about a 1:6666 turn ratio, and to fit it in such a small space the coils would have to be absolutely tiny. This means a lot of resistance, and things just wouldn't work out right. I'm afraid what you are suggesting would be very difficult, unless you use a transformer output to feed another transformer, etc. It would get very complicated. Are you sure you can't adjust your space requirements? We could work with you a bit easier if you increased the space to, say, 3cm x 5cm. Is there any chance of this happening?
Der Strom

 

[LalalaIhaveachair]

Hi, lala. Welcome to ETO
The transformer inside a disposable camera is no where near enough to jump a 1-2cm gap. Using a basic rule of thumb (1kv/1mm, or 10kv/1cm), that would require 10-20 thousand volts. The transformer inside the camera is usually about 300 volts on the output. To get 20kv from two AA batteries, you would need a transformer with about a 1:6666 turn ratio, and to fit it in such a small space the coils would have to be absolutely tiny. This means a lot of resistance, and things just wouldn't work out right. I'm afraid what you are suggesting would be very difficult, unless you use a transformer output to feed another transformer, etc. It would get very complicated. Are you sure you can't adjust your space requirements? We could work with you a bit easier if you increased the space to, say, 3cm x 5cm. Is there any chance of this happening?
Der Strom

I was thinking of having multiple transformers in series. There's an inverter inside that steps up the current, and then another transformer. To flash, I've been told that you need 1-4 kV to jump the gap in that glass tube thing.

I could go to that size (is that the size of the whole transformer, or the size of the device?).

Thanks so much!

 

[DerStrom8]

I could go to that size (is that the size of the whole transformer, or the size of the device?).

That is the size of some photocopier transformers, which often produce around 10-20kv. You would need extra space for the driver, though.

Having multiple transformers in series I think would cause problems like excessive heat and current draw. Your windings could possibly melt, and your battery would probably drain very quickly. Also, you would have problems with the insulation on the transformers. They are not designed for high voltage.
Der Strom

 

[LalalaIhaveachair]

Awesome! do you know where I'd buy one of these? What's a driver?

Also, do you know how I'd make this safe? my ultimate idea is to create a lighter that lights things with a spark gap. Obviously though, if you're sweaty, it could turn you into bacon.

 

[DerStrom8]

Awesome! do you know where I'd buy one of these? What's a driver?

Also, do you know how I'd make this safe? my ultimate idea is to create a lighter that lights things with a spark gap. Obviously though, if you're sweaty, it could turn you into bacon.

I am not sure where you could buy one. I just found one once while tearing apart an old photocopier.
DC transformers most often require a pulse input in order to create and then collapse the magnetic field. The field is what induces the current in the secondary, so the pulse is crucial. A driver is external circuitry that creates this signal with the correct frequency and duty cycle for the transformer's optimal performance. A simple way would be to use a 555 timer with a MOSFET.
As for safety, use only high-voltage insulated wire on the output (you can usually find some in CRT televisions, coming from the transformer and attaching to the back of the screen). That is generally rated at 25-40kv (check the label on the wire). Also, keep the ends of the wire far from the case or anything metal within it to prevent arcs passing through the circuitry, and yourself
Der Strom

 

[LalalaIhaveachair]

Also, I was curious if there's a lower-cost, lower-voltage (I'd only need a few KV) option that I could run off of a 1.5V battery. Ultimately, it would be cool if I could mass-produce these, and sell them in stores.

 

[LalalaIhaveachair]

by the way I didn't intend low voltage to mean a few kV.... just relative to the photocopier transformer.

 

[colin55]

The trigger transformer produces over 5kV in a disposable camera. Here is the circuit I adapted to re-trigger the flash at a few Hz:
**broken link removed**

 

[LalalaIhaveachair]

Thanks so much!!!

the one thing I'm curious of is could this create a moderately continuous flow of charge, or be modified to do so? Camera flashes last for a fraction of a second.

Again, thank you!

 

[colin55]

Put the circuit on 3v and you will get about 10 sparks per second

 

[DerStrom8]

The problem with this circuit is that it won't produce arcs hot enough to light anything. That is why I suggested a different kind of transformer that might be able to do this.

 

[RCinFLA]

The inverter just charges the 120 uF cap across the Xenon flash. The tube does not conduct until the high voltage trigger. Cap is discharged quickly creating the flash.

Haven't you ever heard the 'whine' rising in pitch. It take 5-8 seconds for the inverter to charge the cap up. Many have a little LED to let you know when the cap has reached a high enough voltage.

Sounds like you want a stun gun. I am sure you can find one on eBay.