if inductors don't increase amperage then how does a camera flash circuit boost the current from a AA battery

Question

this has been a very annoying question for me
how does a camera flash circuit get 300 volts out of a AA battery
but i am pretty sure someone on here knows but i now know that inductors don't increase the current so it will have to be some thing else but what is it?

Answer 1

Inductors boost voltage, not current. The photoflash needs a high voltage but not a high current. The circuit can basically be described as this:

An oscillator section creates an AC signal that a transformer then boosts in voltage (DC doesn't work on transformers). The high voltage is rectified (converted back to DC, as AC doesn't work on capacitors), then stored in a large high voltage capacitor. Once that is done, the flash is ready to go off. The energy stored in the capacitor is dumped rapidly into another voltage boosting circuit (with another transformer). The pulse voltage is raised and dumps its energy into the Xenon bulb. The end result is a short flash of light which is short because once the capacitor empties its charge, the light can no longer remain lit.

Here is a circuit and description:
http://www.geocities.com/lemagicien_2000/elecpage/maxflash/maxflash.html

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If there are any other electrical engineers here, keep in mind this was a question asked on a fairly basic level. I've tried to explain this as fundamentally as I could do to answer the question.

Answer 2

In short, it's not exactly an amperage increase, but a two stage voltage increase. The DC voltage is made to switch on and off during charging the flash--in effect making it a square AC wave. A transformer is used to 'step up' the voltage. A transformer that has AC current flow through it's 'primary' or input winding produces a magnetic field that can be coupled to a "secondary" or output winding (a transformer, in simplest terms is two coils of wire--two inductors--insulated from each other but wrapped around a common core--the two coils are only coupled magnetically). If the primary winding has less turns in the coil than the secondary, the voltage measured across the secondary will be increased--stepped up (though the current decreases--the 'power' or wattage--current X volts, has to be a net even transfer (assuming a perfect transfer of energy, though some will be lost in the transfer)). The higher voltage will be rectified, or turned back to DC, then is used to charge a capacitor, which acts like a high voltage rechargeable battery, charging to match the input voltage. A capacitor can discharge the voltage rapidly, in a burst of high current. The flash trigger switch causes the cap to discharge through the primary of another transformer (the voltage from the capacitor drops during discharge, so the transformer can pass what is in effect a voltage spike). The second transformer also steps up the voltage even further, to the 1000+ volts needed to ionize the gas in the flash tube. The gas ionizes, current flows, the ions give of a burst of light until the voltage available no longer lets the current flow. There is a high amperage (current flow) briefly as the high voltage drains from the capacitor.

Hope that helps.

Answer 3

The thing about inductors is that once a current is flowing in one, if you stop it the current has a tendency to remain the same.

You can do all kinds of tricks with this ... like interrupting the current and then pointing it through a big resistor, which will generate a very large voltage. That is a single coil.

If you put two coils together and one has more turns that the other, the one will more turns will have a higher voltage across it almost by magic ... it is INDUCED ... hence the name inductor.

so, if you have a 1.5 volt battery and you put it across a transformer with 200 times more windings on the output than the input, you will get 300 volts out of it ... the tradeoff is that you do not get much current. A flashbulb does not need a lot of current though.

A capacitor, which you probably are talking about charges up and stores a lot of electricity on plates, then when you redirect it across a bulb you get enough current to set it off. That is why you have to wait for the capacity to charge, whereas in the inductor you have to wait for the current to build.

Electrical engineering is cool.

Answer 4

An inductor, like a coil with thousands of turns of wire, resists a current building up in it. When you connect the ends to a battery, the steadily increasing magnetic field due to the current opposes the current, so it takes several seconds for the current to reach a maximum and there's energy stored in the magnetic field. If you disconnect the battery, the field suddenly collapses and you get a very brief high voltage between the two ends of the coil. This is how the ignition coil in a car uses 12 volts from the battery to give a spark of several thousand volts; the points in the distributor continually interrupt the current to the coil. For a very high energy pulse of electrons, you use a Blumlein line, which consists of a series of coils and capacitors. If you charge the capacitors in parallel and start a current flowing through the coils in series, then suddenly reconfigure the circuit so the capacitors are in series and the coils are in parallel, then all the electrostatic field energy in the capacitors and all the magnetic field energy in the coils is suddenly released as a huge jolt of electricity. In theory this could give a pulse of electrons which, if directed at a pellet of tritium, could set off a fusion reaction.

Answer 5

Don't let your interest in electronics annoy you.
It's frustrating at times, but interesting none the less.
The "inductor" you're referring to is actually a transformer - two inductors together in one package. The primary winding (the one receiving the input AC voltage) induces a current in the secondary winding (the output AC voltage).
Here's the great part - the power in will always equal the power out - but the voltage in will be increased or decreased in direct proportion to the number of windings in the transformer.
For example, if you have 100 primary windings and 1000 secondary windings, the ratio is 1:10.
If we put 12 VAC into the primary, the secondary will be 120 VAC.
As you can see, if the ratio were 1:200, a 1.5 volt AA battery converted to AC feeding the primary will out put 300 VAC.
Sometimes it gets a little more complicated - when capacitors are used to double or triple the voltage, but the important thing to remember is that the power in always equals the power out.
Power=Amps*Volts (P=IE)
So no increase in power actually takes place - the voltage increase comes at a sacrifice of amperage potential. If 1 volt at 1 amp, for instance, is the primary of a 1:10 transformer, the output will be 10 volts, but only at 0.1 amps.
The power must equal. 1*1 or 10*0.1 = 1

Answer 6

Yeah, it doesn't have anything to do with the inductors. Regardless of the battery size, you can charge up a capacitor of the right size and get the static release that powers the flash or zaps your buddies...haha.

Answer 7

Capacitors in a circuit can take a charge over a period of time and release it at a much higher rate when needed.

Answer 8

You're talking capacitors, not inductors - they are NOT the same!

Answer 9

it stores it up in a medium sized capacitor, then zap