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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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Old 12-25-2008, 08:48 AM
wasanne wasanne is offline
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Smile step down transformer

is it possible to build a cheap step down transformer that will accept a car ignition coil as the source power and privide a high amp output. I can't measure the voltage or amperage from a coil but I believe the volts to be at least 30,000 but the amps are only milliamps. Stepping down voltage must increase amps but how far can you step down the voltage and what possible amperage could be extracted from it. thanks. wasanne.
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Old 12-25-2008, 02:43 PM
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beenthere beenthere is offline
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Transformers are devices that deliver power, but at different voltage and current.

Let's say an ignition coil still has the same input as ones I am familiar with. The primary is driven with 12 volts and 7 amps, or 84 watts of power. Going the other way, the power it can handle stays the same. So driving the secondary with a high voltage pulse will still only be able to transfer 84 watts to the primary.

There are better transformers for high current applications. How high is the current you wish to use, and at what voltage?
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Old 12-25-2008, 06:23 PM
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SgtWookie SgtWookie is offline
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Well-designed transformers are fairly efficient, but you'll always lose some power when you exchange voltage for current (or vice versa), due to the resistance of the windings, eddy currents, and other losses.

So, when you step up the voltage using an ignition coil, some of the power is lost in the form of heat due to the resistance of the windings. If you then use another transformer to step the voltage back down to increase current, you incur another loss due to the resistance of the windings. You wind up with less effective power than what you started off with.

These losses are acceptable for long distance power transmission; your power company uses this very scheme for power distribution. High voltage at low current requires far smaller sized conductors than high current at low voltage.

If you really wanted more current at a lower voltage, you would be better off to start with a step-down transformer to begin with.

What is it that you're considering?
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