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Ipod charger safe?

Hello members, My son got this idea from Popular Science's March edition and asked me to help him build it. He's got an expensive Ipod and as I was helping him solder the components I was thinking "this is too simple". I don't know enough about power supplies but I've heard terms such as "current limiting" or "inrush" to worry about this damaging his expensive Ipod. It says it can recharge the Ipod, or power it if the internal battery goes low. Should I worry? Here's one link of many about the "charger".

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Any feedback is appreciated, Bart

Reply to
Bart
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View in fixed font or courier ____ 1| |3 +-----|7805|-------+ | |____| | | |2 | | | | ___ LED| +-||----+|___|-->|-+ 9V | | 160 | | +--+ | | | +----------+ | |1 usb 4 | | +----------+ | | +---------------+ (created by AACircuit v1.28.6 beta 04/19/05

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I made this schematic to show the "charger" circuit. I'm still worried about my son plugging it in to his expensive Ipod.

Reply to
Bart

I may have displayed the LED backwards, not sure. It's just to show that current IS flowing from the +5volt side.

Reply to
Bart

Yup, the LED should be the other way round. But if you don't feel comfortable building this then maybe it's better not to, right? :)

Should work as a power supply, though. Just be cautious with the USB connector pin order and triple-check it.

The main problem with the circuit I guess would be that the LM7805 (use TO-220 package version, LM7805CT) can heat up a lot, since something between one third and one half of the battery power is dissipated in the regulator. That's not very good for the 9V battery life either.

The 7805 has short circuit overcurrent protection, but no useful current limiting here. Adding a ~4ohm 1W resistor in series with the 9V could help to limit to around 500mA ("real" USB maximum), "just in case".

- Jan

Reply to
Jan Wagner

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