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Ipod charger safe?

B

Bart

Jan 1, 1970
0
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".

http://www.hackaday.com/entry/1234000270029372/

Any feedback is appreciated,
Bart
 
B

Bart

Jan 1, 1970
0
Bart said:
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".

http://www.hackaday.com/entry/1234000270029372/

Any feedback is appreciated,
Bart
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 www.tech-chat.de)

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

Bart

Jan 1, 1970
0
Bart said:
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 www.tech-chat.de)

I made this schematic to show the "charger" circuit. I'm still worried
about my son plugging it in to his expensive Ipod.
I may have displayed the LED backwards, not sure. It's just to show that
current IS flowing from the +5volt side.
 
J

Jan Wagner

Jan 1, 1970
0
Hi,
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 www.tech-chat.de)

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
 
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