Need advice on making a DIY car MP3 charger - Electronic Circuits Projects Diagrams Free

baristabrian · 5th June 2007, 03:59 PM

Hello all, any advice on how one would construct a charger for an MP3 player to be used in an auto? What would I need to convert the car's power supply (13.2v, ?? amps) into a suitable supply for the MP3 player (5v, 2a)? Any help would be greatly appreciated! Thanks, Brian

audioguru · 5th June 2007, 06:40 PM

Your MP3 player probably has an operating current much less than 2A.
Use an LM317 adjustable voltage regulator set for a 3V output. Its max current is 1.5A. You are throwing away about 10.5V so it will get hot and will need a heatsink.

justDIY · 5th June 2007, 09:00 PM

buy a moto razor cell phone charger off ebay for $1.99 and call it done.

the razor chargers are dirty cheap 'cause the phone is so popular. the charger already contains an efficient switch mode buck converter, and since it's for the razor, it already has the mini-usb connector on it.

if mini usb doesn't work for you, you can lob the end off and solder on whatever end does work.

or yea, you can hack together something using a cold-war era linear regulator like the lm317 or easier still the lm7805. it'll waste more power than it provides.

baristabrian · 5th June 2007, 11:23 PM

Thanks for the input guys. Sounds like the DIY route may not be that feasible. I noticed the PlayStation Portable charger has a 5v 2a output. I may go that route. Sounds like the "switch mode buck converter", whatever that is, is what I need. And it doesn't sound like something I'm going to get for $1.59 at Radioshack. Thanks again for the advice! Brian

audioguru · 6th June 2007, 12:38 AM

I bought some switch-mode 5VDC/2A tiny power supplies for a couple of dollars at a surplus electronics store. They are name-brand and were made for a router that is now obsolete. The power supplies are only 2 years old.
Older ones would cost about $60.00 at Radioshack.

justDIY · 6th June 2007, 01:46 AM

unless your mp3 player is very old, I can't see how it would require 2 amps. 2 amps at 5v is 10 watts - a lot of energy for a battery powered device.

my guess is you're getting the 5v/2a rating from the wall charger or something?

baristabrian · 6th June 2007, 04:43 AM

Yeah, it's kinda old....here's the owner's manual with the specs.

http://www.iriveramerica.com/download/H100/H120_Eng.pdf

I recently replaced the stock iRiver battery with a 1st gen. iPod battery (getting 24+ hr. run times!). Would 550 mA keep it topped up? Or does the player have some charging circuit that requires 2A? Guess I could always hack the USB end off my phone charger and see! Thanks again! B

audioguru · 6th June 2007, 01:56 PM

If the 1st gen. iPod battery has a higher capacity then the stock battery then it will probably take longer than 3 hours to charge from being completely discharged, if the stock 2A charger is used. A 550mA charger would take 4 times longer.

justDIY · 6th June 2007, 01:59 PM

if it's running for 24 hrs on an ipod battery, take the current rating (mah) for that battery, and divide by 24 - that will tell you how many amps your device needs (roughly)

audioguru · 6th June 2007, 03:52 PM

Quote:

Originally Posted by justDIY

if it's running for 24 hrs on an ipod battery, take the current rating (mah) for that battery, and divide by 24 - that will tell you how many amps your device needs (roughly)

But your calculation is for the current used by the MP3 player, it does not include charging current for the battery.

baristabrian · 6th June 2007, 04:14 PM

Wow, you guys are good! I'm sort of an electro-neophyte, but after successfully replacing the battery and building a surprisingly good sounding CMoy headphone amp I was all gung-ho construct a home brew charger as well. I'm beginning to realize the eBay PSP charger may be the practical (and safer) way to go. Thank you all for the input! Having such a knowledgeable group as youselves available to help out on any future projects will bolster my confidence greatly. So glad I stumbled across your forum, it's a wonderful asset!

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5th June 2007, 03:59 PM	(permalink)
baristabrian	Need advice on making a DIY car MP3 charger Hello all, any advice on how one would construct a charger for an MP3 player to be used in an auto? What would I need to convert the car's power supply (13.2v, ?? amps) into a suitable supply for the MP3 player (5v, 2a)? Any help would be greatly appreciated! Thanks, Brian

5th June 2007, 06:40 PM	(permalink)
audioguru	Your MP3 player probably has an operating current much less than 2A. Use an LM317 adjustable voltage regulator set for a 3V output. Its max current is 1.5A. You are throwing away about 10.5V so it will get hot and will need a heatsink. __________________ Uncle $crooge

5th June 2007, 09:00 PM	(permalink)
justDIY	buy a moto razor cell phone charger off ebay for $1.99 and call it done. the razor chargers are dirty cheap 'cause the phone is so popular. the charger already contains an efficient switch mode buck converter, and since it's for the razor, it already has the mini-usb connector on it. if mini usb doesn't work for you, you can lob the end off and solder on whatever end does work. or yea, you can hack together something using a cold-war era linear regulator like the lm317 or easier still the lm7805. it'll waste more power than it provides. __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

5th June 2007, 11:23 PM	(permalink)
baristabrian	Thanks for the input guys. Sounds like the DIY route may not be that feasible. I noticed the PlayStation Portable charger has a 5v 2a output. I may go that route. Sounds like the "switch mode buck converter", whatever that is, is what I need. And it doesn't sound like something I'm going to get for $1.59 at Radioshack. Thanks again for the advice! Brian

6th June 2007, 12:38 AM	(permalink)
audioguru	I bought some switch-mode 5VDC/2A tiny power supplies for a couple of dollars at a surplus electronics store. They are name-brand and were made for a router that is now obsolete. The power supplies are only 2 years old. Older ones would cost about $60.00 at Radioshack. __________________ Uncle $crooge

6th June 2007, 01:46 AM	(permalink)
justDIY	unless your mp3 player is very old, I can't see how it would require 2 amps. 2 amps at 5v is 10 watts - a lot of energy for a battery powered device. my guess is you're getting the 5v/2a rating from the wall charger or something? __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

6th June 2007, 04:43 AM	(permalink)
baristabrian	Yeah, it's kinda old....here's the owner's manual with the specs. http://www.iriveramerica.com/download/H100/H120_Eng.pdf I recently replaced the stock iRiver battery with a 1st gen. iPod battery (getting 24+ hr. run times!). Would 550 mA keep it topped up? Or does the player have some charging circuit that requires 2A? Guess I could always hack the USB end off my phone charger and see! Thanks again! B

6th June 2007, 01:56 PM	(permalink)
audioguru	If the 1st gen. iPod battery has a higher capacity then the stock battery then it will probably take longer than 3 hours to charge from being completely discharged, if the stock 2A charger is used. A 550mA charger would take 4 times longer. __________________ Uncle $crooge

6th June 2007, 01:59 PM	(permalink)
justDIY	if it's running for 24 hrs on an ipod battery, take the current rating (mah) for that battery, and divide by 24 - that will tell you how many amps your device needs (roughly) __________________ If you don't have a planet, what good are gold bars? want to contact me directly? gmail gordonthree check out my project website: http://projects.dimension-x.net Favorite numbers: 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

6th June 2007, 04:14 PM	(permalink)
baristabrian	Wow, you guys are good! I'm sort of an electro-neophyte, but after successfully replacing the battery and building a surprisingly good sounding CMoy headphone amp I was all gung-ho construct a home brew charger as well. I'm beginning to realize the eBay PSP charger may be the practical (and safer) way to go. Thank you all for the input! Having such a knowledgeable group as youselves available to help out on any future projects will bolster my confidence greatly. So glad I stumbled across your forum, it's a wonderful asset!