How do I drop from 12v to 5v
Jul 6, 2007 at 11:40 AM Thread Starter Post #1 of 7

StevieDvd

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I have a couple of 12v SLA (batteries) lying around and thought I could try to use these as a nice clean power supply for my new Squeezebox3 which has a 5v feed.

I've already got a lead made up with a diode in-line to prevent from wrong polarity connections from an earlier project, it's in a small case with an on/off rocker switch.

Have seen the small electronic gizmos which look as if they just wire up the 12v on one pair of connectors with the 5v coming from the other pair. Is that all I need to get and do I need to worry about heat etc?

Any help/advice appreciated.

Thanks

Steve
 
Jul 6, 2007 at 11:51 AM Post #2 of 7
Without using an efficient switching DC-to-DC convertor, this is not going to be a useful exercise. And I believe you are probably thinking about battery power to avoid the switcher...

The Squeezebox3 comes with a switching DC wallwart with 2A of current capability. Assuming that the unit actually draws somewhere close to that (and I've heard that it does), dropping 7 volts in any sort of linear fashion will cause a dissipation of 7V * 2A = 14W. This is wasted as heat, and is not an efficient use of your battery.
 
Jul 6, 2007 at 12:41 PM Post #3 of 7
If you'de rather not waste the power and convert it into heat with the linear regulators, as amb has said, then your only other choice (if you want to use the 12v batteries) is to use a high-quality switching regulator that will hopefully be out of the audio range. But as has been mentioned, the whole point of going battery powered is to get away from the switching power supply and the irregularities related to wall power.
 
Jul 6, 2007 at 3:48 PM Post #5 of 7
There are SLAs configured for 6V. That plus an LDO regulator might be practical.
 
Jul 6, 2007 at 5:41 PM Post #6 of 7
Thanks for the useful and informative replies. I had thought that the voltage drop may have generated heat but not based on any real electronics knowledge thought it best to check.

I'll probably just get a linear psu for the squeezebox, as I've seen recommended by other users.

Those spare 12v SLA will get used eventually!

Steve
 

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