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Rockbox mail archiveSubject: RE: Plugged in Car-charger - smoke out of my box - no chargingRE: Plugged in Car-charger - smoke out of my box - no charging
From: Chris Weaver <cweaver_at_bellsouth.net>
Date: Tue, 16 Mar 2004 20:50:46 -0600 Your reply is certainly not rude but it is a bit misleading as I agree was mine. You are correct that these are unregulated and if the output current was an order of magnitude different and the load was far below the rated load then you are correct it might be a problem. A non regulated supply will certainly have a high output voltage with very little current draw, perhaps 10% of rated output and lower. Specifically, the open circuit DC voltage output is 1.414 times the loaded voltage when using a full wave bridge rectifier. However, this voltage will drop as soon as you start to draw any significant current. Also note that the Archos power input is designed to handle this unregulated voltage and should be able to handle startup and low current draw voltages up to and exceeding the open circuit voltage. As a practical example, I have the V2 and the supplied 6VDC 700ma AC adaptor has an open voltage level of 9VDC which is identical to the open circuit output of my 2100ma 6VDC adaptor. I contend that the Archos would operate fine with either supply as both will operate in the same basic range of voltages given the Archos current draw. Although I admit that I have not measured either supply under load nor am I familiar with the typical range of current draw the Archos demands my point is that the specifics are not of any real concern as they are in the same basic range. -----Original Message----- From: rockbox-bounces_at_cool.haxx.se [mailto:rockbox-bounces_at_cool.haxx.se] On Behalf Of Fred Maxwell Sent: Tuesday, March 16, 2004 4:52 PM To: Rockbox development Subject: Re: Plugged in Car-charger - smoke out of my box - no charging Chris Weaver wrote: > The ability of the charger to supply more current than > required would not have caused the problem. > > It is no different than plugging in a stereo to a wall outlet that > is rated for 15A or 20A. That is the max current. Not to be rude, but you are incorrect. A wall outlet is voltage regulated. It doesn't matter whether you plug in an alarm clock that draws .1 amps or a space heater that draws 12.5 amps. The voltage will remain almost identical. Take a "9V" wall wart and measure the voltage with nothing attached. The 9V, 600ma wall wart that came with my Archos measures 14.5v with no load attached. Now, suppose I had a device that needed 9 volts at 10ma. If I plug the 9 volt, 600ma Archos wall wart into that, it's probably going to be feeding it something on the north side of 14 volts. You have to remember that the voltage and amperage are very much related in an unregulated supply. When a wall wart is rated 9V at 800ma, that means that it will put out 9 volts with an 800ma load. But there's no guarantee about what voltage you will get with a 50ma load (bet on something a lot higher than 9 volts, though). Regards, Fred Maxwell _______________________________________________ http://cool.haxx.se/mailman/listinfo/rockbox _______________________________________________ http://cool.haxx.se/mailman/listinfo/rockbox Received on 2004-03-17 Page was last modified "Mon Nov 16 10:57:21 2020" The Rockbox Crew -- Privacy Policy |