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Post by Tom Maneiro on Nov 5, 2005 20:19:12 GMT -5
Since i now have a spare 24X CD drive, i now want a portable CD player for my weekly boring bus trips (about 6 hours in the same dangerous way, but that's another story). I've just learned to use 78XX power regulators, now i need to know how i can use these. I thinked in a couple of 9-volt batteries (since there are no cheap 12V batteries, only those lithium 23A cells for cameras), and quickly designed this schematic: Now the questions: -How much will last my batteries? I hope at least 6 hours of life, and since my drive does not draw too much amps... (about 300mA for 5V and 500mA for 12V, i'm not sure) -The ground lines are connected OK? -Is there another easy way to do this project? I have some spare 78XX's (now need to check if i have at least one 7805 and a 7812), so building this should be a piece of cake. Another question: "-" terminal of the battery should go connected to GND lines, right? EDIT: Bad news... i only have a 7805, and no 7812! Also 9V batteries are incredibly expensive now!!! Anyway, what's the output current, in amps, of a 9V battery?
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
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Post by oompa loompa on Nov 24, 2005 12:30:05 GMT -5
nononono bad idea tom, don't power a pc cd-rom drive using batteries =P. your batteries will drain faster than you can here a 3 minute song =D. the power rating of the drive should be shown somewhere on a label on your drive. this value is given in milliams (mA) for both 5 and 12 volt ratings. to calculate how much total current will sink into the drive, just do:
((5 * mA for 5 volts) + (12 * mA for 12 volts))/(battery voltage) = total current sink
to calculate how many hours your drive will last, divide the number of milliamp-hours your batteries are expected to perform at, and divide it by the total current sinnk of the drive.
btw, your schematic is correct too, but i would add list a 1uF capacitor to the output of the voltage regulator to ensure there is no huge ripple
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Post by Tom Maneiro on Nov 24, 2005 18:08:41 GMT -5
nice formula... My drive needs 0.5A for 5V and 1.3A for 12V, so it would drain the batteries after loading a CD...
9V batteries can only supply about 150 mA... very low current. The other option is to use 1.5V rechargeables, i've seen packages that can send up to 2.5A, but these are EXPENSIVE! Also, i don't want to carry with 8 batteries...
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Post by Tom Maneiro on Nov 25, 2005 9:53:49 GMT -5
After browsing for datasheets here and here, 9V batteries are definitively discarded, these do not send more than 600 mAh for less than 3 hours!. On the other side, a bunch of AAs seems to be the most powerful choice, at least for a couple of CDs... Each battery can drain up to 2850 mAh (Energizer E91 AA), and i need a 12V set capable to supply at least 1591 mA, just for run a single disc at 1X and output analog audio... so if my calculations are correct, my batteries will last up to 105 minutes (1:45h)... Not bad for AAs, but changing the entire battery set after each trip is not very cheapo... also it's not very comfortable to carry with 8 batteries, a 5,25" drive, and a box with a couple of 78XX's and cables... Remember, i expect at least 3 hours of life! (the average length of my weekly bus trip between home and university). What about 16 AAs? i'm crazy, i know UPDATE: Updated schematic
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
Posts: 1,301
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Post by oompa loompa on Nov 28, 2005 17:53:20 GMT -5
you just can't just pick up a portable cd player from your nearby consumer electronics store =P? in todays technology, portable cd players are now obsolete, its all about the ipods and the mp3 players ;D
anyways, i think you need to look at the battery datasheets more because your expected battery performance changes for how much is beaing drained, and in this case, this is a real high drain application. you might also want to look at the cutoff voltages in the bettery datasheets (for batteries, a cutoff voltage is the minimum amount of voltage your circuit needs before it doesn't work no more, in the pc cd player's case, this is 12 volts)
the more bateries you stick in series, the more voltage you will provide, therefore, it will take a longer amount of time to drain the betteries down to your cutoff voltage. the mA ratings on the cd player are probably for the worst case scenario, where the drive is actually running at a speed of "24x". for playing audio cd's, the cd player doesn't run no faster than 1x =D, so you can check your current sink with a multimeter or something to get a reading that's closer to reality
and hey, what about a cassette player? =P
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Post by GiGaBiTe on Nov 29, 2005 4:54:17 GMT -5
this is true in the united states, europe and probably china and japan, but your not going to find a native down deep in the african jungle carrying around an ipod...
same goes with other countries with weak economies.
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Post by Tom Maneiro on Nov 30, 2005 15:57:46 GMT -5
Very weak economy here, in my opinion.
Let see the costs of this (aproximate, 1$=2200 units of local money, called "Bolivar", abbreviated "Bs", on retail stores, it could be cheaper on auction sites): -Brand new CD player, "generic" brand: $60 -Brand new CD discman, well-known brand w/MP3: $200+ -iPod Nano, 4GB: $375!!! -2800mAh 8x1.5V AA battery pack, rechargeables, WITHOUT charger: $50 -Two packs of 4x1.5V Energizer AAs: $10 -My idea of a "diskman": priceless
So i pick the alkaline AAs, to hell with Sony and their expensive discmans!
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
Posts: 1,301
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Post by oompa loompa on Dec 2, 2005 19:00:38 GMT -5
i know brazil has their own MTV =P
try to use C sized batteries too, since they should last a lot longer. i know those big boombox's take c batteries, maybe you can strap your cd player to one of those, and hook up the sound to the auxiliary =D
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Post by Tom Maneiro on Jan 20, 2006 18:50:51 GMT -5
and carry a boombox in a coachbus? Nope... it barely fits under the seat, AND, most of these already have the CD player.
The project is on hold, until i get funds for purchase batteries (i'm currently saving my cents for replace my ol' fried 32X CD drive)
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Post by jlf65 on Jan 21, 2006 13:18:57 GMT -5
Here's a portable CD/radio from WalMart for $65 that plays CDs for 22 hours on 4 AA batteries.
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Post by Tom Maneiro on Feb 6, 2006 16:18:55 GMT -5
NO, i don't have money for a discman! Also, that is not the point of this project. Today, i built a "ALPHA" version of the adapter: took a cable from a old power supply, put the 7805 inside a floppy-size connector, taped it in place, did some rewiring of the connector, and finally, tested with my only power supply apart from the PC PSU: a 9V 600mA adapter (batteries will go later, i just wanted to test my "adapter"). Schematic: Drive info: CyberDrive 240D (24X): +5V 0.35A, +12V 1.70A However, drive worked with problems: -Sometimes it do not work at all -When it works, i can start to play an audio CD, but when i change track, drive goes crazy and stop working It could be the 9V adapter... any ideas? The 7805 runs HOT! Could i use a 78L05? And... is a 7812 needed? Are there hi-amp 78XX versions?
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oompa loompa
I AM THE GOVERNATOR
"Git 'Er Dun!"
Posts: 1,301
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Post by oompa loompa on Feb 7, 2006 1:23:41 GMT -5
ahahaha, you're lucky you even got the cd spinning by providing only +9 volts. the power requirements are +12 volts, and a 9 volt wall adapter won't do. well, there are some exceptions though =P, try taking a multimeter, and measure the voltage your wall adapter is putting out. some adapters say that they put out 6 or 9 volts, but in reality, put out greater voltages (also depends on your load, and how bad the power supply ripples). anyhow, plugging in a 9 volt adapter directly to the cd player's 12 volt line is bad edit: a 600mA wall adapter should be burning hot!! to make your cd work, you first need to find a power supply that outputs more than 14 volts, and provides a good amount of current required for your cd (remember the formula in the previous posts?). then you will need to regulate the 14 volts to 12 volts, and 5 volts. A regular old 7805T (to-220 package) will work good for your 5 volt supply, since this regulator can provide 1 amp of current, if needed (for a 7805 around currents ~300mA, you have to have some way of cooling the regulator because they will get hot - this is why these regulators are in these kinds of packages =P). You'll regret using a 78L05, since the maximum rated current is only 100 mA !!!! (you should really do your research on this, and look up the datasheets). For the 12 volt regulator, you can use a 7812K. The maximum current load for this regulaot is 1.5 A !!! From your previous post on the power requirements for this drive, it requires 1.3 A. For a 7812K, 1.3A is gonna get the regulator real hot , so you better have some way to cool the regulator down. If you do your research, the 7812K is in a TO-3 package, which is a lot different from the TO-220 package. The package is for higher current loads. In reality, your 0.5A at 5 volts, and 1.3A at 12 volts aren't really high amprage ratings. They are really high for linear voltage regulators though. In applications demanding high current supplies, switching power supplies are often used. Switching power supplies are probably way off from your understanding of power supplies though =P. I think you're going to have lots of hassles with trying to get your cd player to run off batteries because of the high current load
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Post by Tom Maneiro on Feb 7, 2006 8:02:57 GMT -5
Read my last post again: i rechecked my drive specs and it needs 1.7 A for 12V line, and 0.35A for 5V.
My 7805 is already a TO-220 package, so it fitted OK in a floppy connector. But TO-3 package is so big! I need something smaller...
EDIT: After some googling, i found that a 78M05 (0.5A) and a 78S12 (2A) will fit my needs. These are cheap, and are available as TO-220 packages. Add some heatsinks and i'm ready... However, i will need even more batteries! Can just i avoid the use of a 7812 and take the +12V line directly from the batteries?
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Post by jlf65 on Feb 7, 2006 19:44:38 GMT -5
What you should do is go for the work-out angle and use a car battery. ;D
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Post by Tom Maneiro on Feb 8, 2006 7:18:07 GMT -5
It does not fit in my backpack...
The idea of using rechargeable batteries is discarded (too expensive). For now, i will use 8 AA or C cells (to avoid the use of a 78S12 that would require two extra batteries).
I've checked some drive ratings: my ol' Cyberdrive 321D draws just a bit: 500mA on 12V! But it lacks the audio play button (and the PCB requires a LOT of extra work to put that damn button). My dead Samsung SC-152E draws 1.0A@5V and 1.5A@5V, and the play button is easy to install: a pushbutton and a resistor. However, this drive can't play nothing!. Another drive (a Creative 52X crap) draws even more!.
This leads to a question: Do CD drive manufactures forgot the "power saving" thing on their drives? How the heck a 32X CD will draw less than 1 amp and other requires 2A?
Progress: changed the 7805 with a 78M05 and installed a heatsink. Still waiting for a 12V adapter OR a AA bank.
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