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USB Powered MD

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hi people!

I've got tired of recharging my battery of my MZ-R70 every day that i went to work! So i've decided to build my own USB powered interface for my md! allright! blink.gif :grin:

The MD should receive 3 Volt DC, but after measuring the output of the original sony adapter, it was around 5 Volt DC. The USB delivers exactly 5 volts, so there shouldn't be any problem!

So here it is, i've only bought the input jack. The USB cable (white) i had at home... it was a USB to PS/2 converter from my keyboard that i wasn't using... I've connected the red USB wire (+5V) to the middle of the connector, and the black USB wire (GND) to the border of the connector. And i've only spent 0,45 € bahahhah. :laugh: :laugh:

And it works! :happy:

user posted image

funky! :rasp:

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Wow, this is definitely a sticky! You're quite the risk-taker, I'd be afraid that my unit would blow up if I tried anything like this. If you post a full guide it might be able to make front page news on minidisc.org, ya know. I can think of alot of people that would find this handy..

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The output from the Sony adaptor isn't regulated. Under load, it'll drop to around 3V.

Could be potentially dangerous.

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The output from the Sony adaptor isn't regulated. Under load, it'll drop to around 3V.

Could be potentially dangerous.

blink.gif opps... ok thanks for warning me.

I'm going to apply a voltage drop of 0.6 * 3 ~= 2 volts before the main plug using 3 diodes. Like this i'll send around 3 volts to the unit.

i'll post more pictures later, and if i have time a full guide

BTW: i took this risk because i've seen in the service manual that the unit has a 2.5 volt regulator inside :smile:

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ok, with 4 diodes in series i was able to get 3.2 volts in the output :smile:

here's the picture of my outstanding soldering skills (not) :wink: blink.gif :happy:

user posted image

now i'm going to try put this inside the connector :laugh: (lets hope it fits...)

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ok! it's done!

I've tried to put all the 4 diodes inside the connector, but it was wayyy too tight! huh.gif

user posted image

So i decided to put the 4 diodes in a straight line...

user posted image

I had to cut a bit of the usb cable... put everything inside, close bla bla bla and insulate the best i could with the black tape.

And the result is:

user posted image

It looks worst than the first one, because i had to cut the cable, but now its just outputing 3.2 volts to the MD (not so dangerous!). :rasp:

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wow, im guessin you work with electronics or something? i take the route with you can mess with anything as long as you cant get fried, burnt, or lose however much money on a md.... so yeah good work *thumbs up*

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Looking at his soldering skill, no? wink.gif

Keep in mind that the USB port can deliver a limited amount of current and try to not overload it smile.gif

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I tried for myseld, using a diode zener of 3.9V (output is around ~2.9 when meseared)

Guess what happened? My mobo cut the power of those ports biggrin.gif

So there's a difference between low-powered USB device (100mA max) and high-power (500mA)

Now how can I tell the computer I need 500 and not 100...hmm

What diodes did you use?

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I know this is an old thread but since it is stickied...

Why was everyone so concerned about the 5V that the original cable was outputting? Because newer MD units, including pretty much all the NetMD models have a degree of protection on their DC inputs. Since the original cable worked I would say that there wouldn't really be any problems with using it that way. At your own risk of course... But the truth is if you apply about 6 or 7V to the DC in on a newer unit, it won't fry it. Instead you'll get a message on the MD unit saying "Hi DC In" and the unit activates its protection circuitry. Certainly, given enough voltage you will likely fry the unit but 5V DC, even constant, isn't going to harm anything.

Unless you have some sort of power surge through your PCs power supply you'll be okay, plus motherboards usually have some kind of regulation for the USB ports too--if you did get enough voltage through the USB to fry an MD unit your motherboard would probably be fried as well.

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Allow me to tag a "little bit" on to this thread.

Bear in mind that to charge a 3 volt battery, you would need to put more that 3 volts across it. Basically, best way to remove doubt is to measure what the official Sony PSU is putting into the player when under the load of charging. Yes, reasonably new units should be pretty well protected, though I can understand a reluctance to shove unknown quantities into expensive gear.

The newer Sony PSUs, as with most around now, appear to be switch-mode. That makes 'em smaller and cheaper than their transformer-based counterparts. Another advantage of that is that they are multi-region (I bought my NW-HD3 in the UK, and can use the same charger here in Canada. Provided I use an adapter to allow the UK plug to fit in the Canadian socket, of course). If you look on one of these PSUs, it even states "input: AC 100-240V~". Switch-mode has certain other implications to take into account.

Transformer-based PSUs rely on stepping down voltage according to a ratio of independent primary and secondary windings on an iron or ferrite core. For example, a transformer with 1000 primary turns and 200 secondary turns will produce an output at 200 divided by 1000, 20%. 100 volts in yields 20 volts out. Transformers drop power as the load increases because the windings themselves are not perfect conductors, and will be subject to Ohm's law, V=I*R. The current being pulled through the transformer, multiplied by the resistance of the windings, equals the voltage that will lost to that effect, which will be dissipated as heat. Okay, so it's a little more complicated than that, inductive loads, AC and so forth, but that's the jist of it. I shall ignore the bit of electronics responsible for AC-DC conversion for now, though it of course has an effect too (as someone here previously pointed out, a silicon diode, as used in rectification, has a 0.6V difference between anode and cathode).

The idea behind switch mode supplies is that the desired output is created electronically by taking the input voltage and switching it on and off really quickly through a whole bunch of coils, capacitors and other assorted crap. The controlling electronics monitor the output and vary the switching rate when required. If the load increases and the output voltage starts to dip, the 'tronics will pump more juice in, until the required voltage is once again restored. This is why they can generally handle multi region. They just switch the input at a different rate. The switching happens very quickly, which is why switch-mode supplies, like laptop charges, make a kinda squeaky, squealy noise, whereas transformers make that 50-60Hz buzzing sound.

So, where am I going with all this switch-mode talk, and how is it relevant to this, and what the hell am I talking about? Well essentially, switch-mode power supplies, by nature of how they work, are regulated. Not necessarily super-clean, but reasonably consistent under load (at least until the switching process is pushed to the point where it breaks down, or where the current limiter kicks in). The output voltage is rated at 6V on my NW-HD3 charger, and 6V is what ya get, whatever the load.

As for transformers, when they are rated at for example 12V @ 500mA, that means the voltage out of it is around 12V when under load, ie when you are drawing half an amp from it. When not under load at all, the output is more likely to be around 14-15V. If a transformer-based Sony charger is rated at 5V @ 300mA, that means when under a 300mA load (ie charging the battery), the voltage from the supply should be at 5V (...not that Sony would ever deviate from an established rating convention like that, no sireee...).

As far as this case is concerned, PCs use switch-mode supplies, and the motherboard voltage regulators are also switch-mode, on account of better efficiency and lower heat when compared to linear regulators. If the minidisc is rated at 5 volts, in theory it should be absolutely fine to feed it 5 volts from the USB, provided the USB can supply the required current.

This is a somewhat crude breakdown of the theory, but hopefully may prove of some use to those exploring this avenue of alternative charging methods.

Edited by Loonie
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If the minidisc is rated at 5 volts, in theory it should be absolutely fine to feed it 5 volts from the USB, provided the USB can supply the required current.

Actually the MD units are usually rated at 3V which is what the concern was about. I don't know about the new Hi-MD units but the older non-Hi-MD units mainly came pacakaged with transformer-type AC adapters. The float output from a 3V AC adapter is therefore above 5V and as you explained (very well I might add wink.gif ) which is why the original person thought that 5V from the USB was okay. There was a concern that since the transformer adapter would go to closer to 3V under load that 5V constant (from the USB) is too much. However that just isn't true because of the fact that I described above--the newer MD units have a degree of protection--if they are overvoltaged they display a warning on the display and lock out the power to the unit.

This is a somewhat crude breakdown of the theory, but hopefully may prove of some use to those exploring this avenue of alternative charging methods.

Actually I'd say it was a pretty darn good breakdown! smile.gif

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provided the USB can supply the required current

That is the problem, it can't. Best case scenario you will cause an instability and your system will reboot itself. Worst case scenario you will phisically damage the motherboard or yourself.

Now if you tried this with a powered hub it may be a different story.

I highly recommend not trying this from the motherboard USB header or any USB header directly on the computer itself. I am speaking from first hand knowledge.

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That is the problem, it can't.  Best case scenario you will cause an instability and your system will reboot itself.  Worst case scenario you will phisically damage the motherboard or yourself.  ...

How can it do that?

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Due to the nature of my work I cannot go into details.

What I can say is when you overdraw the USB bus strange things can happen like uninitiated reboots or lockups. In extreme cases I have seen motherboard USB headers burned, motherboard traces burned. Small fires started by overdrawing current from the USB bus.

Think about it. Most every item that has some sort of USB cradle has a seperate AC charger that plugs into the base of the charger. Why? Because in most cases the USB bus is not capable of providing the current necessary to charge modern day devices. There are items that can charge via USB like cell phones but the current draw is minimal.

To be compliant with USB specifications a high-power function must not draw more than 500 mA from the bus during normal operation.

Most devices that don't have an AC charger connected to the base do not charge the device. Some devices that come immediately to mind are PDA's. The USB dock always has a seperate AC charger. There are MD units that cannot be charged via USB even though they have a USB dock.

I have to take back my comment that it "can't" be done. Maybe I should reword it to say "Be very very careful!" As long as you fall within the USB specs for current draw you should be okay.

National Semiconductor has an interesting article that is relevant to this discussion. It pertains to Li-Ion charging but maybe some knowledge can be gained from looking at the schematic they have for the charger they propose:

http://www.national.com/appbriefs/files/AppBrief101.pdf

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Any device I've seen that can't draw enough current from one USB port, uses a Y cable to draw power from two ports. Like the faster and larger capacity 2.5" Hard disks.

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If de desire is to charge using the USB port without burning your PC USB ports out, you should take a look at this:

http://www.ladyada.net/make/mintyboost/process.html

You can create a circuit to charge your device using a USB cable and two AA batteries, i think that is much more safe, effective and portable.

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....Think about it. Most every item that has some sort of USB cradle has a seperate AC charger that plugs into the base of the charger. Why? Because in most cases the USB bus is not capable of providing the current necessary to charge modern day devices. There are items that can charge via USB like cell phones but the current draw is minimal.

Most devices that don't have an AC charger connected to the base do not charge the device. Some devices that come immediately to mind are PDA's. The USB dock always has a seperate AC charger. There are MD units that cannot be charged via USB even though they have a USB dock.....

I don't agree with you on this. I've had PDA's which have cradles and AC ports which also charge from USB. Same with Mp3 players, mobile phones etc. The AC and cradle is for convenience not because it can't pull power from the USB port. Main devices that need more power, come with USB Y cables so you can pull power from more than one USB port.

http://www.bixnet.com/5vps2powercord.html

http://www.pexagontech.com/products/cables...it-drive-61.php

I've use these with USB 2.5" Hard Drives for many years with no problems. Even with up to four drives connected to a machine. I usually have 2 connected up to my laptop for example. The only propblem, I've ever experienced where theres not enough power on a single cable is that the device wouldn't charge or power up. Its not unsual in my experience for USB ports to be below the USB spec for power. Even in a machine with 5 or 6 USB ports you might find only two of them meet the spec.

Edited by Sparky191

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I tried for myseld, using a diode zener of 3.9V (output is around ~2.9 when meseared)

Guess what happened? My mobo cut the power of those ports :D

So there's a difference between low-powered USB device (100mA max) and high-power (500mA)

Now how can I tell the computer I need 500 and not 100...hmm

What diodes did you use?

Hi!

I think you should use 1N4148 or 1N4004 or equivalents for the diodes.

But why just not put in a +5V regulator? That would be more relaxing,maybe? ;)

-Chiron

Norway

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