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Old 24 September 2017, 10:00   #1
Sim085
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Power amiga from USB?

Hello, I have an Amiga 500 and at the moment power this through an ATX power supply which I hacked to worker using the information I found online.

I was however wondering if I could create power this amiga with USB connector instead. I have a 5 port 50W / 10A USB charger.

From what I found online the a500 needs; +5v@4.5A, +12v@1.0A, and -12v@0.1A with a total requirement of 35.7W.

I checked the wikis on USB and found that "USB Power Delivery revision 2.0" provides "20 V, 5 A"

So is it possible for me to create a cable which goes out of this charger with the ends side being the Amiga power connector?

Problem is I have little knowledge of electronics and therefore asking this for two main reasons; first to see if there is something already out there and second, if not, why.
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Old 24 September 2017, 14:35   #2
Matt_H
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I'm by no expert in this area, but my understanding is that USB only provides a 5V line. I imagine you'd need a very complex cable with some in-line voltage converters to get the 12V lines out of it.
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Old 24 September 2017, 14:45   #3
Sim085
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In wiki I read "USB Power Delivery revision 2.0" provides "20 V, 5 A" so I thought it would be easy to reduce the voltage from 20V to 12V. I am not too sure about the -12V.

Quote:
Originally Posted by Matt_H View Post
I'm by no expert in this area, but my understanding is that USB only provides a 5V line. I imagine you'd need a very complex cable with some in-line voltage converters to get the 12V lines out of it.
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Old 24 September 2017, 15:33   #4
ptyerman
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I don't know what you've been reading or where but it's nothing to do with USB. USB 2 provides 5 volt at 500ma, you may get 1 amp if using a hub and external PSU, USB 3 provides the same 5 volt but has 1 amp by default. That's it, 5 volt, nothing else.
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Old 24 September 2017, 15:54   #5
thomas
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The PD specs allow higher voltages, but you always needs an intelligent device which identifies itself to the USB hub and negotiates the required voltage and wattage.

Otherwise you only get the default of 5V. And with a simple cable the hub stays in standby mode and you only get 100 mA. To get the full 500 mA you again need some intelligence which identifies the device to the hub.
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Old 24 September 2017, 16:24   #6
Sim085
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As explained I am not expert, just asking to see if possible. What I read was from Wikipedia; https://en.wikipedia.org/wiki/USB

"Power related specifications"
...
"USB Power Delivery revision 2.0 (version 1.2) - 2016-03-25 - 20 V, 5 A"


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Originally Posted by ptyerman View Post
I don't know what you've been reading or where but it's nothing to do with USB. USB 2 provides 5 volt at 500ma, you may get 1 amp if using a hub and external PSU, USB 3 provides the same 5 volt but has 1 amp by default. That's it, 5 volt, nothing else.
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Old 24 September 2017, 16:34   #7
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Look at the chart on the right hand side of that page, that gives you the correct specifications for USB 2 and 3.
What you're looking at is a power delivery specification which is a totally different thing.
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Old 25 September 2017, 02:52   #8
pandy71
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You can buy some DC\DC converter modules - you will need 1 module for boost (12V) based for example on LM2577 or better (higher current capable) and one module capable to invert voltage (changing 12V from boost to -12V, -5V can be created with classical linear LM7905 device).
IMHO better is to take or some notebook PSU and use few buck DC\DC to create +12 and +5V, side to this use something on MC34063 or LM2596 to create -12V and -5V on LM7905.
btw XBOX360 PSU is very capable to provide power for Amiga (with help of few additional modules of the DC\DC converters)...
There is plenty of opportunities nowadays...
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