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FrozenGate by Avery

Wiring a USB to my laser projector

borgqueenx

borgqueenx

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I want to use a usb extension cable to have a usb port in my projector, just for powering a dac i will have soon, wich can runs shows from a sd card but needs power from usb.
Is it okay to connect it to a 5V PSU wich gives about 18A max?
Or will that do damage?
i once heard a device only draws amperage what it needs, but well, i also want to know for sure this can also count for usb.

thanks!
 





You can not use a standard USB Cable to supply 18Amps
of current at 5Volts...The wires used in a typical USB cable
are too small to handle that current.


Jerry
 
lasersbee said:
You can not use a standard USB Cable to supply 18Amps
of current at 5Volts...The wires used in a typical USB cable
are too small to handle that current.


Jerry
Click to expand...

it will be used to power a USB device, wich probaly draws 500mA max, wich is normal for usb devices right? but the PSU can output like 18A max, if a device needs it...
or is this incorrect?
 
If the cable will see no more than 500mA and it is less than 20
feet long I would say that you could use it for that purpose.

You mentioned 18Amps and a USB Cable... I took it from there.
It is important to state facts and data clearly when asking any
technical questions...


Jerry
 
I said in post 1 that i once heard that a device only draws wich is needed?
Does that also go when i connect a usb cable to a psu capable of delivering 18A?
Not sure if you understand now what i ment?:)
 
So they usb wire would draw as much current as it needs. It's just that the psu can supply a max. of 18A. Am I right?
 
Last edited:
The USB wire is a conductor, the load on the other side that is powered by the supply will determine the draw. so your load(DAC) uses 500ma for instance, your supply will only have 500ma drawn from it, or however much it needs to draw as long that the supply can provide the juice in the first place. (you can't draw more then you can supply).

See ohm's law:
http://en.wikipedia.org/wiki/Ohm's_law
 
Last edited:
Seems like this should be in the "laser shows" section... after all that's what we have it for ;).

Regarding your question, YES you can use an 5V supply capable of providing up to 18A of current, since your application will only be drawing 500mA or less. The amperage rating of a PSU is only what the supply is capable of providing. The devices in your application will determine how much current is actually drawn.
 
Last edited:
Be careful that you do not have the USB connected to a computer while it's being powered from the external supply. You're almost guaranteed to blow something up if you do that.
 
Things said:
Be careful that you do not have the USB connected to a computer while it's being powered from the external supply. You're almost guaranteed to blow something up if you do that.
Click to expand...

You would have to try really hard to do that... actually I can't even imagine how you would wire that...

I think the OP should be fine powering the DAC with the projectors supply.
 
is this a etherdream DAC? and yes guyfromhe is right you should be fine powering it from one of the PSUs in the projector
 
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