+5v from serial port?

U

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2[H]4U
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which pin is it? I tried searching in google etc etc and can't seem to find the answer
 
just like what I guessed earlier.. too much work, not worth it

I should go with usb instead
 
Yeah, USB ports have +5V. Or you can get +5V from a game port.

I'm curious, what are you building?
 
I'd definately go for game port over USB port. Should be able to handle more current.
 
or you could just put a socket on the back of your machine with a +5 line going to it instead of trying to fry your chipset/superio/soundcard? :p
 
I don't know your application, but I'll throw it out there anyway: the PS/2 ports also have a 5 volt supply.
 
xonik said:
I don't know your application, but I'll throw it out there anyway: the PS/2 ports also have a 5 volt supply.
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good plan; IIRC, you can buy PS/2 connectors at radio shack.
 
If your PSU has an Auxiliary connector you could get it from there (I believe so anyways).
I believe it's pin 6.
 
fat-tony said:
I'd definately go for game port over USB port. Should be able to handle more current.
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By spec a USB port should only be able to provide like 2ma or or something like that without a proper USB device attached. Normally you'll be fine drawing more - but you have the potential to do some damage.
 
Parallel ports do have 5v, but they're meant for signals only and are generally rated for only 12ma.
 
STRESSTEST said:
LEDs are rated at 20ma
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most LEDs can be run at up to 20mA.

They're still visible though, even with <1mA...
 
Pin 9 on the parallel port is the 7th data pin.

To get +5v, use one of the active low output lines, such as pin 1, and any of the grounds, pin 18-25.
 
mattg2k4 said:
Pin 9 on the parallel port is the 7th data pin.

To get +5v, use one of the active low output lines, such as pin 1, and any of the grounds, pin 18-25.
Click to expand...
The output control lines on parallel ports are open collector, pulled to +5V using a 4.7K or so resistor. You won't get any power from those...

IMO, best thing to do is use a bunch of 1N4148's on the data lines...
 
serial ports don't have a +5V line.
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umm by rs232 standerd they are 5 volt buddy.
ps2 ports can by spec source 100ma
usb ports on powed hubs (including computer hub) can source 500ma
game port is also 500ma

lol i was looking to like up a keyboard with CCFL and EL but it turned out i didnt have enugh current... the point being that i reaserched all this stuff
 
:confused:

The RS232 standard allows for signal voltages from -3 to -25 volts for logic '1', and 3 to 25 volts for logic '0'. As for the serial port as we know it, there is no 5 volt supply to speak of--here, see for yourself:

http://www.camiresearch.com/Data_Com_Basics/RS232_standard.html
Signal State Voltage Assignments - Voltages of -3v to -25v with respect to signal ground (pin 7) are considered logic '1' (the marking condition), whereas voltages of +3v to +25v are considered logic '0' (the spacing condition). The range of voltages between -3v and +3v is considered a transition region for which a signal state is not assigned.

Logic states are assigned to the voltage ranges shown here. Note that this is a "negative logic" convention, which is the reverse of that used in most modern digital designs.

Most contemporary applications will show an open-circuit signal voltage of -8 to -14 volts for logic '1' (mark), and +8 to +14 volts for logic '0' (space). Voltage magnitudes will be slightly less when the generator and receiver are connected (when the DTE and DCE devices are connected with a cable).
Click to expand...
 
theshadow27 said:
umm by rs232 standerd they are 5 volt buddy.
ps2 ports can by spec source 100ma
usb ports on powed hubs (including computer hub) can source 500ma
game port is also 500ma

lol i was looking to like up a keyboard with CCFL and EL but it turned out i didnt have enugh current... the point being that i reaserched all this stuff
Click to expand...
And my day job involves designing this stuff.

EIA232 specifies signal levels of +-3V minimum to +-25V max on its "transmit" pins, with a short circuit current of a maximum of 500mA but no defined minimum. There's no assigned +5V pin, you have to grab power from the TXD/DTR/RTS lines and convert that somehow to 5V.

Feel free to prove me wrong ;)

edit: hah, beaten by xonik
 
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