Can we get 5v on USB port?

lloydi12345

Member

• Jan 16, 2011

• #1

Hi, I created this new thread since I can't get 5v from 9pins serial port. Is it possible to get 5v that can power RF Transceiver(5v) and Max232(5v)? Thank you.

 

blueroomelectronics

Well-Known Member

• Jan 16, 2011

• #2

How much current does your radio need?

 

DerStrom8

Super Moderator

• Jan 16, 2011

• #3

I believe you can get 5 volts DC at 500-900mA between the outer "pins" on a USB plug. You should probably find out how much current your radio draws, as Bill suggested, and check the output of your USB port. Let us know what you find out, and we will do all that we can to help.
Der Strom

 

4pyros

Well-Known Member

Most Helpful Member

• Jan 16, 2011

• #4

I believe you can get 5 volts DC at 500-900mA

Click to expand...

That should be 200ma-500ma. Thats all. Andy

 

lloydi12345

Member

• Jan 16, 2011

• #5

Hi thank you for replying 4pyros, DerStrom8 and blueroomelectronics. The radio's receiving current is less than 30mA and transmitting current is less than 35mA. Here's the datasheet: https://www.electro-tech-online.com/custompdfs/2011/01/model20871-1.pdf. I'm not sure about max232's operating current.

 

P

Pommie

Well-Known Member

Most Helpful Member

• Jan 17, 2011

• #6

Note that an unpowered hub can only supply 100mA.

Mike.

 

Reloadron

Well-Known Member

Most Helpful Member

• Jan 17, 2011

• #7

Read your other thread where Eric suggest using internal PC power. I added a post there. I would use the internal 5 volts and fuse it.

You could get 5 volt power from the USB port but I generally suggest against it.

Ron

 

Last edited: Jan 17, 2011

lloydi12345

Member

• Jan 17, 2011

• #8

Okay, I'll then go for an external power source since I think I'll encounter a lot of problems if I'll use power from PC.

 

ericgibbs

Well-Known Member

Most Helpful Member

• Jan 17, 2011

• #9

lloydi12345 said:

Okay, I'll then go for an external power source since I think I'll encounter a lot of problems if I'll use power from PC.

Click to expand...

hi Lloyd,
Get a regulated +5V supply say 500mA or so.

Using the PC supply is not a problem, the only draw back is that you have to use that PC [ or a modified PC] to drive your project.

 

DerStrom8

Super Moderator

• Jan 17, 2011

• #10

4pyros said:

That should be 200ma-500ma. Thats all. Andy

Click to expand...

Thanks, Andy. I failed to mention that it depends on the version of USB. The USB 1.0 can supply 200-300mA, the USB 2.0 can supply 300-500mA, and the USB 3.0 can supply 500-900mA. It really depends on your particular USB port.
Hope this helps!
Der Strom

 

ParkingLotLust

Member

• Jan 17, 2011

• #11

IIRC, you can only get 100mA from a USB 2.0 port. The device needs to "request" up to 500mA of current, or you will get an overcurrent warning.

 

Last edited: Jan 17, 2011