Can we get 5v on USB port?

[lloydi12345]

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]

How much current does your radio need?

 

[DerStrom8]

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]

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

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

 

[lloydi12345]

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.

 

[Pommie]

Note that an unpowered hub can only supply 100mA.

Mike.

 

[Reloadron]

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

 

[lloydi12345]

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]

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.

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]

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

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]

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.