PNP Transistor Switch for Arduino

igorgumush · Apr 30, 2013

hi ,
Im trying to make a 7 USB-hub that controled from a pc. with arduino

i want to use a transistor as a switch for every usb out voltage , in the way that when a signal came from arduino (5V , 40mA) usb voltage can pass.

usb out (transistor input / out) should support (5v , 500mA) ,
-----
I want to use , transistor array , but couldn't find any that fit
maby some one here can help me ?
or suggest other solution ?

MikeMl · Apr 30, 2013

Use a PFET. Note the VCE(sat) voltage drop across the PNP vs the on-resistance of the PFET. Your USB devices will not be happy on 4.6V. V2 and V4 represent the Arduino Port Pin voltages.

The Arduino Vss will have to be connected to the negative side of the USB Hub's 5V supply. Is that ok? If not, you will need an opto-isolator.

igorgumush · Apr 30, 2013

sorry , I know only the basics of electronics i don't understand what does it meen
can you tell me if this would be ok for me ?
https://www.electro-tech-online.com/custompdfs/2013/04/FFB2907A.pdf

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ronv · Apr 30, 2013

The voltage drop of the PNP transistor is to high for the USB so you need a P Channel MOS FET. Arrays are a little hard to find, but here is one.

http://www.datasheetcatalog.com/datasheets_pdf/4/A/J/1/4AJ11.shtml

igorgumush · Apr 30, 2013

ronv said:
The voltage drop of the PNP transistor is to high for the USB so you need a P Channel MOS FET. Arrays are a little hard to find, but here is one.

http://www.datasheetcatalog.com/datasheets_pdf/4/A/J/1/4AJ11.shtml

thanks
was looking for it like days..

ChrisP58 · Apr 30, 2013

Be aware, p channel mosfets are turned on by taking their gate pin low with respect to their source pin.

So they will be OFF when the arduino pin is at 5V, and ON when the arduino pin is at zero volts.

igorgumush · Apr 30, 2013

ChrisP58 said:
Be aware, p channel mosfets are turned on by taking their gate pin low with respect to their source pin.

So they will be OFF when the arduino pin is at 5V, and ON when the arduino pin is at zero volts.

thanks for the information , didnt know that , it's still good enough for me

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