Using PNP Transistor to switch USB Device on and off

Other Hardware General Electronics
1

Hello guys. I'm trying to setup my Arduino Uno to switch my USB device (5V and 4W) on and off from a USB-powerbank, but my electronics knowledge is very limited.

I have a BD 680 Darlington-Transistor (PNP) and I think it should be suitable from the specifications. Various resistors and diodes are available, too. However, no MOSFETs are available, so I try to setup the switching with transistors.

I drew a circuit hoping to get some help from you guys, it is linked below. Is this correct or should I change the wiring? Or add some parts?

Wiring Diagram

Here is the data for the transistor: BD 680: Transistor PNP-Darl TO-126 80V 4A 40W at reichelt elektronik

2

Please post schematics and other images in line (just drag .jpg or .png images into the post editor window).

PNP transistors (like Q2 below) are used as high side switches and with Arduino, generally require another transistor to switch them. Typical circuit (R3 is not required):


Consider using a Pololu Power Switch instead of DIY.

1 Like
3

I think not.
This is a darlington transistor (high saturation voltage),
so expect to 'loose' about 1volt from your 5volt powerbank supply.

A transistor could switch the load 'off',
but don't expect you can turn your powerbank 'on' again.
Leo..

4

That was very helpful. Indeed I have other transistors, that I can use for the circuit shown by you. Those other transistors are mixed PNP and NPN, but all of those have low Collector Current specs (like 0.2A), so I cannot use them to switch the USB device directly, but I can use them als Q3 to switch my bigger BD 680 Darlington-Transistor.

I tried to upload the image directly to the message, but the website just says "sorry, an error occured".

5

You can't use the BD680, you need to find another transistor.

6

I use these when I want to do USB host switching:-

I know it says out of stock but I have quite a few, if you are in the UK I could send you a few. PM me.

7

That's a very generous offer. Unfortunately I'm from Germany, so shipping costs would be very high :frowning: so that's not possible.

Because another user said that I cannot use my BD680 transistor, I'm currently looking for other technical solutions, but quite planless.

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