very simple output from computer

Thread Starter


Joined Mar 11, 2011
Hello again Everyone!
I have a very simple idea that I know has been done many times before.

Here is my Project
Using a laptop, I want utilize the USB port and to signals out. So what I will do is have a sort of window popup with a few buttons.
Press a button.
X amount of voltage goes out the USB port for Y amount of time.

Has anyone don't this before?


Joined Jul 17, 2007
USB ports have +5v and ground available continuously. Desktop/tower computers have 500mA available; laptops usually have much less current available.

The other USB pins just have data signals on them, and are not suitable for supplying power.

If you want to do something like this easily, then purchase a kit or buy an already-made solution that performs the function you're looking for.


Joined Sep 9, 2010
I use a LabJack U3HV for exactly this sort of thing. It's over $100, so maybe not what you were hoping for, but you can control it's output with just about any programming software you want. I use Excel and Visual Basic. It's powered off your USB port and it can even provide a PWM signal, or a DC voltage, both under your control.