Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: dmehling on February 25, 2009, 04:21:31 PM

Title: USB device to activate switch
Post by: dmehling on February 25, 2009, 04:21:31 PM: I was wondering if there is some kind of USB device which can activate or close a switch. I have very minimal knowledge of robotics and I'm not interested in custom building anything. Also I am on a tight budget.
Title: Re: USB device to activate switch
Post by: galannthegreat on February 25, 2009, 04:29:01 PM: Phidgets has that kind of stuff on their site, check it out http://www.phidgets.com/ (http://www.phidgets.com/)
Title: Re: USB device to activate switch
Post by: dmehling on February 25, 2009, 04:53:41 PM: I'm not really sure that's what I'm talking about. I looked at their products but all I see in terms of USB devices are ones for receiving input. I need to control a switch from my computer.
Title: Re: USB device to activate switch
Post by: MaltiK on February 25, 2009, 06:45:05 PM: I asked a similar question:

http://www.societyofrobots.com/robotforum/index.php?topic=6899.0
Title: Re: USB device to activate switch
Post by: dmehling on February 25, 2009, 07:20:20 PM: I'm beginning to get the idea that such a thing doesn't exist but that it can be made with a microcontroller. There are several inexpensive USB microcontrollers that could probably do the job. But how exactly can I close a switch with a microcontroller? The thread you directed me to read was concerned with controlling a solenoid or motor, but what I'm interested in seems a lot simpler.
Title: Re: USB device to activate switch
Post by: Razor Concepts on February 25, 2009, 08:05:59 PM: A relay is a electronically controlled switch. Put 5v across the inputs of the relay, and a mechanical switch will close and connect two pins together. A microcontroller can provide the 5v to close the relay, activating the switch.
Title: Re: USB device to activate switch
Post by: cooldog on February 25, 2009, 08:57:02 PM: Quote from: dmehling on February 25, 2009, 04:53:41 PM
I'm not really sure that's what I'm talking about. I looked at their products but all I see in terms of USB devices are ones for receiving input. I need to control a switch from my computer.

they sell usb switches there

http://www.phidgets.com/products.php?category=1&product_id=1014
Title: Re: USB device to activate switch
Post by: MaltiK on February 26, 2009, 05:12:18 AM: thats around $50.00 USD there though...
Title: Re: USB device to activate switch
Post by: Admin on March 01, 2009, 09:28:18 AM: Quote
Put 5v across the inputs of the relay, and a mechanical switch will close and connect two pins together. A microcontroller can provide the 5v to close the relay, activating the switch.
Not true . . . relays require quite a lot of current, but a microcontroller can only output like ~20mA. If you want to drive a relay, you'll need to do it with a MOSFET.