usb receive message when relay is triggered?

is there a device that, say when a device like a dryer motor turns on, it triggers a relay. the relay trip is measured by a usb device of some sort, then a message is displayed in a program?

i'm not looking for the program, i'm not looking for a device that usb triggers a relay, i'm looking for a device that receives info, not sends it. thanks

thermacore

Posted 2013-11-21T20:27:40.553

Reputation: 1

yes, Arduino, BeagleBone, integrated circuitry to USB interface, You do need to realize that there will have to be a program of some kind though, whether you make it or you find soemthing close enough and make it work.If you aren't averse to an alert on something other than a computer, you could easily light an LED, place a message on an LCD screen....The possibilities are almost boundless. – PsychoData – 2013-11-21T23:52:50.477

Yes psycho, I understand there needs to be some sort of software. I will program that myself. I don't want a visual alert. I want a cable that when a relay is triggered, I can detect it via USB. I don't want to drop money on an arduino when I have a server already. – thermacore – 2013-11-22T21:18:03.750

Crazy thought here, but why not just use the relay to close the USB contacts. relay connects the four wires from one side of the relay to the other....Essentially when the relay triggers it plugs in the USB. set up some content on the USB to autorun and seems like you'd be golden. The autorun could just run a .exe that literally does nothing more than pop up the message or however you want to do it – PsychoData – 2013-12-10T20:14:57.140

Answers

A USB-to-serial (RS-232) adapter would work. These are readily available and can be purchased for under $10. To tell if relay contacts are closed, you could configure the hardware in one of the following ways:

Route the CTS output through the relay contacts to the RTS input
Route the TxD output through the relay contacts to the RxD input

Software on the computer could test whether the relay contacts are open or closed by doing the following:

Toggle CTS and read RTS, check whether or not RTS follows CTS
Send a character and check whether or not the character is received within a time limit

user275717

Posted 2013-11-21T20:27:40.553

Reputation: 111

Any example of where this is used? I already have a few rs232 converters. – thermacore – 2013-11-22T21:18:56.237

Mind you, I want to receive a signal when the relay is triggered. Not control a relay via USB. – thermacore – 2013-11-22T21:20:20.103

I have no examples, but I am an electronics and software engineer and I am certain that this solution will work. This will allow software on the computer to detect when the relay is triggered. That software needs to be written. – user275717 – 2013-11-22T21:46:44.057

This would require me to constantly poll the serial port. Is there a method to just send a message when the relay contact closes or opens? – thermacore – 2013-11-23T01:49:39.983