Turn on LED using the USB Port without a DAQ card

[NI_User_77]

Thanks alot guys!
I will try this out 🙂

[tbob]

Analog Kid may be right.  The serial output may not be able to drive 20 mA.  Also, some serial ports may put out different voltages.  The ones I am familiar with (older computers) put out +12v and -12v.  You will have to use a DMM to see what your serial port puts out voltage wise, and you will have to use an ammeter to determine if it can't reach 20mA.  Beware, you may blow the serial port if it is rated for 5mA and the circuit wants to draw 20mA.

Best thing to do is spend the $100 for a USB DIO.

[gstanczak]

Hopeless,

Would you (or anyone) save this vi as 7.1 and reply with it?

Thanks,

Greg

[RavensFan]

That VI may be in version 8.2, but you don't want to use it.  It uses ancient functions.

Use a VI that has a property node for the serial port line.

[gstanczak]

RavensFan, after some reading I understand how the DTR property node can switch pin 4 on/off on a 9-pin serial port.  Sorry, I am looking for a similar solution for a USB port.  I plan to buy the USB relay below.  How could I go about turning it on and off?

http://www.dx.com/p/keyes-1-channel-usb-control-switch-relay-module-for-pc-red-5v-308292#.U-Bhu_ldVQ...

Thanks for the reply!

-Greg

[Dennis_Knutson]

Check with the vendor. It says it uses the Windows HID driver.

[RavensFan]

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@gstanczak wrote:

.  Sorry, I am looking for a similar solution for a USB port.  I plan to buy the USB relay below.  How could I go about turning it on and off?

http://www.dx.com/p/keyes-1-channel-usb-control-switch-relay-module-for-pc-red-5v-308292#.U-Bhu_ldVQ...

Thanks for the reply!

-Greg

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As was said earlier, you can't do that with a USB port.  You will need a device such as a DAQ device or the one you linked to.  Another option is to get a USB/RS-232 adapter.

But the device you linked to should work once you find out in the instruction manual the method to communicate with it.

[gstanczak]

I understand.  Thank you both.

-Greg