can i hold digital output value on 5 volts? asking for help!!

[风轻扬]

Hi, i am using the usb-6008 to send digital singals to some devices, when the usb-6008 is not connected to the device, the value measured between the two digital lines was 5 volts. However, when usb-6008 is connected to the device, the value turned down to about 1.76 volts thus not high enough to drive the device. can anyone please tell me how can i hold to value not droping down?

when using analog out, i set the value to 5 volts, it works fine.

the vi i use is in the examples in daqmx base: usb-6008 interactive control.

thanks for helping!!!!

[Dennis_Knutson]

Whatever device you have connected needs more current than the USB-6008 can provide so it's dragging down the output. If you are trying to control a relay, you might want to consider using a driver between the 6008 and the device. Something like a ULN200x should work just fine.

Message Edited by Dennis Knutson on 10-25-2006 08:20 AM

[paulmw]

Dennis is correct.  According to the user guide for that device the Analog current output is 5mA but the max Digital high output current is 0.6mA.  The user guide also states:

"An external, user-provided, pull-up resistor can be added to increase the source current drive up to a 8.5 mA limit per line..."

Follow the user guide for the connection. 

But I think a driver is a better, more robust solution.

[Zyrmax]

Dennis,
Where to find the ULN200x relay? I couldn't find it with major electronic suppliers.



thanks

[paulmw]

ULN200x are a range of darlington array transistor IC's.  Search for a ULN200...

Or follow this link to STMicroelectronics pdf...

http://www.st.com/stonline/products/literature/ds/5279/uln2001.pdf

[Zyrmax]

Wonderful thanks