USB-6501 and Optocoupler SFH615A

[GOB82]

Hi,

I am trying to drive an optocoupler (Siemens SFH615A - spec link attached) using the USB-6501. I am very much a beginner and I'm looking for

help on how I can connect this. I have tried a few options already but no luck.

http://docs-europe.electrocomponents.com/webdocs/009c/0900766b8009c194.pdf

I am using a Servo drive in a project, driving a motor. Unfortuantely as the USB-6501 turns all lines logic High on start up the servo drive is 

receiving a signal. I am hoping that I can pass the INHIBIT line of the servo drive through the optocoupler, so during start up the 6501 will cause the optocoupler

circuit to close and ground the inhibit line preventing the motor from moving. The labview program will make the line logic low to allow the motor to move.

From looking at the USB-6501 manual and previous questions there are 2 ways of doing this, but working out the resistor values etc needed is

still a little beyond me and unfortunately I'm a little stuck for time.

Any help would be greatly appreciated, thank you.

[GOB82]

Hi,

Thought I should add in some of the other threads that I am using for info, but I'm still not clear how this can be done.

http://forums.ni.com/t5/Digital-I-O/USB-6501-and-optocoupler/m-p/1314865#M13677

http://forums.ni.com/t5/Digital-I-O/USB-6501-power-up-state/td-p/1103503

Thank you.

[GOB82 · Accepted solution]

Ok got this to work, hopefully this will come in useful for others.

My problem I think, haven't a clue really, is the high impedance of the I/O device. Regardless I used a unity gain buffer using the 

Intersil ICL7611 powered from the +5V line with the Digital Output line connected to the +IN pin of the ICL7611. On the output I have a

120 Ohm resistor prior to the SFH615A opto. Opto is open at 6501 start up and logic high but closed at logic low. Happy days until 

the next problem arrives 🙂