Not sure where you would get 5v from these boards as I have never used one. If you use a separate supply you will need to connect the 0v of that supply to the 0v(Gnd) of the board so the signal has a reference.
400 Ohms may be ok, you really need to get the specs of the LED and use one of the online LED calculators to see.
Hood

Hi Hood
You should know me by now and electronics. Tried your suggestion and all it kept saying was I needed a bigger/more power supply.
This is the optical sensor
http://docs-europe.electrocomponents.com/webdocs/025c/0900766b8025c315.pdf
What am I doing wrong??
Graham

Hi all
Going to take 5 volts off a usb port, one wire (red) is this ok?

Hood, have ordered some 220 ohm resistors to save confusing the issue.

Graham

Not sure what you are meaning by "all it kept saying was I needed a bigger/more power supply." What was saying that?

If using the USB you will likely need to also take the 0v from the USB and connect it to the Gnd terminal of the inputs plug so that the signal has a reference.
Hood

Hi Hood
From your suggestion
"may be ok, you really need to get the specs of the LED and use one of the online LED calculators to see."
Thanks for the advice about grounding the input plug back to the usb. I will have to find out where that is on my BOB.
Graham

One or more of the pins on the connector that has the inputs will be a Gnd pin I would imagine.
Hood

Should have said 100 ohm resistors

Hi Hood
Thought it was too simple.
Exactly where do you get the 5 volt supply from as there are no obvious connections for it on the BOB TB 6560?
Will I have to get a seperate power supply if so what spec?
I have been given some 200 ohm resisters will two in series be OK as you specify 220ohms?
Graham

200 ohm should be fine.
Hood

Hood
Heres where I am with the wiring.

Pulse from photo cell is sent via serial port pin one to BOB.
GND is via serial port pin 5 and via the usb to computor.
5 volt is from usb.
In ports and pins I have set pin for pulse to 10.
The PDF for the lathe is not very clear.
Will fit 220ohm resister
My question is what do I set PORT to for pin 10???

Graham

It will be port 1 that you set it to, assuming that is what you have the rest of the BOB connected to.
Hood