Interfacing proximity sensors into opto input

[skypoke]

Hi all. I'd like to replace the mechanical home switches on my 6' X 20' Mechmate with inductive proximity sensors, using Mach3 scheme of all switches into one input. I know I can drive mechanical relays with the prox switches but I'd prefer to not use the mech relays.

Anyhow, I'm searching for a scheme that will allow me to tie the prox sensors into a single opto isolated input on my control card. The sensors are PNP N.O., 10-30VDC. The opto input, with my limited understanding, seems to be looking for a simple switch, not an external voltage or current signal. Voltage between the input pins is approx 3.5 volts.

Sure would appreciate some direction on this.

Thanks, Chuck

[wildwestpat]

Hi Chuck

To be able to help I would need some more detail on the interface you are looking for. In particular:-

1. Is the opto coupler photo diode directly available at the input pins?

2. What voltages are available inside your control box? Most inductive proximity switches use 10 to 30 volts and it is not a good idea to use the motor supply.

3. Can your driver software be configured to select either NO (normally open) or NC (normally closed) contact configurations?

Before you get comitted are your switches operated by magnet proximity or by the proximity of any metalic surface. I only ask as there is much confusion about the various types of electronic proximity switch. Some use hall effect magnetic field sensing others the effect of any sort of metal surface that impacts the frequency of the internal circuit (these can be capacitive as well as inductive). Obviously the ones that use magnets can attract swarf if you are cutting steel - obvious point but easily missed.

Regards

Pat

[Al_The_Man]

Are the present switches in parallel or series into one input?
Do you have the exact nature of the input? the 3.5v measured does not necessarily indicate much.
Is there a 24vdc control circuit source present?
Do the present switches sink to common or source to a + voltage?
Al.