Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-23 Thread Sven Wesley
2014-02-22 15:52 GMT+01:00 Peter C. Wallace p...@mesanet.com: for sinking inputs (like 7I70,7I76,7i77,7I84 field inputs) The best is NC PNP type. These will fail open (= limit) with short to ground or open wire faults Peter Wallace Mesa Electronics Dammit, I've already ordered NPN NC,

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-23 Thread Peter C. Wallace
] Preferred sensors for Mesa cards, NPN or PNP? 2014-02-22 15:52 GMT+01:00 Peter C. Wallace p...@mesanet.com: for sinking inputs (like 7I70,7I76,7i77,7I84 field inputs) The best is NC PNP type. These will fail open (= limit) with short to ground or open wire faults Peter Wallace Mesa

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-23 Thread Sven Wesley
2014-02-23 21:49 GMT+01:00 Peter C. Wallace p...@mesanet.com: You can use NPN Proximity switches with the 7I77 but it requires external pullup resistors (say 2K 1W) I know, but the sensors are too cheap to make a special design for the cards that are fine with PNP's. I rather take the cost

[Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-22 Thread Sven Wesley
I am going to shopaholic a bunch of proximity sensors to replace mechanical homing and limit switches for two machines with Mesa cards (5i25/7i77) and then it struck me, what is the best option? NPN or PNP? How do they behave if there's no power to them or if they fail? For example a PNP NO, is it

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-22 Thread Andy Pugh
On 22 Feb 2014, at 10:12, Sven Wesley svenne.d...@gmail.com wrote: then it struck me, what is the best option? NPN or PNP? I can't remember which type is preferred, but you probably want the shielded type as they still work flush-mounted in metal.

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-22 Thread Marius Liebenberg
You want to use NPN NC switches. This means that the circuit is energized when in normal condition. If the switch is made the circuit will open or if the power fails or if the wire breaks, the circuit will be open and hence you will detect the condition on the input. Oh and make sure it is the

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-22 Thread Sven Wesley
2014-02-22 10:27 GMT+01:00 Marius Liebenberg mar...@mastercut.co.za: You want to use NPN NC switches. This means that the circuit is energized when in normal condition. If the switch is made the circuit will open or if the power fails or if the wire breaks, the circuit will be open and hence

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-22 Thread Peter C. Wallace
] Preferred sensors for Mesa cards, NPN or PNP? I am going to shopaholic a bunch of proximity sensors to replace mechanical homing and limit switches for two machines with Mesa cards (5i25/7i77) and then it struck me, what is the best option? NPN or PNP? How do they behave if there's no power

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-22 Thread Dave Cole
I usually use 24 VDC PNP NO proxs for general use for a number of reasons. If you have voltage at the output of the sensor, then the prox is sensing metal. Most logic is positive which seems to help the debugging and troubleshooting process. However if the input card requires a sinking sensor

Re: [Emc-users] Preferred sensors for Mesa cards, NPN or PNP?

2014-02-22 Thread Marius Liebenberg
Yes of coarse it depends on the type of input circuit that you use. Peter is correct for sinking inputs the PNP is best and for sourcing inputs you will use NPN On 2014-02-22 11:27, Marius Liebenberg wrote: You want to use NPN NC switches. This means that the circuit is energized when in