Evidently, I'm not accustomed to the usual NPN proxes. We have some NPN devices at work that have the collector tied to supply, with the emitter as the output. ________________________________ From: Peter C. Wallace <p...@mesanet.com> Sent: Wednesday, September 2, 2020 7:22 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] 7i76 input with NPN NO
On Wed, 2 Sep 2020, James Reed wrote: > Date: Wed, 2 Sep 2020 22:50:25 +0000 > From: James Reed <jsr...@hotmail.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] 7i76 input with NPN NO > > What am I missing here? I see a NPN output transistor as the source to a > sinking input. The sinking input has a 20K input impedance according to > specs. I would think if anything, the input may need a 2 to 10K resistor to > ground so the NPN can switch reliably. This is totally dependent on the > minimum current of the sensor output. ________________________________ From: NPN sensors are effectively a switch to ground so will not work with sinking inputs (the input voltage will be 0 in both states) unless there is a pullup resistor to create a high level when the switch is off. That said the issue is a bit confused as some NPN sensors have built in pullups to their positive power supply. Ideally a PNP sensor should be used with sinking inputs and a NPN sensor used with sourcing inputs. Peter Wallace Mesa Electronics _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
