NPN vs PNP for homing

More
30 Mar 2019 21:35 #129994 by Erikcnc
Hi all,

I am willing to use proximity sensors for my lathe rebuild.
These will be the homing sensors.

I am curious why PNP is recommended more over NPN. I have a wiring diagram that says if use NPN i have to ad a pullup resistor.
But PNP is recommended.

Could some one explain me why?


Erik

Please Log in or Create an account to join the conversation.

More
30 Mar 2019 21:53 - 30 Mar 2019 21:55 #129998 by PCW
Replied by PCW on topic NPN vs PNP for homing
it depends on the input type

For sourcing type inputs ( that have a built in pullup resistor to + control power ),
NPN switches are appropriate.

For sinking type inputs ( that require a connection to + control power to be activated ),
PNP switches are appropriate.

For example, with optocoupler inputs the wiring would be as follows

Sourcing input current path: +control_power --> resistor --> opto_anode --> opto_cathode --> NPN_out --> gnd

Sinking input current path: +control _power -->PNP_power --> PNP_out --> resistor --> opto_anode --> opto_cathode --> gnd
Last edit: 30 Mar 2019 21:55 by PCW.

Please Log in or Create an account to join the conversation.

More
31 Mar 2019 06:59 #130018 by pl7i92
Replied by pl7i92 on topic NPN vs PNP for homing
You may tell us what Brel out Board you are using
LJ12A3-4-Z-BX They are very Stable to use

You can use the NO Normal Open ones
or Normal Close NC ones
NC is better as it showes always functionality if error they wont work
BUT also the NO ones fail signal as they break on the touch and your mashine will notice it
IT Runs to the oposit Home so Defekt is no BREAK

Please Log in or Create an account to join the conversation.

More
31 Mar 2019 07:31 #130020 by Erikcnc
Replied by Erikcnc on topic NPN vs PNP for homing
Ofcourse, I forgot to mention the board I'm using.
I'm using Mesa 7i76e.

Please Log in or Create an account to join the conversation.

More
31 Mar 2019 21:36 #130060 by PCW
Replied by PCW on topic NPN vs PNP for homing
Yeah, the 7I76/7I76E/7I77 use sinking inputs so PNP sensors are the easiest to use

Please Log in or Create an account to join the conversation.

Moderators: cncbasher
Time to create page: 0.086 seconds
Powered by Kunena Forum