Dynomotion

Group: DynoMotion Message: 10809 From: cnc_machines Date: 1/12/2015
Subject: PNP Switch Input
Greetings,

I am trying to use a high precision limit switch to home a blade. Unfortunately the switch is a PNP type. It appears that I cannot use this on any of the inputs of the KStep.

I have tried hooking it up but it doesnt seem to work. I am wanting to keep as much precision as possible. Does anyone have any suggestions on how to get this switch to work?

http://www.omron-ap.co.in/data_pdf/cat/d5a_ds_e_2_2_csm591.pdf?id=340



Thanks,


Scott
Group: DynoMotion Message: 10811 From: Tom Kerekes Date: 1/12/2015
Subject: Re: PNP Switch Input
Hi Scott,

I don't think PNP is a problem.  In this case of a 2 wire device because it is basically isolated from a supply it can either sink or source current like a switch depending on how it is connected.

However the problem may be that unlike a switch it never fully opens the 270K leaks current.  Depending on the voltage it might pass enough to always turn the KStep input on.  Adding a shunt resistor across KStep should solve this problem.   See this post on cnczone:

HTH
Regards
TK 


Group: DynoMotion Message: 10812 From: az@AIMELE.COM Date: 1/13/2015
Subject: Re: PNP Switch Input
cnc_machines

This switch requires a minimun of 5 v or a max of 24 v through the load to operate. It also has a significant amount of leakage current and the turn off voltage is 3 volts so it cannot be used to drive the K flop inputs. You could use it to activate the isolated inputs on the Snap amp, Kanalog, or Konnect boards.   If you don't have one of these, it would require a power supply (12v to 24v) separate from the K flop to work and drive a solid state relay or optocoupler to activate the K flop input.

 AZ


Group: DynoMotion Message: 10817 From: cnc_machines Date: 1/13/2015
Subject: Re: PNP Switch Input
Tom,

Thanks for the help,this makes sense. I will try a resistor and see if it will work. Would this method work on one of the inputs of the KStep? Or is it mainly meant for one of the inputs on the KFlop board?

Thanks,

Scott