Dynomotion

Group: DynoMotion Message: 11227 From: cnc_machines Date: 3/16/2015
Subject: KStep 24V Input / Outputs
Tom,

I am wondering if I could use 12 rather than 24 volts on the KStep board for the inputs and the outputs? I am thinking it would be nice to use an ATX computer power supply rather than getting a separate 5V and 24V PSU?

Does this seem okay to you?

Thanks,

Scott
Group: DynoMotion Message: 11228 From: Tom Kerekes Date: 3/16/2015
Subject: Re: KStep 24V Input / Outputs
Hi Scott,

An ATX power supply is not a good idea.  The +5V GND and +12V GND (as well as Earth GND) are all tied together which would defeat all the benefits of the opto isolation.  It also can create GND loops.  Its better to get two small isolated supplies.  10watt supplies usually cost $15 or less and are smaller than an ATX supply.

Regards
TK

Group: DynoMotion Message: 11332 From: cnc_machines Date: 4/9/2015
Subject: Re: KStep 24V Input / Outputs
Tom,

Thanks, I will do as you suggest. This brings up another question about proper grounding. I see that all of the boards (Kstep, and Kflop, & Kconnect) have a hole through them labled ground. Do all of these need to be tied back to the frame ground?

Also I am confused about where to ground the encoder cable shields. I am using the Kstep in closed loop with shielded encoder cables. Do these go back to the frame ground as well?

Thanks,

Scott
Group: DynoMotion Message: 11347 From: Tom Kerekes Date: 4/10/2015
Subject: Re: KStep 24V Input / Outputs
Hi Scott,

No. The ground lugs on our boards are connected to DC GND.  Connecting those to frame (earth) GND would normally be a bad idea.  All the earth ground noise would be introduced into DC GND.  It would also provide a path for earth GND currents to pass through the boards GNDs.  This is called a GND Loop.

Connecting encoder shields to Frame GND would similarly be bad.  It would tend to couple all the Earth GND Noise direcly into the encoder signals.  The best approach is usually to connect the shields to the more quiet DC GND of the device that the signals are going into.  If the signals are going into KFLOP then the Gnd Lug on KFLOP would be a good choice or any of the GNDs on any of the connectors.

HTH
Regards
TK

Group: DynoMotion Message: 11348 From: cnc_machines Date: 4/10/2015
Subject: Re: KStep 24V Input / Outputs
Thanks Tom! This is pretty basic stuff, but I appreciate your advice.

If I understand correctly the AC side of the power supply would be connected to the earth ground. The DC ground would just be the negative terminal on the power supply?

I see that many servo motors and VFD's suggest using a line filter. I have always been curious about why these are used. Are they actually required? Would my spindle VFD possibly cause interference with the KFlop controller?

Thanks,

Scott
Group: DynoMotion Message: 11352 From: Tom Kerekes Date: 4/10/2015
Subject: Re: KStep 24V Input / Outputs
Hi Scott,

Don't know exactly what you mean by "AC side of the power supply would be connected to the earth ground".

I think AC Line filters block Hi frequency noise from entering into your electonics through the AC lines (or going out).  I suppose it depends on how noisy your AC lines are and how sensitive your electronics are.  I think they are always a good idea.

Regards
TK