Internet PLC Forum

General => Technical support => Topic started by: plc_user on May 03, 2006, 04:04:03 PM

Title: Capacitor really needed???
Post by: plc_user on May 03, 2006, 04:04:03 PM

I was just wondering, is the capacitor really necessary at the power supply connector to your MD series PLC?  What are the major problems with leaving it off?  I understand there might be a potential voltage drop with it not installed but and may help filter some noise.  A strong supply voltage and current rating of the PS should be sufficent.  What might I expect the PLC to do with out the installation of it.  A small list of items to check for would be deeply appreciated.

Thanks

plc_user

Title: Re:Capacitor really needed???
Post by: support on May 03, 2006, 10:30:37 PM

If your power supply is good and the wire from the power supply to the PLC is short and direct then you could do without the capacitor/diode combination for most applicaton. These are needed if you face problem of the PLC being reset whenever a load is turned on, which indicate that the load draw enough current to cause the P/S output voltage to drop momentarily and can reset the PLC. Adding diode and capacitor will help somewhat to filter out the effect of such voltage dip.