EMI problem for PIC 16F630 based controller

[srevish]

Dear All,

I am using a PIC 16F630 based controller and one PLC, both for different applications. These two will share same power line of 110Vac, 60Hz. But in a particular site we are having problem with the PIC 16F630 based controller, this controller start malfunctions and when we power off and restart the system it again starts to work normally. I believe it to be due to EMI issue.

Kindly give your feed back and it will be helpful for us if any one can give the solution to avoid this problem further.

Thanks.

 

[johnjoe]

Maybe you can post a short schematic, do you use capacitors at voltage pins of the pic?

 

[srevish]

Maybe you can post a short schematic, do you use capacitors at voltage pins of the pic?

I have attached the schematic in this mail, please make a note of it.

 

[jpsganesh]

is there any AC supply or motor drive line near by PIC? if so to avoid it route it in different path to maintain enough gap b/w PIC and noisy line.

cove PIC with metal box or metal shield with proper grounding.

use decoupling capacitor near supply pin of PIC as like johnjoe says

 

[srevish]

is there any AC supply or motor drive line near by PIC? if so to avoid it route it in different path to maintain enough gap b/w PIC and noisy line.

cove PIC with metal box or metal shield with proper grounding.

use decoupling capacitor near supply pin of PIC as like johnjoe says

View attachment 105087

Is there is anything that we can add in the circuit to avoid these problems.

 

[johnjoe]

First, before you do any countermeasures, reveal the source of your problem. Use an oscilloscope and check for transients, especially on VCC and Reset pins of your pic. When the malfunction happens? Which part of your circuit in your schematic is active in this situation?

It's also possible that the problem is due some layout mistakes, is the design a commercial one or your one?

 

[jpsganesh]

AC supply side u can use proper filters and decoupling capacitor near controller pin and reset pin.
put it in to a metal box ground it properly. Mostly this will solve ur proble.

in software side u can enable watachdog timer to monitor health of ur controller. this will reset ur controller automatically. :razz:

- - - Updated - - -

What type of power supply u r using? which make/brand?

change the powersupply with standard power supply unit. AC line filter will be available in it and also most standard filtering unit in every stage will reduce the noice due to load side or source side.

 

[chuckey]

First step is to put a .01MF across M1 to try and remove mains transients. Second attempt would be to decouple all the input and output leads with a .1MFD. Third attempt is to properly screen the unit with an earthed metal screen, which it should have as it contains some lethal voltages.
Frank

 

[123jack]

It might be worth putting a scope on the transformer - I've seen some very odd problems with badly wound
transformers in the past.
If you are in a PLC environment you may have equipment with relays around too - if you can - check they are
all properly rigged with their back emf diodes. Also check for ground loops.
Try to log what else is happening when crashes occur.
If it is just this "particular site" that lowers (but not eliminates) the chance of it being a design issue.
I'd have a good check around and follow johnjoe's advice first.
.