Problem in LCD 16x4 due to NOISE

[embpic]

Hello master's
i am doing project in which when i am running project standalone without connecting relay's that time works properly. but when i am connect relays to circuit with isolation of opto-coupler and enable and disable the relays then lcd is out of control.
i have interface 8 relays each having light tube of 230 VAC.
is it due to high frequency in chokes which is used for light tube or any other reason?
controller p89v51rd2
lcd 16x4
compiler keil

 

[kripacharya]

I would seem from your description that the isolation which you expect is not really there. You should examine your physical circuit again to see where this coupling is taking place. Maybe some problem with earthing/ grounding which is sometimes easy to overlook. What about your power supply ? Is it common to both parts of your system ?

You could also post your circuit, pics, diagrams etc.

 

[mathespbe]

Hello master's
i am doing project in which when i am running project standalone without connecting relay's that time works properly. but when i am connect relays to circuit with isolation of opto-coupler and enable and disable the relays then lcd is out of control.
i have interface 8 relays each having light tube of 230 VAC.
is it due to high frequency in chokes which is used for light tube or any other reason?
controller p89v51rd2
lcd 16x4
compiler keil

u have connected the chocks through relays only right?
Are you using the same pins for LCD both indivdually and with relays as well??

 

[embpic]

yes sir power supply is same to operate relay but is dual not isolated.
how i could give proper isolation?

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and i have connect chocks means Ballast which is available in market to operate tube light.

 

[kripacharya]

I don't think your chokes and tubelights are creating the problem, unless you have placed them very close to your circuitry and have used long jumper wires in your controller.

I would suggest you put in some further filtering on your power lines - i.e. caps, inductors, beads etc - and see if that helps.
Also if you have left some input lines on some ic's unconnected, then you should connect these to gnd/ vcc as the case may be.

Lastly - it's not clear to me why you have opto-isolators as well as relays in your setup ? A relay itself would provide sufficient isolation i would think ?

Why don't you post your circuit? Without that it is way too much guesswork, and not really interesting.

 

[embpic]

actually i have not design it in proteus and don't know how to use?
and i am doing whole project on development kit + external hardware.

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is it work if i connect all unused pins to ground?

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i also tried filter using cap

 

[Venkadesh_M]

Did you connected the free wheeling diodes for relays?
post how your relays connected with controller and did you tried with relays connected and tubes not connected???

 

[embpic]

i have used ULN2803 and i think there is free wheeling diode in that.
where u r suggesting?

 

[Venkadesh_M]

yeah then its not problem
First try without connecting relays
then with relays and not tubes
then with relays and tubes then lets conclude where the problem come from....

 

[embpic]

yes sir i tried that one also but no effect.
sir can i switched to triac. or is there any other option for relays due chattering noise.

 

[Venkadesh_M]

where the problem? only relay or relay with tubes?

 

[wp100]

yes sir i tried that one also but no effect.
sir can i switched to triac. or is there any other option for relays due chattering noise.

Hi,

You say the relay ' chatters ' , that does not seem right.
When your relay activates there should be a distinct Click and thats it, if its a series of clicks then something else is wrong - please say what is happening as so many things can cause relay chatter, program code errors, low voltages etc etc.


It would be a lot more helpful if you could give details of your dev board and either a drawing or photo of your extra relay circuitry and your program code.

Switching to a triac may solve your problem but if needs other components like a zero crossover opto coupler /triac driver, so would say that a lasts option.

Have you fitted a mains suppressor across the relay contacts ? Important the capacitor must be a main voltage class X or Y type.
**broken link removed**

 

[Venkadesh_M]

First find the exact problem, using SSR is also easy but it costs some more..

 

[embpic]

as i told you relay chatter means i have connect 8 relays so when i enable all then all click at ones so this noise is come out.so, this could not be problem.
i will update with cirrcuit diagram soon.
thanks.

 

[Venkadesh_M]

did you tested without load on the relays???

 

[embpic]

ya i have tested condition u mentioned above.

 

[Venkadesh_M]

what is the results??

 

[embpic]

lcd run randomely

 

[Venkadesh_M]

post your result for each case i have given in #9..

 

[embpic]

sorry sir when i run it without tube then works fine and after connecting tube it works randomely

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without connecting relay - works fine
connecting relay and conecting tube - go randomely
only relay - remain to test