Relay noise resets microcontroller

mvs sarma · May 2, 2009

abicash said:
That will be the last resort.

Anyways theres also a weird problem with this ckt.
I switch a relay and theres a incandescent lamp in the contacts.When I switch this on/off it does it well.But when I try an Inductive load,the MCU jumps to a routine simulating a key press,which is an active high switch,when used.
Is this also relating to the current issue?...or something else...???

Anyways Thanks so much for taking interest in my woes...

it happenss
you need to put an MOV across the contact . say , if you are using it for 230V, then MOV could be 250V . otherwise and R-C series network acoss the contact would act like spark quench.with R at 1K 1 watt and C at 0.047/600V

abicash · May 2, 2009

Hello sarma

I tried putting an MOV but it doesnt solve the problme.
The RC snubber I used is 10 ohms and 33nf/630V.
Other RC values were useless.

Mikebits · May 2, 2009

As an experiment, can you run your relay circuit on a separate supply?

abicash · May 2, 2009

Mikebits said:
As an experiment, can you run your relay circuit on a separate supply?

Yes I did that and it runs fine..
I also tried using a TRIAC driven by an MOC3021...i used RC snubbers across the TRIAC,but this too created the same problem.
The MCU will take a long time to detect an IR waveform (which is what i am doing).

On a pure DC it works fine

abicash · May 4, 2009

Mikebits said:
Use an LDO and your troubles will be over. I hope...

I replaced the 3 diodes with a 3.3V zener diode.
Now when I switch non-linear loads,the problems still there.

Mikebits · May 4, 2009

You have proved that running seperate supplies solves your problem, so it would then make sense that you know where your trouble is. Zener diodes do not make good regulators, Perhaps if you had a myriad of capacitors on your zener you may solve your woes. A regulator will eliminate all your problems I think. Yes LDO is expensive, but how much is your time worth?

Sceadwian · May 4, 2009

You didn't just swap the diodes for the zener did you? Cause it's not going to regulate properly setup like that.

abicash · May 4, 2009

Sceadwian said:
You didn't just swap the diodes for the zener did you? Cause it's not going to regulate properly setup like that.

Oh no

5V __/\/\/\/\____________ 3.3V
|
-----
/\
---
|
|
-----
--- GND
-

theres also a capacitor acros the zener

(the zenere is after the resistor)

Sceadwian · May 4, 2009

Sorry abicash, I can't read that =)

Mikebits · May 4, 2009

ick, eek, ack, gadzooks. I told ya how to solve your problem, if you want to try a cheap way out, then I give up...

abicash · May 4, 2009

Ok Now I rechecked the whole thing on a 12V Battery generated DC.

When I connect a SMPS load (non linear) to the relay...it behaves erratically (as was the case with the unisolated PSU ,i had mixed things in my mind and apology for that )

So its not the problem with the PSU.

The ckt detects an IR wave from a remote ,decodes it and takes appropriate action on successfull compare..

When a Lamp load is put on the relay,it works flawlessly...The problem arises on non linear loads..The ckt takes number of key presses for a succesfull compare..

I am really confused

Please help guys

Mikebits · May 4, 2009

abicash said:
Ok Now I rechecked the whole thing on a 12V Battery generated DC.

When I connect a SMPS load (non linear) to the relay...it behaves erratically (as was the case with the unisolated PSU ,i had mixed things in my mind and apology for that )

So its not the problem with the PSU.

The ckt detects an IR wave from a remote ,decodes it and takes appropriate action on successfull compare..

When a Lamp load is put on the relay,it works flawlessly...The problem arises on non linear loads..The ckt takes number of key presses for a succesfull compare..

I am really confused

Please help guys

Have you ignored everything I posted? I guess it is not what you want to hear, but it you want to do it right, follow my advice, else, keep searching for a band aid solution. I am sure there is one, but I never was forced to design with minimal cost. What you need is a low cost alternative to an LDO, and sadly I do know what that is.

Good luck.

abicash · May 4, 2009

Mikebits said:
Have you ignored everything I posted? I guess it is not what you want to hear, but it you want to do it right, follow my advice, else, keep searching for a band aid solution. I am sure there is one, but I never was forced to design with minimal cost. What you need is a low cost alternative to an LDO, and sadly I do know what that is.

Good luck.

Hello and thanks for being patient on this with me

I will check with an LDO..I have an MCP1700 with my component supplier..

Thanks again

abicash · May 4, 2009

Hello I just have this doubt again.Please bear with me..

If there was a problem with the 3.3V supply,then why is the problem not sustained on a lamp load and why is it visible with non-linear loads?

If it was the sag on the Vcc then it should occur on No-Load condition too,when the relay switches!

I am only having a hard time understand this

abicash · May 4, 2009

Sceadwian said:
Sorry abicash, I can't read that =)

Please check this

abicash · May 4, 2009

Hello

After adding an LDO...the problems didn't seem to go away so I played around with the RC snubber across the relay contact (that seemed to be the problem)

I found that a larger time constant supresses noise substantially on the neutral path...

I have reached a value of 680ohms/3W and 2 capacitors effectively 66pf/630V at which theres NO problem at all..

Mikebits · May 5, 2009

Well, congrats on fixing your problem. I suspect you had a few problems, and you fixed them both. A good test would be to keep your current configuration and revert back to the diode regulator, if that works then you can yell at me for getting you to fork over the cash for an LDO...

abicash · May 5, 2009

Mikebits said:
Well, congrats on fixing your problem. I suspect you had a few problems, and you fixed them both. A good test would be to keep your current configuration and revert back to the diode regulator, if that works then you can yell at me for getting you to fork over the cash for an LDO...

Currently I am using the Zener Diode after testing it with the LDO and am happy with that..

I can never yell at you though

All help appreciated!!!!!!

Lets hope I dont run into more problems henceforth

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