Latched relays noise problem on 5V supply

[chamarnadh]

Hi,

In one of design I am using latched relays for switch on and Off the eight power outlets.

My problem is when I switching it ON noise is coming on 5V supply even though the supply for Relays is isolated.
Noise is different freq for each relay(some times it is 200khz sometimes it is few tens of Mhz).Due to this noise some times my RS-232 port is hanging.

I was used a LC filter with 100uH and 0.1uF, but the noise is still there.

Can anybody suggested the filter circuit for this.And How we can calculate the filter values.


Thanks and regards
Amarnadh

 

[khetanikrunal]

Is that inductor noise?

If yes then you need to reduce your inductor value.

 

[chamarnadh]

Is that inductor noise?

If yes then you need to reduce your inductor value.

Thank you ,

I was checked on scope the frequency is few Mhz and the Peak to peak voltage is 7.8V on 5V supply.

How can we conform this is inductor noise?

Regards

Amarnadh

 

[dick_freebird]

If it only attends the switching event then it's probably the
flyback energy of the coil being dumped, and inadequately
snubbed (around too large a current loop, left to ring too
long, etc.). Your grounding may also be a problem, if the
current decides your serial lines are a better path than the
explicit coil power path.