TVS diode rating required...

Thread Starter

SHARANYADAS

Joined Apr 13, 2017
53
Dear experts
I have designed a Bluetooth+IR based home automation system with Atmega328p,ULN2003 relay driver and some 5v relays.The unit is being fed by a small 5v/1A SMPS from Hi-link.Normally the unit is running fine.But sometimes,when turning on/off inductive load(In this case,my AC ceiling fan),the micro is getting hanged.The power output from the smps(5v line) is filtered & decoupled with 470uF + 0.1uF cap.Also the clock lines of the Atmega is decoupled as per the datasheet with 27pf caps.I also tried adding snubber (with a 39R+0.1uF in series)at the relay terminals but that didn't change anything.So i thought to use a bidirectional TVS diode at the 5v power line.What should be the value of the TVS diode??Also,part no is much appreciated..Please help!!
 

#12

Joined Nov 30, 2010
18,076
You did good things on the output side of the 5V converter. Try filtering the input of the 5V converter. Maybe a dual choke power line filter or a TVS and a 0.1 uf (ceramic or metal film) cap on the power input of the 5V converter.

This thing about a microprocessor hanging because of power line noise is often happening. You simply must find ways to avoid the noise spikes getting to the MPU. There are several ways to do this. Here are some TVS in the range of 5V to 5.5V

http://www.mouser.com/Circuit-Protection/ESD-Suppressors-TVS-Diodes/_/N-jy72?P=1yzv44wZ1z0x5opZ1z0skp6Z1z0x437Z1z0x7siZ1z0x6cpZ1z0x5plZ1yzxauvZ1z0x456
 

#12

Joined Nov 30, 2010
18,076
Now that you know where to look and you know there is a search parameter engine, look up some bidirectional parts.
 

Thread Starter

SHARANYADAS

Joined Apr 13, 2017
53
Sorry for such a late reply!I have searched and by far,as per my limited knowledge,I have found this one to be perfect.I am attaching the datasheet.Please give your opinion.
 

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Thread Starter

SHARANYADAS

Joined Apr 13, 2017
53
And one more thing,Should I use a PTC fuse to be attached in the 5v line before the TVS??
 
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