how to reduce the electrical noise

[paimpozhil]

Hi MarkT,

Thanks for the answer,

To keep everything out of equation I disconnected all my PIRs and kept the arduino to the minimum.

I measured the voltage across the +5 and GND.. while the Flourascent light is flickering.

I saw voltage spikes upto 6 or 7 sometimes even more during this and hence the AtMega is restarting.. Is that possible?

Will atmega reboot when this happens?

I use the same wallwart to power the ULN2003 for  8 relays as well as the ATmega . will this cause Ground loop?

[paimpozhil]

I use a 7805 with 2x 470uF decoupling capacitors .. and I see more than 5V during the light flickers ..

Input is 12v from the wallwart which already has its own regulators. should i replace wallwart and try?

or should i change the voltage regulator IC to be something better than this?

[paimpozhil]

OK I have measured the voltage across my 12v wallwart lol it goes UPTO 35V during flickering.

I tried to replace my nokia phone charger and see what happens, it keeps its voltage stable..

I think the problem is my cheap crappy wallwart.. everyone agrees?

[Grumpy_Mike]

Yes it sounds like that is right. You could always get a zenner diode across the supply to try and clip any voltage spikes on the line.