Mysterious Reset... HELP

[mitchjs]

I got a Atmel circuit runing my audio system that i built its
controlled from a PC via a COM Port..

I only have pins 2/3 &5 connect to a MAX232 then to the avr

simple... it all works... till.....

I ignite my GAS Range in the kitchen in the other room
the spark that is generated, causes the ATMEL to reset!!!

ok, when i unplug the 1/8" plug that has my rs232lines from the PC
it no longer does!

and the wire is just 10' long, when i coil it up near my plastic enclosure
where the avr project is held... it does not reset when sparked

so... i need to protect the avr circuit, how do it keep this noise out
my guess is its on the ground... maybe traveling though outlets to pc on the nutral wire? i cant belive its being picked up via the wires...
im using belden 9535, the shield is connected to pin 5 and to the db9 houseing... then pin 2 is black, pin 3 is red... i bring that to a 1/8" plug, tip is black, ring is red, and sleeve is the shield/grnd

i cant figure this out!

mitch

 

[bmcculla]

If I had to guess I'd say this was a problem with grounding. A voltage spike coupled from the cable into your ground might be causing a brouwnout reset. Try adding a RC filter between the RS232 sheild and the circuit ground.

 

[BF9000]

Filter Capacitors

Place a capacitor from the reset pin to ground and also from VCC to ground (near the uC VCC and the max232 transceiver VCC). A value of 0.1uF for each should work. The signal you are generating with the spark has very high frequency and should be easily filtered out.

 

[mitchjs]

i got the reset pin tied high through 10k ohm, and decoupled too with .1 cap
i got .1 cap accross vcc and gnd on max232, and on AVR

mitch