Does Arduino have a Dead Man switch?

While researching the reset pin I stumbled across sleep_mode();

For idle (slight reduction in power): SLEEP_MODE_IDLE
For standby (more reduction in power): SLEEP_MODE_STANDBY
For power-down (most reduction in power): SLEEP_MODE_PWR_DOWN

In developing a model railroad Arduino animation project from theoretical to physical, I discovered a scenario, that in theory should not happen. Well add human interaction to the mix and anything can happen. In my case two relays start to chatter by oscillating back and forth. My deadman switch idea is to stop this scenario and force the operator to reset the layout.

There are some great suggestion provided. Responses sometime contain a solution but if it they don't the ideas provided create paths I never thought about. I long for the days when I worked with a crew of people each with different experience diversity and level. Coffee breaks where we just sat and chatted was a wonderful melting pot of ideas.

Are there any downsides to sleep_mode? I'm hoping to take it to the lab this afternoon and do some testing. I still am not confident I have the ideal solution.

Relays can chatter if their coils aren't getting enough voltage or current. Is it possible when both coils get energized, it loads the power supply enough to cause a local voltage drop?

The condition is two relays cycling one on the other off then flip. The relay control turnouts on the layout. Something in my code is owly causing the problem. I'm working on the problem hoping to uncover the cause.

The condition is two relays cycling one on the other off then flip. The relay control turnouts on the layout. Something in my code is owly causing the problem. I'm working on the problem hoping to uncover the cause.

In that case, your sleep mode code may not be working entirely as expected either, if the code is still toggling the relay outputs.

The troubleshooting session today was a disaster. I reversed the DC power input to the controller board and it no longer winky-blinky:(

I failed to notice the two power wires had reversed themselves while I was doing some changes. My mind failed to register the labels and the colour coding of the wires. I hook them up and JASUS!

Two hours later the buck-boost board has been replaced and a diode was installed to prevent the problem in the future. Fortunately, I installed a protection diode for the Arduino Mega so it wasn't taken out. Why I didn't install the diode for the other section on the board escapes me.

Maybe tomorrow will be a better day.

Ouch!

On a more philosophical note though, I guess it finally silenced those chattering relays?

Perhaps more of a crowbar approach than a dead man's switch though...  

These are growth moments. Personally, and hardware-design-wise.

also: