A dead man's switch is a device used as a fail-safe. These switches are usually used as a form of fail-safe where they stop a machine with no operator from a potentially dangerous action or incapacitate a device as a result of accident, malfunction, or misuse.
I'm looking for some method to stop an Arduino to prevent harm. Is there an Arduino code sequence that will stop an Arduino and the only way to recover is to restart the device?
colporteur Owly when working with relays? Don't forget the reverse biased anti-spike diodes across the relay coils. That inductive kick can do some damage - or at least give you odd operating characteristics.
As to the deadman... you can always supply power through the NO contacts on a relay. Use a momentary switch to enable power to the Arduino and have the Arduino act as the seal-in contacts for the power relay. If the watchdog timer drops out, so do the seal-in contacts. Restart is manual.
I keep meaning to make a 555 watchdog, but I haven't got around to it yet. Sure there are chips that do this, but... I have this idea stuck in my brain. 
The missus is leaving town for a few days. Fresh fish is on the menu and the dog and myself are going to watch TV in our underwear.
That tends to suggest that you either a) don't normally wear any while watching TV, or b) that you normally wear someone else's... 
Either way, after this week's incidents I'd strongly recommend going for the fire-proof variety...
