New Thinking For a Bullet Proof Solution

I have not done any work on this for some months now so am eager to pick it up again.

My thinking for this project has changed as I have worked out that using the Pi to directly control the active appliance peripherals will not work for two reasons.

a) There are no native analog inputs which are required for temperature measurements, and
b) There is a need to maintain fail-safe interlock protections and I do not trust the RaspberryPi/Linux platform to operate at the level of unbroken reliability required.

I have researched and sourced a small Atmel based Arduino board which will virtually drop into the main control PCB as a replacement for the existing OTP micro-controller. I plan to program this device to emulate the existing program or pass control over to the RaspberryPi but still take back control in the event the RaspberryPi application were to fail or attempt to do anything unsafe.

A simple serial interface back to the Pi (possible optically coupled for main isolation).

This gives me the best of all solutions, a fail-safe local controller which will work independently of the Pi but also allow the Pi to take over operations in a safe and controlled manner.


... more to come.