Eelements of industrial system using uC

[Windadct]

Eelements of "industrial" system using uC

I work in Power Electronics (components and stacks) and have a few products I would like to develop using uC - very simple, 1-4 channel PWM systems.

My question is - in addition to the core function ( input(s) - process - output(control) - RT feedback ) - What key elements do you routinely implement, in a ruggedized product. For example - how often do you implement a wachdog? Special shutdown, reset, or initializing routines.

In my experience - the "work" of developing a product is all of the accessory functions and features, and making it work in the field reliably, vs doing its job on the bench. -- I would say the typical sell-able product reliability would need to be 100 to 1000x what a typical hobby project would be - and what do you do to ensure this?

 

[berkeman]

I work in Power Electronics (components and stacks) and have a few products I would like to develop using uC - very simple, 1-4 channel PWM systems.

My question is - in addition to the core function ( input(s) - process - output(control) - RT feedback ) - What key elements do you routinely implement, in a ruggedized product. For example - how often do you implement a wachdog? Special shutdown, reset, or initializing routines.

In my experience - the "work" of developing a product is all of the accessory functions and features, and making it work in the field reliably, vs doing its job on the bench. -- I would say the typical sell-able product reliability would need to be 100 to 1000x what a typical hobby project would be - and what do you do to ensure this?

You should definitely include a watchdog timer to reset the application if it is not getting "tickled" routinely. You should also consider the physical robustness of the device -- immunity to external transients and other disruptive things. For example, you could test to the European "CE" mark standards for immunity:

EN 61000-4-2 ESD
EN 61000-4-3 Radiated RF Immunity
EN 61000-4-4 Burst / Electrical Fast Transient
EN 61000-4-5 Surge
EN 61000-4-6 Conducted RF Immunity

These aren't easy tests to do yourself in your personal lab, but you can contract with test houses to perform the tests. The goal is to be sure that the device you've designed (both in hardware and software) is immune to every-day sources of interference and corruption. There are definitely design rules and tricks to use when floorplanning and layout out your device.

 

[Windadct]

Thanks Berkeman - I will be offering these designs to the actual product owners, so testing will be their realm - however advising them that the final design should be tested to x-y-z is how I operate - so it is not on my plate. In the power levels I am looking at (10 to 500KW) the devices are the worst enemy for most of this - -- Line V surge is the biggest unknown outside influence.

At the Real Time control level ( but also some HW isolation issues or best practices) is where I am targeting - there are a few applications that need effectively the same Power Electronics solution. Most of the HW issues I have a handle on - but the RT control level is the disconnect.

[Edit] - yes I have apps in that power that NEED very simple control, less to go wrong - then there is usually an application control layer.

 

[berkeman]

EN 61000-4-11 is the Voltage Sags & Dips standard for the CE Mark test suite, BTW.

 

[Okefenokee]

Don't forget the brown out. Many chips have a hardware interrupt that occurs when the power dips. Chips are fast enough to save some info before the power goes out.