Resource for proven/rugged uController interface circuitry?

Mickster

The internet is awash with all kinds of hobby-standard interfacing ideas but I wonder if a resource exists for designs where component cost is not an issue. I am looking for rugged and reliable solutions.

Beau Schwabe

If price is not an issue .... OMRON and any line of their PLC's

Heater.

What do you want to interface to?

Hobbists solutions can be better spec'ed and built than some commercial, off the shelf, built down to a price equipment.

jmg

Mickster wrote: »

Resource for proven/rugged uController interface circuitry?

'rugged' against what ?

We had one product under aggressive ESD testing, and that was not so much any interface that needed attention, but more providing a pathway for the ESD current to avoid anything sensitive.

Or, if you are worried about EMC testing, ferrite beads are often added.

I recall one story of an Engineer at Philips using a bare wire + metalworking file(!) as a Noisy-mains-contact stress tests on SMPS soft start.

We've also used a 'chattering mains relay wand', as a watchdog recovery test. Quite revealing, and proved on many parts 'reset'; is more like a 'reset request' and showed why power-removal-watchdogs are often the best.

Mickster

Sorry guys, should have been more specific.

I guess it's mostly analog inputs that I'm referring to. For digital I/O, I already have opto-couplers, line-receivers, SSR's, etc. but for analog inputs, I just go with an op-amp and that's it?

I guess the reason for the question was just in case there was a Great Book of Best Practices out there

@Beau: The last time I touched a PLC was a Gould Modicon back in 1981. Somehow I have spent the last 30+ years working with machine tools and factory automation without touching another PLC.
I did take great pleasure in kicking AB's butt in 1988 when they (a whole bunch of engineers) attempted to do with a SLC-500 what I was doing with an office grade PC+motion card+OPTO22-AC5. They failed miserably.

jmg

Mickster wrote: »

I guess it's mostly analog inputs that I'm referring to. For digital I/O, I already have opto-couplers, line-receivers, SSR's, etc. but for analog inputs, I just go with an op-amp and that's it?

Series R's ( & Shunt C) are a simple way to buy extra ESD and RFI immunity, but too much R and you degrade noise and offset errors.
Some opamps have sensitive inputs with limited swing tolerance, those may need additional clamps - better ones will spec ESD & RFI levels.

Phil Pilgrim (PhiPi)

Opto-isolated 4-20 mA is pretty much standard for analog interfacing in harsh environs.

-Phil

Mickster

Phil Pilgrim (PhiPi) wrote: »

Opto-isolated 4-20 mA is pretty much standard for analog interfacing in harsh environs.

-Phil

Yeah, I prefer this. I might just convert every external 0-10v that I come across to 4-20mA.

Beau Schwabe

Just about any transistor or photo-voltaic linearized Opto-Isolator configured as an Optical current mirror will do the trick for conveying an analog signal across an isolated region.

See the datasheet on this item... There are cheaper Opto's but the datasheet on this particular one has lots of application examples.

http://www.digikey.com/product-detail/en/HCNR200-000E/516-1522-5-ND/696022

RickB

Rugged Circuits

rugged-circuits.com/10-ways-to-destroy-an-arduino

Mickster

@Beau: Perfect! Many thanks. I didn't know these existed, need to order some right away.

@RickB: Many thanks also. I came across one of their sample circuits last week but at their site, could find nothing but (VERY nice) product. These are the sort of design precautions that I am interested in.