Standard/Recommended Practice for Discrete I/O in Aircraft Application 1

[jonnycowboy]

Hi all,
I'm wondering if there is a standard specifying voltage levels for aircraft use of Discrete I/Os?

IE: Gnd/Open would be:
gnd, logic 1
open, logic 0
logic 0 lower limit: 12VDC
logic 0 upper limit: 48VDC
logic 1 lower limit: -2VDC
logic 1 upper limit: 5VDC?

Same question for 28V/Open...

Any ideas?

thanks!

 

[DHambley]

j-cowboy, The Airbus ABD0100H standard has the discrete signal interface levels. Every avionics product which I've designed always seems to have a few 28V logic interfaces and a new unique circuit had to be designed for each new system. What you were given was the 28V/open or /ground charachteristics and the DO-160 or D6-16050 (or whatever) noise and susceptibility levels, then you had to design an interface which satisfied all.
The DEI company has several chips which were made specifically to comply with most airframe system spec. I've used these for avionics which had to interface with 28V/open logic for various airframe mfg's.

 

[jonnycowboy]

Hglr, thank you very much for your reponse. I don't have access to the Airbus spec however the DEI part information does mention the spec and its tolerances.
We are aware of the Do-160 reqs.

Thanks again!

 

[kontiki99]

Most discretes that I see in practice are ground/common = disable, open = active active.

I believe it embodies fail safe principles, i.e. recognize sooner or later all wiring fails, a fail open to keeps critical systems active.

 

[kontiki99]

Apologies for two posts, I was interrupted.

You might look at ARINC 607-3 - DESIGN GUIDANCE AVIONIC EQUIPMENT