Why not use capacitors in parallel with the dip-switches? That may slow
down the detection of a on-to-off transition and may erode the
dip-switch contacts but also may allow the use of very large pull-up
resistors.

Cheers,

Isaac



Em 05/04/2017 11:54, Van Horn, David escreveu:
> I agree that using 100k-ohm external pull-ups is PROBABLY safer than usin=
g 1M-ohm pull-ups, that too is more speculation than anything in that my ow=
n tests have not been mass-produces and used in thousands of different cars=
..  Because no one has presented such hard evidence on why a given value of =
a pull-up resistor is bad in a car's noisy environment, the discussion then=
 turned to "well, why even use external pull-ups at all?"  I think that new=
 question is important, but I still am curious about the original question:=
  "HOW BIG IS TOO BIG when it comes to external pull-ups on modern PICs lik=
e the 16F1508 when used in 12-volt automobiles?"
>
>
> You might be able to find some SAE guidelines on EMC that would tell you =
something concrete.
> Car wiring tends to get conductive gunk on it and have leakages.=20
> Ignition and motor noise, RF..
> I once had a car whose rear wiper would kick off if I transmitted on the =
ham VHF band at more than 10 watts.  Never did figure out why.=20
> While the transmitter might not be in your car, you might be next to me i=
n traffic.
> Or a cop, ambulance, taxi, CB....
>
> Can you do something other than dipswitches?  That seems to be the root o=
f all evil here.=20
> Maybe a second board with switches that you connect as needed through a S=
PI interface or ?
>
>
>


---
Este email foi escaneado pelo Avast antiv=EDrus.
https://www.avast.com/antivirus


--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.