[aprssig] KPC Telemetry clarification

[Robert Bruninga]

Ryan,
Since the input impedance of the a/d converter is extrememly
high, the internal series 10K resistor means nothing since it
is in series with the input. (Unless of course you put the 2.4k
resistor internal so tht the 10k now becomes part of 
the needed vltage divider.  To use the other inputs you can put
the voltage divider external.  BUT BE CAREFUL.  You are 
messing directly witht he CPU input pin and stitic charges
can kill it.  Id make sure the divider is rethare permanetly 
connected to protect against external errors.

Bob, WB4APR

>>> Ryan.Tourge at sheriff.co.warren.ny.us 01/02/05 10:47 AM >>>
I've been playing around with the Telemetry feature on my KPC-3's. 

 

I guess I just need clarification on a few things.

 

Inputs AN0 and AN1 have a factory installed 10K Ohm resistor in series
with there respective input pins. I need to install a 2.4K Ohm resistor
across the input and ground (I actually use a pot at 2.35K Ohms
connected to the allocated pads on the PCB).

 

For AN2 AN3 and AN5 I need to install a 10 K Ohm resistor in series as
well as the 2.4K Ohm resistor across the input to ground.

 

Does this look right?

 

Thanks!

Ryan

K2RRT