Re: Comfort / Analogue Input / Op-amp ?

["Nick" <nick@xxxxxxxxxxxxxxx>]

Frank said:

> but quite common for alarm systems
> to have an internal resistor(s)
> connected to +v and the circuit
> connections go to gnd via a
> resistor.....  Do you have to tell
> comfort that its now an analogue input ??

Good point - can't see the need to tell "her" in the
documentation
anywhere.  I have also posted on the Comfort support forum, I'll see
what pops up there on that one.

> Also measure the voltage of the
> comfort analogue input with the
> temp sensor disconnected and see
> what voltage if any is present.........

I should have thought of that one.  The cover is back on at the
moment because it's bedtime, I'll try that tomorrow night.

Ake said:

> put two diodes on the opamp output.
> One from ground to the opamp output
> and one from the opamp output to vcc.
> This is often used to protect an input
> from a negative signal and signal above VCC.

> Have you tried to connect a pot
> (or a variable power supply) to the
> input and see if you get reasonable results?

I'll try those but, first, I'm going to wait for the "official"
answer from the Comfort forum.

> But its very strange if the A/D
> input behaves like this. It should
> only behave like a big resistance.

I guess so, but I'm still bemused by it also being able to be
a "normal" zone input.

Thanks Ake and Frank for the continued help - I'll post again when I
hear from the Comfort support forum.

Nick