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Subject: Re: AW: AW: AW: AW: Still Problems with AJB Remote
From: Ronald Teune (rtwolf_at_gmx.net)
Date: 2004-07-14


Hi,

how did you simulate this?
This schematic is exactly the same (IIRC) as used in old Diode Logic (but
now only 1-input nand) so it should work...
What if we used standard 1N4148 diodes?
The voltage drop on the Schottky diode is 0.6 Volts.
If the uC out port is at 0 V, the AJB remote line will be pulled down to
0.6 V; when the uC Out port is at 5 V, the AJB remote is at ~5 V due to
the pullup. (it's easy to make mistakes though, with this kinda stuff,
especially since it's holiday - so correct me if i'm wrong)
Perhaps PSPICE has some problems with grounding and stuff; how exactly did
you connect a ground to this schematic?

<snip>

> # Forget what I said and simplify to this:
> #
> # +5V
> # |
> # |
> # +-+
> # | |4.7k
> # | |
> # +-+
> # |
> # |
> # Schottky |
> # uC Out port--------|<|---------+-- AJB remote
> #
> # The pullup won't hurt even if a box already has one. The diode will
> allow
> # your uC to pull the pin low, but will prevent it from being
> # driven with high output current to 5V. Instead it "gently" floats up
> via
> the pullup. Use a
> # Schottky because those have low voltage drop across, allowing for a
> better "low" level.
>
> Ok, I also did a PSPice simulation of this (with 1N4148 because the demo
> doesn't have a Schottky).
> The AJB remote level then toggels between high = 0,7V and low 0,612V ???
>
> Well, I know, that these simulations are not very well done, but in
> previous
> cases it worked
> more or less like the final HW.

<snip>

Greets,
Ronald Teune
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