[sdiy] gates and clock inputs to a microprocessor

[Danjel van Tijn]

Hi Chris,

I was thinking about LM338 comparator with threshold set to 2V... this
way 5V pulses/gates from a midi2cv converter will work but also the
larger voltages (up to 12V since I am on a euro system) would also
trigger. The output would be always be a 0/12V pulse which I could
then divide with resistors or use a opamp with attenuation (to provide
further buffering).

On Ray Wilsons site he even put a schmitt trigger after the comparator
(I guess to clean up even more?)

Also I think for my other question about inverse logic at pins it
looks like on other circuits they are using pull down resistors
instead of pullups.

cheers,
Danjel





On Sun, Oct 25, 2009 at 12:57 PM, Chris Muir <cbm at well.com> wrote:
>
> I went with the conservative approach on a recent module:
> - comparator on input (339)
> - voltage follower with gain on output. I needed 10 V gates (optionally 15
> V), you could get away with just a voltage follower if you only need 5 V
> gates.
>
> - C
>
> On Oct 25, 2009, at 11:36 AM, Danjel van Tijn wrote:
>
>> I am working on module where I have a microprocessor receive gate/trig
>> inputs for clock and reset controls.
>>
>> what do I need in terms of analog circuits to condition those inputs?
>> e.g.
>> -for input over voltage protection would I use a resistor plus 5V zener?
>> -comparator to allow low voltage signals trigger?
>> -series diode to protect from negative voltage?
>>
>> Also the uP will be outputting gate signals. Should these be buffered
>> or can I just drive straight from the output pins?  (it is an
>> atmega168)
>>
>> Also if the input pins of the microprocess are using pullups, how
>> would I have an incoming pulse trigger on rising edge? would I need to
>> put it through an inverter?
>>
>> I am sure all this stuff has been covered and well documented in
>> schematics. I am going to head over to MFOS to get some ideas but
>> thought it would be good to check some other resources.
>>
>>
>> cheers,
>> Danjel
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>>
>
> Chris Muir
> cbm at well.com
> http://www.xfade.com
>
>
>
>
>
>
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