Using reset pin

Archiver

Hello Stampers,

I want to use the reset pin as an "emergency stop switch input", thus, when
someone pushes the "emergency" button it pulls the reset pin low, all
outputs will go low and after the button is released (by using a key) the
stamp puts all the outputs in the initial states.

Is there a problem keeping the reset pin low for long periods (some hours of
resolving the emergency causes.....)

Thanks,

Michel


Met vriendelijke groetjes,

> ************************************************
> Michel De Meester
> Biotechnisch Onderhoud
> Universitair Ziekenhuis Antwerpen
> Wilrijkstraat 10
> 2650 Edegem - B
> tel: ++32 (0)3 821 36 47
> e-mail: michel.de.meester@u...
>
> *************************************************
>
>

Archiver

Only thing I can think of is this:

If all the pins of the Stamp go low during a reset, and something that is
tied to a pin (that is an Input during normal use) happens to be outputting
a high, you'll get a short and could kill one of the Stamp's pins.


cheers,

Ben.

--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE

Electronics R&D

Hm: +64 4 972 7567
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> From: "De Meester, Michel" <Michel.De.Meester@u...>
> Reply-To: basicstamps@yahoogroups.com
> Date: Tue, 12 Nov 2002 09:36:09 +0100
> To: "'basicstamps@yahoogroups.com'" <basicstamps@yahoogroups.com>
> Subject: [noparse][[/noparse]basicstamps] Using reset pin
>
> Hello Stampers,
>
> I want to use the reset pin as an "emergency stop switch input", thus, when
> someone pushes the "emergency" button it pulls the reset pin low, all
> outputs will go low and after the button is released (by using a key) the
> stamp puts all the outputs in the initial states.
>
> Is there a problem keeping the reset pin low for long periods (some hours of
> resolving the emergency causes.....)
>
> Thanks,
>
> Michel
>
>
> Met vriendelijke groetjes,
>
>> ************************************************
>> Michel De Meester
>> Biotechnisch Onderhoud
>> Universitair Ziekenhuis Antwerpen
>> Wilrijkstraat 10
>> 2650 Edegem - B
>> tel: ++32 (0)3 821 36 47
>> e-mail: michel.de.meester@u...
>>
>> *************************************************
>>
>>
>
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Archiver

--- "De Meester, Michel"
<Michel.De.Meester@u...> wrote:
> Hello Stampers,
> I want to use the reset pin as an "emergency stop
> switch input", thus, when
> someone pushes the "emergency" button it pulls the
> reset pin low, all
> outputs will go low and after the button is released
> (by using a key) the
> stamp puts all the outputs in the initial states.

Don't the I/O pins all go into INPUT state on RESET?
This could affect your circuit.



=====
Chris Savage
Knight Designs
324 West Main Street
Montour Falls, NY 14865
(607) 535-6777

http://www.knightdesigns.com

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Archiver

Hi Michel,

First of all, bringing the reset pin low makes all the pins inputs,
not low outputs. So you would use pullup or pulldown resistors as
appropriate to determine the emergency states.

Second, reset is not a low power mode. The stamp still draws its
normal operating current. There is no danger of hurting the stamp.
I just bring that up in case the emergency condition has anything to
do with conserving batteries. More on this subject and the behavior
of the Stamp in RESET at this URL:
http://www.emesys.com/BS2power.htm#Brownout

-- best regards
Tracy Allen
electronically monitored ecosystems
http://www.emesystems.com
mailto:tracy@e...



>Hello Stampers,
>
>I want to use the reset pin as an "emergency stop switch input", thus, when
>someone pushes the "emergency" button it pulls the reset pin low, all
>outputs will go low and after the button is released (by using a key) the
>stamp puts all the outputs in the initial states.
>
>Is there a problem keeping the reset pin low for long periods (some hours of
>resolving the emergency causes.....)
>
>Thanks,
>
>Michel
>
>
>Met vriendelijke groetjes,
>
>> ************************************************
>> Michel De Meester
>> Biotechnisch Onderhoud
>> Universitair Ziekenhuis Antwerpen
>> Wilrijkstraat 10
>> 2650 Edegem - B
>> tel: ++32 (0)3 821 36 47
>> e-mail: michel.de.meester@u...
>>
>
> > *************************************************
>>
>

Archiver

A better way is to have an input look at the E-Stop switch. Then under
software control you can deactivate the outputs under a controlled manner.
I use this approach on my industrial controls. Another way is to have the
E-Stop circuit kill all power to the Output circuitry. That way you can leave
the stamp running but kill everything operational. I use this approach when
the E-Stop operation is protecting humans and/or expensive machinery.
I would not trust the reset circuitry for an important mission as this. It is
like replacing the seatbelts in your car with strings.

Alan Bradford
Plasma Technologies


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