Low Power Application

Archiver · 2002-02-13 16:41

Hello,

I'm needing to run a DS1302 and a MAX233 with a BS2p and need to send the stamp
to sleep for long periods to conserve battery power. I'd like to shut off the
power to the DS1302 and MAX232 when the stamp is sleeping.

Can the two chips get their +5v supply from one of the stamp pins? That would
make them easy to turn on and off. I think the DS1302 hardly draws 1ma and the
MAX233 draws 15ma so it is within parameters. I've heard that in sleep mode
the pins "blink" briefly on or off, can someone clarify what kind of Capacitor
would help to reduce this effect?

Thanks,
Stewart

Archiver · 2002-02-13 21:01

I would not worry about the 1302 it uses 1.2mA when talking only
it is in the MICRO amps when not in use.

Original Message

From: "Chris Loiacono (E-mail)" <chris01@t...>
To: <basicstamps@yahoogroups.com>
Sent: February 13, 2002 3:49 PM
Subject: RE: [noparse][[/noparse]basicstamps] Low Power Application

The last time I had a problem like this (the sleep thing), Tracy
had a
pretty simple fix.
I can't recall his method, but it couldn't hurt to measure the
hiccoughs on
a scope and do a little math.
The other alternative is to see if Tracy is listening in to
today's show...
(sorry Doc...)

Chris

I'm needing to run a DS1302 and a MAX233 with a BS2p and need to
send the
stamp
to sleep for long periods to conserve battery power. I'd like to
shut off
the
power to the DS1302 and MAX232 when the stamp is sleeping.

Can the two chips get their +5v supply from one of the stamp
pins? That
would
make them easy to turn on and off. I think the DS1302 hardly
draws 1ma and
the
MAX233 draws 15ma so it is within parameters. I've heard that in
sleep mode
the pins "blink" briefly on or off, can someone clarify what kind
of
Capacitor
would help to reduce this effect?

Thanks,
Stewart

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Archiver · 2002-02-13 23:49

The last time I had a problem like this (the sleep thing), Tracy had a
pretty simple fix.
I can't recall his method, but it couldn't hurt to measure the hiccoughs on
a scope and do a little math.
The other alternative is to see if Tracy is listening in to today's show...
(sorry Doc...)

Chris

I'm needing to run a DS1302 and a MAX233 with a BS2p and need to send the
stamp
to sleep for long periods to conserve battery power. I'd like to shut off
the
power to the DS1302 and MAX232 when the stamp is sleeping.

Can the two chips get their +5v supply from one of the stamp pins? That
would
make them easy to turn on and off. I think the DS1302 hardly draws 1ma and
the
MAX233 draws 15ma so it is within parameters. I've heard that in sleep mode
the pins "blink" briefly on or off, can someone clarify what kind of
Capacitor
would help to reduce this effect?

Thanks,
Stewart

Archiver · 2002-02-13 23:50

Original Message

From: Chris Loiacono [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=RCtzHhMR3131PciNO-yggpgEzITvn1NOgsu2LDr40F-9hWW4QYcqQYQ_qbOn3Di4lsrm_my9QMqlIDTVZQ]chris@m...[/urlOn Behalf Of Chris
Loiacono (E-mail)
Sent: Wednesday, February 13, 2002 3:50 PM
To: 'basicstamps@yahoogroups.com'
Subject: RE: [noparse][[/noparse]basicstamps] Low Power Application

The last time I had a problem like this (the sleep thing), Tracy had a
pretty simple fix.
I can't recall his method, but it couldn't hurt to measure the hiccoughs on
a scope and do a little math.
The other alternative is to see if Tracy is listening in to today's show...
(sorry Doc...)

Chris

I'm needing to run a DS1302 and a MAX233 with a BS2p and need to send the
stamp
to sleep for long periods to conserve battery power. I'd like to shut off
the
power to the DS1302 and MAX232 when the stamp is sleeping.

Can the two chips get their +5v supply from one of the stamp pins? That
would
make them easy to turn on and off. I think the DS1302 hardly draws 1ma and
the
MAX233 draws 15ma so it is within parameters. I've heard that in sleep mode
the pins "blink" briefly on or off, can someone clarify what kind of
Capacitor
would help to reduce this effect?

Thanks,
Stewart

Archiver · 2002-02-14 00:01

I looked through some of the list and found Tracy's response to another similar
question. He had said a 1uf capacitor could be taken from the pin to ground
and that would get rid of the momentary pin change coming out of sleep mode.

Thanks,
stewart

On Wed, 13 Feb 2002 15:49:55 -0800, Chris Loiacono \(E-mail\) wrote:
>The last time I had a problem like this (the sleep thing), Tracy had a
>pretty simple fix.
>I can't recall his method, but it couldn't hurt to measure the hiccoughs on
>a scope and do a little math.
>The other alternative is to see if Tracy is listening in to today's show...
>(sorry Doc...)
>
>Chris

--
Stewart Mayer, stewlist@k... on 02/13/2002

Archiver · 2002-02-14 02:47

>I looked through some of the list and found Tracy's response to
>another similar
>question. He had said a 1uf capacitor could be taken from the pin to ground
>and that would get rid of the momentary pin change coming out of sleep mode.
>
>Thanks,
> stewart

Yes, I use the capacitor trick to keep the output device (e.g. an
LT1121 voltage regulator) turned OFF during the 18ms hiccups that
occur once each 2.3 seconds during SLEEP. The Stamp pin turns to an
input during that hiccup. Without the capacitor, the LT1121 would
turn on briefly. (It turns ON if its "shutdown" input is either high,
or open.) The capacitor holds the pin low.

The capacitor has to be large enough to absorb the current.
change in V = time * current / capacitance
say 10 microamps current, for 18 milliseconds, change less than one volt:
capacitance required > 0.18 * 10E-6/1 = 0.18 microfarad.

>power to the DS1302 and MAX232 when the stamp is sleeping. Can the
>two chips get their +5v supply from one of the stamp pins? That
>would make them easy to turn on and off. I think the DS1302 hardly
>draws 1ma and the MAX233 draws 15ma so it is within parameters. I've
>heard that in sleep mode the pins "blink" briefly on or off, can
>someone clarify what kind of Capacitor would help to reduce this
>effect?

Yes, you could do that with the DS1302, but (1) it is your real time
clock, and you probably don't want to turn it totally off once you
set it [noparse][[/noparse]?huh!], and (2) the '1302 operating as a real time clock
draws less than 15 microamps. It only draws more when you access it
with the SPI commands from the Stamp, and even then less than 1 ma.

Re the MAX232. Better not power it from a Stamp pin. While true
that the Stamp pin can source up to 20 ma, the voltage from the pin
drops off a lot as it has to supply more current. The supply current
to the MAX232 will be about 5 ma when just idling, but it can be a
lot more if the RS232 output has to drive a load. You can turn the
MAX232 off by way of an external transistor switch. Or you can get a
different member of the MAX232 family, one that has a shutdown pin
(e.g. MAX222 or MAX242). The capacitor trick would ensure that it
stays off during sleep. The MAX242 leaves the receivers active
during shutdown (at microamp power consumption), which allows
incoming activity can wake up the system (if the system is wired up
to respond!).

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

Archiver · 2002-02-14 11:21

Hi Chris!...could you check out he information that I asked you for about
Pic microcontroller projects book??.

Thank you very much!.

Gabriel

BS AS,Argentina

Mensaje original

De: Chris Loiacono [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=SC-UJTg5SRWePdbPFUNyd1edFt13B9d5GiHNDacQsOwKY9O3DPq06fgFu5QDe3GkOfQyjBPUPuLvrR0]chris@m...[/urlEn nombre de Chris
Loiacono (E-mail)
Enviado el: Mi

Archiver · 2002-02-14 11:21

Hi Chris!...could you check out he information that I asked you for about
Pic microcontroller projects book??.

Thank you very much!.

Gabriel

BS AS,Argentina

Mensaje original

De: Chris Loiacono [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=onqC6m_K6uHWrqwHo4DGaBq5P3SCLnqdpFB0EyHy8w8XSARI0e6W8Q9sYc086lpWtrtB2x-Q-Bxdyg]chris@m...[/urlEn nombre de Chris
Loiacono (E-mail)
Enviado el: Mi

Archiver · 2002-02-14 15:07

Tracy,

Thank you very much for the in-depth explanation of how it works. VERY VERY
usefull information.

Thanks!
Stew

>Yes, I use the capacitor trick to keep the output device (e.g. an
>LT1121 voltage regulator) turned OFF during the 18ms hiccups that
>occur once each 2.3 seconds during SLEEP. The Stamp pin turns to an
>input during that hiccup. Without the capacitor, the LT1121 would
>turn on briefly. (It turns ON if its "shutdown" input is either high,
>or open.) The capacitor holds the pin low.
>
>The capacitor has to be large enough to absorb the current.
>change in V = time * current / capacitance
>say 10 microamps current, for 18 milliseconds, change less than one volt:
>capacitance required > 0.18 * 10E-6/1 = 0.18 microfarad.
>
--
Stewart Mayer, stewlist@k... on 02/14/2002

Archiver · 2002-02-14 17:29

Sure, but I am uncertain as to what information you want.
please repeat your question or be more specific.

Original Message

From: Gabriel Ciorciari [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=66xqH9nXIg6RB7-E2YtgyqXNr1hS1sLNKzMm4fpHzrw2rvxWEZKg9NE_iYd48L9K6JAMfT3vTBc1sA]geci@c...[/url
Sent: Thursday, February 14, 2002 3:21 AM
To: basicstamps@yahoogroups.com
Subject: RE: [noparse][[/noparse]basicstamps] Low Power Application

Hi Chris!...could you check out he information that I asked you for about
Pic microcontroller projects book??.

Thank you very much!.

Gabriel

BS AS,Argentina

Low Power Application

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