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PICList Thread
'[EE] soft power switch'
2006\06\22@154824 by palam.c

picon face
Hi all,
I am working on PIC project where the whole system
is powered by battery. I am  trying to add soft power
switch , ( push it to on, push it again to off) .

I found lot of solutions using relays, but i am looking for
transistor based solution. Anybody implemented this
before ? Thanks in advance.

regards,
palani

2006\06\22@161339 by Harold Hallikainen

face picon face

> Hi all,
> I am working on PIC project where the whole system
> is powered by battery. I am  trying to add soft power
> switch , ( push it to on, push it again to off) .
>
> I found lot of solutions using relays, but i am looking for
> transistor based solution. Anybody implemented this
> before ? Thanks in advance.
>
> regards,
> palani


How about having the PIC sleep and wake on the power switch being
activated? Or, if the PIC supports two oscillators, drop down to a very
low speed (32kHz) to drop power consumption, then go back to high speed
when "turning the unit on."

Harold




--
FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!

2006\06\22@161649 by Bob Axtell

face picon face
palam.c wrote:
> Hi all,
> I am working on PIC project where the whole system
> is powered by battery. I am  trying to add soft power
> switch , ( push it to on, push it again to off) .
>
> I found lot of solutions using relays, but i am looking for
> transistor based solution. Anybody implemented this
> before ? Thanks in advance.
>
> regards,
> palani
>  
Yes. The easiest way is to  do this is  to use an external CMOS device,
such as
CD4001. This chip draws no measurable power whatever.

The CD4001 always has power, and the PIC VCC is provided by one or more
of the CD4001 gate outputs. The CD4001 is cross-wired to generate a
flop-flop.
The switch is designed so that by pressing the switch, the flip-flop
supplies power
to the PIC, by forcing the CD4001 to turn "ON". The PIC also senses the
switch
using an input pin. so that later it will act on it to turn the supply
off later.

The PIC does its thing, then will sense the switch being pressed again
for OFF.
The PIC notes the press, then waits a second after the switch has been
released
(to ansure that the switch won't be pressed again), then the PIC pulses
an OUTPUT
high through a CAP (0.005uF will do, if the resistor to GND on the
CD4001 is
high in value). The pulse thru the cap will cause the CD4001 flip-flop
to toggle off.

That's it. If you have rouble following me, I can dig out the
schematic.    .

--Bob


2006\06\22@163539 by Kevin

picon face
> Hi all,
> I am working on PIC project where the whole system
> is powered by battery. I am  trying to add soft power
> switch , ( push it to on, push it again to off) .
>
> I found lot of solutions using relays, but i am looking for
> transistor based solution. Anybody implemented this
> before ? Thanks in advance.
>
> regards,
> palani
> --

You may find this page useful

http://www.romanblack.com/self_swi.htm

~Kevin

2006\06\22@170552 by William Bross

picon face
palam.c wrote:

>Hi all,
>I am working on PIC project where the whole system
>is powered by battery. I am  trying to add soft power
>switch , ( push it to on, push it again to off) .
>
>I found lot of solutions using relays, but i am looking for
>transistor based solution. Anybody implemented this
>before ? Thanks in advance.
>
>regards,
>palani
>  
>
Palani,

Something like this?

http://ww1.microchip.com/downloads/en/DeviceDoc/40040b.pdf

tip # 11

Bill

2006\06\24@012948 by Palaniappan C

flavicon
face
On Friday 23 June 2006 02:35, William Bross wrote:
> palam.c wrote:
> >Hi all,
> >I am working on PIC project where the whole system
> >is powered by battery. I am  trying to add soft power
> >switch , ( push it to on, push it again to off) .
> >
> >I found lot of solutions using relays, but i am looking for
> >transistor based solution. Anybody implemented this
> >before ? Thanks in advance.
> >
> >regards,
> >palani
>
> Palani,
> Something like this?
> ww1.microchip.com/downloads/en/DeviceDoc/40040b.pdf
> tip # 11
>
> Bill

Thanks for all replies. I am planning to go with microchip's solution.

I don't have previous experience with FETs. I need to select a FET for a power
switch, can i get the list of popular (or) general purpose FETs .

Is there any website containing list of commonly used (or) popular
electronic devices ?

regards,
palani

2006\06\24@013128 by Palaniappan C

picon face
On Friday 23 June 2006 02:35, William Bross wrote:
> palam.c wrote:
> >Hi all,
> >I am working on PIC project where the whole system
> >is powered by battery. I am  trying to add soft power
> >switch , ( push it to on, push it again to off) .
> >
> >I found lot of solutions using relays, but i am looking for
> >transistor based solution. Anybody implemented this
> >before ? Thanks in advance.
> >
> >regards,
> >palani
>
> Palani,
> Something like this?
> ww1.microchip.com/downloads/en/DeviceDoc/40040b.pdf
> tip # 11
>
> Bill

Thanks for all replies. I am planning to go with microchip's solution.

I don't have previous experience with FETs. I need to select a FET for a power
switch, can i get the list of popular (or) general purpose FETs .

Is there any website containing list of commonly used (or) popular
electronic devices ?

regards,
palani

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