Mosfet circuit -- working circuit: photos and schematics
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Posts: 46,084
Sid,
I put together two working examples, one using a PNP and NPN transistor, and
one using two MOSFETs. Both work fine, but as expected the MOSFET circuit
consumes much less current (0.1 mA vs. 4.5 mA). Schematics, photos, etc.
are here:
http://www.glitchbuster.com/pwrswtch.htm
Comments, suggestions, and bug reports gratefully received. [noparse]:o[/noparse])
-Randy
www.glitchbuster.com
> Can someone tell me if the following mosfet circuit will work. I want to
> turn a battery operated circuit on with a momentary ON pushbutton and have
the
> Stamp keep it on.
>
> Battery plus to mosfet drain
> Battery neg to system ground
> Mosfet source to VR In
> Mosfet gate to drain via pushbutton. Gate has 10K pulldown.
>
> Press PB for 1 or 2 seconds, gate goes high, mosfet conducts, supplies
power
> to VR, then to Stamp. Stamp Pin 15 is held high by program, goes to gate
and
> keeps mosfet conducting. Later P15 goes low, turns off mosfet, turning
off
> battery.
>
> Could this possibly work?
>
> Sid
I put together two working examples, one using a PNP and NPN transistor, and
one using two MOSFETs. Both work fine, but as expected the MOSFET circuit
consumes much less current (0.1 mA vs. 4.5 mA). Schematics, photos, etc.
are here:
http://www.glitchbuster.com/pwrswtch.htm
Comments, suggestions, and bug reports gratefully received. [noparse]:o[/noparse])
-Randy
www.glitchbuster.com
> Can someone tell me if the following mosfet circuit will work. I want to
> turn a battery operated circuit on with a momentary ON pushbutton and have
the
> Stamp keep it on.
>
> Battery plus to mosfet drain
> Battery neg to system ground
> Mosfet source to VR In
> Mosfet gate to drain via pushbutton. Gate has 10K pulldown.
>
> Press PB for 1 or 2 seconds, gate goes high, mosfet conducts, supplies
power
> to VR, then to Stamp. Stamp Pin 15 is held high by program, goes to gate
and
> keeps mosfet conducting. Later P15 goes low, turns off mosfet, turning
off
> battery.
>
> Could this possibly work?
>
> Sid
Comments
randyjones@w... writes:
> I put together two working examples, one using a PNP and NPN transistor,
> and
> one using two MOSFETs. Both work fine, but as expected the MOSFET circuit
> consumes much less current (0.1 mA vs. 4.5 mA). Schematics, photos, etc.
> are here:
>
Hi, Randy
Took a look - very well done. I finally decided on a 30N06L in the ground
return to the Stamp. The Rds is only .047, which at about 100 mils would drop
about .4mv - quite acceptable. The package is a T0-220 - I would have
preferred a TO-92 but you can't have everything.
Thanks for the help, Randy. I downloaded you schematics and saved them in
"New things" for future application.
Working on a low cost LCD backpack - maybe Dave told you. Have it working
quite well with keyboard entry. Now I have to hook it up to another Stamp and
see how it accepts serial communication. Doesn't require the usual LCD command
formatting - all you do is serout the data you want to display and it shows
up on the LCD. Everything is taken care of in the backpack - the LCD I'm
working with is a 16x2, but the program will work with anything up to 24 x 2 - I
might even get it to work with a 40x4 !
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
Several months ago I did something very similar.
In "standby" mode this circuit draws less than 3nA
of current. The PNP transistor on the right can be
omitted, but is designed to be the supply power to
other devices talking to your stamp.
http://www.angelfire.com/wizard/y2kbc/STAMPS/lps.gif
>Sid,
>
>I put together two working examples, one using a PNP and NPN transistor, and
>one using two MOSFETs. Both work fine, but as expected the MOSFET circuit
>consumes much less current (0.1 mA vs. 4.5 mA). Schematics, photos, etc.
>are here:
>
>http://www.glitchbuster.com/pwrswtch.htm
>
>Comments, suggestions, and bug reports gratefully received. [noparse]:o[/noparse])
>
>-Randy
>www.glitchbuster.com
>
>
Beau Schwabe Mask Designer II National Semiconductor Corporation
500 Pinnacle Court, Suite 525
Mail Stop GA1
Very similar indeed! I wasn't able to measure the standby current since my
meter only goes down to 0.1 uA. I'm guessing from the footer at the bottom
of your email that you have access to better test equipment than I do. ;o)
-Randy
www.glitchbuster.com
> Randy & Sid,
>
> Several months ago I did something very similar.
> In "standby" mode this circuit draws less than 3nA
> of current. The PNP transistor on the right can be
> omitted, but is designed to be the supply power to
> other devices talking to your stamp.
>
>
> http://www.angelfire.com/wizard/y2kbc/STAMPS/lps.gif
>
>
> Beau Schwabe Mask Designer II National Semiconductor Corporation
> 500 Pinnacle Court, Suite 525
> Mail Stop GA1
>
of the values. Also I had a similar problem measuring current, so I increased
the test voltage from a 9V supply to a 900V supply in an "OFF" situation and
took my measurements at 100X the actual value.
>Beau,
>
>Very similar indeed! I wasn't able to measure the standby current since my
>meter only goes down to 0.1 uA. I'm guessing from the footer at the bottom
>of your email that you have access to better test equipment than I do. ;o)
>
>-Randy
>www.glitchbuster.com
>
>
>
>
> > Randy & Sid,
> >
> > Several months ago I did something very similar.
> > In "standby" mode this circuit draws less than 3nA
> > of current. The PNP transistor on the right can be
> > omitted, but is designed to be the supply power to
> > other devices talking to your stamp.
> >
> >
> > http://www.angelfire.com/wizard/y2kbc/STAMPS/lps.gif
> >
>
Beau Schwabe Mask Designer II National Semiconductor Corporation
500 Pinnacle Court, Suite 525
Mail Stop GA1
"little" problem of 2N390x not being able to handle 900V too well. ;o)
I've used Multisim some.... hmmm.... Just applied 900V to a 2N3904 with
emitter and base grounded, and it says 0.014 uA. Can't smell any smoke,
heh, heh!
-Randy
www.glitchbuster.com
Original Message
From: "Beau Schwabe" <bschwabe@a...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, June 14, 2004 8:50 AM
Subject: Re: [noparse][[/noparse]basicstamps] Mosfet circuit -- working circuit: photos and
schematics
> After I designed this circuit, I put it together on a simulator to tweak
some
> of the values. Also I had a similar problem measuring current, so I
increased
> the test voltage from a 9V supply to a 900V supply in an "OFF" situation
and
> took my measurements at 100X the actual value.
>
>
> >Beau,
> >
> >Very similar indeed! I wasn't able to measure the standby current since
my
> >meter only goes down to 0.1 uA. I'm guessing from the footer at the
bottom
> >of your email that you have access to better test equipment than I do.
;o)
> >
> >-Randy
> >www.glitchbuster.com
> >
> >
> >
> >
> > > Randy & Sid,
> > >
> > > Several months ago I did something very similar.
> > > In "standby" mode this circuit draws less than 3nA
> > > of current. The PNP transistor on the right can be
> > > omitted, but is designed to be the supply power to
> > > other devices talking to your stamp.
> > >
> > >
> > > http://www.angelfire.com/wizard/y2kbc/STAMPS/lps.gif
> > >
> >
>
> Beau Schwabe Mask Designer II National Semiconductor Corporation
> 500 Pinnacle Court, Suite 525
> Mail Stop GA1
>
>
>
>
>
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