Low budget Power Supply
Archiver
Posts: 46,084
At the risk of sounding naive, is there any reason that a power supply from
a computer wouldn't work as a low budget benchtop supply?
a computer wouldn't work as a low budget benchtop supply?
Comments
Here's what I use:
http://www.al-williams.com/wd5gnr/power.htm
However, be aware that when you short something out, the power supply will
shut down and you risk blowing your computer. Fused leads might help some.
Al Williams
AWC
* Control 8 servos at once
http://www.al-williams.com/awce/pak8.htm
>
Original Message
> From: Mike Slaney [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=pO80J8OQQ7GDY8vzzaSpWqC3_KThYV4w0Sj8-AEO2I4T6WcZLiJOsxSCL_VvnlqnMH9cr0cZ6_RvOEnxkdAf]mike.slaney@v...[/url
> Sent: Wednesday, August 15, 2001 7:27 PM
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
>
>
>
>
> At the risk of sounding naive, is there any reason that a power
> supply from
> a computer wouldn't work as a low budget benchtop supply?
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the
> Subject and Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
What I was thinking was using a power supply from an old PC of something out
of MPJA, Dedicated to the bench, so to speak.... It seems a quite a bit
cheaper than the "real" supplies like the Agilent I use at work. Could you
refer me to a resource that describes the different types of power supplies
(switching, linear etc...)? I'd like to learn the charactaristics and
applications.
Thanks.
Original Message
From: "Al Williams" <alw@a...>
To: <basicstamps@yahoogroups.com>
Sent: Wednesday, August 15, 2001 8:36 PM
Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
> Switching power supplies often require a little load to actually work.
> Here's what I use:
>
> http://www.al-williams.com/wd5gnr/power.htm
>
> However, be aware that when you short something out, the power supply will
> shut down and you risk blowing your computer. Fused leads might help some.
>
> Al Williams
> AWC
> * Control 8 servos at once
> http://www.al-williams.com/awce/pak8.htm
>
> >
Original Message
> > From: Mike Slaney [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=le0m9KNq5snAy0R4FUf9XnxSKEn2EdKxgmScaDMblHD8MPU2ZEerVGgprruszL22G9wCZ12dGQ7SZY9rbA]mike.slaney@v...[/url
> > Sent: Wednesday, August 15, 2001 7:27 PM
> > To: basicstamps@yahoogroups.com
> > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> >
> >
> >
> >
> > At the risk of sounding naive, is there any reason that a power
> > supply from
> > a computer wouldn't work as a low budget benchtop supply?
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
> > Subject and Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
sensing, metering, and adjustable voltages. Elenco makes several cheap kits
that are pretty good. Also, designing a simple lab supply around an LM317 or
similar adjustable regulator is good exercise. Finding a transformer is
often difficult these days though.
A linear supply uses a transformer, a rectifier, and some shunt element that
will draw current until the voltage is stable. A simple example of a shunt
element is a Zener diode. A complex element would be a 7805 regulator IC.
Both do the same job -- they draw current from the source until the source
is loaded down to the correct voltage.
This is very simple and works well. However, it causes a lot of power to be
eaten up as heat. The higher the source voltage the more heat. This is power
just wasted. Also, linear supplies are heavy since the transformer is
usually pretty heavy.
Switchers use an inductors/capacitors to store energy like a flywheel. When
the AC input is low the inductor supplies current, when the input is high,
the inductor absorbs current. The average voltage is a DC voltage.
These power supplies are very efficient, converting most of their input to
output. That also means they don't generate much heat. With no transformer,
they are typically quite light. The average PC power supply is rated at
250W. A 250W 12V linear supply (say 21A) would weight quite a bit (I have a
13.8V 20A Astron supply and it probably weighs 7 or 8kg). I doubt most PC
supplies weigh 1kg.
The down side? Complexity (although some dedicated ICs can help there).
Also, the switching creates noise at the switching frequency which can be a
devil if you are doing A/D conversion, RF reception, or something similar.
Good design can help there. Another problem is the "magnetics" required --
the inductors -- can be hard to obtain in small quantities although that
problem isn't what it used to be.
TI bought a company (Power Trends) that makes a series of switcher modules
made to replace 78xx regulators. Good stuff but not cheap. The modules just
plug and play.
Read http://www.smpstech.com/tutorial/t00con.htm - just a quick look, this
looks pretty comprehensive.
Al Williams
AWC
* Floating point math for the Stamp, PIC, SX, or any microcontroller
http://www.al-williams.com/awce/pak1.htm
>
Original Message
> From: Mike Slaney @ Verizon [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=4lNJFwU8knN-nG4W-gzCH8uRr7MNAJ5JBbNDa__6KYokItHWtgVU7cFP30lPonWraO-5OChXxwylY-Tj7ww]mike.slaney@v...[/url
> Sent: Thursday, August 16, 2001 7:58 AM
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
>
>
> Very cool alternative.
> What I was thinking was using a power supply from an old PC of
> something out
> of MPJA, Dedicated to the bench, so to speak.... It seems a quite a bit
> cheaper than the "real" supplies like the Agilent I use at work. Could you
> refer me to a resource that describes the different types of
> power supplies
> (switching, linear etc...)? I'd like to learn the charactaristics and
> applications.
> Thanks.
>
>
>
Original Message
> From: "Al Williams" <alw@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Wednesday, August 15, 2001 8:36 PM
> Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
>
>
> > Switching power supplies often require a little load to actually work.
> > Here's what I use:
> >
> > http://www.al-williams.com/wd5gnr/power.htm
> >
> > However, be aware that when you short something out, the power
> supply will
> > shut down and you risk blowing your computer. Fused leads might
> help some.
> >
> > Al Williams
> > AWC
> > * Control 8 servos at once
> > http://www.al-williams.com/awce/pak8.htm
> >
> > >
Original Message
> > > From: Mike Slaney [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=4lNJFwU8knN-nG4W-gzCH8uRr7MNAJ5JBbNDa__6KYokItHWtgVU7cFP30lPonWraO-5OChXxwylY-Tj7ww]mike.slaney@v...[/url
> > > Sent: Wednesday, August 15, 2001 7:27 PM
> > > To: basicstamps@yahoogroups.com
> > > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > >
> > >
> > >
> > >
> > > At the risk of sounding naive, is there any reason that a power
> > > supply from
> > > a computer wouldn't work as a low budget benchtop supply?
> > >
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > > from the same email address that you subscribed. Text in the
> > > Subject and Body of the message will be ignored.
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
> Subject and
> Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
>
>
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
related issues with your projects? Do you use this method to power a basic
stamp and assorted logic?
Can the potentioal noise from the switching supply be filtered efficiently?
I do like the idea of binding posts on the face of my PC. I might just put
some dummies there for the kick of it!!
All in all, its starting to seem like a linear supply is better suited for
the bench, regardless of wasted energy. Now the trick is to find or build a
good, cheap one.
One last question and I'll study the links you sent.
To build a multiple output (5, 12, variable) supply, could I use the same
transformer and rectifier to feed each regulator (provided the transformer
meets the required input specs of the regulators)?
Thank you so much for your help!!
Original Message
From: "Al Williams" <alw@a...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, August 16, 2001 9:50 AM
Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
> Well, keep in mind that a good "lab" supply will have remote current
> sensing, metering, and adjustable voltages. Elenco makes several cheap
kits
> that are pretty good. Also, designing a simple lab supply around an LM317
or
> similar adjustable regulator is good exercise. Finding a transformer is
> often difficult these days though.
>
> A linear supply uses a transformer, a rectifier, and some shunt element
that
> will draw current until the voltage is stable. A simple example of a shunt
> element is a Zener diode. A complex element would be a 7805 regulator IC.
> Both do the same job -- they draw current from the source until the source
> is loaded down to the correct voltage.
>
> This is very simple and works well. However, it causes a lot of power to
be
> eaten up as heat. The higher the source voltage the more heat. This is
power
> just wasted. Also, linear supplies are heavy since the transformer is
> usually pretty heavy.
>
> Switchers use an inductors/capacitors to store energy like a flywheel.
When
> the AC input is low the inductor supplies current, when the input is high,
> the inductor absorbs current. The average voltage is a DC voltage.
>
> These power supplies are very efficient, converting most of their input to
> output. That also means they don't generate much heat. With no
transformer,
> they are typically quite light. The average PC power supply is rated at
> 250W. A 250W 12V linear supply (say 21A) would weight quite a bit (I have
a
> 13.8V 20A Astron supply and it probably weighs 7 or 8kg). I doubt most PC
> supplies weigh 1kg.
>
> The down side? Complexity (although some dedicated ICs can help there).
> Also, the switching creates noise at the switching frequency which can be
a
> devil if you are doing A/D conversion, RF reception, or something similar.
> Good design can help there. Another problem is the "magnetics" required --
> the inductors -- can be hard to obtain in small quantities although that
> problem isn't what it used to be.
>
> TI bought a company (Power Trends) that makes a series of switcher modules
> made to replace 78xx regulators. Good stuff but not cheap. The modules
just
> plug and play.
>
> Read http://www.smpstech.com/tutorial/t00con.htm - just a quick look, this
> looks pretty comprehensive.
>
> Al Williams
> AWC
> * Floating point math for the Stamp, PIC, SX, or any microcontroller
> http://www.al-williams.com/awce/pak1.htm
>
>
>
> >
Original Message
> > From: Mike Slaney @ Verizon [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=BaDXuiMOMqdQxITkwcuORdqOOdeyRJY4DzQ023_355n8Hf5MeEfRfLQvROLpQ9Pv1O3MyQmcBVkn5krNxV4]mike.slaney@v...[/url
> > Sent: Thursday, August 16, 2001 7:58 AM
> > To: basicstamps@yahoogroups.com
> > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> >
> >
> > Very cool alternative.
> > What I was thinking was using a power supply from an old PC of
> > something out
> > of MPJA, Dedicated to the bench, so to speak.... It seems a quite a bit
> > cheaper than the "real" supplies like the Agilent I use at work. Could
you
> > refer me to a resource that describes the different types of
> > power supplies
> > (switching, linear etc...)? I'd like to learn the charactaristics and
> > applications.
> > Thanks.
> >
> >
> >
Original Message
> > From: "Al Williams" <alw@a...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Wednesday, August 15, 2001 8:36 PM
> > Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
> >
> >
> > > Switching power supplies often require a little load to actually work.
> > > Here's what I use:
> > >
> > > http://www.al-williams.com/wd5gnr/power.htm
> > >
> > > However, be aware that when you short something out, the power
> > supply will
> > > shut down and you risk blowing your computer. Fused leads might
> > help some.
> > >
> > > Al Williams
> > > AWC
> > > * Control 8 servos at once
> > > http://www.al-williams.com/awce/pak8.htm
> > >
> > > >
Original Message
> > > > From: Mike Slaney [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=BaDXuiMOMqdQxITkwcuORdqOOdeyRJY4DzQ023_355n8Hf5MeEfRfLQvROLpQ9Pv1O3MyQmcBVkn5krNxV4]mike.slaney@v...[/url
> > > > Sent: Wednesday, August 15, 2001 7:27 PM
> > > > To: basicstamps@yahoogroups.com
> > > > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > > >
> > > >
> > > >
> > > >
> > > > At the risk of sounding naive, is there any reason that a power
> > > > supply from
> > > > a computer wouldn't work as a low budget benchtop supply?
> > > >
> > > >
> > > > To UNSUBSCRIBE, just send mail to:
> > > > basicstamps-unsubscribe@yahoogroups.com
> > > > from the same email address that you subscribed. Text in the
> > > > Subject and Body of the message will be ignored.
> > > >
> > > >
> > > > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> > > >
> > >
> > >
> > > To UNSUBSCRIBE, just send mail to:
> > > basicstamps-unsubscribe@yahoogroups.com
> > > from the same email address that you subscribed. Text in the
> > Subject and
> > Body of the message will be ignored.
> > >
> > >
> > > Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
> >
> >
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
I'm satisfied with this one: http://www.fullnet.com/u/tomg/acdc202.htm; it
is a ACDC Electronics Triple Power Supply, +15/-15/+5 VDC adjustable, approx
2+ Amps for $15. He might still have some left.
Regards,
Daniel
_________________________________________________________
Do You Yahoo!?
Get your free @yahoo.com address at http://mail.yahoo.com
be). You can look at the output on an AC-coupled scope probe to see.
Probably 50% of the Stamp, PIC, SX, etc. projects I work on take their 5V
from that supply. The balance connect to something else just because of
geography (I even have a 5V 5A supply sitting on my desk -- go figure).
Al Williams
AWC
* Measure 8 pulses at once
http://www.al-williams.com/awce/pak7.htm
>
Original Message
> From: Mike Slaney @ Verizon [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mmt-ApN2EG6oS887r_8SRWnekyPMMZKM_dQD2nM1WxO9OXIQT5FtXLwyUd84Suc1Ok2EHHRNX_Ohb1Ww6rc]mike.slaney@v...[/url
> Sent: Thursday, August 16, 2001 11:57 AM
> To: basicstamps@yahoogroups.com
> Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
>
>
> With regards to the $8.00 Power Supply plan: Do you experience any noise
> related issues with your projects? Do you use this method to
> power a basic
> stamp and assorted logic?
> Can the potentioal noise from the switching supply be filtered
> efficiently?
> I do like the idea of binding posts on the face of my PC. I might just put
> some dummies there for the kick of it!!
> All in all, its starting to seem like a linear supply is better suited for
> the bench, regardless of wasted energy. Now the trick is to find
> or build a
> good, cheap one.
> One last question and I'll study the links you sent.
>
> To build a multiple output (5, 12, variable) supply, could I use the same
> transformer and rectifier to feed each regulator (provided the transformer
> meets the required input specs of the regulators)?
> Thank you so much for your help!!
>
>
>
Original Message
> From: "Al Williams" <alw@a...>
> To: <basicstamps@yahoogroups.com>
> Sent: Thursday, August 16, 2001 9:50 AM
> Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
>
>
> > Well, keep in mind that a good "lab" supply will have remote current
> > sensing, metering, and adjustable voltages. Elenco makes several cheap
> kits
> > that are pretty good. Also, designing a simple lab supply
> around an LM317
> or
> > similar adjustable regulator is good exercise. Finding a transformer is
> > often difficult these days though.
> >
> > A linear supply uses a transformer, a rectifier, and some shunt element
> that
> > will draw current until the voltage is stable. A simple example
> of a shunt
> > element is a Zener diode. A complex element would be a 7805
> regulator IC.
> > Both do the same job -- they draw current from the source until
> the source
> > is loaded down to the correct voltage.
> >
> > This is very simple and works well. However, it causes a lot of power to
> be
> > eaten up as heat. The higher the source voltage the more heat. This is
> power
> > just wasted. Also, linear supplies are heavy since the transformer is
> > usually pretty heavy.
> >
> > Switchers use an inductors/capacitors to store energy like a flywheel.
> When
> > the AC input is low the inductor supplies current, when the
> input is high,
> > the inductor absorbs current. The average voltage is a DC voltage.
> >
> > These power supplies are very efficient, converting most of
> their input to
> > output. That also means they don't generate much heat. With no
> transformer,
> > they are typically quite light. The average PC power supply is rated at
> > 250W. A 250W 12V linear supply (say 21A) would weight quite a
> bit (I have
> a
> > 13.8V 20A Astron supply and it probably weighs 7 or 8kg). I
> doubt most PC
> > supplies weigh 1kg.
> >
> > The down side? Complexity (although some dedicated ICs can help there).
> > Also, the switching creates noise at the switching frequency
> which can be
> a
> > devil if you are doing A/D conversion, RF reception, or
> something similar.
> > Good design can help there. Another problem is the "magnetics"
> required --
> > the inductors -- can be hard to obtain in small quantities although that
> > problem isn't what it used to be.
> >
> > TI bought a company (Power Trends) that makes a series of
> switcher modules
> > made to replace 78xx regulators. Good stuff but not cheap. The modules
> just
> > plug and play.
> >
> > Read http://www.smpstech.com/tutorial/t00con.htm - just a quick
> look, this
> > looks pretty comprehensive.
> >
> > Al Williams
> > AWC
> > * Floating point math for the Stamp, PIC, SX, or any microcontroller
> > http://www.al-williams.com/awce/pak1.htm
> >
> >
> >
> > >
Original Message
> > > From: Mike Slaney @ Verizon [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mmt-ApN2EG6oS887r_8SRWnekyPMMZKM_dQD2nM1WxO9OXIQT5FtXLwyUd84Suc1Ok2EHHRNX_Ohb1Ww6rc]mike.slaney@v...[/url
> > > Sent: Thursday, August 16, 2001 7:58 AM
> > > To: basicstamps@yahoogroups.com
> > > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > >
> > >
> > > Very cool alternative.
> > > What I was thinking was using a power supply from an old PC of
> > > something out
> > > of MPJA, Dedicated to the bench, so to speak.... It seems a
> quite a bit
> > > cheaper than the "real" supplies like the Agilent I use at work. Could
> you
> > > refer me to a resource that describes the different types of
> > > power supplies
> > > (switching, linear etc...)? I'd like to learn the charactaristics and
> > > applications.
> > > Thanks.
> > >
> > >
> > >
Original Message
> > > From: "Al Williams" <alw@a...>
> > > To: <basicstamps@yahoogroups.com>
> > > Sent: Wednesday, August 15, 2001 8:36 PM
> > > Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > >
> > >
> > > > Switching power supplies often require a little load to
> actually work.
> > > > Here's what I use:
> > > >
> > > > http://www.al-williams.com/wd5gnr/power.htm
> > > >
> > > > However, be aware that when you short something out, the power
> > > supply will
> > > > shut down and you risk blowing your computer. Fused leads might
> > > help some.
> > > >
> > > > Al Williams
> > > > AWC
> > > > * Control 8 servos at once
> > > > http://www.al-williams.com/awce/pak8.htm
> > > >
> > > > >
Original Message
> > > > > From: Mike Slaney [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=mmt-ApN2EG6oS887r_8SRWnekyPMMZKM_dQD2nM1WxO9OXIQT5FtXLwyUd84Suc1Ok2EHHRNX_Ohb1Ww6rc]mike.slaney@v...[/url
> > > > > Sent: Wednesday, August 15, 2001 7:27 PM
> > > > > To: basicstamps@yahoogroups.com
> > > > > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > At the risk of sounding naive, is there any reason that a power
> > > > > supply from
> > > > > a computer wouldn't work as a low budget benchtop supply?
> > > > >
> > > > >
> > > > > To UNSUBSCRIBE, just send mail to:
> > > > > basicstamps-unsubscribe@yahoogroups.com
> > > > > from the same email address that you subscribed. Text in the
> > > > > Subject and Body of the message will be ignored.
> > > > >
> > > > >
> > > > > Your use of Yahoo! Groups is subject to
> > > http://docs.yahoo.com/info/terms/
> > > > >
> > > >
> > > >
> > > > To UNSUBSCRIBE, just send mail to:
> > > > basicstamps-unsubscribe@yahoogroups.com
> > > > from the same email address that you subscribed. Text in the
> > > Subject and
> > > Body of the message will be ignored.
> > > >
> > > >
> > > > Your use of Yahoo! Groups is subject to
> > http://docs.yahoo.com/info/terms/
> > >
> > >
> >
> >
> > To UNSUBSCRIBE, just send mail to:
> > basicstamps-unsubscribe@yahoogroups.com
> > from the same email address that you subscribed. Text in the
> Subject and
> > Body of the message will be ignored.
> >
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
>
>
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output was 9 VDC. Actually anything between 5 VDC & 14 VDC should work
fine. The old commodore computers had real nice supplies on them.
Leroy
Al Williams wrote:
>
> I use it all the time. The PC power supplies are pretty clean (they have to
> be). You can look at the output on an AC-coupled scope probe to see.
> Probably 50% of the Stamp, PIC, SX, etc. projects I work on take their 5V
> from that supply. The balance connect to something else just because of
> geography (I even have a 5V 5A supply sitting on my desk -- go figure).
>
> Al Williams
> AWC
> * Measure 8 pulses at once
> http://www.al-williams.com/awce/pak7.htm
>
> >
Original Message
> > From: Mike Slaney @ Verizon [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=a3jWpbxU3fF3YCWLHNVv_Ga3h_NOa1e4A65_x2c_LaqKTBLhF8TCFlL3JNzJg8kM2rhAFrVzTcM7d3KvodMv2Lc]mike.slaney@v...[/url
> > Sent: Thursday, August 16, 2001 11:57 AM
> > To: basicstamps@yahoogroups.com
> > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> >
> >
> > With regards to the $8.00 Power Supply plan: Do you experience any noise
> > related issues with your projects? Do you use this method to
> > power a basic
> > stamp and assorted logic?
> > Can the potentioal noise from the switching supply be filtered
> > efficiently?
> > I do like the idea of binding posts on the face of my PC. I might just put
> > some dummies there for the kick of it!!
> > All in all, its starting to seem like a linear supply is better suited for
> > the bench, regardless of wasted energy. Now the trick is to find
> > or build a
> > good, cheap one.
> > One last question and I'll study the links you sent.
> >
> > To build a multiple output (5, 12, variable) supply, could I use the same
> > transformer and rectifier to feed each regulator (provided the transformer
> > meets the required input specs of the regulators)?
> > Thank you so much for your help!!
> >
> >
> >
Original Message
> > From: "Al Williams" <alw@a...>
> > To: <basicstamps@yahoogroups.com>
> > Sent: Thursday, August 16, 2001 9:50 AM
> > Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
> >
> >
> > > Well, keep in mind that a good "lab" supply will have remote current
> > > sensing, metering, and adjustable voltages. Elenco makes several cheap
> > kits
> > > that are pretty good. Also, designing a simple lab supply
> > around an LM317
> > or
> > > similar adjustable regulator is good exercise. Finding a transformer is
> > > often difficult these days though.
> > >
> > > A linear supply uses a transformer, a rectifier, and some shunt element
> > that
> > > will draw current until the voltage is stable. A simple example
> > of a shunt
> > > element is a Zener diode. A complex element would be a 7805
> > regulator IC.
> > > Both do the same job -- they draw current from the source until
> > the source
> > > is loaded down to the correct voltage.
> > >
> > > This is very simple and works well. However, it causes a lot of power to
> > be
> > > eaten up as heat. The higher the source voltage the more heat. This is
> > power
> > > just wasted. Also, linear supplies are heavy since the transformer is
> > > usually pretty heavy.
> > >
> > > Switchers use an inductors/capacitors to store energy like a flywheel.
> > When
> > > the AC input is low the inductor supplies current, when the
> > input is high,
> > > the inductor absorbs current. The average voltage is a DC voltage.
> > >
> > > These power supplies are very efficient, converting most of
> > their input to
> > > output. That also means they don't generate much heat. With no
> > transformer,
> > > they are typically quite light. The average PC power supply is rated at
> > > 250W. A 250W 12V linear supply (say 21A) would weight quite a
> > bit (I have
> > a
> > > 13.8V 20A Astron supply and it probably weighs 7 or 8kg). I
> > doubt most PC
> > > supplies weigh 1kg.
> > >
> > > The down side? Complexity (although some dedicated ICs can help there).
> > > Also, the switching creates noise at the switching frequency
> > which can be
> > a
> > > devil if you are doing A/D conversion, RF reception, or
> > something similar.
> > > Good design can help there. Another problem is the "magnetics"
> > required --
> > > the inductors -- can be hard to obtain in small quantities although that
> > > problem isn't what it used to be.
> > >
> > > TI bought a company (Power Trends) that makes a series of
> > switcher modules
> > > made to replace 78xx regulators. Good stuff but not cheap. The modules
> > just
> > > plug and play.
> > >
> > > Read http://www.smpstech.com/tutorial/t00con.htm - just a quick
> > look, this
> > > looks pretty comprehensive.
> > >
> > > Al Williams
> > > AWC
> > > * Floating point math for the Stamp, PIC, SX, or any microcontroller
> > > http://www.al-williams.com/awce/pak1.htm
> > >
> > >
> > >
> > > >
Original Message
> > > > From: Mike Slaney @ Verizon [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=a3jWpbxU3fF3YCWLHNVv_Ga3h_NOa1e4A65_x2c_LaqKTBLhF8TCFlL3JNzJg8kM2rhAFrVzTcM7d3KvodMv2Lc]mike.slaney@v...[/url
> > > > Sent: Thursday, August 16, 2001 7:58 AM
> > > > To: basicstamps@yahoogroups.com
> > > > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > > >
> > > >
> > > > Very cool alternative.
> > > > What I was thinking was using a power supply from an old PC of
> > > > something out
> > > > of MPJA, Dedicated to the bench, so to speak.... It seems a
> > quite a bit
> > > > cheaper than the "real" supplies like the Agilent I use at work. Could
> > you
> > > > refer me to a resource that describes the different types of
> > > > power supplies
> > > > (switching, linear etc...)? I'd like to learn the charactaristics and
> > > > applications.
> > > > Thanks.
> > > >
> > > >
> > > >
Original Message
> > > > From: "Al Williams" <alw@a...>
> > > > To: <basicstamps@yahoogroups.com>
> > > > Sent: Wednesday, August 15, 2001 8:36 PM
> > > > Subject: RE: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > > >
> > > >
> > > > > Switching power supplies often require a little load to
> > actually work.
> > > > > Here's what I use:
> > > > >
> > > > > http://www.al-williams.com/wd5gnr/power.htm
> > > > >
> > > > > However, be aware that when you short something out, the power
> > > > supply will
> > > > > shut down and you risk blowing your computer. Fused leads might
> > > > help some.
> > > > >
> > > > > Al Williams
> > > > > AWC
> > > > > * Control 8 servos at once
> > > > > http://www.al-williams.com/awce/pak8.htm
> > > > >
> > > > > >
Original Message
> > > > > > From: Mike Slaney [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=a3jWpbxU3fF3YCWLHNVv_Ga3h_NOa1e4A65_x2c_LaqKTBLhF8TCFlL3JNzJg8kM2rhAFrVzTcM7d3KvodMv2Lc]mike.slaney@v...[/url
> > > > > > Sent: Wednesday, August 15, 2001 7:27 PM
> > > > > > To: basicstamps@yahoogroups.com
> > > > > > Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > At the risk of sounding naive, is there any reason that a power
> > > > > > supply from
> > > > > > a computer wouldn't work as a low budget benchtop supply?
> > > > > >
> > > > > >
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> > > > > >
> > > > > >
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> > > > >
> > > > >
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--
*******************************************************
* Leroy Hall *
* 317 Cherokee Drive *
* Loveland, Ohio - USA 45140-2404 *
*******************************************************
* Phone: (513) 697-7539 *
* Cell : (513) 300-8632 *
* Email: leroy@f... *
* Home page URL: http://home.fuse.net/leroy/ *
* Resume URL: http://home.fuse.net/leroy/resume.htm *
*******************************************************
* Leroy Hall *
* 317 Cherokee Drive *
* Loveland, Ohio - USA 45140-2404 *
*******************************************************
>I use a 'wallwart' I found at a thrift store. Cost $1.00. Ratings
>output was 9 VDC. Actually anything between 5 VDC & 14 VDC should work
>fine. The old commodore computers had real nice supplies on them.
I agree a Wallwart with appropriate polarity will power a Stamp board nicely.
But the Commodore power supply?.... Maybe real nice in terms of supplying
power to a Stamp project, but their failure rate when powering the C-64 was
abysmal. They were infamous!! I got so many free replacements for that
piece of junk that I finally built my own. It got so bad before I built my
own that Commodore actually gave me (free) an extra power supply in
addition to a replacement to avoid repeated replacement delays. I'd
replace a burned out one with my spare and they'd send me a new spare. The
problem was heat retention due to potting the whole thing in epoxy. It was
heavy and felt hefty and powerful, but it was nothing but a few traditional
power supply components (including an overworked and inadequately
heat-sinked regulator) and a lot of epoxy - too much of it and in the wrong
place - or more accurately the regulator was in the wrong place in the
epoxy. I bet the epoxy was the major cost item by far. I ran my C-64 24/7
as a packet radio controller. A small fan blowing over the power supply
didn't help its life noticeably. Give it a month and it would fail. I
ripped the last one apart and tho I forget the details, I do recall the
regulator they used was marginal even without thermally insulating it. I
think they might have gotten away with it if they'd attached a reasonably
sized piece of cheap flat metal to the regulator and assured it was tight
and flat against the inside wall of the case before potting it.
Jim H
supply is working quite nicely. I'm trying to put more focus on discrete
electronics than the stamp so I'd like a larger supply for the various
projects that include steppers, muscle wires etc.....
MPJA.com has a few decent power supplies that will do the job. Elenco has a
decent kit for $60.00, and building my own from scratch sounds like a good
experience.
Thank you all for your help.
Could any of you recommend a BBS or club like this for electronics rather
than stamping?
Original Message
From: "Jim Higgins" <HigginsJ@s...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, August 16, 2001 6:19 PM
Subject: Re: [noparse][[/noparse]basicstamps]Low budget Power Supply
> At 15:20 08/16/01, Leroy Hall, Senior wrote:
>
> >I use a 'wallwart' I found at a thrift store. Cost $1.00. Ratings
> >output was 9 VDC. Actually anything between 5 VDC & 14 VDC should work
> >fine. The old commodore computers had real nice supplies on them.
>
> I agree a Wallwart with appropriate polarity will power a Stamp board
nicely.
>
> But the Commodore power supply?.... Maybe real nice in terms of supplying
> power to a Stamp project, but their failure rate when powering the C-64
was
> abysmal. They were infamous!! I got so many free replacements for that
> piece of junk that I finally built my own. It got so bad before I built
my
> own that Commodore actually gave me (free) an extra power supply in
> addition to a replacement to avoid repeated replacement delays. I'd
> replace a burned out one with my spare and they'd send me a new spare.
The
> problem was heat retention due to potting the whole thing in epoxy. It
was
> heavy and felt hefty and powerful, but it was nothing but a few
traditional
> power supply components (including an overworked and inadequately
> heat-sinked regulator) and a lot of epoxy - too much of it and in the
wrong
> place - or more accurately the regulator was in the wrong place in the
> epoxy. I bet the epoxy was the major cost item by far. I ran my C-64
24/7
> as a packet radio controller. A small fan blowing over the power supply
> didn't help its life noticeably. Give it a month and it would fail. I
> ripped the last one apart and tho I forget the details, I do recall the
> regulator they used was marginal even without thermally insulating it. I
> think they might have gotten away with it if they'd attached a reasonably
> sized piece of cheap flat metal to the regulator and assured it was tight
> and flat against the inside wall of the case before potting it.
>
>
> Jim H
>
>
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>
>
thing. Like Al said couple of days ago, they just need to have the
output loaded. This means put a small light bulb on the output. A 12
volt bulb on the 12 VDC power supply and across the 5 VDC one as well.
These will also tell you the unit is on. You might also want to
consider some kind of fuse or circuit breaker. The 5 volt supply on a
200 watt AT supply might output 50 amps in a short circuit condition.
This enough current to weld with! A 10 amp fuse would calm the beast a
little. For someone who has little experience, building a well
regulated high current supply can be quite a challenge. I have taught
Electronics for 15+ years and speak from some experience. Outside of
this I would recommend a surplus electronics house, Mendelsons in Dayton
ohio or a Ham Fest. Hope this helps!!
Leroy
"Mike Slaney @ Verizon" wrote:
>
> I am currently using a wallwart for the stamp. A Rack-Shack muliti voltage
> supply is working quite nicely. I'm trying to put more focus on discrete
<snip>
build (about $15) in parts and does not waste lots of power like a 200 watt
PC switcher would when the stamp draws less than 100 ma.
If you want to e-mail me direct with an address I will mail a copy of the
schematic I use for my designs, or a fax number as I can fax them.
Radio Shack sells a book on Building Power Supplies. It may be helpful also.
The wall Wart method is the safest method to power the Stamp as all the
lethal AC voltage is converted to DC at the wall. Something to think about
also.
Alan Bradford
Plasma Technologies
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