Hi,

Last Spring I took Intro to Electronics and this Fall I'm taking
Electronics. I want to start purchasing lab equipment, as most of our
labs this semester are in MultiSim and I want to continue to have the
hands on, and I want to purchase a power supply. However, I don't know
what to purchase; I don't know enough yet to make an informed decision.
I browsed through Ebay and saw listings such as:

Regulated DC Power Supply
Power Supply, 1 Phase 16A
System DC Power Supply Single Output
TRIPLE DC LINEAR POWER SUPPLY 30V 5A w/ Memory
dual dc power supply
Programmable Power Supply PPS-3635 GPIB
Triple Output Power Supply

I want to purchase a power supply that will be a real keeper so that I
don't have to make further purchases down the road. What are the
differences between some of these power supplies? Also, why would I
want a programable power supply? Finally, I if pick up a power supply
that hasn't been calabrated, how much would it cost to have this done?

Thanks,
Ed

writes:

Hi,

Last Spring I took Intro to Electronics and this Fall I'm taking
Electronics. I want to start purchasing lab equipment, as most of our
labs this semester are in MultiSim and I want to continue to have the
hands on, and I want to purchase a power supply. However, I don't know
what to purchase; I don't know enough yet to make an informed decision.
I browsed through Ebay and saw listings such as:

Regulated DC Power Supply
Power Supply, 1 Phase 16A
System DC Power Supply Single Output
TRIPLE DC LINEAR POWER SUPPLY 30V 5A w/ Memory
dual dc power supply
Programmable Power Supply PPS-3635 GPIB
Triple Output Power Supply

I want to purchase a power supply that will be a real keeper so that I
don't have to make further purchases down the road. What are the
differences between some of these power supplies? Also, why would I
want a programable power supply? Finally, I if pick up a power supply
that hasn't been calabrated, how much would it cost to have this done?

If you're serious about electronics, you'll never have too many power supplies.

You'll want some fixed voltage, some variable voltage, various maximum
currents, some brute force unregulated that you don't worry about overloading,
and many others. If you buy decent name brand power supplies, they will
all be "keepers".

What types of electronics do you think you'l be emphasizing?

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wrote in message
ps.com...
Hi,

Last Spring I took Intro to Electronics and this Fall I'm taking
Electronics. I want to start purchasing lab equipment, as most of our
labs this semester are in MultiSim and I want to continue to have the
hands on, and I want to purchase a power supply. However, I don't know
what to purchase; I don't know enough yet to make an informed decision.
I browsed through Ebay and saw listings such as:

Regulated DC Power Supply
Power Supply, 1 Phase 16A
System DC Power Supply Single Output
TRIPLE DC LINEAR POWER SUPPLY 30V 5A w/ Memory
dual dc power supply
Programmable Power Supply PPS-3635 GPIB
Triple Output Power Supply

I want to purchase a power supply that will be a real keeper so that I
don't have to make further purchases down the road. What are the
differences between some of these power supplies? Also, why would I
want a programable power supply? Finally, I if pick up a power supply
that hasn't been calabrated, how much would it cost to have this done?

Thanks,
Ed


How about you start out by building one? It can be something simple, say a
5v regulated supply or a variable one capable of an amp or so. It won't be
the last power supply you'll ever need but as Sam said you can never have
too many. It's a great first project too, simple, lots of circuits out
there, readily available parts, relatively safe voltages, it's what I
started out with.

Your first power supply for simple bench use should be your
own construction. Quite simple. A 12 VAC transformer, line
fuse (or circuit breaker), IEC power cord connector, diode
bridge, some electrolytic (and maybe some tantalum)
capacitors, a 7805 voltage regulator chip and a 723 variable
voltage regulator. Fixed +5V and variable outputs are through
banana plugs mounted in a plastic box. Schematics for both
the 7805 and 723 voltage regulator chips are part of the
manufacturers data sheets.

There is no way to appreciate what is and is not a good
power supply until you have built one yourself. Furthermore,
I am still using my supply built 30+ years ago. That basic
power supply works great AND I know in advance everything it
will and will not do.

Later, as you learn what you want from a supply, then
consider one with more power and other features. Features you
will only appreciate once you have built your first one.
Basic power supply is so simple. Even the IC manufacturers
provide the schematics in the datasheets. This is how you
learn. This is how you better appreicate concepts like
current foldback limiting and ripple voltage.

wrote:
Last Spring I took Intro to Electronics and this Fall I'm taking
Electronics. I want to start purchasing lab equipment, as most of our
labs this semester are in MultiSim and I want to continue to have the
hands on, and I want to purchase a power supply. However, I don't know
what to purchase; I don't know enough yet to make an informed decision.
I browsed through Ebay and saw listings such as:

Regulated DC Power Supply
Power Supply, 1 Phase 16A
System DC Power Supply Single Output
TRIPLE DC LINEAR POWER SUPPLY 30V 5A w/ Memory
dual dc power supply
Programmable Power Supply PPS-3635 GPIB
Triple Output Power Supply

I want to purchase a power supply that will be a real keeper so that I
don't have to make further purchases down the road. What are the
differences between some of these power supplies? Also, why would I
want a programable power supply? Finally, I if pick up a power supply
that hasn't been calabrated, how much would it cost to have this done?

wrote:
I want to start purchasing lab equipment, as most of our labs this
semester are in MultiSim and I want to continue to have the hands
on, and I want to purchase a power supply. However, I don't know
what to purchase; I don't know enough yet to make an informed
decision.

If this is the case, you might want to stay away from Ebay. Ebay is
great when you know exactly what you are buying, but if you're not sure,
you can lose in a hurry.

If you find the power supplies at school satisfactory, you might write
down the make and model and see if you can Google up a price.

I want to purchase a power supply that will be a real keeper so that
I don't have to make further purchases down the road.

I have five different power supplies on my bench right now. I built two
of them and bought three of them. They all do different things, and I'd
probably need a couple more to consider it a well-rounded selection.

For basic electronics stuff, you want at least one output that is
adjustable to 24 to 30 V at at least an amp. If you're doing a lot of
digital stuff, a fixed 5 V 1 A output might be convenient. Adjustable
current limiting is nice, but not required. On the low-dollar route,
a big string of D-cell batteries will supply an amp or two, is adjustable
in 1.5 V increments, is very well isolated, and is portable, non-fattening,
and does not promote tooth decay.

What are the differences between some of these power supplies?

Hard to say, based on those descriptions.

Also, why would I want a programable power supply?

If you had a device that needed different voltages and currents at
different times, and wanted to control the power supply with a computer,
you'd use a programmable supply. It could also be used for automated
testing. As a simple example, suppose you are making 12 V light bulbs.
You could have a computer tell a robot to put the bulb in the socket,
and then have the computer tell the power supply to turn itself up to
12 V. The power supply will report the current drawn by the bulb. If
it's zero or way too high, the bulb is no good and you can have the
robot toss it in the trash.

Finally, I if pick up a power supply that hasn't been calabrated, how
much would it cost to have this done?

For basic electronics stuff, don't worry about this too much. If the
supply you buy has meters on the front, you might hook up a multimeter
that is known to be reasonably good to the output of the supply, and
compare the reading on the multimeter to the built-in meters. If the
built-in meters are way off, you might look for an internal adjustment,
or just disconnect the internal meter. (Often, no information is better
than bad information.)

You might consider building one. Either design it yourself or buy a kit
from somebody like Velleman. If you understand normal precautions for
working with the 120 V line, this can be a good project.

Whether you build it or buy it, get some extra fuses of whatever size it
takes. When you're starting out you'll blow a few fuses and it's nice
to be able to get back up and running quickly. As you gain experience,
you will blow even more fuses.

Matt Roberds

In article om,
wrote:
I want to purchase a power supply that will be a real keeper so that I
don't have to make further purchases down the road.

That's very difficult to assess until you know what you want to do. For
most stuff you'll not need high current supplies, IMHO. +/-15 volts at say
500 mA would be useful, as would 5 volts. And a couple of 0-40. With
perhaps a highish current 13.8 volt one for car type stuff. All with
overload protection.

However, you can never have too many. ;-)

--
*42.7% of statistics are made up. Sorry, that should read 47.2% *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article om,
wrote:
I want to purchase a power supply that will be a real keeper so that I
don't have to make further purchases down the road.

That's very difficult to assess until you know what you want to do. For
most stuff you'll not need high current supplies, IMHO. +/-15 volts at say
500 mA would be useful, as would 5 volts. And a couple of 0-40. With
perhaps a highish current 13.8 volt one for car type stuff. All with
overload protection.

However, you can never have too many. ;-)

--
*42.7% of statistics are made up. Sorry, that should read 47.2% *

Dave Plowman London SW
To e-mail, change noise into sound.


You might also want to consider a variable dual tracking type, as you're
sure to get into opamp circuits on your electronics course. My suggestion on
this would be 0 to + / - 30v @ 1 amp.

Arfa