http://charlesumlauf.com/schmatic.jpg

[Michael Eisenstadt]

http://charlesumlauf.com/schematic.jpg

What does the 2 overlapings circles symbol at the far right of
the schematic stand for?

And the circle enclosing + and - symbol, what is that component.

I understand some of the abreviations such as I_IN, V_IN, I_IC,
but what do the following abreviations stand for?

I_CIN

I_COUT

I_D1

This schematic was generated automatically at the National
Semiconductors site. It is supposed to convert 9-12VDC to 4VDC
@ 300 mA.

These questions may seem very basic and I apologize for having to
ask them.

I have out 5 different amateur DIY electronics books from 2
libraries. All of them want to teach the reader basic
electrical theory. Unfortunately I am not up to this due
to advanced personal chronology.

I.e. I am elderly but capable of DIY projects. So I am trying
to do this project without knowing electronics theory.

I haven't bought the parts yet. Will this schematic work?

In the real world this is in regard to 2 motorized disks.
Their motor/gearboxs nominally 12VDC/300mA run slower with less
voltage the point being to make the disks turn as slowly as
possible. The disks are actually four foot in diameter
circular paintings on canvas with wooden rims and spokes
using D batteries in series. At 4V one of the motors still
runs very slowly. The other motor needs ~6V to run.

Thanks in advance for your help with the abreviations and
symbols.

Michael Eisenstadt

 

[Garrett Mace]

I've replied inline:



"Michael Eisenstadt" <michaele@ando.pair.com> wrote in message
news:8ca868d7e5e57eb54099aaa5ab98be51@news.teranews.com...

http://charlesumlauf.com/schematic.jpg

What does the 2 overlapings circles symbol at the far right of
the schematic stand for?

That appears to be your output. I think that's how they are drawing a barrel
power plug, though you don't need one.

And the circle enclosing + and - symbol, what is that component.

I don't think that's a component; it appears they are symbolizing an AC
source in the feedback loop. The wire should just go straight through that
area.

I understand some of the abreviations such as I_IN, V_IN, I_IC,
but what do the following abreviations stand for?

These abbreviations aren't standard or anything, they are just naming the
current and voltage variables in each part of the circuit for convenience in
their calculation software.

I_CIN

That's the current through the capacitor on the input side.

I_COUT

Current through the capacitor on the output side.

I_D1

Current through the diode.

This schematic was generated automatically at the National
Semiconductors site. It is supposed to convert 9-12VDC to 4VDC
@ 300 mA.

These questions may seem very basic and I apologize for having to
ask them.

I have out 5 different amateur DIY electronics books from 2
libraries. All of them want to teach the reader basic
electrical theory. Unfortunately I am not up to this due
to advanced personal chronology.

I.e. I am elderly but capable of DIY projects. So I am trying
to do this project without knowing electronics theory.

I haven't bought the parts yet. Will this schematic work?

It will work as a DC-DC converter, but is that what you really need....

In the real world this is in regard to 2 motorized disks.
Their motor/gearboxs nominally 12VDC/300mA run slower with less
voltage the point being to make the disks turn as slowly as
possible. The disks are actually four foot in diameter
circular paintings on canvas with wooden rims and spokes
using D batteries in series. At 4V one of the motors still
runs very slowly. The other motor needs ~6V to run.

Thanks in advance for your help with the abreviations and
symbols.

Michael Eisenstadt

Actually, you may be going on a little bit of the wrong path here. If you
really want to slow down the paintings, lowering the motor voltage is not
the best way. You will, as you have seen, lose power and eventually the
motor will get stuck if you are trying to run it just above the point where
it won't move.

What you should really try is a pulse-width modulation circuit, or PWM. It
kicks the motor with pulses of the full 12 volts, instead of continous DC.
This will allow you to adjust the speed of the motor to far less than would
be possible with the voltage method, and prevent it from stalling. You'll
also be able to continuously adjust the speed to whatever you like.

I dug up a few PWM project sites to get you started:

http://www.aaroncake.net/circuits/motorcon.htm
http://www.solorb.com/elect/solarcirc/pwm2/index.html
http://www.nomad.ee/micros/pwm555.html

 

[Michael Eisenstadt]

Thanks, Garrett, for your prompt reply and explanations.

I have looked at your 3 examples of PWM projects which
are whetting my desire to build one. I see why this might
be a better idea than regulating the voltage.

The artist of these paintings wants the speed to
be as slow as possible. As the batteries decay, the
PWM presumably could be turned up to maintain
the minimum of pulses required to keep the motor
turning.

Michael Eisenstadt

 

[John Popelish]

Michael Eisenstadt wrote:

http://charlesumlauf.com/schematic.jpg

What does the 2 overlapings circles symbol at the far right of
the schematic stand for?

It symbolizes a load that draws the specified current (0.4 amps, in
this case), no matter what the output voltage. That is the load
current you specified.

And the circle enclosing + and - symbol, what is that component.

I think that represents an injection of an AC disturbance voltage to
test the stability of the closed loop regulation of the output
voltage. It is part of testing the simulation, but not a component in
the finished supply.

I understand some of the abreviations such as I_IN, V_IN, I_IC,
but what do the following abreviations stand for?

I_CIN

Ripple current in the input capacitor. The input cap has to be rated
for at least this much ripple current.

I_COUT

Capacitor ripple current, again, different capacitor.

I_D1

Diode current, to determine the current rating of the diode.

This schematic was generated automatically at the National
Semiconductors site. It is supposed to convert 9-12VDC to 4VDC
@ 300 mA.

These questions may seem very basic and I apologize for having to
ask them.

No problem.

I have out 5 different amateur DIY electronics books from 2
libraries. All of them want to teach the reader basic
electrical theory. Unfortunately I am not up to this due
to advanced personal chronology.

I.e. I am elderly but capable of DIY projects. So I am trying
to do this project without knowing electronics theory.

You are learning, fast.

I haven't bought the parts yet. Will this schematic work?

I think it is quite likely, if you get the layout right, and we can
help with that, too. Keep in mind that this produces a fixed output
voltage. If you need a range of output voltages, redo the design for
the extremes and mid value for your needs, and you should see a
pattern that will allow you to make a variable design that covers that
range, if only resistor or two changes.

In the real world this is in regard to 2 motorized disks.
Their motor/gearboxs nominally 12VDC/300mA run slower with less
voltage the point being to make the disks turn as slowly as
possible. The disks are actually four foot in diameter
circular paintings on canvas with wooden rims and spokes
using D batteries in series. At 4V one of the motors still
runs very slowly. The other motor needs ~6V to run.

If you have already determined the exact voltage you require,
disregard my comments above about an adjustable version.

Keep in mind that the best way to hold a slow speed accurately is to
have a speed feedback signal to incorporate into the voltage
regulation scheme, so that if the motor or other conditions change
slightly, the voltage will correct for those changes. But that can be
added later as an enhancement, if you want to have another learning
experience.

Thanks in advance for your help with the abreviations and
symbols.

Michael Eisenstadt

--
John Popelish

 

[Peter Bennett]

On Sat, 17 Jan 2004 17:10:14 GMT, Michael Eisenstadt
<michaele@ando.pair.com> wrote:

http://charlesumlauf.com/schematic.jpg

What does the 2 overlapings circles symbol at the far right of
the schematic stand for?

That is the symbol for a current source or sink. It is just there so
that the simulator will work, and would be replaced by your actual
load, in real life.

And the circle enclosing + and - symbol, what is that component.

It represents an ammeter - you would replace it with a short circuit.

I understand some of the abreviations such as I_IN, V_IN, I_IC,
but what do the following abreviations stand for?

I_CIN

I_COUT

I_D1

Current through the respective devices.

This schematic was generated automatically at the National
Semiconductors site. It is supposed to convert 9-12VDC to 4VDC
@ 300 mA.

<snip>

I haven't bought the parts yet. Will this schematic work?

Since this is intended to show how to use one of National's parts, I
expect it would work.



--
Peter Bennett, VE7CEI
peterbb (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

 

[Michael Eisenstadt]

http://www.aaroncake.net/circuits/motorcon.htm

Following G. Ryan's suggestion I am going to try to
build the Pulse Width Modulation DC Motor Control
described on the Web page referenced above.

All the parts listed are available at Radio
Shack except for

0.1uF 25V Ceramic Disc Capicitor

0.01uF 25V Ceramic Disc Capicitor

Radio Shack has a 0.1uF 50VDC Ceramic Disc Capcitor and
a 0.01uF 500VDC Ceramic Disc Capicitor.

Can these be substituted for the 25V ones?

One other question: what does the letter G stand for
which is to the left of the circle representing the
IRF511 MOSFET on the schematic?

Thanks in advance for your help.

Michael Eisenstadt

 

[Garrett Mace]

"Michael Eisenstadt" <michaele@ando.pair.com> wrote in message
news:79e4bcbcca2decd5ccc9bada027b44df@news.teranews.com...

http://www.aaroncake.net/circuits/motorcon.htm

Following G. Ryan's suggestion I am going to try to
build the Pulse Width Modulation DC Motor Control
described on the Web page referenced above.

All the parts listed are available at Radio
Shack except for

0.1uF 25V Ceramic Disc Capicitor

0.01uF 25V Ceramic Disc Capicitor

Radio Shack has a 0.1uF 50VDC Ceramic Disc Capcitor and
a 0.01uF 500VDC Ceramic Disc Capicitor.

Can these be substituted for the 25V ones?

One other question: what does the letter G stand for
which is to the left of the circle representing the
IRF511 MOSFET on the schematic?

Thanks in advance for your help.

Michael Eisenstadt

Yes, the capacitors will work. The voltage rating is nothing to worry about
unless it's lower than the circuit specified.

The "G" stands for gate, mosfets have gate, source, and drain terminals. As
you can probably tell, it's analogous to the base of a BJT. However, fets
are voltage-controlled devices as opposed to BJT devices, which are
current-controlled.

I haven't tried this circuit myself, so I can't guarantee it. I assume
you've got a breadboard somewhere, this circuit will be easy to test on a
breadboard before picking up the soldering iron. I might do that just now.

 

[Garrett Mace]

I haven't tried this circuit myself, so I can't guarantee it. I assume
you've got a breadboard somewhere, this circuit will be easy to test on a
breadboard before picking up the soldering iron. I might do that just now.

I got around to trying it, not really impressed with how the PWM frequency
ramps up with decreased duty cycle, but there isn't much else you can do
with a simple circuit like that. It should let you slow the motors down and
vary the speed a bit. If it doesn't work for you, the second link I posted
looks good; the quad op-amp one.

 

[Michael Eisenstadt]

For this project there is only 1 speed wanted, the slowest.

Garrett Mace wrote:

I got around to trying it, not really impressed with how the PWM frequency
ramps up with decreased duty cycle, but there isn't much else you can do
with a simple circuit like that.

You mean the change was not linear to turning the shaft of the pot?

Is there a do not exceed frequency that the components on the board
can't handle?

It should let you slow the motors down and vary the speed a bit.

I just need one speed, the slowest.