Very confused.
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Hello!
I have a problem understanding your text. On page 10 of "what's a
Micro controller?" you have a circuit that have a LED
and a resister hooked up to the basic stamp. The confusion is on page
15. It states in the third paragraph that the
current flow is from "+voltage through the resister, LED, and into
the stamp P(0) pin. Looking at the schematic in figure
1.6 pictorial, that seems incorrect. It is saying that current flow
is from +voltage through LED, and into the resister
then to the stamps P(0) pin. This is very confusing to me. Could you
clear that up. I tried to think that the stamps P0 pin was sending
the current, but that still doesn't sound right. Please help me
understand what's going on.
P.S. look at the pictorial on page 24 figure 2.2. The LED and
resister is reversed. I don't understand.
Robert P
I have a problem understanding your text. On page 10 of "what's a
Micro controller?" you have a circuit that have a LED
and a resister hooked up to the basic stamp. The confusion is on page
15. It states in the third paragraph that the
current flow is from "+voltage through the resister, LED, and into
the stamp P(0) pin. Looking at the schematic in figure
1.6 pictorial, that seems incorrect. It is saying that current flow
is from +voltage through LED, and into the resister
then to the stamps P(0) pin. This is very confusing to me. Could you
clear that up. I tried to think that the stamps P0 pin was sending
the current, but that still doesn't sound right. Please help me
understand what's going on.
P.S. look at the pictorial on page 24 figure 2.2. The LED and
resister is reversed. I don't understand.
Robert P
Comments
In the electronic world there are two ways to thinks about
electricity, and this is usually the source of the confusion.
Positive electricity flows from + to - and follows the little arrows
on semiconductors as shown on schematics. (hole flow)
Negative electricity flows from - to + and is opposite of the little
arrows on semiconductor schematics. (electron flow)
IF you keep this in mind and the previous information on Logic levels
and the sinking vs. sourcing of current, the confusion will be very
clear. It may seem like mud now, but it gets better!
Ron
Original Message
From: "Chuck Davis" <cdavis@o...>
To: <basicstamps@egroups.com>
Sent: Friday, June 23, 2000 12:42 PM
Subject: [noparse][[/noparse]basicstamps] Re: Very confused.
> --- In basicstamps@egroups.com, Robepark1@j... wrote:
> > Hello!
> >
> > I have a problem understanding your text. On page 10 of "what's a
> > Micro controller?" you have a circuit that have a LED
> > and a resister hooked up to the basic stamp. The confusion is on
> page
> > 15. It states in the third paragraph that the
> > current flow is from "+voltage through the resister, LED, and into
> > the stamp P(0) pin. Looking at the schematic in figure
> > 1.6 pictorial, that seems incorrect. It is saying that current
flow
> > is from +voltage through LED, and into the resister
> > then to the stamps P(0) pin. This is very confusing to me. Could
> you
> > clear that up. I tried to think that the stamps P0 pin was sending
> > the current, but that still doesn't sound right. Please help me
> > understand what's going on.
> >
> > P.S. look at the pictorial on page 24 figure 2.2. The LED and
> > resister is reversed. I don't understand.
> >
> >
> > Robert P
>
> Robert,
>
> Without looking at the diagrams you referenced (I don't have them
> handy) I can tell you that the outputs of the Stamp (and most
> microcontrollers) are designed to either "source" or "sink" current.
> Sourcing simply means that if the output is high (5 volts, or
logical
> 1), current will flow out of the pin, through a load (resistor, led,
> whatever), to GROUND. In this case the pin is wired so a logical 1
> output turns on the current to the load. Sinking means that when the
> output is low (0 volts or logic 0), current can flow from and
> external 5 volt source, through the load, into the pin - in effect,
> the pin acts as the ground. In this case, you set the output to zero
> to turn on current through the load. You will see examples done both
> ways, depending on how the external circuitry is connected. Neither
> is incorrect, it's just a matter of what you are trying to do.
>
> Many ICs built to drive LEDs or other loads such as motors, may only
> sink or only source current, although some can do both (these are
> usually referred to as a "Half Bridge").
>
> Hope this helps a little.
>
> Chuck Davis
> Oak Tree Systems
> www.oaktreesystems.com
>
>
>
>
>
>
>
> Hello!
>
> I have a problem understanding your text. On page 10 of "what's a
> Micro controller?" you have a circuit that have a LED
> and a resister hooked up to the basic stamp. The confusion is on
page
> 15. It states in the third paragraph that the
> current flow is from "+voltage through the resister, LED, and into
> the stamp P(0) pin. Looking at the schematic in figure
> 1.6 pictorial, that seems incorrect. It is saying that current flow
> is from +voltage through LED, and into the resister
> then to the stamps P(0) pin. This is very confusing to me. Could
you
> clear that up. I tried to think that the stamps P0 pin was sending
> the current, but that still doesn't sound right. Please help me
> understand what's going on.
>
> P.S. look at the pictorial on page 24 figure 2.2. The LED and
> resister is reversed. I don't understand.
>
>
> Robert P
Robert,
Without looking at the diagrams you referenced (I don't have them
handy) I can tell you that the outputs of the Stamp (and most
microcontrollers) are designed to either "source" or "sink" current.
Sourcing simply means that if the output is high (5 volts, or logical
1), current will flow out of the pin, through a load (resistor, led,
whatever), to GROUND. In this case the pin is wired so a logical 1
output turns on the current to the load. Sinking means that when the
output is low (0 volts or logic 0), current can flow from and
external 5 volt source, through the load, into the pin - in effect,
the pin acts as the ground. In this case, you set the output to zero
to turn on current through the load. You will see examples done both
ways, depending on how the external circuitry is connected. Neither
is incorrect, it's just a matter of what you are trying to do.
Many ICs built to drive LEDs or other loads such as motors, may only
sink or only source current, although some can do both (these are
usually referred to as a "Half Bridge").
Hope this helps a little.
Chuck Davis
Oak Tree Systems
www.oaktreesystems.com
through the book as well, but as you said, I found examples both ways. I
prefer to have it "source", it seems to make more sense in the program to
have the high be on and the low be off. I did figure it could work either
way, but it was nice to your explanation as why. It has finally "clicked"
in my mind how it actually works!
Thank you Chuck!!!!!!!!!
Shawn
Original Message
From: Chuck Davis [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=0_YwhCMjc-zsYM-xcXcAMlRVtFR6YT_fuIdpftYL5g1S8JWK7eAzHAZD3tOcc_66ej-MFCztuWPXwgnK2w-ADoPbPnw]cdavis@o...[/url
Sent: Friday, June 23, 2000 5:42 AM
To: basicstamps@egroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Very confused.
--- In basicstamps@egroups.com, Robepark1@j... wrote:
> Hello!
>
> I have a problem understanding your text. On page 10 of "what's a
> Micro controller?" you have a circuit that have a LED
> and a resister hooked up to the basic stamp. The confusion is on
page
> 15. It states in the third paragraph that the
> current flow is from "+voltage through the resister, LED, and into
> the stamp P(0) pin. Looking at the schematic in figure
> 1.6 pictorial, that seems incorrect. It is saying that current flow
> is from +voltage through LED, and into the resister
> then to the stamps P(0) pin. This is very confusing to me. Could
you
> clear that up. I tried to think that the stamps P0 pin was sending
> the current, but that still doesn't sound right. Please help me
> understand what's going on.
>
> P.S. look at the pictorial on page 24 figure 2.2. The LED and
> resister is reversed. I don't understand.
>
>
> Robert P
Robert,
Without looking at the diagrams you referenced (I don't have them
handy) I can tell you that the outputs of the Stamp (and most
microcontrollers) are designed to either "source" or "sink" current.
Sourcing simply means that if the output is high (5 volts, or logical
1), current will flow out of the pin, through a load (resistor, led,
whatever), to GROUND. In this case the pin is wired so a logical 1
output turns on the current to the load. Sinking means that when the
output is low (0 volts or logic 0), current can flow from and
external 5 volt source, through the load, into the pin - in effect,
the pin acts as the ground. In this case, you set the output to zero
to turn on current through the load. You will see examples done both
ways, depending on how the external circuitry is connected. Neither
is incorrect, it's just a matter of what you are trying to do.
Many ICs built to drive LEDs or other loads such as motors, may only
sink or only source current, although some can do both (these are
usually referred to as a "Half Bridge").
Hope this helps a little.
Chuck Davis
Oak Tree Systems
www.oaktreesystems.com