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if you look in the files section under sr_gamer you will find the schematic and the program for a clock I'm building. The display is VERY dim.

I'd like the display to be very bright.

These elements are very bright when supplied with 5v, which should be what is coming off of the PIC, so I'm either suffering from low duty cycle or having trouble sourcing enough current. I tried some 1k pull up resistors between the pins labeled anodes and +5v, but this didn't seem to affect the situation.

------------------------------------

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Hi,

Your diagram shows no current limiting resistors for each segment, is this correct or do you have some?
I had a play with 7 segments once, and had a similar problem, it was a long time ago...
I've heard of two versions of updating the segments, using the LSB of Timer0 to update each segment depending on the value (00 = Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over, change segment.
I tried using timers but found the last segment was always the brightest, as all the calculations were happening while it was on, giving a longer on time..

Hope to of helped,
Paul
From: sr_gamer
Sent: Monday, April 13, 2009 9:31 PM
To: p...@yahoogroups.com
Subject: [piclist] 18f4685 6 seg clock - dim display

if you look in the files section under sr_gamer you will find the schematic and the program for a clock I'm building. The display is VERY dim.

I'd like the display to be very bright.

These elements are very bright when supplied with 5v, which should be what is coming off of the PIC, so I'm either suffering from low duty cycle or having trouble sourcing enough current. I tried some 1k pull up resistors between the pins labeled anodes and +5v, but this didn't seem to affect the situation.

______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.


(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

Don't source the current, SINK it. Sometimes an IC can sink more then it
can source.

Alan KM6VV

>
> if you look in the files section under sr_gamer you will find the
> schematic and the program for a clock I'm building. The display is VERY
> dim.
>
> I'd like the display to be very bright.
>
> These elements are very bright when supplied with 5v, which should be what
> is coming off of the PIC, so I'm either suffering from low duty cycle or
> having trouble sourcing enough current. I tried some 1k pull up resistors
> between the pins labeled anodes and +5v, but this didn't seem to affect
> the situation.

------------------------------------

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Oh, just noticed, you'll prob be struggling to light up all 7 segments using one pic output, especially with no current limiting.
I would be tempted to use common cathode segments, with a nice NPN transistor on the pic output to sink the segments, and the pic to supply a "high" to turn on the segment

Paul
From: sr_gamer
Sent: Monday, April 13, 2009 9:31 PM
To: p...@yahoogroups.com
Subject: [piclist] 18f4685 6 seg clock - dim display

if you look in the files section under sr_gamer you will find the schematic and the program for a clock I'm building. The display is VERY dim.

I'd like the display to be very bright.

These elements are very bright when supplied with 5v, which should be what is coming off of the PIC, so I'm either suffering from low duty cycle or having trouble sourcing enough current. I tried some 1k pull up resistors between the pins labeled anodes and +5v, but this didn't seem to affect the situation.



(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

this is correct, no limiting resistors are needed.  I can run this display at 100% duty cycle at 5V

--- On Fri, 5/1/09, Paul Laverick wrote:
From: Paul Laverick
Subject: Re: [piclist] 18f4685 6 seg clock - dim display
To: p...@yahoogroups.com
Date: Friday, May 1, 2009, 5:23 PM

Hi,
 
Your diagram shows no current limiting resistors
for each segment, is this correct or do you have some?
I had a play with 7 segments once, and had a
similar problem, it was a long time ago...
I've heard of two versions of updating the
segments, using the LSB of Timer0 to update each segment depending on the value
(00 = Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over, change
segment. 
I tried using timers but found the last segment was
always the brightest, as all the calculations were happening while it was on,
giving a longer on time..
 
Hope to of helped,
Paul

From: sr_gamer
Sent: Monday, April 13, 2009 9:31 PM
To: piclist@yahoogroups .com
Subject: [piclist] 18f4685 6 seg clock - dim
display

if you look in the files section under sr_gamer you will find the schematic
and the program for a clock I'm building. The display is VERY dim.

I'd
like the display to be very bright.

These elements are very bright when
supplied with 5v, which should be what is coming off of the PIC, so I'm either
suffering from low duty cycle or having trouble sourcing enough current. I tried
some 1k pull up resistors between the pins labeled anodes and +5v, but this
didn't seem to affect the situation.



(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

yeah.. I was hoping to not have to modify the board, but that looks like the way to go.

--- On Fri, 5/1/09, Alan Marconett wrote:
From: Alan Marconett
Subject: RE: [piclist] 18f4685 6 seg clock - dim display
To: p...@yahoogroups.com
Date: Friday, May 1, 2009, 5:27 PM

Don't source the current, SINK it. Sometimes an IC can sink more then it

can source.

Alan KM6VV

>

> if you look in the files section under sr_gamer you will find the

> schematic and the program for a clock I'm building. The display is VERY

> dim.

>

> I'd like the display to be very bright.

>

> These elements are very bright when supplied with 5v, which should be what

> is coming off of the PIC, so I'm either suffering from low duty cycle or

> having trouble sourcing enough current. I tried some 1k pull up resistors

> between the pins labeled anodes and +5v, but this didn't seem to affect

> the situation.



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This is another route that I considered.  For the moment, I'm suffering with the dim display and working on various programs.  Next time I get the iron out to make a display there will be some hefty revisions.

--- On Fri, 5/1/09, Paul Laverick wrote:
From: Paul Laverick
Subject: Re: [piclist] 18f4685 6 seg clock - dim display
To: p...@yahoogroups.com
Date: Friday, May 1, 2009, 5:34 PM

Oh, just noticed, you'll prob be struggling to
light up all 7 segments using one pic output, especially with no current
limiting. 
I would be tempted to use common cathode segments,
with a nice NPN transistor on the pic output to sink the segments, and the pic
to supply a "high" to turn on the segment
 
Paul

From: sr_gamer
Sent: Monday, April 13, 2009 9:31 PM
To: piclist@yahoogroups .com
Subject: [piclist] 18f4685 6 seg clock - dim
display

if you look in the files section under sr_gamer you will find the schematic
and the program for a clock I'm building. The display is VERY dim.

I'd
like the display to be very bright.

These elements are very bright when
supplied with 5v, which should be what is coming off of the PIC, so I'm either
suffering from low duty cycle or having trouble sourcing enough current. I tried
some 1k pull up resistors between the pins labeled anodes and +5v, but this
didn't seem to affect the situation.

______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.


(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

No wonder your display is dim. You can't drive it like that.
Assuming this PIC is like the earlier 18series it'll have some limitations:
Max 20mA sink on any one pin, and max 20mA on all pins summed.
You have 6x8 = 48 segments, and for top brightness expect 20mA pr segment...
thats 960mA when all are lit (which should also be a design goal).
No way a PIC can deliver that without burning up, and certainly not without
excessive voltage drop on outputs.

You'll have to use both segment driver and display driver. Thats the only
way to get it 'very bright'. I'd suggest using MOS drivers for both
digit and segmens
as this way you can drop all those base resistors.

Here in this clock I've used bipolar drivers, good bright display but
with MOSFET
drives 22 resistors could have been removed (8 in the SIL).

HTH
Shadowrun Gamer skrev:
> this is correct, no limiting resistors are needed. I can run this
> display at 100% duty cycle at 5V
>
> --- On *Fri, 5/1/09, Paul Laverick //* wrote:
>
> From: Paul Laverick
> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> To: p...@yahoogroups.com
> Date: Friday, May 1, 2009, 5:23 PM
>
> Hi,
>
> Your diagram shows no current limiting resistors for each segment,
> is this correct or do you have some?
> I had a play with 7 segments once, and had a similar problem, it
> was a long time ago...
> I've heard of two versions of updating the segments, using the LSB
> of Timer0 to update each segment depending on the value (00 =
> Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,
> change segment.
> I tried using timers but found the last segment was always the
> brightest, as all the calculations were happening while it was on,
> giving a longer on time..
>
> Hope to of helped,
> Paul
>
> *From:* sr_gamer
> *Sent:* Monday, April 13, 2009 9:31 PM
> *To:* piclist@yahoogroups .com
> *Subject:* [piclist] 18f4685 6 seg clock - dim display
>
> if you look in the files section under sr_gamer you will find the
> schematic and the program for a clock I'm building. The display is
> VERY dim.
>
> I'd like the display to be very bright.
>
> These elements are very bright when supplied with 5v, which should
> be what is coming off of the PIC, so I'm either suffering from low
> duty cycle or having trouble sourcing enough current. I tried some
> 1k pull up resistors between the pins labeled anodes and +5v, but
> this didn't seem to affect the situation.
>

--
*******************************************
VISIT MY HOME PAGE:

LAST UPDATED: 23/08/2003
*******************************************
Regards
Eirik Karlsen
______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.


(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

There are the newer "digital" transistors out there that have the bias resistors 'built-in' to save board space, part count, and costs... The lowest cost ones are $0.015 each and come in a nice small but not too small SOT23 package. Here is one from On-Semi, MMUN2214LT1G.
--- In p...@yahoogroups.com, Eirik Karlsen wrote:
>
> No wonder your display is dim. You can't drive it like that.
> Assuming this PIC is like the earlier 18series it'll have some limitations:
> Max 20mA sink on any one pin, and max 20mA on all pins summed.
> You have 6x8 = 48 segments, and for top brightness expect 20mA pr segment...
> thats 960mA when all are lit (which should also be a design goal).
> No way a PIC can deliver that without burning up, and certainly not without
> excessive voltage drop on outputs.
>
> You'll have to use both segment driver and display driver. Thats the only
> way to get it 'very bright'. I'd suggest using MOS drivers for both
> digit and segmens
> as this way you can drop all those base resistors.
>
> Here in this clock I've used bipolar drivers, good bright display but
> with MOSFET
> drives 22 resistors could have been removed (8 in the SIL).
>
> HTH
> Shadowrun Gamer skrev:
> >
> >
> > this is correct, no limiting resistors are needed. I can run this
> > display at 100% duty cycle at 5V
> >
> > --- On *Fri, 5/1/09, Paul Laverick //* wrote:
> >
> > From: Paul Laverick
> > Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> > To: p...@yahoogroups.com
> > Date: Friday, May 1, 2009, 5:23 PM
> >
> > Hi,
> >
> > Your diagram shows no current limiting resistors for each segment,
> > is this correct or do you have some?
> > I had a play with 7 segments once, and had a similar problem, it
> > was a long time ago...
> > I've heard of two versions of updating the segments, using the LSB
> > of Timer0 to update each segment depending on the value (00 =
> > Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,
> > change segment.
> > I tried using timers but found the last segment was always the
> > brightest, as all the calculations were happening while it was on,
> > giving a longer on time..
> >
> > Hope to of helped,
> > Paul
> >
> > *From:* sr_gamer
> > *Sent:* Monday, April 13, 2009 9:31 PM
> > *To:* piclist@yahoogroups .com
> > *Subject:* [piclist] 18f4685 6 seg clock - dim display
> >
> > if you look in the files section under sr_gamer you will find the
> > schematic and the program for a clock I'm building. The display is
> > VERY dim.
> >
> > I'd like the display to be very bright.
> >
> > These elements are very bright when supplied with 5v, which should
> > be what is coming off of the PIC, so I'm either suffering from low
> > duty cycle or having trouble sourcing enough current. I tried some
> > 1k pull up resistors between the pins labeled anodes and +5v, but
> > this didn't seem to affect the situation.
> >
> >
> > --
> *******************************************
> VISIT MY HOME PAGE:
>
> LAST UPDATED: 23/08/2003
> *******************************************
> Regards
> Eirik Karlsen
>

------------------------------------

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Yes I've seen these used extensively in some high value industrial
electronics (radars etc)...
Nice puppys but who has these laying around when yah need'em ?
demolitron skrev:
> There are the newer "digital" transistors out there that have the bias
> resistors 'built-in' to save board space, part count, and costs... The
> lowest cost ones are $0.015 each and come in a nice small but not too
> small SOT23 package. Here is one from On-Semi, MMUN2214LT1G.
>
> --- In p...@yahoogroups.com ,
> Eirik Karlsen wrote:
> >
> > No wonder your display is dim. You can't drive it like that.
> > Assuming this PIC is like the earlier 18series it'll have some
> limitations:
> > Max 20mA sink on any one pin, and max 20mA on all pins summed.
> > You have 6x8 = 48 segments, and for top brightness expect 20mA pr
> segment...
> > thats 960mA when all are lit (which should also be a design goal).
> > No way a PIC can deliver that without burning up, and certainly not
> without
> > excessive voltage drop on outputs.
> >
> > You'll have to use both segment driver and display driver. Thats the
> only
> > way to get it 'very bright'. I'd suggest using MOS drivers for both
> > digit and segmens
> > as this way you can drop all those base resistors.
> >
> > Here in this clock I've used bipolar drivers, good bright display but
> > with MOSFET
> > drives 22 resistors could have been removed (8 in the SIL).
> >
> > >
> > HTH
> >
> >
> > Shadowrun Gamer skrev:
> > >
> > >
> > > this is correct, no limiting resistors are needed. I can run this
> > > display at 100% duty cycle at 5V
> > >
> > > --- On *Fri, 5/1/09, Paul Laverick //* wrote:
> > >
> > > From: Paul Laverick
> > > Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> > > To: p...@yahoogroups.com
> > > Date: Friday, May 1, 2009, 5:23 PM
> > >
> > > Hi,
> > >
> > > Your diagram shows no current limiting resistors for each segment,
> > > is this correct or do you have some?
> > > I had a play with 7 segments once, and had a similar problem, it
> > > was a long time ago...
> > > I've heard of two versions of updating the segments, using the LSB
> > > of Timer0 to update each segment depending on the value (00 =
> > > Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,
> > > change segment.
> > > I tried using timers but found the last segment was always the
> > > brightest, as all the calculations were happening while it was on,
> > > giving a longer on time..
> > >
> > > Hope to of helped,
> > > Paul
> > >
> > > *From:* sr_gamer
> > > *Sent:* Monday, April 13, 2009 9:31 PM
> > > *To:* piclist@yahoogroups .com > >
> > > *Subject:* [piclist] 18f4685 6 seg clock - dim display
> > >
> > > if you look in the files section under sr_gamer you will find the
> > > schematic and the program for a clock I'm building. The display is
> > > VERY dim.
> > >
> > > I'd like the display to be very bright.
> > >
> > > These elements are very bright when supplied with 5v, which should
> > > be what is coming off of the PIC, so I'm either suffering from low
> > > duty cycle or having trouble sourcing enough current. I tried some
> > > 1k pull up resistors between the pins labeled anodes and +5v, but
> > > this didn't seem to affect the situation.
> > >
> > >
> > >
> >
> > --
> > *******************************************
> > VISIT MY HOME PAGE:
> > > >
> > LAST UPDATED: 23/08/2003
> > *******************************************
> > Regards
> > Eirik Karlsen
> >

--
*******************************************
VISIT MY HOME PAGE:

LAST UPDATED: 23/08/2003
*******************************************
Regards
Eirik Karlsen


(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

I never seem to have one or two things on hand when I need them! No matter how large my parts bin gets, its never enough. But at the price per piece most things like this are I usually order a good surplus to have on hand latter.

-- In p...@yahoogroups.com, Eirik Karlsen wrote:
>
> Yes I've seen these used extensively in some high value industrial
> electronics (radars etc)...
> Nice puppys but who has these laying around when yah need'em ?
> demolitron skrev:
> >
> >
> > There are the newer "digital" transistors out there that have the bias
> > resistors 'built-in' to save board space, part count, and costs... The
> > lowest cost ones are $0.015 each and come in a nice small but not too
> > small SOT23 package. Here is one from On-Semi, MMUN2214LT1G.
> >
> > --- In p...@yahoogroups.com ,
> > Eirik Karlsen wrote:
> > >
> > > No wonder your display is dim. You can't drive it like that.
> > > Assuming this PIC is like the earlier 18series it'll have some
> > limitations:
> > > Max 20mA sink on any one pin, and max 20mA on all pins summed.
> > > You have 6x8 = 48 segments, and for top brightness expect 20mA pr
> > segment...
> > > thats 960mA when all are lit (which should also be a design goal).
> > > No way a PIC can deliver that without burning up, and certainly not
> > without
> > > excessive voltage drop on outputs.
> > >
> > > You'll have to use both segment driver and display driver. Thats the
> > only
> > > way to get it 'very bright'. I'd suggest using MOS drivers for both
> > > digit and segmens
> > > as this way you can drop all those base resistors.
> > >
> > > Here in this clock I've used bipolar drivers, good bright display but
> > > with MOSFET
> > > drives 22 resistors could have been removed (8 in the SIL).
> > >
> > > > >
> > > HTH
> > >
> > >
> > > Shadowrun Gamer skrev:
> > > >
> > > >
> > > > this is correct, no limiting resistors are needed. I can run this
> > > > display at 100% duty cycle at 5V
> > > >
> > > > --- On *Fri, 5/1/09, Paul Laverick //* wrote:
> > > >
> > > > From: Paul Laverick
> > > > Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> > > > To: p...@yahoogroups.com
> > > > Date: Friday, May 1, 2009, 5:23 PM
> > > >
> > > > Hi,
> > > >
> > > > Your diagram shows no current limiting resistors for each segment,
> > > > is this correct or do you have some?
> > > > I had a play with 7 segments once, and had a similar problem, it
> > > > was a long time ago...
> > > > I've heard of two versions of updating the segments, using the LSB
> > > > of Timer0 to update each segment depending on the value (00 =
> > > > Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,
> > > > change segment.
> > > > I tried using timers but found the last segment was always the
> > > > brightest, as all the calculations were happening while it was on,
> > > > giving a longer on time..
> > > >
> > > > Hope to of helped,
> > > > Paul
> > > >
> > > > *From:* sr_gamer
> > > > *Sent:* Monday, April 13, 2009 9:31 PM
> > > > *To:* piclist@yahoogroups .com > > >
> > > > *Subject:* [piclist] 18f4685 6 seg clock - dim display
> > > >
> > > > if you look in the files section under sr_gamer you will find the
> > > > schematic and the program for a clock I'm building. The display is
> > > > VERY dim.
> > > >
> > > > I'd like the display to be very bright.
> > > >
> > > > These elements are very bright when supplied with 5v, which should
> > > > be what is coming off of the PIC, so I'm either suffering from low
> > > > duty cycle or having trouble sourcing enough current. I tried some
> > > > 1k pull up resistors between the pins labeled anodes and +5v, but
> > > > this didn't seem to affect the situation.
> > > >
> > > >
> > > >
> > >
> > > --
> > > *******************************************
> > > VISIT MY HOME PAGE:
> > > > > >
> > > LAST UPDATED: 23/08/2003
> > > *******************************************
> > > Regards
> > > Eirik Karlsen
> > >
> >
> > --
> *******************************************
> VISIT MY HOME PAGE:
>
> LAST UPDATED: 23/08/2003
> *******************************************
> Regards
> Eirik Karlsen
>

------------------------------------

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(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

actually further testing has revealed I can run all six segments at once with no trouble and get pretty good brightness, the problem is I only have so many output pins so I want to multiplex the output which reduces my duty cycle to about 18%.  The only solution I can see is to put latches between each segment and the PIC or switch to a different type of display.

-Simonious

--- On Mon, 5/4/09, Eirik Karlsen wrote:
From: Eirik Karlsen
Subject: Re: [piclist] 18f4685 6 seg clock - dim display
To: p...@yahoogroups.com
Date: Monday, May 4, 2009, 5:27 PM

No wonder your display is dim. You can't drive it like that.

Assuming this PIC is like the earlier 18series it'll have some
limitations:

Max 20mA sink on any one pin, and max 20mA on all pins summed.

You have 6x8 = 48 segments, and for top brightness expect 20mA pr
segment...

thats 960mA when all are lit (which should also be a design goal).

No way a PIC can deliver that without burning up, and certainly not
without

excessive voltage drop on outputs.

You'll have to use both segment driver and display driver. Thats the
only

way to get it 'very bright'. I'd suggest using MOS drivers for both
digit and segmens

as this way you can drop all those base resistors.

Here in this clock I've used bipolar drivers, good bright display but
with MOSFET

drives 22 resistors could have been removed (8 in the SIL).



HTH

Shadowrun Gamer skrev:

this is correct, no limiting resistors are needed.  I can
run this display at 100% duty cycle at 5V

--- On Fri, 5/1/09, Paul Laverick
wrote:

From:
Paul Laverick

Subject: Re: [piclist] 18f4685 6 seg clock - dim display

To: piclist@yahoogroups .com

Date: Friday, May 1, 2009, 5:23 PM

Hi,
 
Your diagram shows no
current limiting resistors for each segment, is this correct or do you
have some?
I had a play with 7 segments
once, and had a similar problem, it was a long time ago...
I've heard of two versions
of updating the segments, using the LSB of Timer0 to update each
segment depending on the value (00 = Segment 1, 01 Segment 2 etc), or
every time Timer0 rolls over, change segment. 
I tried using timers but
found the last segment was always the brightest, as all the
calculations were happening while it was on, giving a longer on time..
 
Hope to of helped,
Paul

From: sr_gamer
Sent: Monday, April 13, 2009 9:31 PM
To: piclist@yahoogroups .com
Subject: [piclist] 18f4685 6 seg clock - dim
display

if you look in the files section under sr_gamer you will
find the schematic and the program for a clock I'm building. The
display is VERY dim.

I'd like the display to be very bright.

These elements are very bright when supplied with 5v, which should be
what is coming off of the PIC, so I'm either suffering from low duty
cycle or having trouble sourcing enough current. I tried some 1k pull
up resistors between the pins labeled anodes and +5v, but this didn't
seem to affect the situation.

--
************ ********* ********* ********* ****
VISIT MY HOME PAGE:

LAST UPDATED: 23/08/2003
************ ********* ********* ********* ****
Regards
Eirik Karlsen



(You need to be a member of piclist -- send a blank email to piclist-subscribe@yahoogroups.com )

What about using serial to parallel shift registers?

74HC595 ? You will need 3 "control" lines from a pic
Regards

Kenneth

2009/5/5 Shadowrun Gamer

> actually further testing has revealed I can run all six segments at once
> with no trouble and get pretty good brightness, the problem is I only have
> so many output pins so I want to multiplex the output which reduces my duty
> cycle to about 18%. The only solution I can see is to put latches between
> each segment and the PIC or switch to a different type of display.
>
> -Simonious
>
> --- On *Mon, 5/4/09, Eirik Karlsen * wrote:
>
> From: Eirik Karlsen
> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> To: p...@yahoogroups.com
> Date: Monday, May 4, 2009, 5:27 PM
> No wonder your display is dim. You can't drive it like that.
> Assuming this PIC is like the earlier 18series it'll have some limitations:
> Max 20mA sink on any one pin, and max 20mA on all pins summed.
> You have 6x8 = 48 segments, and for top brightness expect 20mA pr
> segment...
> thats 960mA when all are lit (which should also be a design goal).
> No way a PIC can deliver that without burning up, and certainly not without
> excessive voltage drop on outputs.
>
> You'll have to use both segment driver and display driver. Thats the only
> way to get it 'very bright'. I'd suggest using MOS drivers for both digit
> and segmens
> as this way you can drop all those base resistors.
>
> Here in this clock I've used bipolar drivers, good bright display but with
> MOSFET
> drives 22 resistors could have been removed (8 in the SIL).
> > 20circuit/>
> HTH
> Shadowrun Gamer skrev:
>
> this is correct, no limiting resistors are needed. I can run this
> display at 100% duty cycle at 5V
>
> --- On *Fri, 5/1/09, Paul Laverick * wrote:
>
> From: Paul Laverick
> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> To: piclist@yahoogroups .com
> Date: Friday, May 1, 2009, 5:23 PM
>
> Hi,
>
> Your diagram shows no current limiting resistors for each segment, is this
> correct or do you have some?
> I had a play with 7 segments once, and had a similar problem, it was a long
> time ago...
> I've heard of two versions of updating the segments, using the LSB of
> Timer0 to update each segment depending on the value (00 = Segment 1, 01
> Segment 2 etc), or every time Timer0 rolls over, change segment.
> I tried using timers but found the last segment was always the brightest,
> as all the calculations were happening while it was on, giving a longer on
> time..
>
> Hope to of helped,
> Paul
>
> *From:* sr_gamer
> *Sent:* Monday, April 13, 2009 9:31 PM
> *To:* piclist@yahoogroups .com
> *Subject:* [piclist] 18f4685 6 seg clock - dim display
>
> if you look in the files section under sr_gamer you will find the
> schematic and the program for a clock I'm building. The display is VERY dim.
>
> I'd like the display to be very bright.
>
> These elements are very bright when supplied with 5v, which should be what
> is coming off of the PIC, so I'm either suffering from low duty cycle or
> having trouble sourcing enough current. I tried some 1k pull up resistors
> between the pins labeled anodes and +5v, but this didn't seem to affect the
> situation.
>
> --
> ************ ********* ********* ********* ****
> VISIT MY HOME PAGE:
>
> LAST UPDATED: 23/08/2003
> ************ ********* ********* ********* ****
> Regards
> Eirik Karlsen
>
>



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Well, I think you're heading nowhere with that approach, and I think
most other
people with some experience will agree. Do it right 1st time and there
will be no need to do it over again.
Consider using one of these display drivers:
STLED316
MAX7219
MAX7221
Shadowrun Gamer skrev:
> actually further testing has revealed I can run all six segments at
> once with no trouble and get pretty good brightness, the problem is I
> only have so many output pins so I want to multiplex the output which
> reduces my duty cycle to about 18%. The only solution I can see is to
> put latches between each segment and the PIC or switch to a different
> type of display.
>
> -Simonious
>
> --- On *Mon, 5/4/09, Eirik Karlsen //* wrote:
>
> From: Eirik Karlsen
> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> To: p...@yahoogroups.com
> Date: Monday, May 4, 2009, 5:27 PM
>
> No wonder your display is dim. You can't drive it like that.
> Assuming this PIC is like the earlier 18series it'll have some
> limitations:
> Max 20mA sink on any one pin, and max 20mA on all pins summed.
> You have 6x8 = 48 segments, and for top brightness expect 20mA pr
> segment...
> thats 960mA when all are lit (which should also be a design goal).
> No way a PIC can deliver that without burning up, and certainly
> not without
> excessive voltage drop on outputs.
>
> You'll have to use both segment driver and display driver. Thats
> the only
> way to get it 'very bright'. I'd suggest using MOS drivers for
> both digit and segmens
> as this way you can drop all those base resistors.
>
> Here in this clock I've used bipolar drivers, good bright display
> but with MOSFET
> drives 22 resistors could have been removed (8 in the SIL).
> > 20circuit/>
> HTH
> Shadowrun Gamer skrev:
>
>> this is correct, no limiting resistors are needed. I can run
>> this display at 100% duty cycle at 5V
>>
>> --- On *Fri, 5/1/09, Paul Laverick //*
>> wrote:
>>
>> From: Paul Laverick
>> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
>> To: piclist@yahoogroups .com
>> Date: Friday, May 1, 2009, 5:23 PM
>>
>> Hi,
>>
>> Your diagram shows no current limiting resistors for each
>> segment, is this correct or do you have some?
>> I had a play with 7 segments once, and had a similar problem,
>> it was a long time ago...
>> I've heard of two versions of updating the segments, using
>> the LSB of Timer0 to update each segment depending on the
>> value (00 = Segment 1, 01 Segment 2 etc), or every time
>> Timer0 rolls over, change segment.
>> I tried using timers but found the last segment was always
>> the brightest, as all the calculations were happening while
>> it was on, giving a longer on time..
>>
>> Hope to of helped,
>> Paul
>>
>> *From:* sr_gamer
>> *Sent:* Monday, April 13, 2009 9:31 PM
>> *To:* piclist@yahoogroups .com
>> *Subject:* [piclist] 18f4685 6 seg clock - dim display
>>
>> if you look in the files section under sr_gamer you will find
>> the schematic and the program for a clock I'm building. The
>> display is VERY dim.
>>
>> I'd like the display to be very bright.
>>
>> These elements are very bright when supplied with 5v, which
>> should be what is coming off of the PIC, so I'm either
>> suffering from low duty cycle or having trouble sourcing
>> enough current. I tried some 1k pull up resistors between the
>> pins labeled anodes and +5v, but this didn't seem to affect
>> the situation.
>>
>> --
> ************ ********* ********* ********* ****
> VISIT MY HOME PAGE:
>
> LAST UPDATED: 23/08/2003
> ************ ********* ********* ********* ****
> Regards
> Eirik Karlsen
>
>

--
*******************************************
VISIT MY HOME PAGE:

LAST UPDATED: 23/08/2003
*******************************************
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Eirik Karlsen
______________________________
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> What about using serial to parallel shift registers?
>
> 74HC595 ? You will need 3 "control" lines from a pic

If you're considering additional chips and non-multiplexed drive, I like
the http://www.allegromicro.com/en/Products/Part_Numbers/6276/index.asp .
This is a latched serial input parallel output 16 bit shift register with
current regulated sink outputs. Just hook up the LEDs and shift in the
data.

Harold
(The ideal design has zero parts... and resistors count).
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I think you have several problems here:
In your circuit, you MUST multiplex the anodes because all similar segments are connected together, so if you split the time between digits, you will have one sixth of the full brightness at best.
In second place; not all the segments in one display are always ON, so sometimes you will have just one ON, and sometimes you will have seven (or eight with the dot) so the brightness will change with the number displayed.
I'm not expert in software but as i can see, mat be you have some errors in the program you posted (btw, this doesnt have to deal with brightness):

movf flipflop,0,0 ; load value of flipflop into w
xorwf b'00001000' ; xor it with bit 3
movlw flipflop ; store the result into flop
movlw 2 ; load 2 into w to multiply by 2

I think that if you want to use the configuration of that circuit, may be you need to use a higher voltage (more current but less time on), limiting devices in each segment, and drivers in anodes and segments.

HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH

--- In p...@yahoogroups.com, "sr_gamer" wrote:
>
> if you look in the files section under sr_gamer you will find the schematic and the program for a clock I'm building. The display is VERY dim.
>
> I'd like the display to be very bright.
>
> These elements are very bright when supplied with 5v, which should be what is coming off of the PIC, so I'm either suffering from low duty cycle or having trouble sourcing enough current. I tried some 1k pull up resistors between the pins labeled anodes and +5v, but this didn't seem to affect the situation.
>

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Just to be pedantic I don't think this is quite
right. The circuit is multiplexing the 7-segs so only one display is on
at a time so at 20mA the max will be 160mA.  Still too much and I
endorse the suggestions to use an NPN to source the current on each
device. I use 560 ohm current limiting
resistors on each segment and get a
good bright display using a 1/2 duty cycle (2 digits) with either the
MAN71a or MAN6730 (two segment) displays. No need for segment drivers.



The OP's circuit uses 6 displays so some of the dimness will be because
of the 1/6 duty cycle of each display - no easy way round that.



Eirik Karlsen wrote:

No wonder your display is dim. You can't drive it like that.

Assuming this PIC is like the earlier 18series it'll have some
limitations:

Max 20mA sink on any one pin, and max 20mA on all pins summed.

You have 6x8 = 48 segments, and for top brightness expect 20mA pr
segment...

thats 960mA when all are lit (which should also be a design goal).

No way a PIC can deliver that without burning up, and certainly not
without

excessive voltage drop on outputs.



You'll have to use both segment driver and display driver. Thats the
only

way to get it 'very bright'. I'd suggest using MOS drivers for both
digit and segmens

as this way you can drop all those base resistors.



Here in this clock I've used bipolar drivers, good bright display but
with MOSFET

drives 22 resistors could have been removed (8 in the SIL).

href="http://tech.groups.yahoo.com/group/piclist/files/sensi-touch%20circuit/"><http://tech.groups.yahoo.com/group/piclist/files/sensi-touch%20circuit/>

HTH





Shadowrun Gamer skrev:

type="cite">

style="font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-size: inherit; font-size-adjust: inherit; font-stretch: inherit;"
valign="top">this is correct, no limiting resistors are needed.  I can
run this display at 100% duty cycle at 5V



--- On Fri, 5/1/09, Paul Laverick <paul@paullaverick.co.uk>
wrote:

From:
Paul Laverick <paul@paullaverick.co.uk>

Subject: Re: [piclist] 18f4685 6 seg clock - dim display

To: piclist@yahoogroups.com

Date: Friday, May 1, 2009, 5:23 PM

Hi,

 

Your diagram shows no
current limiting resistors for each segment, is this correct or do you
have some?

I had a play with 7
segments
once, and had a similar problem, it was a long time ago...

I've heard of two versions
of updating the segments, using the LSB of Timer0 to update each
segment depending on the value (00 = Segment 1, 01 Segment 2 etc), or
every time Timer0 rolls over, change segment. 

I tried using timers but
found the last segment was always the brightest, as all the
calculations were happening while it was on, giving a longer on time..

 

Hope to of helped,

Paul

style="font-family: Tahoma; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; font-size-adjust: none; font-stretch: normal;">

From: rel="nofollow" title="s...@yahoo.com" target="_blank"
href="mailto:s...@yahoo.com">sr_gamer

Sent: Monday, April 13, 2009 9:31 PM

To: rel="nofollow" title="p...@yahoogroups.com" target="_blank"
href="mailto:p...@yahoogroups.com">piclist@yahoogroups .com

Subject: [piclist] 18f4685 6 seg clock - dim
display

if you look in the files section under sr_gamer you will
find the schematic and the program for a clock I'm building. The
display is VERY dim.



I'd like the display to be very bright.



These elements are very bright when supplied with 5v, which should be
what is coming off of the PIC, so I'm either suffering from low duty
cycle or having trouble sourcing enough current. I tried some 1k pull
up resistors between the pins labeled anodes and +5v, but this didn't
seem to affect the situation.

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*******************************************

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 href="http://home.online.no/%7Eeikarlse/index.htm"><http://home.online.no/~eikarlse/index.htm>

LAST UPDATED: 23/08/2003

*******************************************

Regards

Eirik Karlsen

  

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Yes I summed the display currents, which is wrong of course.
Other than that I won't give a penny.
Once you've tried proper driving you'll agree.

Prune skrev:
> Just to be pedantic I don't think this is quite right. The circuit is
> multiplexing the 7-segs so only one display is on at a time so at 20mA
> the max will be 160mA. Still too much and I endorse the suggestions
> to use an NPN to source the current on each device. I use 560 ohm
> current limiting resistors on each segment and get a good bright
> display using a 1/2 duty cycle (2 digits) with either the MAN71a or
> MAN6730 (two segment) displays. No need for segment drivers.
>
> The OP's circuit uses 6 displays so some of the dimness will be
> because of the 1/6 duty cycle of each display - no easy way round that.
>
> Eirik Karlsen wrote:
>
>> No wonder your display is dim. You can't drive it like that.
>> Assuming this PIC is like the earlier 18series it'll have some
>> limitations:
>> Max 20mA sink on any one pin, and max 20mA on all pins summed.
>> You have 6x8 = 48 segments, and for top brightness expect 20mA pr
>> segment...
>> thats 960mA when all are lit (which should also be a design goal).
>> No way a PIC can deliver that without burning up, and certainly not
>> without
>> excessive voltage drop on outputs.
>>
>> You'll have to use both segment driver and display driver. Thats the only
>> way to get it 'very bright'. I'd suggest using MOS drivers for both
>> digit and segmens
>> as this way you can drop all those base resistors.
>>
>> Here in this clock I've used bipolar drivers, good bright display but
>> with MOSFET
>> drives 22 resistors could have been removed (8 in the SIL).
>>
>> HTH
>> Shadowrun Gamer skrev:
>>
>>> this is correct, no limiting resistors are needed. I can run this
>>> display at 100% duty cycle at 5V
>>>
>>> --- On *Fri, 5/1/09, Paul Laverick //* wrote:
>>>
>>> From: Paul Laverick
>>> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
>>> To: p...@yahoogroups.com
>>> Date: Friday, May 1, 2009, 5:23 PM
>>>
>>> Hi,
>>>
>>> Your diagram shows no current limiting resistors for each
>>> segment, is this correct or do you have some?
>>> I had a play with 7 segments once, and had a similar problem, it
>>> was a long time ago...
>>> I've heard of two versions of updating the segments, using the
>>> LSB of Timer0 to update each segment depending on the value (00
>>> = Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,
>>> change segment.
>>> I tried using timers but found the last segment was always the
>>> brightest, as all the calculations were happening while it was
>>> on, giving a longer on time..
>>>
>>> Hope to of helped,
>>> Paul
>>>
>>> *From:* sr_gamer
>>> *Sent:* Monday, April 13, 2009 9:31 PM
>>> *To:* piclist@yahoogroups .com
>>> *Subject:* [piclist] 18f4685 6 seg clock - dim display
>>>
>>> if you look in the files section under sr_gamer you will find
>>> the schematic and the program for a clock I'm building. The
>>> display is VERY dim.
>>>
>>> I'd like the display to be very bright.
>>>
>>> These elements are very bright when supplied with 5v, which
>>> should be what is coming off of the PIC, so I'm either suffering
>>> from low duty cycle or having trouble sourcing enough current. I
>>> tried some 1k pull up resistors between the pins labeled anodes
>>> and +5v, but this didn't seem to affect the situation.
>>>
>>> --
>> *******************************************
>> VISIT MY HOME PAGE:
>>
>> LAST UPDATED: 23/08/2003
>> *******************************************
>> Regards
>> Eirik Karlsen
>>
>

--
*******************************************
VISIT MY HOME PAGE:

LAST UPDATED: 23/08/2003
*******************************************
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I'm a bit late to this story, but how about this idea...

Use a series of serial to parallel chips daisy-chained together. Each
segment driven but 1/8 of that one chip. The PIC doesn't drive any of
them, none of the segments is multiplexed (solves the brightness issue).

My apologies if this has already been suggested.

DLC

Eirik Karlsen wrote:
> Yes I summed the display currents, which is wrong of course.
> Other than that I won't give a penny.
> Once you've tried proper driving you'll agree.
>
> Prune skrev:
>>
>> Just to be pedantic I don't think this is quite right. The circuit is
>> multiplexing the 7-segs so only one display is on at a time so at 20mA
>> the max will be 160mA. Still too much and I endorse the suggestions
>> to use an NPN to source the current on each device. I use 560 ohm
>> current limiting resistors on each segment and get a good bright
>> display using a 1/2 duty cycle (2 digits) with either the MAN71a or
>> MAN6730 (two segment) displays. No need for segment drivers.
>>
>> The OP's circuit uses 6 displays so some of the dimness will be
>> because of the 1/6 duty cycle of each display - no easy way round that.
>>
>> Eirik Karlsen wrote:
>>
>>> No wonder your display is dim. You can't drive it like that.
>>> Assuming this PIC is like the earlier 18series it'll have some
>>> limitations:
>>> Max 20mA sink on any one pin, and max 20mA on all pins summed.
>>> You have 6x8 = 48 segments, and for top brightness expect 20mA pr
>>> segment...
>>> thats 960mA when all are lit (which should also be a design goal).
>>> No way a PIC can deliver that without burning up, and certainly not
>>> without
>>> excessive voltage drop on outputs.
>>>
>>> You'll have to use both segment driver and display driver. Thats the only
>>> way to get it 'very bright'. I'd suggest using MOS drivers for both
>>> digit and segmens
>>> as this way you can drop all those base resistors.
>>>
>>> Here in this clock I've used bipolar drivers, good bright display but
>>> with MOSFET
>>> drives 22 resistors could have been removed (8 in the SIL).
>>>
>>> HTH
>>>
>>>
>>> Shadowrun Gamer skrev:
>>>
>>>> this is correct, no limiting resistors are needed. I can run this
>>>> display at 100% duty cycle at 5V
>>>>
>>>> --- On *Fri, 5/1/09, Paul Laverick //* wrote:
>>>>
>>>> From: Paul Laverick
>>>> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
>>>> To: p...@yahoogroups.com
>>>> Date: Friday, May 1, 2009, 5:23 PM
>>>>
>>>> Hi,
>>>>
>>>> Your diagram shows no current limiting resistors for each
>>>> segment, is this correct or do you have some?
>>>> I had a play with 7 segments once, and had a similar problem, it
>>>> was a long time ago...
>>>> I've heard of two versions of updating the segments, using the
>>>> LSB of Timer0 to update each segment depending on the value (00
>>>> = Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,
>>>> change segment.
>>>> I tried using timers but found the last segment was always the
>>>> brightest, as all the calculations were happening while it was
>>>> on, giving a longer on time..
>>>>
>>>> Hope to of helped,
>>>> Paul
>>>>
>>>> *From:* sr_gamer
>>>> *Sent:* Monday, April 13, 2009 9:31 PM
>>>> *To:* piclist@yahoogroups .com
>>>> *Subject:* [piclist] 18f4685 6 seg clock - dim display
>>>>
>>>> if you look in the files section under sr_gamer you will find
>>>> the schematic and the program for a clock I'm building. The
>>>> display is VERY dim.
>>>>
>>>> I'd like the display to be very bright.
>>>>
>>>> These elements are very bright when supplied with 5v, which
>>>> should be what is coming off of the PIC, so I'm either suffering
>>>> from low duty cycle or having trouble sourcing enough current. I
>>>> tried some 1k pull up resistors between the pins labeled anodes
>>>> and +5v, but this didn't seem to affect the situation.
>>>>
>>>>
>>>
>>> --
>>> *******************************************
>>> VISIT MY HOME PAGE:
>>>
>>> LAST UPDATED: 23/08/2003
>>> *******************************************
>>> Regards
>>> Eirik Karlsen
>>>
>
> --
> *******************************************
> VISIT MY HOME PAGE:
>
> LAST UPDATED: 23/08/2003
> *******************************************
> Regards
> Eirik Karlsen

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I *think* this is roughly equivalent to the latches idea - I haven't redesigned/built this board yet, but my plan is:
-Essentially leave the PIC program alone and the display multiplexed, with one exception
- I put latches between the PIC and each 7 segment element, so as you suggested, the display elements themselves won't be multiplexed and the PIC won't be sourcing/sinking them.

Thanks!

--- On Sat, 5/30/09, dlc wrote:

From: dlc
Subject: Re: [piclist] 18f4685 6 seg clock - dim display
To: p...@yahoogroups.com
Date: Saturday, May 30, 2009, 8:45 AM

I'm a bit late to this story, but how about this idea...

Use a series of serial to parallel chips daisy-chained together. Each

segment driven but 1/8 of that one chip. The PIC doesn't drive any of

them, none of the segments is multiplexed (solves the brightness issue).

My apologies if this has already been suggested.

DLC

Eirik Karlsen wrote:

>

>

> Yes I summed the display currents, which is wrong of course.

> Other than that I won't give a penny.

> Once you've tried proper driving you'll agree.

>

> Prune skrev:

>>

>> Just to be pedantic I don't think this is quite right. The circuit is

>> multiplexing the 7-segs so only one display is on at a time so at 20mA

>> the max will be 160mA. Still too much and I endorse the suggestions

>> to use an NPN to source the current on each device. I use 560 ohm

>> current limiting resistors on each segment and get a good bright

>> display using a 1/2 duty cycle (2 digits) with either the MAN71a or

>> MAN6730 (two segment) displays. No need for segment drivers.

>>

>> The OP's circuit uses 6 displays so some of the dimness will be

>> because of the 1/6 duty cycle of each display - no easy way round that.

>>

>> Eirik Karlsen wrote:

>>

>>> No wonder your display is dim. You can't drive it like that.

>>> Assuming this PIC is like the earlier 18series it'll have some

>>> limitations:

>>> Max 20mA sink on any one pin, and max 20mA on all pins summed.

>>> You have 6x8 = 48 segments, and for top brightness expect 20mA pr

>>> segment...

>>> thats 960mA when all are lit (which should also be a design goal).

>>> No way a PIC can deliver that without burning up, and certainly not

>>> without

>>> excessive voltage drop on outputs.

>>>

>>> You'll have to use both segment driver and display driver. Thats the only

>>> way to get it 'very bright'. I'd suggest using MOS drivers for both

>>> digit and segmens

>>> as this way you can drop all those base resistors.

>>>

>>> Here in this clock I've used bipolar drivers, good bright display but

>>> with MOSFET

>>> drives 22 resistors could have been removed (8 in the SIL).

>>>

>>> HTH

>>>

>>>

>>> Shadowrun Gamer skrev:

>>>

>>>> this is correct, no limiting resistors are needed. I can run this

>>>> display at 100% duty cycle at 5V

>>>>

>>>> --- On *Fri, 5/1/09, Paul Laverick //* wrote:

>>>>

>>>> From: Paul Laverick

>>>> Subject: Re: [piclist] 18f4685 6 seg clock - dim display

>>>> To: piclist@yahoogroups .com

>>>> Date: Friday, May 1, 2009, 5:23 PM

>>>>

>>>> Hi,

>>>>

>>>> Your diagram shows no current limiting resistors for each

>>>> segment, is this correct or do you have some?

>>>> I had a play with 7 segments once, and had a similar problem, it

>>>> was a long time ago...

>>>> I've heard of two versions of updating the segments, using the

>>>> LSB of Timer0 to update each segment depending on the value (00

>>>> = Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,

>>>> change segment.

>>>> I tried using timers but found the last segment was always the

>>>> brightest, as all the calculations were happening while it was

>>>> on, giving a longer on time..

>>>>

>>>> Hope to of helped,

>>>> Paul

>>>>

>>>> *From:* sr_gamer

>>>> *Sent:* Monday, April 13, 2009 9:31 PM

>>>> *To:* piclist@yahoogroups .com

>>>> *Subject:* [piclist] 18f4685 6 seg clock - dim display

>>>>

>>>> if you look in the files section under sr_gamer you will find

>>>> the schematic and the program for a clock I'm building. The

>>>> display is VERY dim.

>>>>

>>>> I'd like the display to be very bright.

>>>>

>>>> These elements are very bright when supplied with 5v, which

>>>> should be what is coming off of the PIC, so I'm either suffering

>>>> from low duty cycle or having trouble sourcing enough current. I

>>>> tried some 1k pull up resistors between the pins labeled anodes

>>>> and +5v, but this didn't seem to affect the situation.

>>>>

>>>>

>>>

>>> --

>>> ************ ********* ********* ********* ****

>>> VISIT MY HOME PAGE:

>>>

>>> LAST UPDATED: 23/08/2003

>>> ************ ********* ********* ********* ****

>>> Regards

>>> Eirik Karlsen

>>>

>

> --

> ************ ********* ********* ********* ****

> VISIT MY HOME PAGE:

>

> LAST UPDATED: 23/08/2003

> ************ ********* ********* ********* ****

> Regards

> Eirik Karlsen

>

>

>

>

--

Question with boldness even the existence of a God;

because, if there be one, he must more approve of the

homage of reason, than that of blind-folded fear.

Thomas Jefferson

------------ --------- --------- --------- --------- -

Dennis Clark TTT Enterprises

www.techtoystoday. com

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> I *think* this is roughly equivalent to the latches idea - I haven't
> redesigned/built this board yet, but my plan is:
> -Essentially leave the PIC program alone and the display multiplexed, with
> one exception
> - I put latches between the PIC and each 7 segment element, so as you
> suggested, the display elements themselves won't be multiplexed and the
> PIC won't be sourcing/sinking them.

Pretty much, my idea simply means you only need 2 I/O lines on the PIC
instead of 8 or 9 for the parallel latch + the multiplex lines to enable
the displays. Multiplexing the displays will also use less power - You
could combine the two ideas and use a serial/parallel chip for the
segments, and a mux to select which display (each with a transistor of
course) which reduces your I/O lines and saves power all while driving
the LED segments as hard as possible.

have fun,
DLC
> Thanks!
>
> --- On Sat, 5/30/09, dlc wrote:
>
> From: dlc
> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
> To: p...@yahoogroups.com
> Date: Saturday, May 30, 2009, 8:45 AM
>
> I'm a bit late to this story, but how about this idea...
>
> Use a series of serial to parallel chips daisy-chained together. Each
>
> segment driven but 1/8 of that one chip. The PIC doesn't drive any of
>
> them, none of the segments is multiplexed (solves the brightness issue).
>
> My apologies if this has already been suggested.
>
> DLC
>
> Eirik Karlsen wrote:
>
>>>> Yes I summed the display currents, which is wrong of course.
>
>> Other than that I won't give a penny.
>
>> Once you've tried proper driving you'll agree.
>
>>> Prune skrev:
>
>>>>> Just to be pedantic I don't think this is quite right. The circuit is
>
>>> multiplexing the 7-segs so only one display is on at a time so at 20mA
>
>>> the max will be 160mA. Still too much and I endorse the suggestions
>
>>> to use an NPN to source the current on each device. I use 560 ohm
>
>>> current limiting resistors on each segment and get a good bright
>
>>> display using a 1/2 duty cycle (2 digits) with either the MAN71a or
>
>>> MAN6730 (two segment) displays. No need for segment drivers.
>
>>>>> The OP's circuit uses 6 displays so some of the dimness will be
>
>>> because of the 1/6 duty cycle of each display - no easy way round that.
>
>>>>> Eirik Karlsen wrote:
>
>>>>>> No wonder your display is dim. You can't drive it like that.
>
>>>> Assuming this PIC is like the earlier 18series it'll have some
>
>>>> limitations:
>
>>>> Max 20mA sink on any one pin, and max 20mA on all pins summed.
>
>>>> You have 6x8 = 48 segments, and for top brightness expect 20mA pr
>
>>>> segment...
>
>>>> thats 960mA when all are lit (which should also be a design goal).
>
>>>> No way a PIC can deliver that without burning up, and certainly not
>
>>>> without
>
>>>> excessive voltage drop on outputs.
>
>>>>>>> You'll have to use both segment driver and display driver. Thats the
>>>> only
>
>>>> way to get it 'very bright'. I'd suggest using MOS drivers for both
>
>>>> digit and segmens
>
>>>> as this way you can drop all those base resistors.
>
>>>>>>> Here in this clock I've used bipolar drivers, good bright display but
>
>>>> with MOSFET
>
>>>> drives 22 resistors could have been removed (8 in the SIL).
>
>>>> >>>> 20circuit/>>>> HTH
>
>>>>>>>>>> Shadowrun Gamer skrev:
>
>>>>>>>> this is correct, no limiting resistors are needed. I can run this
>
>>>>> display at 100% duty cycle at 5V
>
>>>>>>>>> --- On *Fri, 5/1/09, Paul Laverick //*
>>>>> wrote:
>
>>>>>>>>> From: Paul Laverick >>>> Subject: Re: [piclist] 18f4685 6 seg clock - dim display
>
>>>>> To: piclist@yahoogroups .com
>
>>>>> Date: Friday, May 1, 2009, 5:23 PM
>
>>>>>>>>> Hi,
>
>>>>>>>>> Your diagram shows no current limiting resistors for each
>
>>>>> segment, is this correct or do you have some?
>
>>>>> I had a play with 7 segments once, and had a similar problem, it
>
>>>>> was a long time ago...
>
>>>>> I've heard of two versions of updating the segments, using the
>
>>>>> LSB of Timer0 to update each segment depending on the value (00
>
>>>>> = Segment 1, 01 Segment 2 etc), or every time Timer0 rolls over,
>
>>>>> change segment.
>
>>>>> I tried using timers but found the last segment was always the
>
>>>>> brightest, as all the calculations were happening while it was
>
>>>>> on, giving a longer on time..
>
>>>>>>>>> Hope to of helped,
>
>>>>> Paul
>
>>>>>>>>> *From:* sr_gamer >>>> *Sent:* Monday, April 13, 2009 9:31 PM
>
>>>>> *To:* piclist@yahoogroups .com >>>> *Subject:* [piclist] 18f4685 6 seg clock - dim display
>
>>>>>>>>> if you look in the files section under sr_gamer you will find
>
>>>>> the schematic and the program for a clock I'm building. The
>
>>>>> display is VERY dim.
>
>>>>>>>>> I'd like the display to be very bright.
>
>>>>>>>>> These elements are very bright when supplied with 5v, which
>
>>>>> should be what is coming off of the PIC, so I'm either suffering
>
>>>>> from low duty cycle or having trouble sourcing enough current. I
>
>>>>> tried some 1k pull up resistors between the pins labeled anodes
>
>>>>> and +5v, but this didn't seem to affect the situation.
>
>>>>>>>>>>>>>>> --
>
>>>> ************ ********* ********* ********* ****
>
>>>> VISIT MY HOME PAGE:
>
>>>> >>> LAST UPDATED: 23/08/2003
>
>>>> ************ ********* ********* ********* ****
>
>>>> Regards
>
>>>> Eirik Karlsen
>
>>>>>> --
>
>> ************ ********* ********* ********* ****
>
>> VISIT MY HOME PAGE:
>
>> > LAST UPDATED: 23/08/2003
>
>> ************ ********* ********* ********* ****
>
>> Regards
>
>> Eirik Karlsen
>
>>>>> --
>
> Question with boldness even the existence of a God;
>
> because, if there be one, he must more approve of the
>
> homage of reason, than that of blind-folded fear.
>
> Thomas Jefferson
>
> ------------ --------- --------- --------- --------- -
>
> Dennis Clark TTT Enterprises
>
> www.techtoystoday. com
>
> ------------ --------- --------- --------- --------- -
--
Dennis Clark
TTT Enterprises

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