> 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...
> 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
Reply by Shadowrun Gamer●June 1, 20092009-06-01
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...
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.
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...
>>>> 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
-------------
Reply by Eirik Karlsen●May 30, 20092009-05-30
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...
>>> 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
Reply by Prune●May 29, 20092009-05-29
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).
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..
To:
rel="nofollow" title="p..." target="_blank"
href="mailto:p...">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:
href="http://home.online.no/%7Eeikarlse/index.htm"><http://home.online.no/~eikarlse/index.htm>
LAST UPDATED: 23/08/2003
*******************************************
Regards
Eirik Karlsen
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.
--- In p..., "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.
>
Reply by Harold Hallikainen●May 5, 20092009-05-05
> 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).
--
FCC Rules Updated Daily at http://www.hallikainen.com - Advertising
opportunities available!
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...
> 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.
>>
>> --
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Reply by "Kenneth (K) Macrae"●May 5, 20092009-05-05
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...
> 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
>
>
Reply by Shadowrun Gamer●May 5, 20092009-05-05
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...
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: