Driving LCD''s
Archiver
Posts: 46,084
When I was messing around with LCD's a while back...
The trick is to use the freqout function and run a 1-2khz signal out to
each segment on the LCD. You don't just use a simple DC signal to a LCD
display, but a clocked or alternating (0 to 1) signal instead. The smaller
the LCD digit sizes, the faster the clock rate you, can use. The larger the
LCD digit the slower the clock rate. I have some small three digit displays
that work at 1 to 2khz, but my big size LCD's use a 60-100hz clock because
they are so slow (big 3 inch digit).
I didn't have any resistors on mine as the LCD was a very high impedance
device to start with, but you could use a small cap. You could run a cap
like a .001 or so between the output pin and the LCD segment) and run the
0-5 volt alternating signal through that. Thus you didn't have any current
flow to speak of. I won't take credit for the AC signal trick as I got that
from Tracy a while back.
All you should have to do is, use the freqout function on the output
enable of the 4094 shift registers and you should be in business, a zero out
pin won't do anything wheras the pin that is one should alternate between 0
to 5 volts. Of course the clock speed would have to be experimented with.
Original Message
From: Ben Lennard [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ZkqR015nnJ_5kDszJKDpn4GnMIXi_v22Zp9JnkBuYzaW2CL3T-lQra8szhQz0m7HrqIrwY-7kzc1lxuhQw]postmaster@s...[/url
Sent: Monday, February 25, 2002 1:55 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Driving LCD's
Firstly, re the virus scare: Got about 5 emails with .pif on the end.
Thankfully, I use a Mac. Pretty much immune to most destructive viruses.
Anyway, does anyone know how to drive an LCD without killing it?
I've come up with a circuit using 4 4094's to drive 4 digits of an LCD and
fed with 6 lines from the BS2. It works, in that the LCD segments light up.
BUT, I think I may be driving the LCD too hard and may eventually kill it.
I believe a maximum of 50mV DC component should be applied, but the average
(as measured with my DMM) is 2.5v.
However, I checked the voltage from the pins of a 7106 evaluation board I
have, and the average on it's pins is 6.3V.
Reason I'm concerned, is because after a few hours, segments seem to be a
bit "lazy" turning off with my circuit. However, I'm a little miffed due to
the reading from the 7106 board.
Should I just throw in some 10Meg resistors on each line??
To see the circuit I've come up with, just go to
http://www.lennard.net.nz/electronics/45lcdstamp.html
Of course, the circuit also works with LED displays, with a little
modification.
--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE
Web Hosting and Electronics R&D
Club Coordinator, Victoria University of Wellington Hockey Club
Hm: +64 4 972 7567
Mb: +64 21 536 627
87 Spencer Street
Crofton Downs
Wellington
New Zealand
"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."
No animals were harmed in the transmission of this email, although the
Dog next door is living on borrowed time, let me tell you! Those of you
with an overwhelming fear of the unknown will be gratified to learn that
there is no hidden message revealed by reading this warning backwards.
From: "debu_sen_22" <debu_sen_22@y...>
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Watch out a virus running loose.
Date: Mon, 25 Feb 2002 6:46 PM
Yup
I got the same email. Good thing that it goes to my yahoo account,
and i checked it first before downloading it.
Debu
--- In basicstamps@y..., "Earl Bollinger" <earlwbollinger@a...> wrote:
> Watch out.
> Someone tried sending a response to a old email attaching a
> W32 virus variant it looked to be some sort of screensaver SCR file.
>
> I don't know who this is Nilaweera [noparse][[/noparse]ndharmashri@c...] that sent the
email
> but watch out for that person.
>
>
> 'Earl Bollinger' wrote:
> ====
> - I forgot the original details of this, but
> - did any of you run across this website with a lot of DDS info?
> - http://sss-mag.com/dds.html
> -
> -
> -
Original Message
> - From: Tracy Allen [noparse][[/noparse]mailto:tracy@e...]
> - Sent: Friday, February 22, 2002 10:07 PM
> - To: basicstamps@y...
> - Subject: Re: [noparse][[/noparse]basicstamps] freqout command
> -
> -
> - >Thanks! The Intel chip would be perfect except it has been
obsolete and
> - >DigiKey has No stock. Do you know of a ...'
>
>
> > Take a look to the attachment.
To UNSUBSCRIBE, just send mail to:
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Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
[noparse][[/noparse]Non-text portions of this message have been removed]
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The trick is to use the freqout function and run a 1-2khz signal out to
each segment on the LCD. You don't just use a simple DC signal to a LCD
display, but a clocked or alternating (0 to 1) signal instead. The smaller
the LCD digit sizes, the faster the clock rate you, can use. The larger the
LCD digit the slower the clock rate. I have some small three digit displays
that work at 1 to 2khz, but my big size LCD's use a 60-100hz clock because
they are so slow (big 3 inch digit).
I didn't have any resistors on mine as the LCD was a very high impedance
device to start with, but you could use a small cap. You could run a cap
like a .001 or so between the output pin and the LCD segment) and run the
0-5 volt alternating signal through that. Thus you didn't have any current
flow to speak of. I won't take credit for the AC signal trick as I got that
from Tracy a while back.
All you should have to do is, use the freqout function on the output
enable of the 4094 shift registers and you should be in business, a zero out
pin won't do anything wheras the pin that is one should alternate between 0
to 5 volts. Of course the clock speed would have to be experimented with.
Original Message
From: Ben Lennard [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ZkqR015nnJ_5kDszJKDpn4GnMIXi_v22Zp9JnkBuYzaW2CL3T-lQra8szhQz0m7HrqIrwY-7kzc1lxuhQw]postmaster@s...[/url
Sent: Monday, February 25, 2002 1:55 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Driving LCD's
Firstly, re the virus scare: Got about 5 emails with .pif on the end.
Thankfully, I use a Mac. Pretty much immune to most destructive viruses.
Anyway, does anyone know how to drive an LCD without killing it?
I've come up with a circuit using 4 4094's to drive 4 digits of an LCD and
fed with 6 lines from the BS2. It works, in that the LCD segments light up.
BUT, I think I may be driving the LCD too hard and may eventually kill it.
I believe a maximum of 50mV DC component should be applied, but the average
(as measured with my DMM) is 2.5v.
However, I checked the voltage from the pins of a 7106 evaluation board I
have, and the average on it's pins is 6.3V.
Reason I'm concerned, is because after a few hours, segments seem to be a
bit "lazy" turning off with my circuit. However, I'm a little miffed due to
the reading from the 7106 board.
Should I just throw in some 10Meg resistors on each line??
To see the circuit I've come up with, just go to
http://www.lennard.net.nz/electronics/45lcdstamp.html
Of course, the circuit also works with LED displays, with a little
modification.
--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE
Web Hosting and Electronics R&D
Club Coordinator, Victoria University of Wellington Hockey Club
Hm: +64 4 972 7567
Mb: +64 21 536 627
87 Spencer Street
Crofton Downs
Wellington
New Zealand
"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."
No animals were harmed in the transmission of this email, although the
Dog next door is living on borrowed time, let me tell you! Those of you
with an overwhelming fear of the unknown will be gratified to learn that
there is no hidden message revealed by reading this warning backwards.
From: "debu_sen_22" <debu_sen_22@y...>
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Re: Watch out a virus running loose.
Date: Mon, 25 Feb 2002 6:46 PM
Yup
I got the same email. Good thing that it goes to my yahoo account,
and i checked it first before downloading it.
Debu
--- In basicstamps@y..., "Earl Bollinger" <earlwbollinger@a...> wrote:
> Watch out.
> Someone tried sending a response to a old email attaching a
> W32 virus variant it looked to be some sort of screensaver SCR file.
>
> I don't know who this is Nilaweera [noparse][[/noparse]ndharmashri@c...] that sent the
> but watch out for that person.
>
>
> 'Earl Bollinger' wrote:
> ====
> - I forgot the original details of this, but
> - did any of you run across this website with a lot of DDS info?
> - http://sss-mag.com/dds.html
> -
> -
> -
Original Message
> - From: Tracy Allen [noparse][[/noparse]mailto:tracy@e...]
> - Sent: Friday, February 22, 2002 10:07 PM
> - To: basicstamps@y...
> - Subject: Re: [noparse][[/noparse]basicstamps] freqout command
> -
> -
> - >Thanks! The Intel chip would be perfect except it has been
obsolete and
> - >DigiKey has No stock. Do you know of a ...'
>
>
> > Take a look to the attachment.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
[noparse][[/noparse]Non-text portions of this message have been removed]
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/