MAX7219 interfacing
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Posts: 46,084
I need to operate a 12V LED display (about 20mA/seg) with the
Max7219 which is TTL. Is it simply a matter of using source drivers
on the outputs (segment lines) and sink drivers on the 8 cathode
lines.
I have the BS2 operating properly with the Max7219 but need that
upgrade in voltage.
Any help?
many thanks
Al
Max7219 which is TTL. Is it simply a matter of using source drivers
on the outputs (segment lines) and sink drivers on the 8 cathode
lines.
I have the BS2 operating properly with the Max7219 but need that
upgrade in voltage.
Any help?
many thanks
Al
Comments
enough to figure out the source and sink drivers and where to hook them
up???
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I need to operate a 12V LED display (about 20mA/seg) with the
Max7219 which is TTL. Is it simply a matter of using source drivers
on the outputs (segment lines) and sink drivers on the 8 cathode
lines.
I have the BS2 operating properly with the Max7219 but need that
upgrade in voltage.
Any help?
many thanks
Al
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Consider this. Take the pin for segment A to the input of of a Darlington
ULN2003. Tie the collector of the Darlington channel to +12 and the emitter
to segment A on the LED. When the 7219 wants segment A on, the 7219 pin will
go high, turn on the Darlington and supply 12V to segment A. Use a smilar
arrangement for D0, D1 and so on. You will only have about 10.5 volts on the
LEDs because of the drop across the Darlingtons, but possible you could
increase your supply voltage to 13 or 14 volts.
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
On second thought, you could use a 2N2222 for D0, D1, etc. but you would have
to use an inverter between D0 and the 2N2222 so that when D0 goes low it
would turn on the 2N2222 and ground D0 on the LED. You can get a chip with 8
inverters on it very cheaply.
Sid
[noparse][[/noparse]Non-text portions of this message have been removed]
http://pdfserv.maxim-ic.com/arpdf/MAX7219-MAX7221.pd
Would this help? It has suggestions for hook up inside..
Leroy
daniel.d.dangremond@j... wrote:
>
> I have the same problem. I can figure the 7219 out but am not well versed
> enough to figure out the source and sink drivers and where to hook them
> up???
>
> |
+
>
> | | brownstamp@yahoo|
> | | .com |
> | | |
> | | 04/28/2002 02:38|
> | | PM |
> | | Please respond |
> | | to basicstamps |
> | | |
> |
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>
>
>
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> |
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> | To: basicstamps@yahoogroups.com
|
> | cc:
|
> | Subject: [noparse][[/noparse]basicstamps] MAX7219 interfacing
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>
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>
> I need to operate a 12V LED display (about 20mA/seg) with the
> Max7219 which is TTL. Is it simply a matter of using source drivers
> on the outputs (segment lines) and sink drivers on the 8 cathode
> lines.
>
> I have the BS2 operating properly with the Max7219 but need that
> upgrade in voltage.
>
> Any help?
>
> many thanks
>
> Al
>
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do it was using an op-amp comparator on the output of each segment source line
(a-g, dp). I used a 1 volt reference voltage on the inverting input and fed the
output lines (A-G) into the non-inverting input. It seemed to work plenty fast
enough.. the hardest part is wiring it.. If you need a schematic let me know and
I will help.. I understand that there are many ways to do this.. I just found
that this one works great and is pretty cheap to build ! Just supply the op-amp
with about 13.5 volts and it shouldn't have a problem supplying the current.
Jay
Leroy Hall <leroy@f...> wrote: THe Data sheet is at:
http://pdfserv.maxim-ic.com/arpdf/MAX7219-MAX7221.pd
Would this help? It has suggestions for hook up inside..
Leroy
daniel.d.dangremond@j... wrote:
>
> I have the same problem. I can figure the 7219 out but am not well versed
> enough to figure out the source and sink drivers and where to hook them
> up???
>
> |
+
>
> | | brownstamp@yahoo|
> | | .com |
> | | |
> | | 04/28/2002 02:38|
> | | PM |
> | | Please respond |
> | | to basicstamps |
> | | |
> |
+
>
>
>
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> | |
> | To: basicstamps@yahoogroups.com |
> | cc: |
> | Subject: [noparse][[/noparse]basicstamps] MAX7219 interfacing |
>
>
\
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>
> I need to operate a 12V LED display (about 20mA/seg) with the
> Max7219 which is TTL. Is it simply a matter of using source drivers
> on the outputs (segment lines) and sink drivers on the 8 cathode
> lines.
>
> I have the BS2 operating properly with the Max7219 but need that
> upgrade in voltage.
>
> Any help?
>
> many thanks
>
> Al
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
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[noparse][[/noparse]Non-text portions of this message have been removed]
I don't think you will need anything on the sinking (D0,D1) outputs because they
are able to sink up to .5A each.. ( I THINK)
therefore you should only have to worry about the segment drive lines (a-g)
Jay
daniel.d.dangremond@j... wrote: I have the same problem. I can figure the
7219 out but am not well versed
enough to figure out the source and sink drivers and where to hook them
up???
|
+
>
| | brownstamp@yahoo|
| | .com |
| | |
| | 04/28/2002 02:38|
| | PM |
| | Please respond |
| | to basicstamps |
| | |
|
+
>
>
\
|
| |
| To: basicstamps@yahoogroups.com |
| cc: |
| Subject: [noparse][[/noparse]basicstamps] MAX7219 interfacing |
>
\
|
I need to operate a 12V LED display (about 20mA/seg) with the
Max7219 which is TTL. Is it simply a matter of using source drivers
on the outputs (segment lines) and sink drivers on the 8 cathode
lines.
I have the BS2 operating properly with the Max7219 but need that
upgrade in voltage.
Any help?
many thanks
Al
To UNSUBSCRIBE, just send mail to:
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from the same email address that you subscribed. Text in the Subject and
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[noparse][[/noparse]Non-text portions of this message have been removed]
I would love to see your schematic. I read the data sheet months ago but
it only shows a schematic for a 2 digit display to boost the voltage and
they use a source driver? If it works for you then that's all I need.
Thanks for your help!!!
Dan
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| | jay_mann2000@yah|
| | oo.com |
| | |
| | 04/29/2002 06:53|
| | PM |
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I used the MAX7219 for a similar appication... The best way that I was
able to do it was using an op-amp comparator on the output of each segment
source line (a-g, dp). I used a 1 volt reference voltage on the inverting
input and fed the output lines (A-G) into the non-inverting input. It
seemed to work plenty fast enough.. the hardest part is wiring it.. If you
need a schematic let me know and I will help.. I understand that there are
many ways to do this.. I just found that this one works great and is pretty
cheap to build ! Just supply the op-amp with about 13.5 volts and it
shouldn't have a problem supplying the current.
Jay