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Dot matrix display

R

Roger Dewhurst

Jan 1, 1970
0
I have been given a number of 7x5 dot matrix display segments. There are 7
pins at the top and 7 at the bottom. The ID on the segment is:

LTP2157AE
927 TAIWAN P

Can someone be kind enough to explain the pin-out for me.

R
 
B

BobG

Jan 1, 1970
0
Try an ohmmeter on diode test setting both ways.... could be common
anode or common cathode
 
C

Chris

Jan 1, 1970
0
I have been given a number of 7x5 dot matrix display segments. There are 7
pins at the top and 7 at the bottom. The ID on the segment is:

LTP2157AE
927 TAIWAN P

Can someone be kind enough to explain the pin-out for me.

R

Hi, Roger. Can't find the part -- I'd guess you might have to get out
your DMM and use the diode tester.

Here's a standard pinout that might help:

http://www.lumex.com/images/pdf/LDM-21257NI.pdf

ood luck
Chris
 
R

Roger Dewhurst

Jan 1, 1970
0
Chris said:
Hi, Roger. Can't find the part -- I'd guess you might have to get out
your DMM and use the diode tester.

Here's a standard pinout that might help:

http://www.lumex.com/images/pdf/LDM-21257NI.pdf
I have printed out the document but how do I work out what the pins do.

I can see that there are 8 anode pins and 6 cathode pins but that is about
as far as I get.

R
 
R

Randy Day

Jan 1, 1970
0
Roger Dewhurst wrote:

[snip]
I have printed out the document but how do I work out what the pins do.

I can see that there are 8 anode pins and 6 cathode pins but that is about
as far as I get.

Connect 3 to 5 volts (through a current-limiting
resistor), negative to one cathode, positive to
each anode in turn; each time a different spot
should come on. Move neg. to the next cathode,
then pos. to each anode again - different spots
come on.

R
|-----/\/\/\--- cathode
-
--- 3-5VDC
|-------------- anode

Choose the resistor value to limit current to
25mA. As the small schematic in the doc with all
the diodes shows, they're arranged in a row-col
matrix.
 
C

Chris

Jan 1, 1970
0
I have printed out the document but how do I work out what the pins do.

I can see that there are 8 anode pins and 6 cathode pins but that is about
as far as I get.

R- Hide quoted text -

- Show quoted text -

Hi, Roger. Driving the displays you have might not be the easiest
thing for a newbie. They work on the time multiplexing principle. If
you apply 7 bits of data to the anode pins, and then activate one of
the cathode pins, one row of the diplay will light. By using a
computer or microcontroller amd appropriate high current latching
drivers, you can scroll across the rows at a fast rate (say, 1000
times a second or so), and due to persistence of vision it will appear
that all the rows are on at once. A typical microcontroller can
easily handle this and also take care of other things such as
maintaining a communications link and taking care of other business.

But unless you've got that microcontroller, it is going to be really
difficult to get a whole lot of use out of your display.

Good luck
Chris
 
R

Roger Dewhurst

Jan 1, 1970
0
Chris said:
Hi, Roger. Driving the displays you have might not be the easiest
thing for a newbie. They work on the time multiplexing principle. If
you apply 7 bits of data to the anode pins, and then activate one of
the cathode pins, one row of the diplay will light. By using a
computer or microcontroller amd appropriate high current latching
drivers, you can scroll across the rows at a fast rate (say, 1000
times a second or so), and due to persistence of vision it will appear
that all the rows are on at once. A typical microcontroller can
easily handle this and also take care of other things such as
maintaining a communications link and taking care of other business.

But unless you've got that microcontroller, it is going to be really
difficult to get a whole lot of use out of your display.

Thanks. I just wanted to use them to display a time in milliseconds between
two events. Since I got a bunch of these 7x5 LED matrix devices I thought
that I might try and use them. Obviously there are easier ways.

Roger
 

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