36 seven segment display with pic.. need advise..

[dani]

74ls4511

Hello all,

I want to do make a pannel which has 7-segment displays on it. these displays display different values of weight and its units etc. Altogeather they are total 36 digits which i need to incoprate. I want to use PIC 16f877a. What type of muliplexing hardware and software technice i shoule follow .. i need advise for this from professionals..

Regards
Dani

 

[The Puma]

seven segment display deiver using pic

Look for the max7219 or max7221 (SPI interface)
h??p://www.maxim-ic.com/quick_view2.cfm/qv_pk/1339

One chip can drive 8 digits,and you only need 3 pins of the UC

 

[kender]

74hc138

Maxim MAX7221: 8 digits, SPI interface, avail. in DIP
Maxim MAX6955: 16 digits, I2C interface with 4 different slave addresses, avail in DIP

 

[GrandAlf]

scan pic 7 segment

You are going to need a lot of I/O for rows and column addressing unless you use use further decoding. There are available serial displays that are commonly 4 digit devices. These require 2 lines clock and data. You can cascade them for more digits, or switch them in banks, bit heavy going in software to drive them though. Another way would be to drive a few digits (say 4) with a smaller pic and then communicate serially with each of them on a common bus, each part of the display having it own address, i.e (pic1address "message") (pic2address "anothermessage") etc. Just a few thoughts, hope it helps. Common clock signal would be better for this scheme.

Added after 1 minutes:

I2C would be good also

 

[dani]

icm7228 et pic

helo all and thanks for reply

Max 7221 or Max7219 is not available to me in local market so you guys please suggest me is there any other easily madeable solution ....

regards

 

[The Puma]

cascade of 4511 ic and 7-segment

You can sample it by maxim

 

[dani]

74ls164 +7 segments

yess i can but dear it will take time... and i dont have much time for this assignment...
Can you tell me that can i use some BCD to 7 segment latch/decoder/Driver chip like 74LS4511 etc...
?????????????

 

[The Puma]

max7219 18v

it would only take one or two weeks

I think the other solutions take to many uC lines

 

[rtfm]

7-segment 36-pin display

With 36 seven segment LED displays, one simply cannot scan fast enough to make an useable display.

I would suggest then you scan the individual segment instead. This would give a 1/7 duty cycle, regardless of how many LEDs are connected.

Connects all the corresponding "a" segment of 36 LEDs together, and fed it power in turn using one port pin of the MCU, with suitable interfacing using transistors. Same for all other segments.

In your software program, you examine all the data byte for each of these 36 values and determine which "a" segment should be ON. You then clock these 36 bits into a 36-bit serial-in, parallel out shift register, with each shift register parallel output pin controlling the power to the common of one 7-segment LED.

Of course you do these clocking with the segment drive OFF. When all 36 bits has been transferred, you turn ON the segment drive.

This method only need 7 data pins for segment drive and one additional pin for serial clocking of the shift register, so total is 8.

Edited: I could not be more specific unless I know what type of 7-segment display you are using. Common anode or common cathode?

 

[garg29]

edaboard 7segment 74ls164

there is a simple way but bit more mesy. use 36- 74ls164. u'l need only 2 uC lines. if u can use 36 ics then this idea will work. if u still need help pm me.

 

[mrcube_ns]

power darlington max7221

In this situations I use cmos 4094 (serial to paralel interface with latch).

If you need details pm me, or ask here.


Regards.


Mr.Cube

 

[PaulHolland]

74hct164 working

Hi, Believe that sombody already told you: Use 36 74HCT164 chips, cheap and can be ordered fron any source. Shift the bits in serial using a clock and data line and connect all common pins using a high power MOSFET that switches the dispaly off during load. if you do this fast you will not see it. The other way is multiplexing everything but you need 36 I/O lines for common signal and 7 + 1 (point) for segments. Top do it properly you need to do fast multiplexing at a rate (refresh) of 10 mseconds per display. so 10 ms/ 36 = 275 uSeconds. That is NO PROBLEM !!. Since you do not have a 36 PIN I/O on the display there must be an easy way in solving this. One way is to use logic to scan the common signals using 74HCT164 chips. They have 8 I/O lines so 36/8 = 5 chips. Now connect the clock and data line top you PIC and just shift ONE bit in. All other times you simply shift one clock until you get to 36 and the bit is lost and shift out of the register. Now you simply shift a new bit in etc.. in the time between the shifts you put the correct driving signal on the bottom 8 lines for the segments and your done !!.. Only needing:

5 * 74HCT164
1 * PIC with 2 + 8 I/O lines + some lines for other things like an UART to connect it to the PC.
36 * MOSFET/ NPN/PNP transistor to drive Display common lines

regards,

Paul.

Added after 9 minutes:

Hi, I just had a better and more simple idea:

Use a simple PIC with UART to make it easy for you. The PIC only needs 9 I/O Lines and internal RC osc (to make it simple) and UART. Now make a small program that is doing the following:

The RX of the UART is going to your text string source: and it send the string into the first PIC that is connected to the first 7 segment display. this first chip takes the first char from the string and put's it on the display bu driving with 8 I/O lines the segments on the display and with a FIXED common signal. Now the pic sends the rest of the string to the TX port that is connected to the second PIC RX PIN of the chip and this one has the same program as the first chip etc... so yopu simply connect 36 cheap and small PIC chips in a string and you can make your chain as long as you like )..

Paul.

 

[hermin]

7 segment pic driver

One suggestion i could give would be connecting the 7 segments altogether, and let a microcontroller display each digit one by one by controlling the common pin of the 7segment displays, you might need aditional 7 segment drivers and a decoder to do this, so the microcontroller will display the digit one by one on the microcontroller but it so fast that you wont notice it...


if you want a diagram, just give me a pm if its hard to visualise

 

[pvinbox@yahoo.com]

seven segment display driver ics

hai


connect all datalines from a to h then control the display by switching
the common pin through controller.

 

[fireball003]

pic seven segment shift

Hi,
I am working on this type of system too. But I need to control only 17 seven segment displays. I have two plans in my head and I need to verify which one is easier, cost effective and efficient.

Solution1:-
Use 4511 for each display. connect 4 pins with all 4511's A,B,C,D pins. And then connect each pin to LE (storage pin of 4511). Each time the value changes of a perticular display, you just low the LE pin of that display.Then change the value of the previous 4 pins connected to all A,B,C,D pins. Again high the LE pin. it is done.

It is also good for long distance set up since the output voltage depends upon Vcc, so you can control perticular Vcc of each 4511 for each display. And its Vcc range is 3v to 18v.

It will take total 4pins (for A,B,C,D)+ 36 pins (for 36 LE pins) = 40 I/O. Then you need 2 PIC 16f877a.

Solution2:-
Intersils' ICM7218 and ICM7228 controls 8 seven segment. You need 4 of those ICs and your PIC. nothing else.

But you need to use sepserate voltage amplifier if the distance of the displays and the controller is long .

Please tell me if there any other better idea to control 17 or 36 segments.

 

[tanbinh_mu]

connecting 2 seven segment displays on a pic chip

I think use the 74HC595. Can control to 100 digits

 

[dani]

uln2803 4511 need

hello and thanks to all,


I have found Max7219 finaly from one source.. I tried it on protues and it is working fine ... So i am going to make ciruit based on this chip. Any how thank you onece again who reply..

regards

 

[gidimiz]

uln2803 4511

Hi,

Use one of the "new" PIC they can drive your LDC without any problem.
See the PIC16F9XX for more information on the microchip web site. They will do the job for you even if you put the part in sleep, and the code that you have today you can use it on that part.
Good luck.

 

[Nandulal]

4 seven segment need i/o pin

I have designed 24 seven segment LED display. Attaching schematics here. Here is the point of design is the pin count required and time of refreshing the display.
I'm giving here the details,
There is 1*4 display module is available market. I took 6*4 seven segments displays(common anode) which are easily available in market just cost 80Rs($2) per display. Then each display needs one control voltage. and 8 display pins. Remember, at any time only one display is in active state or all off.

So I need 24 control pins + 8 data pins. Here I used 74HC154 as 4:16 decoder to control 15 display and 74HC138 3:8 decoder for controlling the rest. The display segments are driven by ULN2803 Darlington IC. The voltage of each anode is controlled by PNP transistor. Here one thing I want add that PNP transistor is good for the current source which improves the display visibility. So you can extend it to any number of displays you want by considering above things.

It is also true that maxim has some multiplexed seven segment driver ICs but they are not readily available in market. So this imposes limitation on your design.

Enjoy
Nandu

 

[hassan1980]

max7221

yess i can but dear it will take time... and i dont have much time for this assignment...
Can you tell me that can i use some BCD to 7 segment latch/decoder/Driver chip like 74LS4511 etc...
?????????????

Use shift register like 4094.