# max7219 question

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#### kpshamilsagar

##### New Member
does it shows only one number at a time on all the 8 seven segment display or it shows different numbers on different displays(if so does it require any specific code to be written so that it goes to different displays?)

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#### picbits

##### Well-Known Member
It shows one number at a time but switches between all the digits at a high frequency so it appears that all 8 digits are lit at once.

The code to drive these is pretty simple. The MAX7219 takes care of which digits are lit and when and what is on the display, all you need to do is write the code to tell the 7219 what to display (in the datasheet !!!)

I will warn you that they are expensive chips to purchase if you are planning on using them a lot.

#### kpshamilsagar

##### New Member
does it costs much?i need atleast 4.how much this will cost?

#### DSGarcia

##### New Member
does it costs much?i need atleast 4.how much this will cost?

You can order the part directly from Maxim for under $15 (USD) each +S&H. When you say you need "4", do you mean you want 4 driver chips (to display up to 32 digits) or four digits (which can be driven by one chip)? You can order two free samples of the chip from Maxim if you qualify. Check their web site for different chips to identify the part that best fits your application. You may find a less expensive option. You should also check with other manufacturers to evaluate your options. #### kpshamilsagar ##### New Member actually i need 4 board and in one board 1ic is required.so that i need 4 ic's..any compatible version from any other company? Last edited: #### blueroomelectronics ##### Well-Known Member Nope, MAXIM makes lots of proprietary (and very cool) ICs You could use a microcontroller and a handful of latches / drivers. #### DSGarcia ##### New Member What exactly are you trying to do? What are your requirements? What is your budget? There are lots of parts from which to choose and lots of different solutions. The Maxim (and also Intersil) ICM7218 is a few$ less expensive but is still over \$11 (USD) but there is a 28 pin DIP version which will make it easier to breadboard. However, you need lots more I/O pins to interface with the chip. The highly integrated parts tend to be more expensive, but it saves on room and circuit complexity.

When it comes to engineering, you can have it good, fast, and cheap... pick any two [and only two].

Dale

#### kpshamilsagar

##### New Member
here i am planning to develop a highly sophisticated traffic signal...i cant tell u much because its going to be my final year projects.we use digital image processing,ai and swarm intelligence.
lemme tel you my requirements...
1.i need to run 12 diff LED's seperately(3 colors ie red,yellow,green for 4 sides).
2.i need 1 lcd screen to display some messages.
3.i need 8 seven segmented displays (2 each on 4 sides).
4.i need the count down timer(seven segment display) to be controlled from a computer(i mean how much time it should run and all..)
5.i am planning to use atmega32 ic.
6.we uses swarm intelligence here so we need atleast 4 boards of the same.
7.i am planning to use xbee for communication between computer and board.
8.money not a problem(but still a problem).

so can anyone tell me the seven segment display part.the rest all i have done.first time i am using a seven segment display.

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#### DSGarcia

##### New Member
How high do you want the characters? How bright do you need the characters; e.g., is this for an indoor status display or will the display be used outside?
Dale

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#### kpshamilsagar

##### New Member
7 segment display characters are numbers(0-9) and its indoor only..just a project.and lcd displays need both char and numbers(a-z,0-9)....

#### blueroomelectronics

##### Well-Known Member
Since the original circuit uses a small micrcontroller, just update it to one with enough I/O to run the displays.

#### kpshamilsagar

##### New Member
thats not possible...i have given all my requirements na...which ever way i do.i need more ics...

#### mvs sarma

##### Well-Known Member
thats not possible...i have given all my requirements na...which ever way i do.i need more ics...
Assuming that you are in India, Sagar,

Then, perhaps the only way is to order on either Farnel India. and part number is 9725245

Browse for Products | Farnell India

they sell at Rs723,+,+,+.

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#### kpshamilsagar

##### New Member
hey it costs 750rs?that is too much...come on any other ic that is low cost and does the same job?i thought it will be around 200rs...but i cant afford this....tel some other ic's that does the job fine...pls...i am not familier with 7 segment display...

#### mvs sarma

##### Well-Known Member
hey it costs 750rs?that is too much...come on any other ic that is low cost and does the same job?i thought it will be around 200rs...but i cant afford this....tel some other ic's that does the job fine...pls...i am not familier with 7 segment display...

How do you expect all characters A thro Z on seven sigment displays? Perhaps you need to look at a seven seg display datasheet.

I am not aware of any Indian supplier for MAX7219.
and even if some one supplies, they are cross checking the farnell and RS component catalogs and boosting the prices.
why at all you need a hardware converter? and why not use another chip that would do only display unction as per the data sent by the main controller? even the MAX7219 is doing same thing!!!
by the way if you use 40 pin chips perhaps you can drive display directly.
But your reply to Bill of blueroomelectronics - Smart Kits Build Smart People made me feel that you need 7219 more pieces at any cost.......

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#### blueroomelectronics

##### Well-Known Member
thats not possible...i have given all my requirements na...which ever way i do.i need more ics...

So you can change the Maxim chip but have to use a tiny MCU? Doesn't make sense really.

#### DSGarcia

##### New Member
You should select your display then decide which driver method to use. Some 7 segment displays are common cathode and some are common anode. Your driver and display need to be the same type.

Could you consider an 8 character LCD display module? It has the controller, drivers, and display all in one unit. You just send ASCII characters to it from your microcontroller.

Here is one example: https://www.newhavendisplay.com/specs/NHD-0108FZ-RN-YBW.pdf
Dale

#### kpshamilsagar

##### New Member
How do you expect all characters A thro Z on seven sigment displays? Perhaps you need to look at a seven seg display datasheet.
i have told you that i will be using lcd display also...and i use characters there only(a-z,0-9)
i want to use 7 segment for count down timer..(0-9)

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