Need Help To Build 7 Segment LED Display Circuit

Discussion in 'General Electronics Chat' started by iccool, Apr 8, 2010.

  1. iccool

    Thread Starter New Member

    Apr 3, 2010
    5
    0
    I had only little bit of knowledge of electronics. I had done some very small projects from circuits in books. I need a circuit that will display 5 digit display which uses 4" Seven Segment display (Please see the datasheet attached - KLS402I) that receives input from a 0-9 digit number pad (Individual Number Pad, not from PC).

    I searched and found some ICs that can be used, please advice me which one can be used, if anyone can give a circuit that would he very helpful.
    CD4511
    CD4543
    PIC 16F877
    7447

    I know PIC ICs had to be programmed, I like programming but don't know which IC to purchase and how to connect it to PC to program the IC. Read about PICAXE ICs, but not sure it is available in India or not. I would like to make it both ways, with a PIC IC and with a Pre-programmed IC.

    Also give me a idea how I can make the number pad input (not from PC) to IC. I read that CD4511 is a BCD CMOS IC, but how to give input to that IC?

    Thanks in advance..
     
    Last edited: Apr 10, 2010
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Take a look at using a CD4543 with a CD4553. One is a 3-digit BCD counter, the other is a 7-segment display counter. You can cascade the 3-digit counter to create a 6-digit counter.

    You will find schematics for connecting them together in ONSemi's datasheet for the MC14553B. Note that Motorola uses an MC1 prefix instead of the CD prefix. Phillips/NXP Semiconductor uses prefix HEF.

    The PIC16F87x series is obsolete.
    The replacement series is PIC16F88x. They are much less expensive, and have their own internal clock so that a crystal oscillator is not absolutely necessary for operation.

    Programming a PIC has a rather steep learning curve. Once you can master the basics of it, you will be able to do a lot of things that would require a great many discrete logic ICs.
     
  3. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    If you want to look at what's involved in programming you can go to:
    http://www.mikroe.com/en/download/
    And download the free software, in it you will find the code for a 4 digit 7 segment counter already written in the example directory.
     
  4. iccool

    Thread Starter New Member

    Apr 3, 2010
    5
    0
    First of all thanks to..SgtWookie & gerty

    @SgtWookie
    I will start with MC14553B & PIC16F88x, I will work around those ICs and will post the updates. I had done VB & Java programming but I know this part is entirely different.

    @grety,
    I saw a lot of links, can I download and start with mikroC PRO for PIC 2009?
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    If you know Java, then you know about 80% of C++. However, you will also need to learn some of the peculiarities of PIC Assembly language, and how to set the various options for the uC itself.

    There are a practically bewildering array of PIC uC's out there nowdays.

    If you are going to want to use the MikroC demo program for the 4 digit counter, you should look in the source code first to determine which PIC they used.

    I'd downloaded MikroBasic awhile back. There is a demo MikroBasic program like Gerty mentioned for a 4-digit 7-segment display.
    At that that time, the demo program required:
    1) A PIC16F887
    2) An EasyPIC5 Development Board.

    The requirements may have changed; you will need to look in the demos for the software suite that you download.

    There may be a similar demo program in MikroC; I don't know as I have not downloaded it.
     
  6. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
  7. MMcLaren

    Well-Known Member

    Feb 14, 2010
    759
    116
    iccool,

    Which 4 inch LEDs do you have? The common Anode or common Cathode ones?
     
    Last edited: Apr 9, 2010
  8. iccool

    Thread Starter New Member

    Apr 3, 2010
    5
    0
    Thanks for the quick reply...

    @SgtWookie
    Sorry, I downloaded and installed mikroC, but cannot find 4-digit 7-segment display in example folder. For PIC16F88x, the 'x' is still in search. I found in microC that PIC16F88x ranges from PIC16F88, PIC16F882, PIC16F883, PIC16F884, PIC16F885, PIC16F886 & PIC16F887.

    When PIC16F882 is searched, it has also sub-sections, still in confusion which IC to start with. Here is the link of PIC16F882:

    http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en530146

    In MC14553B datasheet there are some words used in electronics, 'cascading', 'clock input', 'latch' and 'strobe', what is that mean. DC Input Current per Pin is 10mA, there will be any loss in output, it will be enough power to light 4" LEDs?

    @Bill_Marsden
    I had already went through the information you given, from that tutorial I got the name of IC 4511. Because of that I had that IC in my first preference when I started. Only problem is can I choose it for large display (4").

    @MMcLaren
    KLS402i & KLS402SR are Common Cathode type 7 Segment LEDs. Here are the details of those LEDs (datasheet is attached in my first post):

    KLS402i (High Intensity Red):

    Forward Voltage - Typical @ 10mA: 2.10
    Forward Voltage - Maximum @ 20 mA: 2.40
    Reverse Current @ VR = 5V: 100
    Peak Emission Wavelength: 630
    Emission Wavelength Half Width: 35
    Luminous Intensity per Segment: 3500

    KLS402SR (Superbrite Red)

    Forward Voltage - Typical @ 10mA: 1.90
    Forward Voltage - Maximum @ 20 mA: 2.10
    Reverse Current @ VR = 5V: 100
    Peak Emission Wavelength: 660
    Emission Wavelength Half Width: 20
    Luminous Intensity per Segment: 6000

    ABSOULTE MAXIMUM RATINGS AT 25C (Same for both LEDs)
    Reverse Voltage: 5
    Forward Current (avg): 20
    Peak Forward Current (T<1ms): 80
     
  9. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    It's the current, not the size, of the LEDs. I've thought about making my own 7 segment displays using discrete LEDs where the digits were over 1' high. The drivers would be virtually identical.

    Some displays have the LED all linked together, and you have to clock between each digit. The extra pins are to enable this function.

    When I was in college (over 30 years ago) I did a similar project with a multiplexed display just to see how it worked. Everybody who is serious goes through this stage.
     
  10. iccool

    Thread Starter New Member

    Apr 3, 2010
    5
    0
    @Bill_Marsden

    Sorry, bit late to reply..

    It is really a struggle to get the components here in our small town. I got some components from nearby town. Still to get the desired 4" 7 Segment Display. When I made contact with them & got info that, Forward voltage is not 2.10, but it is 7.20. The info in the datasheet is wrong!

    I was able to purchase these products and my first part almost went success. :)

    1) HCF4511

    2) 4" LED 7 Segment Display (Only got one, there is no more stock) No datasheet and no information, so I started from 1.5v.. which worked well around 7.5v.

    3) PIC16F882 (Yet to purchase Programmer Board which is bit costly)

    4) Keypad Diebold P/N 19-019062-001Z Rev1 DIOX, Assembled in Mexico, 02.27.2004

    5) Resistance, Breadboard etc..

    I was happy to see the circuit almost working well (hxxp://www.allaboutcircuits.com/vol_6/chpt_7/9.html)

    Unfortunately two segments not working which worked well at the start. I will get new LEDs to test in coming week.

    Can anybody tell what is the Pinout of Keypad (16 Keys = 10 Digits + 1 Dot + 5 Extra Keys) and how it functions. How I can integrate it with PIC16F882. In that way I can see through the starting of programming.
    Any links I can check for that. Unfortunately I cannot find much info when I searched.

    Many Thanks...
     
  11. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    I was in the same boat back then. Radio Shack is not a great parts source. I would use the phrase "barely adequate". A teen generally has to depend on their parents for checks (I did), or credit cards to pay for mail order. As I got older I got a checking account to pay for my parts.

    Where to get parts is a legitimate subject for this site. This is why most of the experienced folks put their location as part of their profile to be displayed on the corner of a post.

    If you are in need of parts, ask for some good sources. It will help.

    BTW, here are some plans I drew many moons ago for a set of stadium lights, They have never been built, but maybe some day. Multiplexing has several functions, a big one is to reduce the number of wires carrying the information for a display. For example, the first attachment got 4 digits down to 8 wires, I was thinking of using Cat5 wire.
     
    Last edited: Apr 18, 2010
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    (snip)
    Did you use current limiting resistors for each of the segments?

    If you did not, that is likely why they are no longer working.
     
  13. iccool

    Thread Starter New Member

    Apr 3, 2010
    5
    0
    @Bill_Marsden
    Yes, getting deisred parts is difficult in some regions, especially ours & as you mentioned early about learning, I was still in nurserry of electronics.

    I will try to reduce the number of wires, but my problem is in the function of keypad. It has 16 keys and 8 output pins. Testing continuity of pins after pressing a key do not give any result.

    @SgtWookie
    You are right, it may be because of the current limiting resistor. I missed that:(, because I started with very low voltage I do not put resistor. I was eager to see the result & increase the voltage. That may caused the problem. I had no information about the mA of the 7 Segment LED that I got. So not able to calculate correct value of resistor (I saw one of your post about the resistor value calculation).

    Keypad and PIC16F882 is where I am stuck. (I know it is too much for a student)
     
  14. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
Loading...