Advice needed - multiplexing 7 segment displays.


+ Reply to Thread
Results 1 to 13 of 13
  1. #1
    Senior Member Mellbreak's Avatar
    Join Date
    Jun 2012
    Posts
    571
    Thumbs Up
    Received: 36
    Given: 27
    Total Downloaded
    4.63 GB

    0 Not allowed!

    Default Advice needed - multiplexing 7 segment displays.

    I'm trying to build a 5-digit 7-segment display. The LEDs I'm using are 2.3" (approx 6cm) high type FJS23101AH. Unfortunately, I can't find a datasheet on these devices although I know that each segment requires 7.5v at 15-20mA to drive it.

    Not being an EE, I'm not sure what current I should drive the segments at if they are being multiplexed. Given that there are five digits is it safe to drive the segments at 75mA for 1/5 of the time?

    Thanks,

    Bob

  2. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  3. #2
    Senior Member GAMBOA's Avatar
    Join Date
    Nov 2004
    Posts
    445
    Thumbs Up
    Received: 21
    Given: 0
    Total Downloaded
    203.73 MB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Bob,

    you need to know the peak current that LED diodes can withstand. In a design I did a few years ago I used discrete diodes and the peak current that the diodes supported was 100mA. In my design I adjusted a maximum current to 80mA. It was also a multiplexed system. The calculation you have made is correct. If you lower the excitation time you have to proportionally raise the intensity but only up to the maximum peak current that the LED supports.

    Regards,
    Gamboa
    Last edited by GAMBOA; 28th December 2018 at 10:21.

  4. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  5. #3
    Senior Member Mellbreak's Avatar
    Join Date
    Jun 2012
    Posts
    571
    Thumbs Up
    Received: 36
    Given: 27
    Total Downloaded
    4.63 GB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Thanks Gamboa, that's very helpful. I'll have to see if I can find a value for the peak current from somewhere.


    Bob

  6. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  7. #4
    Senior Member Mellbreak's Avatar
    Join Date
    Jun 2012
    Posts
    571
    Thumbs Up
    Received: 36
    Given: 27
    Total Downloaded
    4.63 GB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Having had a good look around the Internet, I still haven't found any information on the peak segment current for this display. In general terms the peak current seems to be about 5 times the average current. Would this be a reasonable assumption to make?

    Bob

  8. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  9. #5
    Senior Member GAMBOA's Avatar
    Join Date
    Nov 2004
    Posts
    445
    Thumbs Up
    Received: 21
    Given: 0
    Total Downloaded
    203.73 MB

    1 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Bob,

    I have used the TOS-40101AMRL-B (Taiwan Oasis) and the technical data in the data sheet says:

    Peak Forward Current per segment: 80mA
    Continuous Forward Current per segment: 20mA

    Regards,
    Gamboa

  10. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  11. #6
    Senior Member Mellbreak's Avatar
    Join Date
    Jun 2012
    Posts
    571
    Thumbs Up
    Received: 36
    Given: 27
    Total Downloaded
    4.63 GB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Thanks again Gamboa, I'll start by using something around 60mA and see how that goes.

    Bob

  12. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  13. #7
    Fanatical Contributor fanie's Avatar
    Join Date
    Oct 2005
    Posts
    7,989
    Thumbs Up
    Received: 31
    Given: 15
    Total Downloaded
    434.52 MB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    The very first program I wrote was a 3 digit multiplexed display, and I'm still using the same today for a basic volt and amp meter. There however is a problem, and that is it limits the pic to do other things which will disrupt the timing.
    Hence, I use some 4094's to drive the 7 segments and the pic only write to the display when it is suitable which can be any amount of segments, (I tested up to around 30 x 4 digit displays which changed the 5V regulator to double as a finger toaster).
    I have found this to be a lot more practical and am using it in almost all projects requiring a display. It just makes life so much easier. My displays are 4 digit each but can be added as many as the supply can handle. Another advantage is you use only 3 output pins of the pic for clock, data and strobe, a small pic can drive a lot of displays without using more pins, and if you are out of pins, you can even share the clock and data pins.
    The software is also easy, I use the same call routine, just change the amount of digits to write to.
    Last edited by fanie; 7th January 2019 at 22:37.
    Fanie

  14. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  15. #8
    Member basparky's Avatar
    Join Date
    Oct 2006
    Posts
    231
    Thumbs Up
    Received: 9
    Given: 27
    Total Downloaded
    751.86 MB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Hi, i have build a few displays using HC 595.https://www.google.com/url?sa=t&sour...fS84xBi0Wr_0D3
    Works great! I you want I can share my programs on the forum.

  16. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  17. #9
    Fanatical Contributor fanie's Avatar
    Join Date
    Oct 2005
    Posts
    7,989
    Thumbs Up
    Received: 31
    Given: 15
    Total Downloaded
    434.52 MB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    That's it, the same functionality. The 4094 is a bit cheaper here than the 74 595 and unfortunately they are not pin compatible.
    Fanie

  18. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  19. #10
    Prolific Poster joesaliba's Avatar
    Join Date
    Sep 2004
    Posts
    2,560
    Thumbs Up
    Received: 76
    Given: 33
    Total Downloaded
    6.56 GB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    A few years ago I took Fanie circuit diagram and made a PCB for it. If someone needs it I can share EAGLE files.
    Regards

    Joseph

  20. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  21. #11
    Fanatical Contributor fanie's Avatar
    Join Date
    Oct 2005
    Posts
    7,989
    Thumbs Up
    Received: 31
    Given: 15
    Total Downloaded
    434.52 MB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    While the displays are discussed I want to ask if there is a shorter way of allocating the values to write to the display than this ?
    To explain, In the program I allocate values to each segment, which will then be changed by the table to appear as that character on the display.
    So if there is zero in Dis1, it needs to become 126 to show a 0 on the display, if there is 1 in dis1 it needs to become 34 to become a 1 on the display and so on.

    Instead of

    Dis1 = LookUp Dis1, [126, 34, 188, 186, 226, 218, 222, 50, 254, 250,....
    Dis2 = LookUp Dis2, [126, 34, 188, 186, 226, 218, 222, 50, 254, 250,.... etc

    I do like this -

    Table:
    Frame = LookUp Index, [126, 34, 188, 186, 226, 218, 222, 50, 254, 250, 152].... (40 or so characters)
    Return

    Index = Dis1 : GoSub Table : Dis1 = Frame
    Index = Dis2 : GoSub Table : Dis2 = Frame
    Index = Dis3 : GoSub Table : Dis3 = Frame

    Is there a shorter way to do this ?
    Last edited by fanie; 12th January 2019 at 15:21.
    Fanie

  22. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  23. #12
    Prolific Poster joesaliba's Avatar
    Join Date
    Sep 2004
    Posts
    2,560
    Thumbs Up
    Received: 76
    Given: 33
    Total Downloaded
    6.56 GB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Fanie,

    Have a look here for low cost PT100.

    Also, as I said, the problem with this car booth spray was a wire.

    The sensor reading was around 57ohms at 14deg room temperature, so I assume at 0deg would be around 50ohms.

    But I cannot locate these sensors or what they are called. Tried looking for PT50 but found nothing.

    Readings after I fixed the wire where spot on using another temperature for reference.
    Regards

    Joseph

  24. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

  25. #13
    Prolific Poster joesaliba's Avatar
    Join Date
    Sep 2004
    Posts
    2,560
    Thumbs Up
    Received: 76
    Given: 33
    Total Downloaded
    6.56 GB

    0 Not allowed!

    Default Re: Advice needed - multiplexing 7 segment displays.

    Looking for these sensors I encountered these ready made units.

    Worth peanuts so I bought one, and they use the K-type thermocouple.

    For longer leads I also bought another K-type thermocouple.
    Regards

    Joseph

  26. Attention

    This valuable resource relies upon the very small amount of revenue generated by displaying online advertisements to our visitors.

    The advertisements we display are relevant to this web site and your browsing history

    Please consider supporting us by disabling your ad blocker.


    Note: Some users have reported issues related to ad-blockers rendering parts of this wesite unusable,
    where possible we will rectify the issues to enable you to use this resource with adblocking enabled.

    If you can, please report issues in the forum area WebSite / Forum Issues


    Thank you for your attention.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

     

Similar Threads

  1. Code for Driving 2,3 or 4 seven segment displays
    By AlbertoFS in forum WIKI Discussion
    Replies: 25
    Last Post: 24th July 2018, 21:47
  2. AlbertoFS has just uploaded Driving 2,3 or 4 seven segment displays.!
    By AlbertoFS in forum Proton Users File Server
    Replies: 0
    Last Post: 11th June 2018, 20:58
  3. Replies: 1
    Last Post: 3rd August 2008, 10:20
  4. LED 4x1 7 Segment CC displays
    By Eagleeye in forum Proton Plus Compiler v3
    Replies: 8
    Last Post: 4th June 2007, 04:01
  5. 6 digit 7-segment led display multiplexing
    By Hans Chr in forum The Lounge
    Replies: 7
    Last Post: 7th January 2006, 07:46

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts