Comments on: Seven segment display explained

By: Laci

Laci — Wed, 26 Aug 2009 20:22:06 +0000

Yep, for 4 digits that is the cheapest solution, above 8 digits you should consider alpha numeric LCD’s 15-20$.
I strongly suggest that you use some timer interrupt for the multiplexing(like I did in the demo), you should try to port the C code to Basic, that would be the easiest way, since the code is really straight forward and commented.

By: Walter Flores

Walter Flores — Wed, 26 Aug 2009 18:28:53 +0000

Hi there, my name is walter and i’m working on a project that will measure the distance of an object up to 35 feet, and i was currently using a serial 7 segment display, but i would like to use 4 7 segments instad, i find it way cheaper than the serial 7 segment displays which run for about 30 – 60 dfollars, the language i’m using is Bascom 8051 but i’m having a little bit of trouble trying to multiplex the data into the segments, i was wondering if you could help me with this i understand exactly what i need to do the problem is that i don’t know how to do it and i’m not really familiar with C language, i understand that in order to display the digits i must do it one digit at a time but in a fast enough manner so that the eyes won’t see any flickering that’s where my problem is, i don’t know how to start, please help,
Thanks.

By: Florin

Florin — Sun, 23 Aug 2009 18:24:41 +0000

Yup, I know what you mean now. It’s an issue with the social plugin for wordpress, cause that’s behind the bookmarking buttons. I’ll have to wait for an update to fix it.

Until then you’ll have to copy and paste the URL
Thanks for letting me know.

By: Silly(c)One

Silly(c)One — Sun, 23 Aug 2009 12:07:04 +0000

It’s probably a Wordpress config mistake or something minor, I had no will to pollute your excellent tutorials

By: Silly(c)One

Silly(c)One — Sun, 23 Aug 2009 12:05:15 +0000

The Google button below this sentence “Do you like this article ? Bookmark it on:” does not work because the URL is html encoded : & are expanded to & amp ; so they don’t work anymore.

By: Florin

Florin — Sun, 23 Aug 2009 11:23:48 +0000

what URL’s are you referring to ?

By: Silly(c)One

Silly(c)One — Sun, 23 Aug 2009 11:20:38 +0000

Great article, thanks a lot.

Just one error, the google bookmarking isn’t working, HTML encoding galore (URLs are composed with & instead of &)

By: 4 Digit PIC Counter | YourITronics

4 Digit PIC Counter | YourITronics — Thu, 04 Jun 2009 09:45:26 +0000

[...] counting up or down. The whole display is multiplexed, more information about that you can find here. There are five push buttons you can use to configure the [...]

By: Laci

Laci — Wed, 03 Jun 2009 07:46:41 +0000

@Nocturnal: The purpose of multiplexing is to reduce the pin count.
Let’s take as example the display presented in the article, 4 digits, each segment can support 20mA, for maximum light intensity we want to drive each segment with 20mA this gives 160mA/digit that’s about correct, but what happens when you drive each digit 1/4 of the time? Because of the multiplexing at any moment only 1 digit is powered, what would be the average current passing trough the segments? The worst-case scenario assumed is to drive each segment at its maximum power, in that case the permissible pulse handling capacity plot of the segments(see datasheet) has to be considered too.

By: Nocturnal

Nocturnal — Wed, 03 Jun 2009 02:02:02 +0000

Ummm… how exactly are you arriving at your worst case current scenario? The transistors in question are only powering a single digit each, there is NO way they could have to supply power to ALL the digits (that would kinda defeat the purpose of multiplexing), which would be at maximum 8 leds. So the worst case current for a single transistor is 160mA regardless of number of digits.