# How to display 20 2-digits numbers?

I'm working on something where i need to display 20 independent 2-digit numbers that are located in different places. In current prototype there are 20 extruded in plastic numbers with led backlight. The drawback for my application is that I cannot change the order of numbers. I can live with that, but dynamic numbers would be cool and would enable some other useful features.

Long story short, while I was going to sleep last night I thought "woah, I can probably use some displays". Well, after some thinking it became obvious that 7-segment displays would require enormous amount of pins or expensive driver ICs. Also, my application is in very limited space. So, could someone help me out and give an advice how to implement this? Or prove that it's too stupid. I know that it sounds like an absurd idea, I just want to be sure. Thanks.

• Multiplexed 7-segment LED displays are both cheap and easy to use, no "expensive driver ICs". There are plenty of examples on the Interwebs. Commented Mar 8, 2020 at 13:46
• You won't beat 7 segment displays, as Dave says. But at some stage of complexity, a big monitor or TV screen becomes a simpler cleaner solution (as long as all these displays are in the same plane).
– user16324
Commented Mar 8, 2020 at 13:51
• What size are the individual digits? What is the total length or area filled with digits? Commented Mar 8, 2020 at 14:14
• @BrianDrummond well yeah, every number is in individual plane, that's the main problem Commented Mar 8, 2020 at 15:50
• @Neil_UK size is not determined yet, but I guess acceptable digit height can be in a range of 1-1.5mm Commented Mar 8, 2020 at 15:53

## 1 Answer

... i need to display 20 independent 2-digit numbers that are located in different places. ... I guess acceptable digit height can be in a range of 1 - 1.5 mm

It's not at all clear what you're trying to do here and how far apart these "different places" are (within 10s of mm of each other or on different continents) and I haven't seen 1.5 mm seven-segment displays since I peered into the TI30 calculator I purchased in 1977.

Well, after some thinking it became obvious that 7-segment displays would require enormous amount of pins or expensive driver ICs.

Figure 2. Seven segment displays typically require seven pins (one for each segment and, optionally, an extra one for the decimal point) + one pin for each digit. Source: Multiplexed seven-segment displays.

If the displays are in close proximity then you need seven pins + one per digit. (So the eight-digit display in the TI30 would require 16 pins to drive it.) If you haven't got that many pins you may need to look at shift registers or some other way of multiplexing at each display or group of displays.

See the linked article for a little more on the topic. Edit your question to clarify if this doesn't answer your question.