Wiring a Dual Digit Display

Thread Starter

kainotk

Joined Mar 31, 2009
10
How does one wire a dual digit 7-segment LED to display different characters, when there is only 1 set of a,b,c,d,e,f,g. :confused:

For example, how do I display a "0" and a "1" at the same time?

thanks
 

SgtWookie

Joined Jul 17, 2007
22,221
By multiplexing of the commons pins.
The display is either common cathode or common anode.

Find the datasheet for your particular display.
You'll find something like:
CC1, CC2
or
CA1, CA2
for the respective digits.
[eta]
Here's an example using a PIC uC:
http://www.picbasic.com/resources/articles/ledart.htm
It starts out nice and simple, with the basics of powering LEDs, and works up to multiplexing 7-segment displays.
 
Last edited:

SgtWookie

Joined Jul 17, 2007
22,221
What are you trying to do? Display a count of items?

If so, look at using the CD4543 and CD4553 IC's together.
One is a 3-digit BCD counter with a multiplexing output, the other is a 7-segment display driver.
 

Thread Starter

kainotk

Joined Mar 31, 2009
10
For starters, I just want to display a "0" on the left and a "1" on the right of a dual digit display. Eventually, I'd like to built a counter.
 

SgtWookie

Joined Jul 17, 2007
22,221
Oddly enough, it would either require a microcontroller or more parts than just the 4543/4553 IC's, a few resistors and transistors to just display a "01".

See the attached schematic for a simple project using the 4543 and 4553 IC's. It's using three separate 7-segment displays, but the idea is the same; you would just have one set of abcdefg connections to make instead of three.

The clock input to the 4553 3-digit BCD counter is a Hall-effect sensor, it provides logic-level pulses. It's a design to count revolutions of a shaft.
 

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SgtWookie

Joined Jul 17, 2007
22,221
If you really just want to display a "01" for starters, then you could begin with just a 4543 and resistors wired up like I show on the schematic.

Inputs B, C, and D would be connected to ground.

A 555 timer with some resistors, a cap and some transistors could be used to alternate sourcing/sinking current from the display common anode/common cathode, and changing input A to a logic 1 or 0.

But you need to know if your display has common anode or common cathode. Pin 6 of the 4543 is the "phase" input. For common anode displays, the phase input is connected to ground; for common cathode it's connected to Vdd.
 
I have a really good question I'm building a timer replioca from the show sliders but I don't know how to wire up the numeric l.e.d. display chips I have 3 dual digit and the ic chips I have 7 CD40110BE and 1 TLC551CP CHIP but no one can tell me how to wire them up I need it to be able to count up/down I'm not sure if your familiar with that show but I'm looking to build all the timers from that show but like I said no one can tell me I have called the place mouser.com where I bought them from to see if they could help me and they were no help at all so I went all the way to the manufacture which is Texas Instruments and they couldn't even help me I'm lost to is what to do I have these parts and can't do a thing cause Idk what to do can you help me please.
 

SgtWookie

Joined Jul 17, 2007
22,221
Well, the 40110 is a CMOS decade up/down counter with built-in 7-segment decoders, and the TLC551 is compatible with the industry standard 555 timer.

You might find ST Microelectronics HCC40110B datasheet easier to read.

Not familiar with the show "Sliders".
 

Wendy

Joined Mar 24, 2008
22,547
Sliders was about an inventor/mathematician who solved the theory of everything, and created a device that moved between alternate universes, or earths in this case. It became a lost in time format. Started off OK, and went downhill over several seasons.

There are several CMOS chips that will do what you want quite nicely, besides the ones Wookie mentioned. How much do you know about electronics in general?

I like the CD4029 myself.
 

SgtWookie

Joined Jul 17, 2007
22,221
Bill,
The 40110 will work just great for what they want to do (I think) - as they want to drive 7-segment displays; the 4029 would require an additional IC, whereas the 40110 would not.

I don't know what the "Sliders" counter did, though...
 

Wendy

Joined Mar 24, 2008
22,547
As I understand the OP wants a BCD counter that you can input the numbers (presetable) and counts down, possibly with the ability to count up also. This describes a 4029 pretty closely. The mod six counters may present a problem though.

To the OP:

You may want to put up your proposed control panel and display, it will give people a better idea what you want.
 
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