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Need Help on how to build 7 - Segment Display circuit with Series of LED's

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Jun 20, 2011
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Hi there,

I'm a beginner and wanted to build a circuit that can count 2-digits up/down using the follwing:

- 2 digit (3" 7-seg using 3 LED's per seg - in series connection) So, 21 LEDs all together in 1 7-Segment display
- using a 9V power supply (is this possible?)

Please let me know if how I can utilize or connect the following ic's;

- 74HC163 (Up/Down Resettable Sync counter)
- 74LS47 (Drive/Decoder)

What else do I need aside from transistors? and how can I connect them together?

Can someone direct me or show me a schematic and do I need a swith to make it work?

Any HELP is much appreciated

The '163, 'LS163A, and 'HC163 are 4-bit binary counters. For your application you need decade counters, example: '160, '162, 'LS160, 'HC162.

---------- Post added at 17:38 ---------- Previous post was at 17:27 ----------

Also for the UP/DOWN application you may use a CD4510
**broken link removed**
I gave you an example here:
(Single digit, standard LEDs, it’s not so complicated to extend for two digits and more LEDs)

Hi mister_rf,

Thanks again...
- my 3 LED's per segment connection is a SERIES type, is that matter?
- Should I use a Common Anode or Common Cathode connection?
- Also, do I need a uController to swithch it on?

Question: do you already have the counters?

If you use standard LEDs you can connect in both ways :grin: , here you can see some details


  • LEDs in series.GIF
    LEDs in series.GIF
    17.4 KB · Views: 450

Hello mister_rf...

So, with all your recommendation, here's what I understand;

- OK to use the (own build) 3- LED per segment display in "series" connection.
- use C4510 Counter or HEF4510B
- use 74LS47 Display driver/decoder
- 9V power supply

Is there a switch I could use or do I need uController?

---------- Post added at 13:12 ---------- Previous post was at 13:05 ----------


I use 3mm standard LEDs

So, with your attachment, I can use; 74HC47 instead of the 74LS47 then, I can connect with my counter CD4510.

No controller needed. :grin:
What's the color for LEDs?

It's a red 3mm LED.

So, If i don't need a controller, could you help me design the schematic diagram then with the proper connections? I'm building a simple "SCORE BOARD" that can only count up to two digits. with a push botton to count "ones" Up and down counts. So, I will label the botton with a (+) to count up and (-) to count down. Two digit on left side of the score borad and two on the right.

- using C4510 Counter and 74LS47 Display driver/decoder
- 9V power supply
- 3 LED per segment (series connection)

What switch do I need? or I don't need it?

Please and thank you.

So you need also a manual pulse generator, but one of the problems with is that any mechanical pushbutton exhibits a phenomenon known as "contact bounce." To prevent this and obtain single digital pulses, we need to include with the switch a digital circuit that will react to the first contact closure, but will ignore subsequent contact bounce . We therefore may simply use a CD4093 Schmitt NAND gates, a resistor and a capacitor.

You asked the question "do I need a microcontroller" two times..
If you want to use a uC for this, then you can use, then don't consider it just for switching... Instead, a single uC can replace those drivers, counters etc...But the total cost may increase...(about 3 times). So, in this case ,better not to use a microcontroller.

Any way, just look this circuit to get some idea.
Then you can modify it according to your need.
One version for 2 digits counter


  • counter CD4510 v1.GIF
    counter CD4510 v1.GIF
    49.1 KB · Views: 326
Hi vinosatanur,

Thanks, this is also helpful.

So, to make it work, I can simply use NE555 (or CD4093 Schmitt NAND gates), a counter 74LS192 or C4510 and a driver/decoder 74LS47 and cascade this for a 2 digit requirement each side? as I mentioned earlier, I need 2 digit counter on the left and 2 digit on the right with up/down (+/-) switches on the bottom?

Please advise.


A more complete version, to include a RESET button and two dedicated buttons, one for UP and one for DOWN.


  • counter CD4510 v2.GIF
    counter CD4510 v2.GIF
    52.4 KB · Views: 507

Thanks a lot...

the attached One version - for 2 digits counter
is really HELPFUL.

Check also the second version, it's more simple to operate. :grin:

---------- Post added at 21:07 ---------- Previous post was at 20:58 ----------

By the way, you need to do some tests in order to choose the right value for the LEDs resistors (R1 to R14). Put 3 LEDs in series with some resistors, starting from 150 ohm down to 82-100 ohms, use a 9V power supply and check the intensity for the LEDs. A normal LED need 15-20mA to operate. Choose to use the resistor witch give you the most appropriate value.


Thanks...yes, the diagram its more simpler.

One more question: I see, looks like I will need - 4 NAND gates then? I appreciate any comments.

The CD4093B consists of four 2-input NAND Schmitt-trigger circuits.
So in this case you need only one circuit.


Thanks. I will do some testing but, first I'll find the parts list.

- I have the LEDs (3mm red)
- I will get some resistors - 150oms for R1-R14
- I need the CD4093B NAND gates
- 9V power supply (which I already have)
- CD4510 counter
- 74LS47 driver/decoder (which I already have)
- R15-R17 100K ohms resistors

did I missed any parts? please let me know...

Thanks a lot
Please let me know if

DIY 2 digits counter:
1 pcs CD4093
2 pcs CD4510
2 pcs 74HC47
42 pcs red LEDs
3 pcs 100k resistors
14 pcs 100 up to 150 ohms resistors
3 pcs push buttons
and don't forget, some decoupling capacitors, a common arrangement is ~100 nF ceramic/multilayer per logic IC
5 pcs 100nF


where will I connect the - "some decoupling capacitors, a common arrangement is ~100 nF ceramic/multilayer per logic IC" ?

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