# 3 digit number on 1 seven seg. display

#### picaxester

##### Senior Member
This idea probable isn't original, but what ever.

I was trying to think of a way to drive three seven seg. displays with a 18x.
I thought of multiplexing them but my head started to hurt lol
Then I had the idea of showing one digit at a time on a signal display.
Heres a video.

eric

#### moxhamj

##### New Member
That works! Very nifty solution. Can you post the code by any chance?

#### picaxester

##### Senior Member
Thanks

Heres what it's running now:

Code:
``````eeprom 0, (%11111100)
eeprom 1, (%01100000)
eeprom 2, (%11011010)
eeprom 3, (%11110010)
eeprom 4, (%01100110)
eeprom 5, (%10110110)
eeprom 6, (%10111110)
eeprom 7, (%11100000)
eeprom 8, (%11111110)
eeprom 9, (%11110110)

do
segout:
b13 = b0 // 10
b10 = b0 / 10
b12 = b10 // 10
b11 = b10 / 10

pins = b7
pause 1000
pins = 0
pause 100
pins = b8
pause 1000
pins = 0
pause 100
pins = b9
pause 1000
pins = 0
pause 2000
loop

'    ABCDEFGH
'0 = 11111100 = 252
'1 = 01100000 = 96
'2 = 11011010 = 218
'3 = 11110010 = 242
'4 = 01100110 = 102
'5 = 10110110 = 182
'6 = 10111110 = 190
'7 = 11100000 = 244
'8 = 11111110 = 254
'9 = 11110110 = 246``````
It needs to be cleaned up a bit, but it works.

#### Brietech

##### Senior Member
If you want an easy way to "multiplex" a SSD, you just wire the 7 anodes of each display to the same 7 pins, and then take the "common" (cathode) line for each SSD, and control it with an individual pin. This way, 3 SSD's only cost you 7+3=10 output pins. "time"-multiplexing works as well, though =)

#### Michael 2727

##### Senior Member
You can drive 1, 2 or 3, 7-Seg Displays from just 2 pins
if you use 4026 chips cascaded together.
Only an Increment or Count # in pulses and/or reset
lines are needed.

I use an 08M to read a DS18B20 and display
the Temperature on 2 or 3 Digits.

Email me for the circuit, I think it's too big
to fit here, I'll have a look, maybe resize it.

#### picaxester

##### Senior Member
Thanks for the ideas guys.

Brietech, that would work but I only have 9 outputs to work with.

Michael 2727, I didn't want to use an external chip to do the work, but I would like to see the circuit anyway

#### Jeremy Leach

##### Senior Member
I've done exactly the same thing with an 18X, and have been meaning for a long time to write it up. I created a self-contained one-digit-display 'module' that could receive serial commands to display numbers in various formats on a single digit using the same principle. My objective was to have an alternative to an LCD module that was small enough to fit into a small plastic box.

#### BeanieBots

##### Moderator
Jez, was wondering where you'd been.
Get those projects written up and posted in the projects area.

#### ArnieW

##### Senior Member
You can drive 1, 2 or 3, 7-Seg Displays from just 2 pins
if you use 4026 chips cascaded together.
Only an Increment or Count # in pulses and/or reset
lines are needed.

I use an 08M to read a DS18B20 and display
the Temperature on 2 or 3 Digits.

Email me for the circuit, I think it's too big
to fit here, I'll have a look, maybe resize it.
Michael 2727: I think that circuit would be good to have on this site so that anyone can reference it. Any chances of posting it as a jpg or something like that?

thanks, Arnie

#### picaxester

##### Senior Member
Heres the circuit that he sent me.

Thanks Michael 2727

Last edited:

#### Michael 2727

##### Senior Member
Here is some code to make the above circuit work,
as a Thermometer only -
NOTE: There is a mistake in the GIF.
( I thought I had fixed that one )
The Switch goes to Leg4 / Pin3 (pin3 is an input only)
The DS18B20 goes to Leg3 / Pin4.
(whichever version is posted )
You don't need the switch for the basic circuit.
Code:
``````symbol counter = b3
main:
low 0
pause 20
high 0
pause 20
for counter = 1 to b1
high 2
low 2
next counter
pause 10000                   '<<<<<< Display refresh rate = 10 seconds.
goto main``````

Last edited:

#### picaxester

##### Senior Member
Thanks

Are C2 and R2 needed?

#### picaxester

##### Senior Member
If anyone has ever wanted to use a SSD from an alarm clock but didn't know where to begin then this might help.
It's just a PCB with exposed LEDs under a plastic screen.
The black letters are - and the red letters are +, the green dots are jummers and the black dots are the LED chips.
The picture sucks because I used a scanner and when I saved as a .JPG in MS Paint it went all ta crap
Keep in mind that this is a 12 hour clock.

#### Michael 2727

##### Senior Member
The clock input to the 4026 is very sensitive,
any stray voltage can cause a count, even
your fingers touching it will produce a 50/60 Hz
pulse stream from your body if you are standing
near mains wiring or equipment. (induced voltage,
try touching a CRO probe and you will see this )
Ths Cap will only allow a high pulse to be seen
by the 4026 input even if the Picaxe output pin
remains in a high state.

#### picaxester

##### Senior Member
I see.

BTW, I updated the link to your circuit with the corrected one that you sent me.