Yes for four display you need four IC.
The IC are just power shift registers and the schematic shows that they are connected in chain
You can use common anode display
View attachment 74012
If I were to build something like above picture 7 segment which each segment contain 14 led, how do I design the current limit resistor for the led? Is it each led one resistor? Then if each segment is 14 led then I need 14 resistor. Then one character have 14led x 7 segment = 98 led = 98 resistors. Aren't that too much?
Or can design such that two led share one resistor?
I don't think one segment (14 led) can share just one resistor, won't have enough voltage. Or will it?
From the picture above, I've design two circuits. Each represent one segment which contain 14 led.
View attachment 74014
Which design can work? The left one or right one?
I've tried connecting all 14 led in series and just one resistor to 12V. The led won't turn on.You will use one resistor for each segment, it doesn't matter if the segment has 1,2 or 3 leds.
See post #96
I think there will not be enough voltage to light the seven leds in series, in addition the led coupled may not share the current equally.
Depending on the led type used you will need about 2v for each led so for 7 leds you need 14v.
The 14 led version can work too but not with 12v, you need about 24v.
Both designs can work , usually display with many leds in each segment use the leds in series.
The in series connection will requite a lower total current too.
This one needs seven times the current of the previous one where everything was in series, if you prefer it then use this.
How do we calculate the total amount of current for a segment (14 led)? Is it still 20mA?Usually leds operate at about 20mA , 50mA seems high for a display but I don't know if the leds have a bigger size that normal and operate with more current.
The display in the link that you posted earlier was for 20mA
If you have 14 leds in series they they all share the same current, the 20mA flow through all of them.
If each two are in parallel and then the seven sets in series like in post #108 then the current will be shared for each couple that is in parallel so you may need 40mA but you don't have control of how is the current shared.
It may be 20+20mA or 15+25mA etc.
I don't know the max current of your leds so I can't give you a random suggestion.
This is parameter you should check in the datasheet but you don't have one so...
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