Current issue in 4 digit seven segment display module

[ilias.cas]

Hi,
I m using 4 digit display modules in my project as many as 20 numbers. I could successfully run the displays but the major problem came up is the amount of current drawn by it. When I glow all the digits, its drawing about 250 mA for 4 digits. If it is so the total sum of the current for all my 20 modules would go out of range.
So please help me out in modifying the design as if each module could drawn least amount of current with a ample visibility in the displays.
The schematic has been attached.

Thanks

 

[crutschow]

You can increase the value of each of the 470R resistors in series with the displays to reduce the current.

You'll have to experiment to see how high you can go and still get an adequate display brightness.

Edit: You can just experiment with one resistor and look at the segment it controls to view the brightness change. When you determine the desired value, then you can change all the rest of the resistors to that value.

 

[ilias.cas]

Thanks crutschow,
Would there be any other way other than that..

 

[ronsimpson]

You could reduce your supply votage. Maybe drop the supply through a diode. The supply would now be 4.3 volts.

 

[crutschow]

You could reduce your supply votage. Maybe drop the supply through a diode. The supply would now be 4.3 volts.

If that gives any problem with operating the circuit then you could instead put a diode in series with each digit's ground connection for the same effect.

 

[Mosaic]

Since that kit is fed by an MCU signal...you should consider multiplexing the 595's.....it will cut your part count by nearly 3/4 and give u s'ware control over the current / brightness