Regarding Scrolling Display

[tiwari.sachin]

Hello Everyone

I am planning to design a scrolling display. i intend to use 74HC595 for columns and ULN2803 for driving rows.

I got a circuit from this forum which is attached along with this message. Its a circuit provided by blueroomelectronics.

I initially want to use 8, 5X7 display units and later on connect 2 such boards in series to form a 16display units in all.

I am very much confused with the overall current variations that can effect the circuit. The design aspect of it etc. I have thought of using a 100 ohm resistor instead of 150ohm as shown in the attachment.

Kindly suggest me if i am going on the right path. I dont want to blow my displays as i just have 4 of them with me right now.

Kindly suggest me a appropriate circuit or let me know if the attachment works fine.

 

[dougy83]

I am very much confused with the overall current variations that can effect the circuit. The design aspect of it etc. I have thought of using a 100 ohm resistor instead of 150ohm as shown in the attachment.

Probably not a good idea as this would increase the current that the '595 has to provide. They already have potential to be run outside of the specified 'absolute maximum limits' when certain LEDs are on.