ULN2803A & 74HC595 Wiring

Albatroon:
And U are welcome in this board design post :slight_smile: http://forum.arduino.cc/index.php?topic=601144.0

Long time posters tend to avoid helping cross-posters, as it creates double answers and wastes time.
Leo..

Wawa:
Not all eight channels 'on' at the same time I hope.
The ULN2803 can't have more than two channels 'on' at that current.
Leo..

Yes it can - but the limit is thermal, you get about 1/4W per channel at 0.25A, typically, so
I suspect 4 channels is probably going to be OK. The output devices are rated at about 1.1V
Vsat for those current levels, better than many darlington devices.

@Albatroon, why did you start another thread?

I thought the new post not related to this one.
This post for an issue with a design.
The other one is a new design…
Sorry for any inconveniences

MarkT:
Yes it can - but the limit is thermal, you get about 1/4W per channel at 0.25A, typically, so
I suspect 4 channels is probably going to be OK.

Agreed. Four is probably just ok if you don't mind a stinking hot chip.
How hot also depends ofgourse on board layout and airflow.
Bad practice to design for parts that can get too hot to touch (65C+).
Leo..

Thread locked. Do not cross-post again.