can i use 2 555 isntead of a 556? i know i have to connect the power pins from the 2 555's but apart from that is there any difference?

 

I always use 555s instead of 556s. This is only as I have a box full of 555s & i'm too lazy to order some 556s.

The 556 will run warmer than the 555, as each timer can sink/source 200mA, despite the greater surface area.

Otherwise, no operational differences that I am aware of.

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thanks. i thought that there was no problem. but i just needed someone to confirm my thoughts.

 

If you do have trouble, add a capacitor across the power supply pins. I've run into trouble with lousy power supplies.