Possibly stupid questions from the start here robot

Community General Discussions
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1

A few things that have bothered me.

From the start Here robot

http://www.youtube.com/watch?feature=player_embedded&v=z-MgYD-bQSM.

At 1:18 he took out the darlington chip and replaced it with I think a servo control chip. I still have the darlington and I'm wondering could I still control the servos with the darlington? What does it do? 

 

And on a broader question how do I know when to take out chip like the darlington or keep them on?

2

Picaxe boards

The second chip is a resistor array.  This is to current limit the signal to the servo.  The darlington is used as an ampilfier, greatly increasing the current and voltage (if supplied seperatly) available, compared to that which the Picaxe can supply netively from it’s output pins.