inflating and deflating a air bladder continuously?
I am interested in a project however what i need to do is to inflate and deflate a air bladder repeatedly on a continuous cycle (so inflation and the deflation). This making me think of a piston style pump hooked up to a motor which I can control through use of a variable resistor. Is there any piston style pump i can use or is there a alternative which would be better. (I do have a budget of around 70usd)