need help on circuits

Hi, I'm pretty new to the world of electronics, and I'm attempting an small project that I need some help upon.
1. If there are three wires carrying input voltages, how can i make it so that the output voltage equal to the sum of the three input voltages? Please see image below.

2. If there are two wires carrying two input voltages, how can I make it so that the motor turns one way when Vx>Vy then turn the other way when Vy>Vx? Vx and Vy are voltage outputs from a colorimeter. Please see image below. By "V" i mean voltage.




**broken link removed**

Thank you very much.

What kinds of voltages are we talking about here? For small voltages, you would typically use a voltage summer to get the sum of the three voltages.

As for reversing a DC motor, you would use either an H-Bridge or relays. What kind of motor are you using? As for detecting which input voltage is higher, you can use a comparator.

Here are two circuits for you to try.

Thanx vm, i'll try it out

Oops, I almost forgot. The summing amp in the first circuit inverts the signal. That is, Vo=-(V1+V2+V3).