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.
http://server6.uploadit.org/files/battlestar-motor.jpg


Thank you very much

Hi there battlestar, and welcome to ECN.

1. Assuming that we're talking about relatively low-voltages, the typical way that such a task is carried in modern electronics is by using an operational amplifier (frequently called an op-amp). These come in integrated circuit form, and require just the addition of a few components to set up the correct conditions for whatever task is required.

A simple adder circuit is fairly easy to achieve, and in fact was one of the earliest applications of the op-amp in analog computers.

Have a look here for some information about the op-amp and some of its uses:
http://www.phys.ualberta.ca/~gingrich/phys395/notes/node99.html

Check the page Current Summing Amplifier for your specific task.

2. Assuming we're talking about a small DC motor, a bridge circuit can be employed for this task. The exact arrangement will depend very much on the signal levels and power required for the motor, but you might like to explore some of the links here for ideas:
http://www.epanorama.net/links/motorcontrol.html



[This message has been edited by pauluk (edited 02-20-2004).]

Battlestar;

Paul has given very good information, and will be of great assistance for the applications you refer to.

I was wondering a few things.
<OL TYPE=1>

[*]Any AC inputs, or AC coupled to DC,


[*]What polarity will the three voltage sources be at any given time,


[*]Will the Motor's input polarity ever change,


[*]What type / level of components are to be used for monitoring / control.
</OL>

For #2 above, will the inputs be "+" or "-" (in respect to ground)? Will any input be the opposite of another input?

Per #3, will the power supply for the Motor be a 3 wire DC type (+ / GND / -), or will the Motor's input be sampled from another source?

Per #4, what level of "Tech" do you need?
May be simple - like with all passive components,
May be more complex - like with Opamps and/or discrete components,
May be really complex - like with interfacing capabilities.

Sounds like fun!

Scott35