Adding absolute value of a voltage

[electroniks]

Hi everyone,
I have two motors that run in arbitrary directions, if I run them in series and one of them is going the opposite way then the net voltage will be decreased. Is there and electrical component or circuit that adds the absolute value of voltages together? I don't know the name... does it even have a name?

Thanks.

 

[alec_t]

What do you mean by 'net voltage'? If a supply voltage V is applied to two items in series, the sum of the respective voltages across each item will be V.

 

[electroniks]

Sorry, I should have clarified better.

Let's say the first motor is running at 50rpm clockwise and generating 5v, the other motor is running 20rpm counterclockwise and generating -2v. If the voltages are added together I get 3v. I want a circuit or a chip or whatever that flips the negative voltage so the added would be 7v. Is there such a system?
The motors run in arbitrary ways so I don't know which one is generating +v or -v before hand and may change at any time. I want the output to always be the sum of absolute value of two voltages.

 

[alec_t]

The motors run in arbitrary ways

How can they do that if they are simply in series with a fixed supply? Is there some switching arrangement you haven't told us about?
Between which points are you measuring voltages?
A schematic of your setup might clarify things for us.

 

[electroniks]

The motors are wired as generators... so they turn either CW or CCW and they create a voltage. If they are wired in series I want their output voltages to be the absolute value of two voltages combined added. They don't necessarily have to be connected together, there could be device or circuit in between. I like to know if there is a way to do it and how?
So... input: 2 motor generators running in arbitrary ways generating either +v or -v, output: vout=|v1|+|v2|

 

[Grossel]

Hi. What kind of motor? What voltage level?

I might have two possible solutions for you, but you must be more specific. I won't post a solution based on a guess, and just for you to turn the actual problem as something else.

 

[Nigel Goodwin]

As often, the question is extremely vague - but how about putting a bridge rectifier on the output of each motor and series connect the outputs from the bridges (these will 'steer' the voltages the correct way).

 

[electroniks]

This is only an idea... my idea is having two generators that spin in different directions and each outputting a voltage. I want all voltages to be added.
Rectifier on the output of each one might work... But doesn't he rectifier only change from AC to DC? not the polarity?

 

[electroniks]

Ok, I think full-bridge rectifiers may work on the output of each motor.
What if the motors were switched to DC generators of some kind? How would you do the same?

 

[Grossel]

One important thing OP need to mention before it is any worth going further, VOLTAGE LEVEL (seldom I need to use capital letters).

There is a huge difference between - bicycle dynamos that is supposed to deliver some effect, and - DC motors that you're trying to measure speed from (delivers no effect).

 

[audioguru]

When the rotating direction of a DC generator is changed then the polarity of its output voltage is also changed. A full wave rectifier will keep the output polarity always the same.
Rectifiers cause a voltage loss. A full wave bridge rectifier causes 1.4V to 2.0V of loss. There is a way to use Mosfets as a low voltage loss rectifier.

 

[dr pepper]

If one of the motors allways goes the same direction that one doesnt need a rectifier.
If both motors never reverse directions you dont need any rectifiers, just series them up as if they were batteries.