How to choose a battery if we know the voltages of motors and microcontrollers

[MBJ]

Different electronics require different voltages. For example a microcontroller will require 5V, and motors 12V then what should be the voltage of the batteries?
Thanks in advance

[mklrobo]

  Hello!
I would offer some info that I posted off another related thread;
The ampere/hour of the battery will be of interest to you, in relation
to the amount of work desired, and the motor that is consuming the amperage.
Batteries Plus+ may have a good direction of what you would require.
I would base the load on the servos, doing what you want them to do for
a specified amount of time. (not forever) OR, the opposite, acquire the
amps of the servos moving, and convert that to ampere hours. The ampere
hours will determine how long you can run the servos.
The process will help you navigate the limitations of the batteries
that are avaliable, VS. time worked.
Basically, you are adding up the amperage of the load(s), and determining how
long you want to run them continously. Since this is a worst case scenario,
reasonable factors must be taken into consideration.
Voltage of the batteries --   I would use a larger battery with 15 - 20 volts,
then use voltage regulators to give the exact voltages that certain devices need. This helps
in future expansion, power regulation, and life of the project. More time consuming, but
worth the headache?   Keep me posted....Good Luck!   

[bdeuell]

I would recommend using a battery back that matches the voltage of the motors. motors typically draw large currents so regulating their power requires a large power supply which is both costly and space consuming. Space and weight are usually scarce and in high demand for any mobile robotics system.

for the control voltage (which is typically less than the motor voltage, 3.3 and 5 VDC are common) there are a couple options:

you can add a second battery which has an advantage of isolating the sensitive control electronics from the very noisy motors. of course you would tie the grounds together.

the other option is to regulate the voltage down.There are many different designs to do this but a linear regulator is probably the simplest. However a linear regulator is rather inefficient (it will essentially burn up the voltage you are dropping as heat so it is not ideal for any significant current).  with a regulated voltage design you may need (and probably recommended as good practice) to a filter caps and other electrical elements to prevent noise issues. Unfortunately i am not an electronics expert so i cant provide more detailed standard design practices, perhaps one of the other forum members can answer this part better.

[MBJ]

Thank you Mr. mklrobo and Mr. bdeuell Your answers are very helpful. Thanks again