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What Supply Voltage Should I Choose?
Given the wide range of motors available, choosing the right supply voltage for your mobile robot may not be an easy task. To make this decision easier, the supply voltage can either be chosen initially or after a motor has been chosen.
Selecting a supply voltage before choosing a motor has the great advantage of allowing you to narrow the search for the proper motor quickly and effectively. Choosing a lower motor voltage does not automatically mean the list of motors available to you will be low power. However, a high motor voltage (36V, 48V, 60V) tend to be reserved for large DC motors. The second method is to first select the ideal motor and design your robot's electronics system around the indicated nominal voltage. Both approaches have their advantages and disadvantages and it is up to you to choose which you prefer.
The DC Motor Calculator uses a standard list of voltages based on the voltage supplied by one standard non-rechargeable cell: 1.5V. This means the standard voltages are 3V (few motors operate with less than 2V), 6V, 9V, 12V, 24V, 36V, 48V and 60V. Robots using servo motors tend to operate at 4.8V, 6V and 7.2V. Small robot motors are often rated at less than 12V, medium sized motors tend to use 12 to 36V and large robot motors most often use 24V and higher (see useful liks below for information about robot sizes).
Voltage dividers allow you to power electromechanical devices at different voltages. Voltage dividers are purely electrical devices with no programming involved. If you do not want to use voltage dividers, most electronics operate at 5 to 9V, so choosing either 6 or 9V as your robot's supply voltage is the best choice (never assume an electronic device operates at 6 or 9V: you always need to read the supply voltage specifications for each electronic component). The other option is to use two different power supplies: one for the motors and another (smaller one) for the electronics.
Should you wish to operate your robot at 9V, you can often still choose a 12V motor, though you must keep in mind the rpm will be less that that listed (estimated as a fraction of the nominal value) and the motor efficiency will be slightly reduced.
Useful Links
Tips
How do I decide what mass my mobile robot should be (wheels or tracks)?
How do I interpret Motor Specifications?
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