Designing the Power System of Your Robot

Every electrically powered robot needs a battery and a power system for autonomous operation. This chapter will teach you how to select the right battery, how to safely integrate it into your robot, and how to generate different voltages for all the components of a robot. We will also cover how to safely handle high currents and integrate safety measures to prevent power-related damage to your robot. This chapter is structured as follows:

• Fundamentals of electrical power systems
• Understanding the power demands of your robot
• Safety considerations and hazards when working with high-power batteries
• Components and design of a robot power system

Technical requirements

This chapter is full of information and will enable you to select the right components for the power system of your robot. However, the provided information is broadly applicable and does not only pertain to a specific example, and there is no specific hardware you need in order to get the most out of this chapter.

Fundamentals of electrical power systems

Most DIY robots that you will build use electricity to power all their components. It is possible (but very unusual) to use other sources of energy for the actuators of your robot, such as compressed air, rocket motors, or combustion engines. However, for most DIY robotics projects, electric actuators are the most practical and cost-effective choice.

Since our robots run on electrical power, it is important to equip them with a reliable and appropriately designed power system to make them run. The power system’s main job is to distribute the power from the batteries to the different components of your robot. The power system can be quite simple or quite complex, depending on the robot. It usually contains at least one voltage regulator or DC/DC converter to provide a stable logic voltage, but it might also contain sensors for monitoring voltages, currents, and power consumption, and safety mechanisms to prevent damage to the batteries...

Understanding the power demands of your robot

Most commonly, an Arduino robot requires electric power on at least two voltage levels:

• Low voltage (LV) or logic voltage of 5V or 3.3V (or both) for the electronic components
• High voltage (HV) or motor voltage for the electric motors—for example, 12V

Depending on the specific components of your robot, other intermediate voltage levels might also be required. Some sensors or analog circuits need an additional input voltage that is lower or higher than their logic voltage. Before you start designing the power system, you need to understand what voltage levels are required for your robot and how much current your robot will draw from them. As a rule of thumb, the current required at the low-voltage level is typically small, and the current drawn at the motor voltage level is orders of magnitude higher. For example, the ATMega microcontroller inside your Arduino Uno consumes around 0.1 W (or 100 milliwatts) of power...

Safety considerations and hazards when working with high-power batteries

Since modern batteries can unleash a lot of power, the power distribution system is one of the components of a robot that can be dangerous for the robot itself, but also for the environment, and even for you. Let us spend a little bit of time looking at the risks that come from using electrical power and how we can mitigate them.

Electric shock

If you touch two conductors and too much electrical current flows through your body, pain and lasting damage can occur. The best way to prevent this is to limit the voltages of your robot power system to safe levels. For DC power systems such as the ones in Arduino robots, the upper limit of what is considered safe to touch is 36V. If all the voltages in your robot are below 36V, it is safe to touch any part of your robot without the risk of serious eclectic shock (it might still tingle, especially when your fingers are not dry).

Arcing

Even lower voltages can...

Components and design of a robot power system

Now that we have a good understanding of the various considerations that go into designing a power system, let us look more closely at the individual components that may go into it. We will organize the components into three categories: the core components that are used to distribute the power, components that can be used to monitor the power system’s status, and components to control the power system and ensure its safe operation.

Power distribution

Distributing the power from the batteries to the components that need it is the fundamental function of the power systems. Everything else is optional.

Batteries

The batteries are what power your robot. The two most important parameters of a battery are its nominal voltage and its capacity.

During normal operation, the voltage of a battery will vary: it will be a little higher than nominal when it is fully charged, and lower when it is empty. It also changes depending...

Summary

In this chapter, we discussed the importance of careful power system design for your Arduino robots, especially when using powerful rechargeable lithium batteries that have the potential to cause substantial damage by virtue of their immense power density and current capacity. We got to know the key components of a robot’s power system that can serve you well even in advanced and power-hungry robots. Not all Arduino robots need an elaborate power system, and the smallest ones can even run off USB power. But whenever you use powerful batteries in your robot designs, it is a good idea to spend some thought on a power system that makes your robot safe and reliable.

In the next chapter, we will learn how to give your robot the ability to express itself with LEDs, displays, and sound.

Further readings

There is much more that we could discuss about a robot’s power system and electrical power in general. The following resources can help you get started to dive deeper into those topics:

• A blog post about different types of voltage regulators: https://www.digikey.com/en/maker/blogs/2020/what-is-a-voltage-regulator
• An article on Ohm’s law, a fundamental relation in electronics, on Wikipedia: https://en.wikipedia.org/wiki/Ohm%27s_law
• A comprehensive list of battery types with links to their specific articles on Wikipedia: https://en.wikipedia.org/wiki/List_of_battery_types
• A brief safety guide for working with different types of batteries: https://iaeimagazine.org/electrical-fundamentals/a-safety-guide-for-working-with-batteries/
• Lessons learned from the Jet Propulsion Laboratory (JPL) robot battery fire in 2015: https://llis.nasa.gov/lesson/23701