The power supply of a project is the beating heart that enables our electronic components to work as desired. Even for experienced makers, choosing a suitable power supply is an important process that must be done carefully.
Today, we will take you through a complete guide of power supplies for projects. We’ll cover their different types, power ratings, connectors, and most importantly, how to choose one.
Introduction to Power Supplies
Electronic products are all fundamentally made with circuits that contain various components. When electricity flows across these components as directed by the internal circuit, the device comes to life to provide function to the user.
So, when we talk about power supplies, we are looking for a component that can supply the electricity to the circuits in our projects.
If you are new to electricity and circuits, we highly recommend that you read some of our introductory articles for better understanding.
- What happens in an electric circuit: Voltage vs Current
- Electronics Circuit: Voltage Dividers
- Basic Electronics: Alternating Current (AC) vs Direct Current (DC)
- Introduction to Electronic Component: What is Capacitor?
- Integrated Circuits (ICs): Overview, Applications and Projects
Power Supply Requirements
The most important question to ask when selecting a power supply is: How much power do we need?
To answer this question, we have to look at both voltage and current.
Voltage – The voltage of our power supply creates a ‘pressure’ to push our current through the circuit. If we do not have sufficient voltage, a current will not be able to flow. This means that our appliance will not receive electricity and cannot function.
If you are using a development board such as an Arduino, they often have voltage ratings of 3.3V or 5V. Most of them are also often equipped with voltage regulators to convert larger power supply voltages to the appropriate value.
Current – The current is essentially the fuel that powers our electronics. The amount of current required will depend on what the components in our circuits need to run properly. For example, a motor required to operate at higher torques will need a greater current supplied to function as intended. Without sufficient current, our components may not function as expected or intended.
Voltage and current are inseparable. In our projects, we must take care to meet both requirements so that the electrical components in our circuits can function properly.
For best results and safe practice, check the datasheet for the components that you are using to see what voltages and currents are recommended by their manufacturers.
Measuring Power Consumption
It is possible to estimate the voltage and current required by your circuit by using the data of the individual components. However, that method is not accurate and may be difficult for beginners.
A more straightforward way to measure the voltage and current required by your circuit is to use a variable power supply or to simply attach a multimeter to the circuit while it is running.
A multimeter is a device that can conveniently measure and display the voltage and current when we attach it to our circuit. Read more at our Introduction to Measuring Instrument: What is a Multimeter?.
For advanced users, you may sometimes require more information than a multimeter can provide. In that case, an oscilloscope is your best bet. You can also read about the oscilloscope and how to use it in our article here: What is an Oscilloscope? – Functions and Tutorial.
Different Types of Power Supplies
There are many different kinds of power supplies for a variety of uses. These include variable power supplies, AC to DC wall adapters, and batteries.
Ultimately, the power supply that you want to choose is one that will fit with your project’s requirements.
Variable DC Power Supply
Variable DC power supplies are a flexible and important tool when it comes to testing our electronic devices or selecting a power supply. The variable power supply can allow you to set different voltages and currents to power up your device.
Although you can definitely power your project with variable DC power supplies, they tend to be used more for prototyping. Once the power requirements of the circuit are determined, a smaller, cheaper power supply will be used instead.
Recommended: ZKETECH EBD-A20H Variable DC Power Supply
If you are in the market for a variable DC power supply, we recommend the ZKETECH EBD-A20H. Supporting up to 30V/20A/200W, the ZKETECH EBD-A20H even comes with its custom EB Software for data visualisation and recording.
Many development boards can use a single USB connection for both power and data transmission. In that case, you will simply need a USB cable to wire and power your device from any USB port.
For example, the Seeeduino Xiao is equipped with a USB Type-C port which can be used for power and uploading code. You may use a USB C to C cable or a USB C to A cable, depending on what ports are available on your computer.
AC to DC Wall Power Supply
After we have tested and understood the power requirements of our circuit, we will often switch to an AC to DC wall power supply. AC to DC wall power supplies are lightweight and convenient solutions that can even be reused for any compatible device.
When choosing a wall power adapter, be sure to check the device compatibility. Some adapters will come with a specific USB form factor or barrel jack, while others allow you to use interchangeable USB A cables.
Note: Wall adapters typically produce fixed voltage and current outputs. If your power requirements change later on, you may have to get another wall adapter!
Here are some recommended AC to DC wall adapters to get you started:
- Wall Adapter Power Supply – 5VDC 3A Type-C
- Wall Adapter Power Supply – 6.5VDC 2A
- American Standard USB Wall Power Supply 5VDC 2.5A – FCC/UL Certified
- European Standard USB Wall Power Supply 5VDC 2.5A – CE Certified
If we want to make our project portable, exploring batteries will be inevitable. Batteries store chemical energy, which is then converted to electricity through chemical reactions when connected in a circuit.
There are many different kinds of batteries, varying also in power rating, rechargeability, charge retention, and required maintenance.
If you have already decided to use batteries in your project, you must definitely check out our detailed Guide to Batteries for Embedded Devices.
Here are also some battery options that you can explore:
- Battery Kit – 3.7V 520mAh
- Lithium Ion polymer Battery pack – 3A
- Lithium Ion polymer Battery – 1A
- Polymer Lithium Ion Battery – 2200mAh 11.1V
Getting The Right Power: Power Converters
It isn’t uncommon to find that the existing power supply options can’t fit your needs. When this happens, you can simply use a more powerful power supply, together with a power converter to step the voltage down to the desired value.
I’ve listed some of the power converter recommendations below. Be sure to check the operational voltage ranges offered by each power converter, so that you can get one that works with your power supply and for your project.
- Adjustable DC&DC Power Converter (1.25V – 35V&3A)
- Adjustable DC&DC Power Converter (1V – 12V&1.5A)
- CPT-C5 power converter 12V&24V switch to 5V
In some cases, you can also use a booster to step up the voltage supplied. One example is the Lipo Rider Plus, which can output up to 5V/2.4A from a 3.7V battery.
Understanding Power Supply Connectors
When it comes to connectors, there are many that you can use to hook up your power supply.
Banana & Alligator Cables
Variable DC power supplies typically use banana or alligator cables like those shown below.
Alligator cables can be easily clipped onto the circuit’s wires to form a connection. Pick up a set of alligator cables here.
Breadboards & Jumper Wires
Breadboards are a great way for beginners to learn to build circuits. With strips of conductive material underneath, jumper cables can be inserted into the holes to form circuits to your power supply without soldering.
However, circuits on breadboards tend to be more messy and flimsy, so you won’t often see them in final designs. Instead, PCBs, or printed circuit boards, are more widely used. PCBs are basically electrical circuits shrinked into a compact form factor.
Once you have finalised your circuit design, you can conveniently order your very own PCB with Seeed Fusion.
Barrel jacks or barrel connectors are typically found on finished circuit boards. While they may differ in size, they are commonly offered as a convenient and reliable way to power various devices. With the right adapter, you can power a device with a barrel jack via USB or a wall adapter.
Most batteries are designed to fit within a case, which will then have wires to connect to your circuit. These wires are typically simple positive and negative connections to the battery. However, battery cases may come with other connectors like a barrel jack.
Notably, lithium polymer batteries commonly use a JST connector, which is a convenient way to hook power up with compatible boards.
Here are some battery cases offered by Seeed:
- AA Battery Holder Case – 2 Slot
- 18650 Battery Holder Case – 2 Slot with Switch
- Lithium Ion polymer Battery pack – 3A with JST Connector
Testing Your Power Source
While we may have chosen an appropriate power source in theory, it is always important to test the performance of your circuit or device over a period of time. This is because under different usage loads, you may find that the power supplied is insufficient to maintain the device’s function.
There are also other factors to consider. For example, if the voltage of your power supply falls too low, your microcontroller may reset and stop functioning. If you are using batteries, be mindful also of the operating temperature, since it can drastically affect battery life and performance.
If you add or remove components or rewire your circuit, don’t forget that power requirements may also change. It is worthwhile to be careful with your power supply, since your project can be damaged if a poor choice of power supply is used.
Other Factors to Consider
Before finally deciding on a power supply for your project, here are some questions you may wish to ask yourself:
Is form factor a consideration for my project’s power supply?
If yes, incorporate considerations for the power supply in the project design as early as possible. A bulky power supply hardly makes for a user-friendly portable device!
Will I need more power in the future for more components?
If yes, get a more powerful power supply and supplement it with a step-down converter. This will save you a lot of trouble if you require more power in the future.
Do I need a Power Supply IC for my Project?
Power supply ICs are regulators to transform unregulated input to a steady output voltage. Power supply ICs can be critical to electrical components which are sensitive to input voltages, such as microprocessors and memory at high speeds.
If your electrical components require specific input voltages to function correctly, you will have to consider a power supply IC. Visit this tutorial by maxim integrated for more information.
Summary & More Resources
I hope you’ve learned a thing or two about how to power your projects today! Choosing a suitable power supply is ultimately trial and error, depending heavily on what your project needs.
Fortunately, if you are working with one of the popular development boards, you’ll have an extensive pool of documentation to rely on. The Raspberry Pi 4 even has an official power supply, so you’ll definitely be safe going with it.
To read more about power supplies and power requirements, feel free to visit the following:
- What happens in an electric circuit: Voltage vs Current
- Guide to Batteries for Embedded Devices
- What Is Brown Out Reset in Microcontrollers? How to Prevent False Power-Downs
For an advanced tutorial on tuning power supplies for your project, visit this article by Evaluation Engineering.