The Power Distribution Board (PDB) is often overlooked as an outdated component in drone building. While it used to be an essential component, technology has advanced significantly in recent years. Today, PDBs not only distributes power from the battery to the drone’s electronic speed controllers (ESCs), but also to other peripherals such as FPV cameras and transmitters, and even the quadcopter’s flight controller.
Some modern flight controllers have built-in PDBs, but they can be limited by space and may not effectively filter voltage spikes caused by heavy current draws. Despite this, PDBs are still preferred by some builders as they can reduce stress on the flight controller and provide better electrical noise filtering. Additionally, it is often cheaper to replace a single ESC than a 4-in-1 ESC unit.
PDB Sizes & components
Power Distribution Boards (PDBs) come in two standard sizes: 20x20mm and 30.5×30.5mm. The larger 30.5×30.5mm size is more commonly used, as it can handle higher currents and heat generated by larger quadcopters.
High-end PDBs use boards with higher copper content to handle these high currents and heat. A typical PDB includes tabs for soldering the battery and 4 or 6 sets of pads for soldering the Electronic Speed Controllers (ESCs).
The PDB also includes tabs marked as S1, S2, S3, and S4, which indicate the signal tabs for motors 1, 2, 3, and 4 respectively. This is how the Flight Controller communicates with the ESCs and controls the motors. Some PDBs may also include a current sensor and voltage regulators to power the FPV cameras and VTx.
Flight Controllers (FCs) have evolved significantly in recent years, with the integration of voltage regulators being one of the most notable advancements. The inclusion of these voltage regulators allows FCs to provide power to other peripherals and removes the need for additional components.
However, the quality of these voltage regulators on PDBs is often higher than those found on Flight Controllers (FCs). Due to the compact size of modern FCs and the addition of advanced features, manufacturers may cut corners on the quality of the voltage regulators.
The PDBs use switching voltage regulators, which are more efficient and produce less heat compared to the linear voltage regulators found on FCs. This makes PDBs a more reliable and efficient choice for providing power to other peripherals.
Voltage & Current
The size of a PDB (power distribution board) can vary, ranging from smaller 3-inch quads to larger 10-inch X-Class quads. As the size of the quadcopter increases, so do the power requirements. Ultimately, the size of the quadcopter will determine the appropriate type of PDB to use. For smaller quads, a small 20×20 PDB or an integrated PDB with a flight controller will suffice. As the size of the quadcopter increases, a medium-power PDB is necessary for quads between 5 to 7 inches, and anything larger than 7 inches will require an X-class PDB.
I previously mentioned that PDBs have evolved over the past decade. They are no longer just devices for distributing power but have become multi-functional. Manufacturers recognized the potential of the unused space on PDB boards and, with an eye toward innovation and potential sales, began creating multipurpose PDBs. Matek was the first company to design these types of PDBs.
PDB with VTx
A popular PDB combination is the PDB and VTx combo. Matek was the first company to introduce this concept with the launch of the FCHUB-VTX. This product was a game-changer in the drone community and it continues to be popular today. It eliminates the need for an extra stack in cramped frames and performs the tasks of two separate components. The VTx on the FCHUB-VTX is also noteworthy, as it is one of the highest-performing VTx on the market. It offers 40 channels, a switchable video power supply at 25, 200, and 500mW, and a 184A current sensor. Additionally, when using a Matek F405 FC or similar, the PDB and FC can be connected with a 30-pin ribbon cable, reducing the clutter of cables between the FC and PDB.
Power Distribution Board with FC
The integration of a Flight Controller (FC) with a Power Distribution Board (PDB) is a significant advancement in the drone industry. The compact design of the FC-integrated PDB combo is truly impressive. One of the first companies to introduce this concept was Matek with the F405 CTR.
Despite the combination of two boards into one, the manufacturers did not make any sacrifices in terms of features and performance. The Flight Controller includes all the standard components such as barometers for measuring atmospheric pressure and flash storage for flight data. Additionally, the PDB also maintains a high level of performance, with a current carrying capacity of over 30A.
Current sensors are an essential feature in today’s drone building. They measure the amount of current that the quadcopter draws, which is crucial for ensuring the proper functioning of the PDB and the batteries. This is particularly important for 22xx motors, which can draw more than 30A per motor. Many manufacturers don’t provide accurate measurements of current draws, so current sensing is necessary to monitor the motors and prevent overloading the PDB or stressing the batteries.
4 in-1 ESC
A 4-in-1 ESC, as the name suggests, is a single board that includes four ESCs (Electronic Speed Controllers). They are highly compact, lightweight, and greatly reduce the complexity of wiring. Due to the integration of multiple ESCs on a single board, the need for using a separate PDB is eliminated.
4-in-1 ESCs tend to be more cost-effective compared to using individual ESCs. For example, the HolyBro Tekko 65A metal 4-in-1 ESC costs $90, while four individual HolyBro Tekko 65A metal ESCs would cost $124. Both options have similar specifications in terms of voltage and current support, but the 4-in-1 ESC offers a 25% cost savings.
In addition to cost-effectiveness, 4-in-1 ESCs are also becoming more reliable. However, one downside to using a 4-in-1 ESC is that if one of the ESCs fails, the entire board becomes useless, even if the other three ESCs are still working properly.
For further reading about ESC, read our post on how to choose ESC for your quadcopter
The necessity of a Power Distribution Board (PDB) for quadcopters is a topic of debate. Some argue that advancements in the drone industry have made PDBs obsolete. However, I believe that PDBs are a classic and fundamental component of building a quadcopter. They play a crucial role in distributing power evenly throughout the circuit, which is an important task that cannot be replaced.
I also believe that using a standalone PDB with an integrated VTx (Video Transmitter) is a better option than using separate PDB and VTx components. The high quality and efficient voltage regulators of a standalone PDB justify the cost.