r/arduino • u/AffectionateFix442 • 20h ago

Title: PDB design for mid-size servos (TowerPro MG996R grade)

Hello everyone,

I am planning to design a generic Power Distribution Board (PDB) with 12 × 3-pin 2.54 mm male headers, where the servos can be plugged directly into the PCB.

The main purpose of the PCB is to properly distribute power/current to all the servos. The PWM signals will be provided from an external controller, so the PCB will mainly handle power distribution.

I’m using KiCad for the design.

I’m fairly new to PCB design, so I’d really appreciate any suggestions, especially regarding high-current power distribution, copper pours/traces, connectors, capacitors, grounding, and current handling.

Also, if you know any good resources, tutorials, or example PCB designs to learn the basics of power distribution on a PCB/PDB, especially for higher-current applications, please share them.

For inspiration, I’m also studying the Stanford Pupper PDB design.

Any suggestions or feedback would be really helpful. Thanks!

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u/n_sh_44 17h ago

Budget current from stall, not running current. An MG996R can pull around 2.5 A stalled, so 12 of them moving under load can briefly ask for 15-30 A, even though the average is much lower. That number sets everything else: use a proper input connector (XT60 or screw terminals rated for it, not a barrel jack), and run the 6V and GND as wide pours on both layers, stitched with plenty of vias, instead of thin traces. 2 oz copper helps if your fab offers it cheaply. Put one big bulk electrolytic (1000 uF or more, rated well above your supply voltage) near the input, plus a smaller cap (around 100 uF) near each group of 3-4 headers to absorb the start-up spikes that otherwise reset the controller. Also bring a GND pin out to the external controller so the PWM signals share a reference, but keep the servo return current from flowing through the controller's ground wire. One more thing: 2.54 mm header pins are only rated for about 3 A each, which is fine per servo but means you shouldn't use headers anywhere in the main power path.

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u/FedUp233 16h ago

If it was me I’d also include some fuses. At least one master fuse, maybe a slow blow rated so that if every thing stalks it will blows after a bit. I might also add regular fuses in the supply to each servo just to handle cases like something g in the wiring getting shorted or something.

It might be interesting to provide so e dividers and a set digital outputs to tell if the fuse to an individual servo blew as well.

If you are using two sider, I’d try to keep power on one side and gnd on the other as much as possible to have continuous large ground and power planes. If you need to break these up to get the signal lines through be sure to use plenty of vias where things jump sides.