Powering 18-servo hexapod w/ Maestro 24

Support Servo controllers and servos
1

Hi Folks,

I’m working on the design for an 18-servo hexapod. I’ve built one leg to test my gait control and inverse kinematics code; that leg uses three digital servos driven by a Mini Maestro 24-channel controller. So far, everything’s gone well, but I have concerns about powering the final 18-servo hex.

Right now, I’m using a Pololu 5V/9A buck converter (connected to 3-cell LiPO battery packs) to provide servo power to the Maestro, and it works fine with three servos. I’m worried, though, that 9A will not be enough to drive all 18 servos (plus maybe two more for a tilt/pan mount), particularly under load. The digital servos draw 500mA when running under no load, and about three times that much when stalled.

One way to go, I guess, would be to create modular systems, e.g., a 12-channel Maestro w/ dedicated power converter for each of two groups of three legs. I’d rather not do that, so I’m wondering what options there might be for sticking with a single 24-channel servo controller. Has anyone ever connected the buck converters in parallel? If so, what sort of external circuitry is required?

Not all 18 servos will be moving at once, so maybe 9A turns out to be enough, if only barely. But even in that case, I’d like my design to have a bit of headroom.

I’d appreciate any thoughts you have.

Thanks!

2

Hello.

It sounds like you plan to break the 18 servos into smaller groups with a voltage regulator powering each group of servos. You can do this on a single 24 channel Maestro by breaking up the servo rail into separate power banks. Brandon explains in this forum post how to do this. Although I have not personally tried it, I do not see any reason that powering each group of servos from a separate voltage regulator would not work, and you should not need any additional circuity.

- Grant

3

Thanks, Grant, for the quick and helpful reply. Cutting the +V trace is a good idea; I hadn’t thought of that. Looking at the bottom of my Maestro 24, there’s not much room to make the cut. What’s the best way to do it?

I also didn’t consider just powering the servos directly and tying in the power supply grounds to the Maestro – duh! The wiring will be a bit messier (which is a consideration with so many servos), but it should work in a pinch.

Thanks again!

4

The traces can be cut by a sharp object, like a hobby knife. When cutting the trace, you should be careful to only cut the servo voltage rail and make sure to not accidentally cut the ground trace or knock off components.

- Grant

5

Roger – thanks again!