Projects

Servo Power

The Handy Breakout Board

Andy Clark & Daniel Koch

Issue 26, September 2019

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This tiny project allows you to power multiple servos or sensors with only one set of connections to the power pins on your Arduino or Raspberry Pi.

BUILD TIME: 1 Hour
DIFFICULTY RATING: BEGINNER

When approaching projects which involve multiple connected modules, sensors, servos, or other input and output devices, many makers find that they fast fun out of pins to power them. Most boards have at most three connections for each of +5V and GND, yet almost every item that we connect requires its own power connections.

This problem exists on larger projects, but is most annoying on tiny projects using an ATtiny or ESP-style microcontroller where you don't have a prototyping board as part of the build. There are large breakout boards available with an UNO shield size footprint, but that might be much more than you need too.

This breakout board solves the problem for many cases. It contains one row of header pins to connect to up to 5 microcontroller GPIO (which is passed to the three-pin header data pins).

Five sets of three pins for servo or sensor connections, a power indicator, and screw terminals for additional power. Its layout accepts the headers for standard servos, as well as many sensors and add-ons like relay boards, MOSFET boards, and the like.

CREATING THE MODULE

This build is designed to save you time and hassle wiring up multiple servos or sensors to a simple board. But we don't want to make the build itself difficult either!

While we have included PCB files you can use to mill or order your own PCB, it's important to have a version which can be constructed using off the shelf parts also.

The PCB version is compact and robust.

The components list for both versions is identical, with the exception of PCB vs solderable breadboard. Given the relative simplicity of this circuit, it's easy enough to create using solderable breadboard. PCBs will always be at least marginally more convenient however.

The solderable breadboard version can be easily expanded.

Naturally, this board could be expanded to handle variable input voltages, reverse polarity protection and other features. However this benefits from being very simple, while very functional.

HOW IT WORKS

The operation of this board is very simple. Power is applied via the terminal block, and distributed to six different points. When running a number of servos or other more demanding modules, power supply via an Arduino is often limited also, so this board is still very useful for a full size Uno or similar too.

The other advantage of using this board is that the project is expandable. You simply keep adding headers along the length of the board, following the established pattern.

You will have to consider the current limits of the tracks involved, although this will rarely be an issue for most makers, with the low-power nature of most projects.

The last feature of this board is the presence of a large capacitor near the power screw terminals. This allows devices which have short but significant spikes in their current draw to function without causing voltage drop on the supply.

If your devices need more power than the GPIO pins in the microcontroller can provide, you can use the screw terminals to add a separate power supply. This needs to be 5V DC but may come from a plugpack, lithium-ion battery with step-up converter, or a lead-acid battery/solar power set-up with a step-down converter.

In doing so, you can mount this board with its sensor/motor array well away from the microcontroller, with only the I/O connections running the distance over suitable cable. Incidentally, if you did connect the power pins to your microcontroller, it would be plausible to power the board from the screw terminals.

The Build:

Servo Tester Breakout Board

The schematic for both builds is identical. There is no change between versions in terms of components or electrical connections. Merely the way of creating the electrical connections is changed.

The only real challenges here are ensuring the polarity of the LED and capacitor are correct, as they're the only polarised components in the circuit.

Parts Required: JaycarAltronicsCore Electronics
1 × Solderable Breadboard or Custom PCBHP9570H0701#-
1 × 2-Way Terminal BlockHM3172P2038POLOLU-2442*
28 × Header Pins*HM3211**P5430FIT0084
1 × Blue LEDZD0185Z0869CE05103
1 × 150Ω Resistor*RR0552R7538CE05092
1 × 1000μF 16V Electrolytic CapacitorRE6220R5182COM-08982
8cm Tinned Copper Wire (Solderable Breadboard Option Only)WW4032W0420-

Parts Required:

* Quantity required, may be sold in packs.

** Total number of pins needed. Strip length varies.

# This item has pads instead of busses in the middle. You will need to solder bridge these into a bus.

† 25V version which may have larger pitch.

ASSEMBLY:

Solderable Breadboard Version

Anyone who can source the components needed for this project can also source various prototyping boards.

Recently, solderable breadboards have become commonly available. The one we use here is a fibreglass/copper cladding copy of a regular 400-hole breadboard, but with the addition of centre power rails where the IC gap is on a regular breadboard. It is also slightly shorter.

If you can't locate the recommended solderable breadboard, you can use standard strip / veroboard too - however you'll need to make the layout a little larger to accommodate track cuts and additional links. The solderable breadboard takes out so much heavy lifting, it's really worth grabbing.

Assembling the breadboard version is somewhat straight-forward. The catch is in soldering the jumpers.

Start by soldering the wire links, followed by the single resistor and the LED. Use the component overlays to guide you. The LED is polarised so ensure you insert it the correct way around.

As an easy reference, the LED and capacitor cathodes (negative sides) point to each other. The LED cathode is the flat side, and the capacitor's negative is marked with a large band with "-" on it. If you ensure that these will point to each other, you should have correct polarisation.

We have provided an underside view so that you can count holes to get everything inserted in the right places. This is shown as you look at it when soldering; that is, a mirror image from the top view.

The next task is soldering the jumpers. These do not protrude far enough through the board to bend the legs.

You can hold them onto the board with masking tape or a tacky putty product. Alternatively, you can use your finger to hold one end, solder the other, then solder the remaining pins once the first join has cooled enough for the solder to turn solid again.

This will largely depend on your soldering experience and preference for burning fingers!

You can now add the capacitor and screw terminal block.

Take another look over your board to ensure it matches our images and diagrams. You can then skip forward to the testing portion of this project.

ASSEMBLY:

PCB Version

If you are using the PCB version, construction is very much the same as the solderable breadboard version. The major benefit of the PCB is compact layout, and a few less links to deal with. The layout is somewhat different from the veroboard version, however the hardware requirements are the same (with the exception of link wire, of course).

As with the breadboard version, you need to take care with the installation of the LED and capacitor. They're the only polarised components.

The major benefit of the PCB is simplicity of construction, as it will literally take you just a few minutes to solder together.

It may be useful to add mounting holes to this PCB in some instances. However with such a small footprint and low overall weight, it's not really necessary.

Testing

Testing is fairly straight forward but an important aspect of any build. It's also perhaps more important on the solderable breadboard version, than it is on the PCB version, due to the additional connections and solder bridges required.

Before you do anything, visually inspect the board for dry joints, missed connections, and solder bridges. Use a multimeter to check for continuity between the GND terminal on the terminal block, and the GND pin on each of the servo/sensor jumpers, plus the GND pin in the microcontroller I/O row. Do the same for V+.

Finally, check continuity between the data pin on each servo jumper, and the corresponding pin on the I/O row. Check either side as well in case of shorts.

Now all that is left is to connect it up and try it out. Take care with your power connections, as there's no reverse polarity protection. If you don't see the LED illuminate when you apply power, immediately remove power and go back over everything. Do this BEFORE you connect anything from your microcontroller - it might save you from the one-time-only "microcontroller lets out smoke" show.