Around the Adafruit Playground II: How to Make Expansion Cards

We have seen in

https://www.instructables.com/Around-the-Adafruit-Playground-I-a-Motherboard-Wit/

how to make a "motherboard" for the Adafruit Playground Classic card (also works for Express and Bluefruit). Here is a simple prototyping board, to expand the capabilities of the board by adding new sensors, wirelesss communication etc...

The introductory image shows a breadboard with a connected HC05 Bluetooth emitter/recepter.

Equipment to make printed circuits

3D Printer

Male DB15 connector

170 holes mini breadboard

Break Away Headers 2.54 mm Male (or Female) Pin Header Connector

3 mm diameter, 6 mm or 10mm long screws,

As a Female DB15 connector has been used for the "motherboard", the choice is obvious for exension boards: a Male DB15 connector.

One just has to replicate the layaout of the Female connector from the motherboard, see pdf file.

Note: as the Male and Female connectors face each others, the pin numbering is left/richt symmetric. Do not forget to take this into account when designing an extension board.

For a simple prototyping board, the idea is to simple have a replication of the eight I/O of the Playground easily accessible via Dupont cables to be connected to a 170 holes mini-breadboard, onto which additional components are to be plugged.

The Ground, 3.3 V and VBatt pins have also to be available.

The design is then very simple. Just connect the male DB15 pins to male or female (depending on your preferences) connectors.

Unfortunately, Instructables does not allow KiCad project uploading. The pdf file of the mask if provided below. I will later provide a link to download the whole KiCad project.

When the circuit has been etched or engraved, cut and drilled, or manufactured by a third party, one can install it in its case, to check it fits well.

As for the "motherboard" the Ruiz Brothers's hexagonal case has been adapted (https://learn.adafruit.com/case-for-circuit-playground)

Here are the step files for 3D printing the case. There is no peculiar specification, PLA printing works well for such cases.

Three screws allow for attaching the board in the box. You may redrill the hole in the support if screwing is too tigh, or alternately, use 2.5 mm screws.

First you have to solder the DB15 connector. Beware when inserting the connector in the printed board, tolerances are very tight, and it's easy to bend/break a pin. Be precise when soldering, as pin layout is quite dense (Image 1)

Then, cut the label layer, and glue it to the board upper face. Fix the 170 holes mini breadboard (they are often delivered with double-face scotch tape on their base)

Cut the Break Away Headers and solder the 8 individuals pins (male or female, at your preference, in the exemple, male pins were used, Images 1 and 2)

Add Ground (Black), 3.3 V (Red) and VBatt (Orange) alimentations. A little bit of hot glue permits to keep the wire well in place when using the board (Image 2).

Test and re-test to check that all connections with DB15 are OK, and that no shortcut did appear.

Screw the board in the case (Image 3).

Designing/Manufacturing such a simple board is a nice simple exercice for first year students. For example, this board was designed/manufactured by one of my former students, Matthieu Grimm-Kempf.

You can now use this prototyping board to test fonctions you would like to add to the Adafruit Playground. In the video below, a 3.3V HC-SR04 ultrasonic sensor is connected to the Playground, which displays the measured distance as a bar graph using the NeoPixel leds.

Many thanks to my colleague Joël Lambert for the case modifications.