January 9, 2023 Chris Rush

Add A Rotary Encoder to Your JustBoom Boards

This guide will show you how to install a Rotary Encoder on your JustBoom.

You can use a Rotary Encoder to control the volume of the JustBoom HATs and pHATs.

This guide shows you a specific type of rotary encoder and knob but a similar approach can be used for other models and types.

Identify on the PCB the location of the header to be used for the Rotary Encoder.

Use the picture on the left to help you find it.

Section 1 – Rotary Encoder Soldering

Step 1 – The Rotary Encoder has five pins. Three are used for the increments/decrements of the volume and two are used for the mute/unmute function. Solder one end of your wires to those terminals. The wires should be 10 cm long and it is preferable to use AWG between 23 and 28.

The JustBoom cases are rather tight in terms of extra room so it is important that especially in the case of this addon attention is payed to reduce to the minimum the volume we are going to occupy. With that in mind on the Rotary Encoder you can slightly bend the pins inwards so to reduce its overall. Also note that the thinner the wires the easier it will be to fit them in whilst taking very little space.

Step 2 – You will have to use a different approach depending on which board you are wiring the Rotary Encoder to.

For the JustBoom Zero Boards it is advisable to use a low profile SMD female header and solder the wires directly on its pads.

On the JustBoom DAC and Digi HATs you can use right angled or straight 20×2 male headers. The right angled type is particularly indicated as it will allow for a more comfortable wiring. The wires will have to be terminated with Dupont connectors. Alternatively you can buy ready made cables and simply cut one end to solder it on the Rotary Encoder pins.

For the JustBoom HAT and in case you use 20×2 straight male header for the JustBoom DAC and Digi HATs you will have to make sure that the Dupont connectors are of a suitable height.

Step 3 – Dupont connectors come in different heights. The majority are 14 mm but the maximum height for our HAT cases is 12 mm. Often you will find that you can shorten the plastic casing of the Dupont connector. With the help of a flat screw driver remove the case and cut off to the top part so that it levels with height of the metal connector.

Step 4 – The script we provide on our Github repository comes with default pins to which you can connect the Rotary Encoder to but it also allows for customisation and for additional type of encoders. Refer to the documentation on Github for further details.

If you are using a right angled 20×2 header for the JustBoom DAC or Digi HATs please refer to this FAQ for further information.

When connecting the low profile SMD female header to the JustBoom Zero boards please note that you will have to connect it upside down i.e. with the connectors facing up.

Section 2 – Case opening

Step 1 – Identify within the case the round indentation with a plastic pin in the middle.

Step 2 – In order to produce the opening you can use a pen, a chopstick or anything that will be about the same size of the round indentation.

Step 3 – Push the plastic pin from inside the case and outward to break it off the case.

Step 4 – Push through the rest of the tool you are using to remove the thin plastic remaining and completely open the hole for the Rotary Encoder.

Step 5 – Remove the nut and washer from the Rotary Encoder and insert it through the whole. Make sure that the locking pin of the Rotary Encoder fits in the housing.

Step 6 – You can now place the washer and the nut to fix the Rotary Encoder in place.

Step 7 – Unscrew the bolt on the knob just enough so that you can insert the shaft of the Rotary Encoder. Note that the flat part of the shaft faces the bolt.

You can find silver aluminium knobs or black aluminium knobs on our website.