Lynn Electronics CTR2-Mini+ User manual

CTR2-Mini+ Assembly Manual
Version 1.1 Page 1
CTR2-Mini+ Assembly
Manual
Version 1.1
November 18, 2022

CTR2-Mini+ Assembly Manual
Version 1.1 Page 2
Contents
Introduction ..................................................................................................................................................3
Tools You Will Need......................................................................................................................................4
Bill Of Material (BOM)...................................................................................................................................4
PCB Kit...........................................................................................................................................................5
Pre-Cut Enclosure..........................................................................................................................................5
Cutting your Own Enclosure .........................................................................................................................6
Drill Mounting Holes .................................................................................................................................6
Interconnect Ribbon Cable ...........................................................................................................................8
Installing the Components............................................................................................................................9
Base PCB Assembly .......................................................................................................................................9
16-Pin Ribbon Connector –J3.............................................................................................................10
Jacks....................................................................................................................................................10
Dual-Row 8-Pin Header.......................................................................................................................11
Internal or External Radio I/O.............................................................................................................11
Isolated PTT and Key Output Relays...................................................................................................12
Front Panel PCB Assembly ..........................................................................................................................12
GPIO Connector ..................................................................................................................................12
16-Pin Ribbon Connector –J1.............................................................................................................13
Installing the Controls.............................................................................................................................13
Headphone Jack, J4.............................................................................................................................14
Volume Control...................................................................................................................................16
Encoder...............................................................................................................................................17
Pushbuttons........................................................................................................................................18
Speaker ...............................................................................................................................................19
Assembly.....................................................................................................................................................19
Quick Start Guide........................................................................................................................................21
Appendix A - Schematics.............................................................................................................................23
Appendix B –Top Section Grubbing Template...........................................................................................25
Appendix C –Radio Wiring Diagrams .........................................................................................................26

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Introduction
CTR2-Mini+ is an expanded version of CTR2-Mini. Like CTR2-Mini, the CTR2-Mini+ is a small radio
controller based on the Wio Terminal from Seeed Studios. The Wio contains the processor, a 2.4” color
LCD display, three user buttons, a 5-way switch, a micro-SD slot, and a 40-pin GPIO bus. The GPIO bus is
compatible with many Raspberry Pi accessories.
CTR2-Mini+, herein referred to as the Mini+, shares the same DNA as the Mini. It is named Mini+
because of the extras included that are not standard or available on the Mini. These include:
A built-in function keypad
A built-in radio I/O circuit that eliminates the external Radio I/O module used on the Mini if you
are only controlling one radio. The Mini+ still supports the RJ45/CAT5 connection to a manual
RJ45 switch and external Radio I/O modules if you have two or more radios you wish to control.
A built-in 12 volt power supply that allows you to power the Mini+ from your station’s 12 volt
system or from the USB-C connector on the bottom of the Wio Terminal.
A new sidetone amplifier with built-in volume control with On/Off switch
Several different enclosure options including the PacTec KEU-5 shown in the lead photo, a
custom acrylic enclosure similar to the Mini, and panel mount.
The basic layout of the Mini+ is similar to the Mini. The photo below shows the Mini+ connected to an
FTdx101. The straight key and PC are optional.
Basic Mini System

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As we’ll see in this manual, the Mini+ only requires two circuit boards (and a back panel board) so it is
easier to build and slightly less expensive to construct if you are controlling a single radio.
The Mini+ is available as a bare PCB kit (with SMT components installed and mounting hardware
included). I’ve created a Bill-of-Material (BOM) on Mouser.com for you to order the necessary
components with just a few clicks. It is also available as a complete, fully assembled unit complete with
an updated and pre-programmed Wio Terminal through my blog, https://ctr2.lynovation.com
Tools You Will Need
This manual assumes you will be installing the Mini+ in the PacTec KEU-5 enclosure. To build this kit you
will need basic hand tools like a Phillips screwdriver, diagonal cutters, needle nose pliers, a small wrench
to tighten the nuts on the control shafts, and a temperature controlled soldering iron. I prefer a beveled
tip but you can use what you like. You’ll also need a coping saw or a Dremel tool to grub out the top of
the KEU-5 enclosure so the front panel PCB will mount flush with the top. You’ll also need solder and
possibly solder braid if you create any solder bridges. The boards are manufactured using leaded solder
so consider that before purchasing.
Bill Of Material (BOM)
As mentioned above, I’ve created a BOM on Mouser.com that includes everything you’ll need to build
the Mini+, except the boards. I can supply the boards for a minimal cost. The link to the Mouser BOM is
https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=22e0705943

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PCB Kit
The Mini+ PCB Kit consists of two PCBs, a back panel, and mounting hardware. All the SMT components
are preinstalled at the PCB factory. You only need to install the through-hole components and build a
ribbon cable. The front panel, shown on the left in the photo below, mounts flushes in the recess in the
KEU-5 enclosure. The base board, shown on the top-right mounts in the lower half of the enclosure. The
PCB kit includes the back panel board and the mounting hardware as shown below.
Pre-Cut Enclosure
I can supply a CNC cut PacTec KEU-5 enclosure if you don’t want to cut your own. If you purchase an
enclosure from me be sure to delete it from your Mouser order.
You can order PCB and the pre-cut enclosure on the order form on my blog.
Printed Circuit Board Kit with Mounting Hardware
Pre-cut PacTec KEU-5 Enclosure

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Cutting your Own Enclosure
If you choose to purchase the KEU-5 enclosure from the Mouser BOM you’ll need to prepare it for
mounting the circuit boards.
Drill Mounting Holes
The first task is to drill the
mounting holes in the
bottom and top sections of
the KEU-5 enclosure. Take
the Base PCB and lay it
bottom up (with the ICs on
top) in the bottom half of
the enclosure as shown in
the photo to the right. The
concave notches on the
board should fit next to the
original mounting bosses in
the box.
Insert the enclosure’s back panel in the slot on the back of the bottom half and push the PCB toward the
back panel until it touches it. This is where the base PCB is to be mounted. A piece of tape will help hold
it in place. Drill 1/8” holes into the enclosure bottom at the four mounting holes on the PCB. The base
will mount to these holes using M3-6mm standoffs supplied with the PCB kit.
CAUTION: Be careful when drilling these holes so that the drill bit doesn’t cut into the through-hole
plating on the board’s mounting pads.
Next, lay the blank front
panel PCB face-down
(IC-1 on top) in the
recess on the top
section of the enclosure
as shown here. Drill a
1/8” hole at each
corner mounting pad.
NOTE: Drill these holes
before grubbing out the
center so you can leave
plenty of material
around the holes for
the mounting screws.
Drilling Front Panel PCB Mounting Holes
Drilling the base board’s mounting holes

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Next, print out the template in Appendix B and cut it out. Lay it in the recess in the top panel and mark
the cut lines as shown the left photo below. Use a fine-tooth coping saw or a Dremel tool to grub out
the inside of the recess. It doesn’t have to be pretty. Just make sure you leave about 1/8” of the
recessed portion for the board to sit on and be sure to leave flanges in each corner where the mounting
holes are located. Once complete the top section should look like the photo on the right. The front panel
PCB should fit into this void.
NOTE: The notch for the encoder is on the bottom (narrow end) of the top section of the enclosure.
Grub Template
Grubbing Complete

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Interconnect Ribbon Cable
A 60mm 16-conductor ribbon cable connects the front panel PCB to the base PCB. To build this cable,
cut an 80mm length of 16-conductor ribbon cable then install the ribbon cable connectors on each end
as shown below. The finish length after the strain-reliefs are installed should be around 60mm. You can
build this cable longer if you want more space between the board when you assemble or disassemble
the enclosure but I find 60mm to be about right.
NOTE: When building the cable, make sure that the #1 pin of both connectors is on the same conductor
(indicated by the red stripe). The #1 pin is marked by a small triangle on side of the connector as shown
in the photo on the left. When the connectors are properly installed the cable should look like the cable
in the photo on the right with the key for each connector facing toward the ribbon cable.
When building the ribbon cable be very careful that you cut the ends square. I use a ruler as a straight-
edge. Hold the cable under it flush to the upper edge then use a pair of sharp scissors to cut the end
square as shown in the photo below.
Pin 1 Marker
Finished ribbon cable
Cutting the ribbon cable

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Installing the Components
I find it’s much easier to install components if the board is installed in a PCB vise. Working with the
bottom of the board facing up I insert each connector into its holes from under the board. I hold the
solder with my left thumb and index finger and use my left middle finger to hold the connector in
position. Once I have soldered one or two pins, I remove the board and check to make sure the
connector is positioned properly and laying flat against the board. It’s easy to reposition it with only a
couple of the pins soldered. Once I’m happy with its placement I solder the rest of the pins. You’ll see
me using this technique throughout this manual.
Base PCB Assembly
The base PCB is the easiest to build. All the components are through-hole and mount to the top of the
board. There are silkscreen outlines for each component.
A WORD OF CAUTION
If you use a PCB vise like I do be extremely careful when installing the base PCB into the vice. There’s a
row of SMT resistors and capacitors next to the ULN2803A Darlington driver chip on the bottom of the
board. If your vice has slots to hold the PCB it may break these components when you tighten it. I
recommend clamping the board as shown in the photo below to eliminate this problem.
Watch out for these components!

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16-Pin Ribbon Connector –J3
Let’s start by installing J3, the 16-pin ribbon cable connector. As shown in the photo below this
connector mounts on the top of the PCB and the pins face backwards toward the connectors on the rear
of the board. Place it in position then use one finger to hold it to the board while you solder it. While it is
hard to do, be careful that you don’t form solder bridges between the pins. If you do, use some copper
braid (SolderWick or equivalent) to remove the bridge.
Jacks
Next, mount the RJ45 jack, the four 1/8”
stereo jacks, and the barrel connector for
the power.
When mounting these jacks, place your
finger on the jack to hold it in place and
gently pull the jack toward the rear edge of
the board. The pins on the jack should
touch the rear edge of the holes they’re in,
as shown the photo at the left. This will
insure that the jacks are all lined up across
the back of the board and their barrels
extend past the back edge of the rear panel.
Make sure the power connector is square to the board. Once it’s soldered in it is very difficult to
reposition.
Be very careful when soldering the pins on the RJ45 jack. They are close together and you can easily
form solder bridges between them. Also, don’t forget to solder the four leads for the LEDs on this
connector.
Installing J3
Install connector with pins close to the edge