See also: 5.2 V Regulator
See also: Robust Power For Raspberry PI
See also: Purchasing and wiring a Meanwell RS-15-15
See also: Assembling the Switchover Circuit

Control Panel / Raspberry PI Shelf

This part of the project takes your pre-wired USB to Raspberry PI supply, Gel Cel, Meanwell power supply, switchover bridge-rectifier/trickle charger circuit, and Raspberry PI and assembles it onto a node-box.

TARPN Brew and Home Brew Components
Almost everything on this list can be cheaper or easier in quantity. Work with a group!
Quantity	Description	Source
(1)	Raspberry PI 3B, 3B+, 4B 1Gbyte, 4B 2Gbyte, 4B 4Gbyte.	Mouser, Digikey, Newark, ChicagoDist, Adafruit, Canakit
(1)	TARPN Control Panel, board + parts	More info [TARPN]
(1)	DC-DC regulator device with 5.2 V adjustable output like the DC-DC DROK Power Supply Module LM2596	More info [TARPN]
(1)	Meanwell RS-15-15 14.2volt variable power supply.	More info [TARPN]
(1)	Assembled main-power/backup-power switchover and charger circuit	More info [TARPN]
(1)	3d printed NinoTNC mounting plate.	inquire on TARPN list, or Discord server
Store-Bought Parts
(1)	2 Amp SLA battery PS-1220 prefered	Amazon B078T35B14
(1)	6 or 7 inch short USB cable	Amazon B07PYT3VM3
(4)	3M Scotch 311DC Heavy Duty 1-Inch Double face tape for mounting the Meanwell power supply.	Amazon B07DM7VDNL
15 feet	VELCRO Brand - Sticky Back Hook and Loop Fasteners – 15ft x 3/4in Tape \| White - for attaching Raspberry PI to the shelf	Amazon B000GR9X28
6-foot	of hookup wire, 16 to 20 AWG. BNTECHGO 20 gauge 5 colors	Amazon B06Y58W228
(1)	8 position (or more) Square D ground bus bar	Amazon B06Y58W228
(4)	female Crimp-on lugs for the Gel Cel and for the back of the Control Panel. Amazon Lugs Assortment kit	Amazon B078PMWNJC
(20)	4 inch Tie Wraps	Amazon B087MKMSDY
(10)	Fancy adhesive clips to grab wires and hold them in place.	Amazon B01HR9VS4I
Nuts/Bolts/Screw Hardware
(4)	M3x0.5mm thread Hex Nuts - for inserting into the mounting plate.	McMaster-Carr 91828A211
(4)	M3x0.5mm thead 8mm long machine screws - - for screwing the Raspberry PI onto the mounting plate	McMaster-Carr 92000A118
(9)	1/2 inch #4 brass phillips decorative rounded head wood screw Raspberry PI shelf to top of Control Panel rails - and mount regulator to shelf	McMaster-Carr 98685A330
(4)	3/8 inch #4 brass phillips decorative rounded head wood screw Control Panel into rails	McMaster-Carr 98685A540
(4)	insulating spacers to space the regulator off the shelf. Use large-gauge nylon nuts as spacers.	McMaster-Carr 90089A305
Wood Pieces
(2)	control panel rails - 1+1/4 inch x 2 inch (or longer) Blondwood plywood blocks	(Lowes hardware)
(1)	Raspberry PI mounting plate - 3 inches by 5+1/4 inches out of 1/4" plywood	(Lowes hardware)

Tools

(2) 2 inch jaw spring loaded clamps
(3) 2 inch openning C clamps
Sacrificial scissors for cutting gooey Velcro
Soldering equipment for tinning wires
8 inch square
small, medium and big flat-head screwdrivers.
small, medium and big Phillips-head screwdrivers.
4.5" needle nosed pliers
6" slip joint pliers
4" diagonal cutters
Volt-Ohm-Meter
1/16th inch drill bit
1/8th inch drill bit
1/4 inch drill bit
speed drill
soldering iron (could be station or gun)
lug crimpers
wire strippers
knife for stripping wire
(4) extra wooden blocks out of the thicker plywood
Tight Bond II or equivalent wood glue
paper towel for cleaning glue off your hands
rectangular wood pieces for use as chocks during construction

The first step is to glue two front-to-back rails into place to support the control panel and the Raspberry PI plate. Using some extra wood blocks (chocks), space the control back from the edge so the buttons are less likely to get broken.

Make it easy to get the control panel rails into the desired location by putting guidance blocks ("chocks") to the left and right of the control panel mount rails..

Clamp the front chock as well so it is easy to position the control panel and the two pieces of wood.

All the chocks are now easy to place. Test fit the control panel and the two pieces you are gluing.

Put glue on the bottom of the two control panel rails and wipe smooth with a finger.
Immediately clamp the two glued pieces and make sure they are up against the chocks.

Remove the side chocks to reveal glue that spread out from under the two pieces. Clean up the visible glue with your finger.

That looks better.

While the glue is drying, find your plastic Raspberry PI plate, velcro, M3 nuts and screws, and the Raspberry PI.

The M3 screw will not fit through the hole in the Raspberry PI

CAREFULLY use a 1/8th inch drill bit and variable speed drill to enlarge the 4 holes in the Raspbery PI to fit the M3 screw. A reemer is actually prefered because it is easier to control.

This picture shows the desired result.
In order to get this, you first need to press or hammer or squeeze with pliers to press the four nuts into the bottom of the mounting plate. Try to line up the hex nut with the hex shaped hole in the bottom of the plate, and then squeeze with pliers. The plates are a little fragile, but they are also cheap.

Cut 2+1/4 inch loop velcro (the soft side) and apply it to the fat portions of the plastic Raspberry PI plate.

Now that an hour has elapsed and the glue has dried:

Using a 1/16 inch drill bit, pre-drill the wood-screw holes for the Control Panel. Drill a hole that is something less than 1/2 inch deep as close to the center of the mounting hole as you can. You'll eventually be mounting a finished control panel using 3/8 inch #4 wood screws.

Cut a piece of wood about 3 inches by 5+1/4 inches out of 1/4" plywood. This will be the Raspberry PI mount and we will use wood screws to attach this to the top of the control panel mount rails.

Assemble the control panel. TARPN Control Panel

Using a 1/16th inch drill bit, drill 1 starter hole through the Raspberry PI wooden mounting plate into the control panel rail and apply one 1/2 inch #4 wood screw.
Then finish by drilling 3 more holes but don't screw them down yet.

Remove Raspberry PI shelf and work on the Meanwell supply and the bridge rectifier switchover/charge circuit.
See also: Purchasing and wiring a Meanwell RS-15-15
See also: Assembling the Switchover Circuit

Use a 1/2" #4 wood screw to mount the switchover circuit under the Raspberry PI mounting plate.

Attach the main-power-supply input wire (red) from the switchover circuit to the Meanwell +V screw terminal.

Attach a 10 inch black wire to the Meanwell -V screw terminal. This will be run to the ground bus.

Tape the Meanwell down to your box/shelf using double-faced tape. Use a 2 inch by 2 inch section (four smaller squares) of 3M Scotch 311DC Heavy Duty 1-Inch Mounting Squares and then cover the entire bottom of the supply where there are no ventilation holes.
You'll want the Meanwell screw-terminals to be facing forward, behind the control panel and under the screw-down Raspberry PI plate.
Use some form of cable management for the AC cord so pulling on it stiffly will lift the node box before ripping it off of the Meanwell supply.

Install a ground bus screw terminal with at least 8 screw down locations. Put it on the back edge of the shelf.
Starting in a few steps, we'll be grounding the battery, the Meanwell, and the input to the regulator.
Later, the ground bus will support one side of the main power supply, and then one side of each radio powerpole wires.

Assemble the regulator and USB cable as described on the 5.2 V Regulator page.

Place the regulator here. Run the USB cable over to the Raspberry PI and prove that it reaches.

Pre-drill a hole to secure the regulator using your 1/16th inch drill bit.
Use washers or nylon nuts to space the regulator off the wood and screw the one corner of the regulator down using a 1/2 inch #4 wood screw.

Pre-drill the remaining 3 holes. Loosely secure the opposite corner, again with the spacer of some kind.
Wire the bridge-rectifier output (pink) to the +V input to the regulator and wire a black ground wire to the -V input.
Connect the black ground wire to the ground bus.
Apply power to the Meanwell supply.
Exercise the two buttons on the regulator. One button will turn the display on and off. The other button selects whether you are displaying the INput voltage or the OUTput voltage. Both voltages should read 13.4 V. Note: it is 13.4 V because your Meanwell is set to 14.2 V and then there are two diode drops before it reaches the regulator.

Configure the regulator to show the OUT voltage.

Using a small flat head screwdriver, turn the multi-turn pot counterclockwise. Pay attention to the voltage. It won't change at all at first. When you hit the critical range, it moves rather quickly.
adjustment-movie - this may take a while to load

That will do.

Now screw down all 4 corners of the regulator using 1/2 inch #4 wood screws and the same spacers you used before.

Place the battery where it will be permanently located. If you are using the Jay-box, put the battery in the side-car with the lugs against the front of the box. Plus should be up so it is protected against some stray wire touching it under the side-car. The lugs should be front so they can't touch the metal HP power supply.

Make a custom length orange jumper with lugs on each end to connect the + terminal of the battery to the back of the control panel. This will connect the battery + terminal to the lug on the back of the control panel.

Make a custom length black jumper with lug on one end, and tined wire on the other for connecting the - (minus) terminal of the battery to the ground bus.
Hook up the wires.
Plug in the Meanwell.
Remove the memory card from the Raspberry PI, if any.
Plug the USB cable into the Raspberry PI.
The lights come on.
If you turn on the battery switch on the Control Panel, you should be able to unplug the Meanwell and have the regulator and PI stay on.

Turn off the battery using the Control-Panel switch, for now.

Screw down the four 1/2 inch #4 wood screws to hold the Raspberry PI shelf to the Control Panel rails.
Apply hook Velcro from side to side across the Raspberry PI shelf so it meets the Raspberry PI's vecro toward the front of the shelf (by the Control Panel) and toward the back of the shelf (toward the Meanwell).

Place the Raspberry PI, bracket down, and USB connectors to the left, down on the velcro pad.

Now we're going to break four pins off of the Raspberry PI's 40-pin auxiliary connector to make room for the 2x5 ribbon cable connector. There must be space on both sides of the connector. Row 7, measured from the SDcard end of the Raspberry PI must be removed, as well as row 13. See the next several images for the steps I use to do this.

Grab first pin, on row 7. We'll bend this with a long nose plier.

You'll need to wiggle the pin toward the CPU and then straight back up, and repeat several times.

7th row now removed

On the 13rd row, break both pins

You can see in this image there is now room for a 2x5 header, in the middle of the Aux connector.

Cut a 4 inch piece of ribbon cable.
Crmip IDC connector on each end of the ribbon cable such that the IDC connectors are separated by 2.5 inches with an inch of spare on each side. Make sure they are square to the ribbon cable. Eyeballing it should be sufficient.

If you have enough extra on the ends, wrap it around the connector and install the straign relief part of the IDC connector.

Attach ribbon cable to control panel and Raspberry PI as shown

Your Raspberry PI shelf is complete. If you have an SDCard node already built, you can power it up and see the control panel light up. Otherwise, initialize your Raspberry PI to be a TARPN Node.