John's Musings


Yeah, Me Neither

Building The Perfect DMR Beast

Thanks Don Henley for the Subject Line inspiration.



Decided to transition my Raspberry Pi / DVMega combo into a proper enclosure. I had previously just printed a Pi/DVMega Case which was fine and all but a proper enclosure is a completed project and a conversation piece.



I've included a Build Of Materials (BOM) but only included major items. There are a few things that you'll also need to include some hook up wire, a USB cable with a micro-USB connector on one end that you use to power the Pi. You'll have to cut it and wire it to the Output on the Power Supply. Also i didn't include an SD Card for the Raspberry Pi.


Also I've left off a small kit of stand offs. These are invaluable for a variety of projects.









Ok, so here is the Build Of Materials. You don't have to use these exact parts. Almost everything can be substituted including the DVMega. You could use a Zumspot or the dreaded JumboSpot (Chinese Clone of MMDVM_HS board).


NAME

Price

Notes

Raspberry Pi 3

$36.39

Can substitute Raspberry Pi Zero W. To utilize older Pi variants you will require a USB WiFi Dongle

USB to TTL Conv.

$8.99

There are others you can use but this one is inexpensive

DVMega

$129

UHF only

Buck Power Supply

$8.89

There are multiple power supplies that can be utilized to power the Raspberry Pi. Pi Requires 5v and 2 amp minimum (recommended)

Enclosure

$17.40

Shipping costs $16.40. Hey, still cheap for this enclosure

D.C. Input Connector

$11.99

Bag of 25. Hard to find just one. Can order singles from Mouser or Digikey

Ant. Panel Mount Connector

$7.33

SMA male to SMA Female

Power Switch

$6.99

Pack of 10. Mouser or Digikey for single panel switches.

Nextion 2.4

$19.99

Must program screen for DRM with HMI file.

Bezel

?

Must 3D Print


Optionally, since the box is so freaking big you could add a panel mount ethernet connector on the back to just hook it up to your home network and not rely on wireless. If you go this route realize that you'll need a short hunk of Cat 5 or better cable. I have a spool of cable and connectors and an RJ-45 tool so I can make my own cable that is the perfect length.

Wow! Where to start. Probably the first thing you want to do it program the Nextion 2.4" screen. I have directions to do this here. Once you have it programmed you'll have to cut a hole for the screen in the front panel and fit the bezel into it. It's not too hard. I did it by tracing the bezel, drilling holes on the inside of the lines and cutting with a hacksaw blade in a handle. It's not rocket science and the bezel is wide enough to cover tiny mistakes.




Then you need to mount the Raspberry Pi on 4 stand offs. Make sure to give yourself access to the SD card, the Pi power micro USB connector and leave plenty of room for the FTDI USB to TTL Converter.




Before mounting the power supply take a micro-USB cable and cut the appropriate length to reach between the Pi and the place where you intend to mount the power supply.


A micro-USB cable has 4 wires (and 5 pins). The wires are as follows:

  1. Red - Vcc 5 volts
  2. White - Data Transmit
  3. Green - Data Receive
  4. Black - Ground


We only need the red and black wire to carry power to the pi. So prep the cable like this and tin the ends of the red and black wire with solder.



We're not transmitting data or doing any mode detection here, we're just sending 5 volts to the Pi.


Before you connect this and plug it in make sure your power supply output is 5V


Hook the red wire to the + side of the output on the power supply and hook the black wire to the - side of the power supply.







The pic below shows the output side of the power supply. Again lets not power this up just yet.



Ok now lets wire up the power supply. Right for the moment let's keep it simple. We can add a switch later. On the DC input jack are two legs. Place the red wire on the short leg and the black wire on the longer leg. Apply the red wire to the IN+ and the black wire to the IN-


DO NOT have power routing from the output terminals to the Raspberry Pi at this point. We need to adjust the output voltage first. You'll need a power brick with a 5.5 mm connector on it. The power supply goes from 4-32 volts DC. Obviously you need something more than 5 volts. Tons and tons of old electronics hardware around the house probably have 12 volt or 18 volt bricks on them. You probably have 10 laying around the house on stuff you don't use anymore.





Once the proper voltage is obtained you can connect the Raspberry Pi.





Essentially this is all you really need to do to be up and running. Once you plug it in it should power up beautifully and function.





At this point you can wire in a switch and fuse if you want. To add a switch just take the red wire from the DC input plug and put it on one terminal of the switch. Continue the other leg on the switch to the IN+ on the power supply board. The black wire still goes from the long let of the DC input plug to the IN- on the power supply board.






An external antenna cable can be added at this time as well. I swiped that small antenna off of another radio I have laying around the house and it may just be that this project remains with an internal antenna. Haven't made my mind up yet.


Since this thing occupies a lot of space no real reason for it to be using WiFi. Might as well hard wire it. Ordered that panel mount ethernet connector and installed it. Works great.




And just for a nice finishing touch I added a dust cap to the ethernet port.




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