Carsten Groen's (OZ9AAR) personal place
Interests and experiences
REPAM - Remote PA Monitor
For some of my projects (Ham related) I need some way of remote monitoring (and controlling) the remote power amplifiers (PA) I use. I decided to make this board with enough I/O for most of my projects.
It communicates via 10/100 MBit Ethernet (RJ45 connector).
It has the following interfaces:
- 4 x digital inputs (opto isolated), has separate ground
- 6 x analog inputs, 12 bit resolution, 0 to 5V (can be changed via resistor divider at inputs). Calibrated.
- 6 x relay outputs. COM/NO brought out for each relay (50V/2Amp).
- CAN bus.
- Dallas 1Wire bus, for multiple temperature sensors etc. Initially REPAM supports 8 sensors.
- Two separately PWM controlled 12V/2A FAN outputs (0..100%) Can be controlled autonomously.
- RJ45 connector for Ethernet.
- 2.1mm DC plug for 12V power.
- USB port for update/diagnostic.
It contains two autonomous fan controller loops, each one can use one of the 8 temperature sensors to control a fan. You set the lowest temperature for the fan to kick in and the speed for that, the highest temperature and the corresponding fan speed for that temperature. The fans will then be regulated according to the measure temperatures (for cooling of PA modules etc).
You can set alarm triggers on high/low thresholds on the analog inputs and on the temperature sensors. The triggers can bring one of the relay output s on/off/pulse. They can also signal an alarm on the JSON data etc.
A few more things will be added along the way.
The board uses a 220 MHz Cortex M4 processor, a NXP LPC54628, ethernet Phy is LAN8270. I have a complete (LwIP) TCP/IP stack running on the board (and RTOS of course).
Communication to the outside world is via TCP socket connection. JSON formatted data flows both ways. Multiple clients are handled by the box. Has also a simple command interface using netcat over UDP.
Currently the hardware has been tested 100%, a small number of boards has been produced and software is being finalized.
More info will follow!
Box design
I designed a box for the REPAM board. I made the design so it can both be 3D printed and be milled (I use JLCPCB for that). The size is 99 x 84 x 24 mm.
The milled housing (2 parts, top and bottom) ended up costing a total of €45.78,- (€26.24 for top, €19.54 for bottom). Surface treatment is conductive anodizing. Shipping with 3 days DHL express added another €18.67.
3D printing it will obviously be cheaper.
First prototype box arrived from JLCPCB. Quality, fit and finish are absolutely perfect! I can only recommend JLCPCB's PCB and CNC milling service!
The front plate is designed in CAD as a normal PCB (without any copper), produced in 0.8 mm thick PCB with black soldermask.
Simple test application in C#
To test the implementation in the REPAM device, I made a small super simple C# project that would receive and send JSON formatted data from the box. It just has the simplest possible interface for now.
