Monday 30 July 2018

Completed: DC Power Distribution Unit

I have completed the DC power distribution unit for the EMF Hub.

It takes DC In from a 13.8V, 23A power supply and splits it into 4x Anderson PowerPole outputs and 3x 5V USB Outputs. It also has a Voltmeter / Ammeter on the front panel for added bling.

There are fuses protecting the overall current, and also the current to the USB DC/DC convertor - I would have liked to have fused each PowerPole individually, but ran out of room inside the enclosure.

Front of PSU + DC Distribution
Rear of PSU + DC Distribution

Originally the DC distribution was designed to handle a maximum of 40A, but I've dropped it down to 20A as I'm not comfortable with the PowerPoles which are connected with cable rated for 20A being protected by the fuse sized for a total load of 40A. This isn't a huge issue as the PSU is only rated for 23A and the total load of the EMF Hub will be well below 20A.

I need to replace the resistor in series with the LED as its currently brighter than the sun and will likely light up the entire EMF Field at night.

I was also hoping to add relays to individually switch 2 of the 4 PowerPoles, but again room was an issue so I had to give up on that - I totally underestimated the size of the crimp connectors and "Bend Radius" of the thick cables required to carry the required current.

I plan to revisit this in the future, but its fairly low down the list of priorities. Maybe it will be ready for EMF 2020?? If I were to do this again I would:

  • Use a Laser Cutter to create front / rear panels for an ABS box, which will result in a much neater finish and engraved labels / logos
  • PCB Mount the PowerPole and USB Connectors to cut down on internal wiring.
  • Fuse each PowerPole individually 
  • Add relays to the 2 of the 4 PowerPoles, and allow switching them from the front panel or via IP
  • Add voltage / current monitoring to each of the PowerPoles, exposing it over IP
  • Add failsafe timers so if a radio has been transmitting (Using more current) for X minutes continuously, the power is switched off - useful for scenarios where software or a repeater controller has crashed