DDDAC 1794 AC Power Distribution

The current power distribution can be cleaned up. Multiple wires in a too small terminal block and separated relay board. Time to clean it up.

My build of the DDDAC1794 The 230VACpower distribution exists out of:

  • 1x AC 230VAC coming from the mains connector
  • 1x Power Supply for the DAC
  • 1x Toroidal Transformer with dual secondaries for the clean an dirty digital supply
  • A (solid state) relay controlled by the soft power down controller
  • A momentary switch to start the system until the soft power down controller takes over

It would be nice if all could connect to a small power distribution PCB. And for size and stability the current relay replaced by a solid state relay.

power distribution schematic,

The Omron G3GMB-202P 5 volt version is a 2A solid state relay with zero-crossing detection. It already contains an internal resistor, so you can directly control with 5V/10mA.

The controller activating the solid state relay is described in Raspberry Soft Power Off. There a conventional relay is used which is directly activate after the controller is booted . This happens when the momentary switch is pressed, which temporary bypasses the relay until released. The start of the controller is fast enough to be unnoticed by the user.

With a solid state relay including switching on the 0 crossing this is different, while the momentary switch is closed the relay can’t be activated, it requires that some current can flow. And then it requires 1/2 a power cycle + 1 mS = 11mS. The system load (on the dirty 5V supply) is required to run at leased this time without AC to startup the solid state relay, before dropping below the 4.5VDC. That will not be a problem.

The used parts are in the table below.

U1Omron G3MB-202P 5V version
part list

Next is to design a small PCB with those components:

PCB Layout

An impression of how the final result would look:

PCB Render with Kicad

But before we create a real PCB, lets first create a proto to see to see if we are satisfied with the practical use.

proto top side

For safety remove unused pads between the phase, neutral and control signals:

proto bottom side

And mounted in the actual DDDAC 1794:

proto mounted to the side panel of the enclosure

It works great and organize the power distribution in a neat way. It is time to order a real PCB. With the current proto in place I’m not in a hurry, so lets order it at oshpark with their famous PCB color.


In case you also want to order a PCB, the PCB is shared at oshpark. OSHPark supplies a great quality at nice price, only it take a while be fore the good are delivered.

Update: September 26th the PCB’s have finally arrived:

Finished PCB’s.

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