Alternative power supply connections

We have recently bought an EmonTx V3.4 (among other things) and have calibrated it, aswell as done some other tests.

We are going to use two EmonTx's to build a system that uses a single 5V DC power supply to power an EmonBase and both EmonTx's, in a plastic housing along with other components.


We don't want to make the housing much larger than its need to be, so I was wondering if, instead of using either the 9V AC or 5V USB connector on the front, we can power the EmonTx V3.4 by supplying +5V and 0V to the screw terminals on the opposite side of the PCB.


If we can, then we can just cut a rectangular hole in the side of our plastic housing and have the EmonTx stick (and the CT sockets) through it, while supplying power from the inside of the plastic housing.



We have already tested a method to use the CT inputs to measure voltage instead:

The SCT-013-000 current transformers output 0 to 50 mA, so that is also the maximum we can feed into the EmonTx.

We used a 230V AC to 8V AC transformer and connected a 220 ohm resistor connected to the secondary side.

Using our 0 to 260V variable transformer feeding into the 230/8 volt transformer, we measured approximately 0 to 50 mA through the resistor.

With this, we want to have a system to (temporarily) measure and log voltage and current on a 3-phase installation.

Robert Wall's picture

Re: Alternative power supply connections

The screw terminals are indeed connected in parallel with the USB connector, so can be used to receive a clean 5 V dc supply.

The schematic is here:

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