I’m keen to get the project to feed data from my CurrentCost CC128 energy monitor up to Cosm via an Arduino out of the way, so that – if nothing else – I can put it in a little box and tuck it out of the way and let it just get on with accumulating some data.

To be able to do that I need to power it from an external PSU, which will firstly power the Xino (an Arduino-alike) and an ethernet shield and then provide power to the CC128. I’ve had all the elements working at one stage or another over the last month or so, but putting them altogether into one finished unit is proving to be a bit of a pain. Thus far, everything has been running fine when it’s been powered from the USB on my dev box, and the last thing to do was to “simply” switch over to external power.

This is where the problems creep in – powering through an external source is causing the ethernet shield to not function correctly … and it’s doing my head in.

When the combination is powered by an FTDI adapter, everything works fine; the leds on the network magjack light up, network connectivity works as expected. The 3.3V pad on the shield gives 3.3V and the 5V pad gives 4.69V. Measuring the supply current gives me a draw of 171mA when powered thus.

When powered by an external PSU, however, the leds on the magjack initially light up, but flicker and fade away to nothing over a period of about 10 seconds. There’s no network connectivity either, unsurprisingly. The 3.3V pad on the shield gives 3.3V and the 5V pad gives 3.45V. In these cases, the supply starts at about 199mA on initial powerup and then slowly drops away to around 168mA. I’ve tried 7.5V/200mA and 9V/600mA supplies with the same outcome.

I’m floundering around trying to deduce the cause of the problem with, to be frank, only a basic knowledge of this stuff and wondering if I should have just ignored the cost and gone for a ready-packaged  solution in an Arduino Ethernet and saved myself a load of grief. We’ll see what Ciseco support can suggest – I’m off for a cuppa …