Alternative Power Supplies and VTs

USB Power Supplies and AC reference transformers are commodity items. The store stocks two plug types: US 120V two blade Type A and European style two pin Type C. You may need a different plug type or local safety certification in your country. This page provides some limited guidance in selecting alternatives and also provides some links to specific sources.

Power Supply

IoTaWatt is powered by 5VDC through a micro-USB adapter. It is important to use a switching power supply designed to provide quality power to electronic devices. While you may have limited success with phone and battery chargers, these devices do not always provide suitable quality power. IoTaWatt requires low ripple and at least 3 watts. In general, a USB supply sold for use with Raspberry Pi with a micro-USB connector works well.

AC Adapter

The AC adapter is nominally 9VAC. It does not power the IoTaWAtt and draws only about 0.4mA. Its only, but critically important purpose is to provide a reference for the AC voltage and frequency. While any transformer with a no-load voltage between 6 and 15 VAC RMS will work electrically, there is a phase shift that must be factored into the power calculations. VTs that are listed in the IoTaWatt configuration dropdown have known phase-shift. When using an unrecognized transformer, it is configured as generic, and the phase shift should be determined.

Useful Links

CountryMerchant9VACUSB Power
Australia plug-type I 230VAmazonN/ALink
Australia plug-type I 230VJaycarMP3027N/A
New Zealand plug-type I 230VJaycarMP3027N/A
UK plug-type G 240VFarnell77DB-06-09T6090DV
Euro plug-type C 230V
(Ordinary 2 pin plug)
Farnell (UK)
Newark (USA)