AVR465 datasheet(39/40 Pages) ATMEL

39 / 40 page

AVR465

2566A-AVR-07/04

This application note is written with the ATmega88 in mind, but the design is easy to

migrate to almost any other AVR. Alternative design ideas include:

• Remove tamper detection logic and turn the design into a standard single-phase

meter. Firmware should then fit into 4kB and the microcontroller can be replaced

by an ATmega48, for example.

• Add functions such as remote reading, demand recording or multiple tariffs.

Upgrade to ATmega168, for example, if the firmware exceeds 8kB.

• Add integrated LCD support simply by migrating to ATmega169.

No software is ever complete and there are probably as many potential improvements

as there are readers of this document. The good news is the firmware is open source

and can be edited to fit any application.

Some recommended starting points for software enhancements include:

• Put the MCU to sleep as often as possible.

• Add apparent power, S, to measurement set. Hint: S = UI.

• Add reactive power, Q, to measurement set. Hint: S2 = P2 + Q2.

• Consider alternate reactive power approach. Hint: If u(t) is delayed 90 degrees

then reactive power can be calculated the same way as active power, i.e. Q =

Int{u(t-90) x i(t)}. Note: academic discussion on this method’s validity under non-

sinusoidal conditions has been recorded since 1927 (see C. I. Budeanu,

“Puissances reactives et fictives”, Instytut Romain de l’Energie).

Meter Firmware

AVR465 Datasheet(PDF) 39 Page - ATMEL Corporation