Armstrong, 21, recorded a blood alcohol reading of 0.213 when breath tested in September 2010.
Late last year the Crows banned Armstrong from the first four rounds of the 2011 AFL season, fined him $5000 and ordered him to attend counselling.
Magistrate Paul Foley said that because Armstrong's alcohol reading was "in the order of four times" the limit, he could not impose the minimum penalty.
He disqualified Armstrong from driving for 18 months and fined him $800, plus costs. He was also ordered to pay a $440 fee because his car was impounded for seven days following the incident.
The Crows have required Armstrong to take part in a rehabilitation clinic for victims of car accidents and participate in a program to promote indigenous health and sport for up to nine months.
Armstrong played nine AFL games for the Crows in 2010.
