Note 3 - Significant Accounting Policies - Reserve for Product Warranty Activity (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Balance, beginning of the period	$ 40,000	$ 240,980
Provision for product warranty	115,000	40,000
Product warranty expirations		(238,967)
Product warranty costs paid	(24,630)	(2,013)
Balance, end of the period	$ 130,370	$ 40,000