Note 3 - Significant Accounting Policies - Reserve for Product Warranty Activity (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Balance, beginning of the year	$ 240,980	$ 359,654
Provision for product warranty		1,800
Product warranty expirations	(238,967)	(86,301)
Product warranty costs paid	(2,013)	(34,173)
Balance, end of the period		$ 240,980