Note 3 - Significant Accounting Policies - Reserve for Product Warranty Activity (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Balance, beginning of the period	$ 153,723	$ 40,000
Provision for product warranty		142,000
Product warranty expirations	(40,400)
Product warranty costs paid	(12,488)	(28,277)
Balance, end of the period	$ 100,835	$ 153,723