Note 3 - Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Product Warranty Liability [Table Text Block]

	December 31,
	2018			2017
Balance, beginning of the period	$	40,000		$	240,980
Provision for product warranty		142,000			40,000
Product warranty expirations		-			(238,967	)
Product warranty costs paid		(28,277	)		(2,013	)
Balance, end of the period	$	153,723		$	40,000

Research and Development Expense [Table Text Block]

	Year ended December 31,
	2018		2017
Salaries	$	74,694	$	228,610
Other costs		69,528		64,117
	$	144,222	$	292,727