Tenergy via Amazon offers its Tenergy Odev Dynamo Lantern STEM Building Toy for $14.99. Coupon code "RBN73HB5" cuts that to $7.49. Plus, Prime members bag free shipping. That's $2 under last month's mention and the lowest price we could find by $8. It allows kids to build a hand-cranked generator which powers a light bulb. Deal ends July 26.