Stroboscope

Stroboscope.

This was made to check the fan speeds on a new computer build.
Four leds from

http://www.amazon.co.uk/gp/product/B008AGOLQA?psc=1&redirect=true&ref_=oh_aui_detailpage_o02_s00

are driven via a BC639 npn transistor from the arduino Microview.