Testing human reaction speed is not only a fun way of spending time, but also allows the drawing of conclusions, for example on the skills of a momentary driver.
How does the reflex tester works
When the contact closes the power button, the astabil multivibrator that is built with IC1 produces pulses that are applied to IC3 counter. D1…D10 LEDs light up fast and sequentially (one after another).
Once the tested person pushes the stop button (S2) the astabil multivibrator is blocked and the last ordered LED lights up next. The reaction time can be read easily if the frequency of the multivibrator (adjustable with P1) generates a pulse every 10 seconds. The test can be repeated after pressing the reset button (S3). Reflex tester circuit consumes about 120 mA current, the supply voltage of 5V must be regulated. The frequency can be adjusted with P1 between 10 Hz and 80 Hz.