Experiment 18: Reaction timer part 3

The next step in Experiment 18 of Make:Electronics is the addition of a 555 timer in astable mode to the circuit (pg. 175 of the book). This addition drives the decade counter therefore the tactile switch that was connected to pin 1 of the first decade counter from the previous part of the experiment had to be removed. At first I had the two capacitor exchanged so instead of four pulses per second the display counted frantically. After solving this I encountered no further problem. For the larger capacitor connected to pin 6 of the 555 chip I used 100uF instead of the 68uF so my circuit is probably down to three pulses per second.

Circuit with the 555 timer included however the two capacitors (above the 555 timer) were exchanged.

Circuit with the capacitors in the right place.