Maker Factory ELECTRONICS EXPERIMENTS BOX Manual page 274

Circuit 78 – 80: Button S1 is used to fully charge the electrolytic capacitor C1/C2. At R2 discharge occurs. For
as long as the capacitor voltage exceeds the threshold voltage of T1 plus T2, T2 remains connected, LED1 is
lit.
276
Fig. 3.78: Circuit 78 –
Quiztimer 3 seconds
Fig. 3.79: Circuit
79 – Quiztimer 8
seconds