This circuit was found in a 1990 Electronics Handbook. It can serve to indicate the level of liquids, for example, when a water tank is full or an overflow occurs. The transistors can be the BC548 and the sensors bare wire ends in contact with water. The transformer can also be 12 V secondary with 100 mA or more if the relay used is 12 V. R1 is can be 330k-ohm and C2 470nF.
| Clique na imagem para ampliar |
| Clique na imagem para ampliar |
