This circuit is from Popular Electronics of the 90's. It makes use of NO and NC sensors. The relay depends on the supply voltage which can actually be between 6 and 12 V. The transistor can be a BC548 The number of sensors can be increased.
This circuit is from Popular Electronics of the 90's. It makes use of NO and NC sensors. The relay depends on the supply voltage which can actually be between 6 and 12 V. The transistor can be a BC548 The number of sensors can be increased.