This laser transmitter receiver circuit use light from a laser torch to transmit an receive signal from a distance up to 500 meters. This laser transmitter receiver use a laser torch as the carrier in the circuit .This laser transmitter receiver circuit project can be used as an spy device by mounting the transmitter in one building and the receiver in other building , but the phototransistor of the receiver must be oriented towards the laser beam of the torch .
This simple water level indicator alarm circuit is based on transistors and few electronic components . The circuit is very simple and it has a very low current consumption , so you can use a 9 volts battery to powering this water level indicator alarm . This water level indicator alarm circuit can be used even for rain alarm or short circuit alarm , a resistance with a value from 0 to about 1 M ohm will trigger it . The Q1 transistor acts as a switch which applies current to the unijunction relaxation oscillator Q2 .
An electronic dice circuit can be build using this schematic diagram . This electronic dice circuit is based on some logic IC circuits and is very simple to build . The dots from the dice are made using 5 red LEDs . The PB switch is a normally closed switch , the Q1 transistor can be a BC557 type or similar .
The IC1 is a 7400 TTL which contains independent gates , which performs the logic NAND function .