This circuit react in presence of any conductor object including humans. This circuit does not detect object movement but can act as an proximity sensor!
Sensitivity is adjustable with P1 which will be located at a great distance from the rest of the presence detector circuit.

This is a very simple liquid detector that use a relay to open an evacuation van. You can use it for water or any liquid that conduct electricity. Use any PNP transistor that can stand the relay current. Check out the new water level sensor circuit.

With the help of this revolution regulator circuit you can control the number of revolutions of your drilling machine.
After you finish construct this mini drill revolution regulator measure the output voltage. First rotate P2 to the right completely, P1 to the maximum. Now the measured voltage must be 20% less than the maximum allowed motor voltage. If it isnt then R1 must be lowered or increased.
After this connect the drilling machine. P1 must pe on the middle position. P2 is adjusted that the motor revolutions doesnt increase. The optimum adjustement is when at the maximum drill motor load the number of revolutions is constant.

This regulated power supply can be adjusted between a few volts and 15V with P1 and with P2 adjust the upper limit ( 15.0V ). R6 value is 0.7V / Imax where Imax is the maximum current. At Imax = 5A, R6 is 0.14Ω
T1 and T2 must have heatsinks because power losses are great at a low output voltage and a Imax equal current but you can connect the lamp L to reduce this losses.
I’ve build this adjustable power supply and works great! I hope you’ll enjoy it too and have fun build this great stabilized power supply.