Hobby diy
Liquid detector, water sensor
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.
Electronic Metronome circuit schematic
This metronome schematic is not modern but is cheap and reliable. The well known 555 is presented in this metronome circuit and produces regulated impulses wich can be heard at a speaker. The metronome frequency can be adjusted with P1. The power supply is a 9V battery and if you use a 8Ω speaker insert [...]
Mini drill revolutions, speed regulator 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 [...]
