SEE a simple salinometer or salinity tester in food and water. Good for health. Using LM324 and few parts and LED display easily use, with 9V batts
his is Digital multimeter circuit using ICL7107. dc digital meter circuit to smart full function, measure DCV, ACV, DC Amp meter, AC Amp meter, Ohms [...]
This Diode tester circuit can check the diode the good or bad and also can indicate its polarity. using op-amp 741IC and LED for display. [...]
This is an simple op-amp IC tester circuit that cheap and easy to build. for test many op-amp ICs fast check. for LM741, LM324, LM339, LM358, LM311 and more [...]
The TV test pattern generator circuit with wireless model. To assemble circuit easy, can transmit signal in wireless to video and audio As horizontal line.
This is Crystal tester circuit using NPN transistors as main. LED1 is light up when a crystal is good and simple oscillator circuit works.