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Digital Clock with MM5314N... [read more]

When the water-level is below the steel rods, no contact is occurring from the metal can and the rods, which are supported by a small insulated (wooden) board. The small circuit built around IC1 draws no current and therefore no voltage drop is generated across R5. IC2A, IC2B and Q1 are wired as a window comparator and, as there is zero voltage at input pins #2 and #5, D3 will illuminate. When the water comes in contact with the first rod, pin #13 of IC1 will go high, as its input pins #9 to #12 were shorted to negative by means of the water contact.... [read more]

his remote transmits a tone using an infa-red LED. This tone is decoded by the receiver. Since the receiver only switches when it "hears" the tone, there are no accidental activations.... [read more]

This accurate one-pulse-per-second clock is made with a few common parts and driven from a 50 or 60 Hertz mains supply but with no direct connection to it. A beep or metronome-like click and/or a visible flash, will beat the one-second time and can be useful in many applications in which some sort of time-delay counting in seconds is desirable. The circuit is formed by a CMos 4024 counter/divider chip and 3 diodes, arranged to divide the frequency of the input signal at pin #1 by 50 (or 60, see Notes).... [read more]

The ICL7107 is a 3 1/2 digit LED A/D convertor. It contains an internal voltage reference, high isolation analog switches, sequential control logic, and the display drivers.... [read more]

Have you ever seen the stairs to one of the upper stories in your house turn into a waterfall? Or maybe you’ve come home to find your aquarium fish trying to swim across the carpet? For your sake, we hope not, because the consequences are usually fairly dramatic. With a handful of electronic components, you can at least ensure that you will be warned before you have to put on your waders. It’s better to prevent water problems than to have to correct them. But no how many precautions you take, an occasional leak can still happen.... [read more]