D-FLIP/FLOP OSCILLATORS (19) (dfliposc2) Yes you can turn flip/flop ICs into low current oscillators. This schematic shows you how. |
PUSHBUTTON ONESHOT AND LATCH (52) (4013oneshots) This circuit uses a single IC to convert a noisy pushbutton switch signal into a clean pulse or a sustained push on-push off signal. It can operate from 3v to 18v. |
D-FLIP/FLOP ONE SHOT CIRCUITS (68) (dflip1shots) Yes you can use cheap D flip/flop logic circuits as nice one-shot pulse generators. This schematic shows how the popular CD4013 and the CD74HC74 can be used to generate pulses ranging from nanoseconds to seconds. |
FLASHING LED ADVERTISING BADGE (81) (badgfls1) I have seen numerous flashing light badges at trade shows and conventions. They are often handed out as gifts to promote some business. The devices often use inefficient circuits, which cause the battery power source to be quickly depleted. My circuit is simple but efficient enough to provide months of continuous LED flashing. It also has a tiny push-button switch to turn on and off the light flashing, extending battery power. |
TIME TO DUST INDICATOR (85) (dust2) I thought about this circuit when I heard that a lot cleaning personal in hotels were either dusting rooms more often than necessary or not enough. I have not yet built and tested this circuit completely but in concept it should work. The circuit draws very low current from a +3v battery and could be housed in a package similar to a small ashtray. The assembly might be placed in a suitable out of the way area to collect dust. It would alert a maid when it was time to dust the room. The circuit detects dust with an infrared LED that is pulsed so its light shines onto a smooth flat plate. Any dust settling onto the surface is detected by a phototransistor, mounted at a 90-degree angle from the LED. When the dust reaches a particular level, sufficient light is reflected into the phototransistor to change the logic state of the circuit to an alarm condition. The alarm output could be connected to a beeper, a flashing LED or to one of the LED flashing circuits in this Tutorials circuit section. |
HONEYBEE COUNTER (86) (beectr) I designed a circuit similar to this one a long time ago to help a beekeeper count the number of bees going into or out of a hive. The low power circuit uses a slotted opto-sensor to detect the passing bees. The circuit advances an electronic counting module whenever a honeybee passes through the sensor. The device only counts the number of bees going through the sensor. A different circuit would be needed to count the number of bees only going out or only coming into the hive. |
1.5V TOUCH ACTIVATED SWITCH (102) (mom1v1) A single 1.5v silver oxide button cell powers this complete touch activated switch circuit for 5 years. It features both a normally open and a normally closed set of solid-state switch thermals. It also has an adjustable sensitivity, which can be set for a touch capacitance change as small as 1 picofarad. |
-3V CAPACITANCE PROXIMITY SWITCH (108) (3VTCHMOM2) This circuit was designed to provide a touch activated switch function without an external power supply. It draws so little power that a single 3v battery will operate the circuit for many years. It is discussed in more detail in the section on Capacitance Proximity Switch Technology. (Note: link is off-site) |
FLASHING LED ADVERTISING BADGE (125) (badgfls2) This circuit is similar to schematic #81. It uses a CD4013 dual D Flip/Flop IC. The 74HCT74 IC in #81 does not always work. As in #81, a single lithium battery will provide months of continuous LED flashing. It also has a tiny push-button switch to turn on and off the light flashing. |
Soft On / Off Switch: Modern electronic equipment incorporate "push-to-on-push-to-off" switches that do not make the clicking noise as with old equipment. An example of this is the power button on a ATX computer cabinet. Here is a circuit that does the same. It can be used to turn on/off any electronic/electrical equipment that operates on any range of voltages. FAIR WARNING -- THIS SITE HAS ANNOYING POP UP ADS. |
Telephone Line Based Audio Muting & Light on Circuit: FAIR WARNING THIS SITE HAS ANNOYING POP UP ADS. |
Telephone Line Based Audio Muting & Light On Circuit: The circuit would automatically light a bulb on arrival of a telephone ring and simultaneously mute the music system/TV audio for the duration the telephone handset is off-hook. Lighting of the bulb would not only indicate an incoming call but also help in locating the telephone during darkness. |
