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Timers & Counter Circuits
Designed by David A. Johnson, P.E.

Last Updated on: Friday, July 18, 2008 11:34 AM
Master Category List - Dave's Circuits
 
  • 555 Timer Forms Simple PWM Motor Controller
    Using a CMOS version of the 555 timer, this circuit can be used to control the speed of a motor by adjusting the duty cycle of the pulses sent to the motor. (added 7/06)
  • CIRCUIT FORMS DIVIDE BY 1.5 COUNTER
    Two inexpensive ICs divide a TTL clock signal by 1.5. By following the circuit with another flip/flop, you could also generate a divide by three function.
  • DARKROOM CAMERA SHUTTER TIMER
    This circuit was designed to control a film exposure shutter for a darkroom. It has 8 time steps ranging from 0.35 seconds to 4 seconds. It is activated by a foot switch and draws power from an external 12 volt DC supply.
  • HONEYBEE COUNTER
    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.
  • LONG PERIOD COMPUTER WATCH DOG TIMER
    This circuit uses a simple 4060 IC oscillator/timer which is reset periodically by a computer. Should the computer fail to send a pulse, the output changes state. The time can easily be set from seconds to hours.
  • On/Off Flip/flop Circuit with Automatic Timeout
    This circuit is ideal when a device needs to be turned on and off with a single pushbutton switch, but also needs to turn itself off after some period of time. With the components shown, the output will stay on for only about 20 seconds. 


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