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Timers and Counters Circuits, Page 2a
Timers & Counters:  #-A     Next B-E   Previous B-E    F-L     M-S     T-Z
Last Updated on: Wednesday, November 29, 2017 05:38 AM
Circuits Designed by Dave Johnson, P.E. :
  • 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.
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  • 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.

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:
D - Flip-Flop Made With A LM556 Timer -  Uses the LM555 timer or its cousins with other letter prefixes. There can be minor differences between 555 timer IC's from different manufacturers but they all should be useable for any circuit.   Designed for Model Trains…. [from Rob Paisley's Model Train web site]
Dark Detector -  When the level of light on the photo-cell decreases, the 555 is activated. Photo-cells (Photo-resistors) have a wide range of specifications. Some cells go down to 100R in full sunlight while others only go down to 1k. Some have a HIGH resistance of between 1M and others are 10M in total darkness. For this circuit, the LOW resistance (the resistance in sunlight) is the critical value....
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DCC Zero Stretching Simulator (LM555) -  This circuit is designed to simulate the 'Zero Stretching' function of Digital Command Control systems used by model railroads. This circuit was used drive the booster while testing the operation of block occupancy detectors and DCC signal failure circuits while in the zero stretching mode.... [from Rob Paisley's Model Train web site]
Delayed Re-Triggering -  Uses the LM555 timer or its cousins with other letter prefixes. There can be minor differences between 555 timer IC's from different manufacturers but they all should be useable for any circuit.   Designed for Model Trains…. [from Rob Paisley's Model Train web site]
Dice -  Press the push switch to 'throw' the dice: this makes the circuit rapidly cycle through the dice numbers so that an effectively random dice number is displayed by the LEDs when the push switch is released.… [Designed by John Hewes]
Driving A Bi-Coloured LED -  Some 3-leaded LEDs produce red and green.  This circuit alternately flashes a red/green bi-coloured LED
Driving A Relay -  The 555 will activate a relay. When pins 2 and 6 are connected as an input, the chip requires only about 1uA to activate the output.  This is equivalent to a gain of about 200,000,000 (200 million) and represents about 4 stages of amplification via transistors....
Driving Loads Of Greater Than 15 Volts -  Uses the LM555 timer or its cousins with other letter prefixes. There can be minor differences between 555 timer IC's from different manufacturers but they all should be useable for any circuit.   Designed for Model Trains…. [from Rob Paisley's Model Train web site]
Driving White LEDs -  The 555 is capable of sinking and sourcing up to 200mA, but it gets very hot when doing this on a 12v supply.  The following circuit shows the maximum number of white LEDs that can be realistically driven from a 555 and we have limited the total current to about 130mA as each LED is designed to pass about 17mA to 22mA maximum. A white LED drops a characteristic 3.2v to 3.6v and this means only 3 LEDs can be placed in series. 
Dummy Alarm -  This project makes a superbright LED flash briefly once every 5 seconds to imitate the indicator light of a real alarm. The circuit is designed to use very little current to prolong battery life so that it can be left on permanently. This is a simple project, ideal for a beginner.... [Designed by John Hewes]
Eight LEDs Random Flasher -  This project uses a 4026 counter and display driver IC to flash eight LEDs in an apparently random manner. It can be used to create a display of your choice.… [Designed by John Hewes]
Electronic Time Constant Control -  Uses the LM555 timer or its cousins with other letter prefixes. There can be minor differences between 555 timer IC's from different manufacturers but they all should be useable for any circuit.   Designed for Model Trains…. [from Rob Paisley's Model Train web site]
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