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Timers and
Counters Circuits, Page 3 Timers & Counters:
#-AB-ENext F-LM-S T-Z Last Updated on:
Monday, October 03, 2011 06:08 PM
Circuits
Designed by Dave Johnson, P.E. :
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.
Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
Fastest 555 Oscillator - The highest frequency can be obtained by
connecting the output to pins 2 and 6. This arrangement takes about
5mA and produces an output as shown:
Fixed 50% Output Duty Cycle Using Logic Devices - 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]
Flashing Indicators - Need to flash "turn indicators" using a 555
and a single 20 amp relay. Here is our suggestion. The timing resistor needs
to be selected for the appropriate flash-rate.
Flashing LED - This simple project makes a good low-cost first
project to check your soldering skills and learn to identify common
components. The LED flashes at about 3Hz (3 flashes per second).… [Designed
by John Hewes]
Flip Flop - When output pin 3 is HIGH, the 220n charges through the 220k to
6v. When pin 3 is LOW, the 220n discharges through the 220k to 0v. Pressing the switch
upsets the 3v created by the two 10k voltage dividers, triggering the flip flop inside
the 555 and changing the state....
H-Bridge - This circuit drives a motor clockwise / anticlockwise via a 10k
to 100k pot.
H-Bridge with PWM - This circuit drives a motor clockwise / anticlockwise
via a pot and reduces the speed to zero when the pot is in mid-position. The current
is limited to 200mA and the voltage across the motor is less than 6v, but the circuit
shows the principle of Pulse Width Modulation (providing powerful bursts of current to
the motor to create a high or low RPM under load) and both forward / reverse RPM via
the H-bridge arrangement.
Heart-shaped Badge - The badge consists of eight LEDs arranged in the shape
of a heart. One LED is lit at a time and this 'chases' round the shape. It would be
easy to adapt this project to create other shapes with the eight LEDs.… [Designed by
John Hewes]
Hee Haw Siren - Build the circuit and listen. Change the resistors and
capacitors to get all sorts of different results.
High Frequency 555 Oscillator - 360kHz is the absolute maximum as the 555
starts to malfunction with irregular bursts of pulses above this frequency. To improve
the performance of the oscillator, a 270R and 1n can be added as shown in the second
circuit:
Ignition Timer - ….must register on this site.... [Published in Elecktor
July/August 2010]
Increasing Output Current - The 555 will deliver 200mA to a load but the
chip gets extremely hot (12v supply). The answer is to use a buffer transistor.
Increasing Output Push-Pull Current - Some 555's do not swing rail-to-rail
when 200mA is being delivered and the chip gets very hot when trying to deliver 200mA.
The solution is to add a push-pull output. The following arrangement has been chosen
as it swings almost rail-to-rail but two faults need to be addressed....
Interlocked Monostable Timers - 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]
Knight Rider - In the Knight Rider circuit, the 555 is wired as an
oscillator. It can be adjusted to give the desired speed for the display. The output
of the 555 is directly connected to the input of a Johnson Counter (CD 4017). The
input of the counter is called the CLOCK line.
