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Delay Circuits
Delay Circuits:  #'s - H     I - Z

Last Updated on:
Saturday, August 30, 2014 10:27 AM

Circuits Designed by Dave Johnson, P.E. :
  • LONG PERIOD COMPUTER WATCH DOG TIMER
    This circuit uses a simple 4060 IC oscillator/timer that 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:

Long Period Computer Watch Dog Timer -  This circuit uses a simple 4060 IC oscillator/timer that 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. . [Designed by David A. Johnson]
Low Voltage , High Current Time Delay Circuit -  (diagram added 05/07)
Power Off Time Delay Relay Circuit -  (electronic circuit added 7/03)
Power on Time Delay Relay Circuit -  (circuit / schematic design added 6/06)
Power-Off Time Delay Relay -  The two circuits above illustrate opening a relay contact a short time after the ignition or light switch is turned off. The capacitor is charged and the relay is closed when the voltage at the diode anode rises to +12 volts. The circuit on the left is a common collector or emitter follower and has the advantage of one less part since a resistor is not.....
Power-Off Time Delay Relay Circuit -  (electronic circuit added 4/05)
Power-on sequencing using TL431 in comparator mode -  TL431 as a comparator. Delay timers. Power-on sequencers. TL431 without feedback can be considered as an NPN or N-MOS device with high transconductance and precise 2.5V turn-on voltage. Tube heads beware: the upper (+supply) pin on TL431 is cathode, lower (-supply), anode.....it's another world. .(design added 07/07)
Power-On Time Delay Relay -  Here's a power-on time delay relay circuit that takes advantage of the emitter/base breakdown voltage of an ordinary bi-polar transistor. The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a higher turn-on voltage for the Darlington connected transistor pair. Most any bi-polar transistor may be used, but the zener voltage will vary from about 6 to 9 volts depending on the particular transistor used. Time delay is roughly 7 seconds using a 47K resistor and 100uF capacitor and can be reduced by reducing the R or C values. Longer....
Relay Delay -  This circuit waits for a set time and then activates a relay. With the cap that is in the schematic you will get about a 6 sec delay till power on. You can change the cap in this circuit to 470uF for about a 20 sec delay.....
Relays: Delayed Turn-On -  This circuit is a delayed turn-on relay driver and can produce time delays for up to several minutes with reasonable accuracy. The 14001 (or 4001) CMOS gate here is configured as a simple digital inverter. Its output is fed to the base of a regular 2N3906 (PNP) transistor, Q1, at the junction . [Tony van Roon's circuit]
Smooth Tone Clickless CW SideTone Generator -  This circuit is about as good as it gets for generating morse code tones. It may be used as a code practice oscillator, a tone generator for a keyer, a sidetone oscillator for a CW transmitter or an audio Modulated CW (MCW) generator for an FM transmitter or repeater..... [G. Forrest Cook]
Soft-Start Circuit For Power Amps -  Although the soft start circuit can be added to any sized transformer, the winding resistance of 300VA and smaller transformers is generally sufficient to prevent a massive surge current. Use of a soft start circuit is definitely recommended for 500VA and larger transformers..... [Rod Elliott (ESP)]
Switch on delay circuit -  Schematic only, no circuit description
time delay circuit -  Schematic only, no circuit description
Time Delay Generator -  Circuit Ideas for Designers Application Notes Advanced Linear Devices, Inc.....[App Note]
Time Delay Relay -  A time delay relay is a relay that stays on for a certain amount of time once activated.  This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to about 20 seconds with the parts specified. The current capacity of the circuit is only limited by what kind of relay you decide to use..... [Aaron Cake]
Time Delay Relay II -  When activated by pressing a button, this time delay relay will activate a load after a specified amount of time.  This time is adjustable to whatever you want simply by changing the value of a resistor and/or capacitor. The current capacity of the circuit is only limited by what kind of relay you decide to use.... [Author: jawaharlal@excite.com]
Time-delay relay reduces inrush current -  7-Mar-02 Issue of EDN  A transformer switching onto a line can sometimes cause a circuit breaker to trip or a fuse to blow.  This phenomenon occurs even if the transformer presents no load, such as when the secondary is open. The problem arises because of the heavy magnetizing inrush current in the transformer. The amplitude of the current depends on the instant on the ac waveform at which the transformer become..... [Design Idea by P Seshanna, Assumption University, Bangkok, Thailand]
Timer Circuits for Very Long Delays Using a CD4541B -  Very Useful Timers.....(design added 12/08)
Transistors offer overload delay -  16-Sep-04 Issue of EDN  Although an SMPS (switch-mode power supply] can protect itself against permanent short circuits, it sometimes has problems when dealing with transient overloads. Transient overloads are not short circuits but can push the power supply above its nominal load value.  This scenario occurs with typical loads such as printer heads and small motors..... [Design Idea by Christophe Basso, On Semiconductor, Toulouse, France]
Windshield Wiper Delay -  The intermittent wiper circuit shown above causes the auto's windshield wipers to wipe once every several seconds instead of constantly wiping. The circuit may be added to older cars to provide the intermittent function or it.....(electronic circuit added 08/08/08)

Delay Circuits:  #'s - H     I - Z


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