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Schmitt Trigger Circuits
Schmitt Triggers:  #'s - C      D - Z
 

Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

VCO from CMOS Schmitt Trigger IC -  By changing the supply voltage fed to a classic 4584 Schmitt trigger type oscillator, the oscillator frequency can be changed over a range of 50:1.  A 74HCU04 inverter is used at the output of the 4584 to maintain a constant TTL logic level signal . . . Hobby Circuit designed by David A. Johnson P.E.-March, 2002


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Desktop Power Supply from a PC -  if you find building your own desktop power supply from a recycled PSU and a few parts from the local electronics store appealing, then grab some tools, pour yourself a cup of coffee (or personal preference) and let's get started. The LED (light emitting diode) was also salvaged from an old PC.  If you want to add a power on indicator,  __ Designed by Andy Batts

DPP adds versatility to VFC -  14-Nov-02 EDN Design Ideas:  The basic VFC (voltage-to-frequency converter] in Figure 1 comprises an integrator (IC 1] and a Schmitt-trigger circuit (IC 2].  The integrator converts the dc input voltage, ViN , to a linear voltage ramp, and the Schmitt trigger sets the limits of the integrator's output voltage.  Feedback around both circuits provide as the condition for oscillation __ Circuit Design by Chuck Wojslaw, Catalyst Semiconductor, Sunnyvale, CA

Fidelity Testing for A to D Converters -  Linear Technology AN132 __ Designed by Jim Williams - Oct 1st, 2011

Form Constant-Current SCR -  02/01/01 EDN Design Ideas:  A typical SCR (silicon-controlled rectifier) requires a trigger current, which causes the SCR structure to latch on.  Once the device latches, the current through the SCR is solely a function of external component values.  The SCR has no inherent ability to limit the current flow once it latches on.  Current continues to flow, as long as the current exceeds a minimal value known as the holding current.  The circuit in Figure 1 is similar to an SCR, because it also requires a trigger current to latch into its on state.    __ Circuit Design by Robert Buono, Ringwood, NJ

Good 12 Volt Switching Power Supply -  This is a good Circuit for those persons needing to Boost or drop a voltage.  The Output is High Frequency, but can be Rectified and Filtered to give DC Out.  When Rectifying High Frequencies, You MUST use the Appropriate types of HIGH SPEED Diodes to handle these frequencies.  Normal diodes Will OVERHEAT and Burn out.   __ Designed by G.L. Chemelec

Greatly improve dV/dt immunity of SCRs -  12/09/13  EDN Design Ideas:  improve dV/dt immunity of SCRs by three orders of magnitude - The SCR is a switching semiconductor device, whose theoretical basics were published by Moll et al.  in 19561.   __ Circuit Design by Marian Stofka

Inverter 12 volt unit Mos-Fet Design -  A Very Reliable, Efficient and Practical Design.  Do Not ask how to Build this for Power ratings over 1000 watts, That is NOT Practical.   __ Designed by G.L. Chemelec

Lamp Dimmer Full Wave SCR (120 Volt AC) -  The full wave phase control circuit below was found in a RCA power circuits book from 1969.  The load is placed in series with the AC line and the four diodes provide a full wave rectified voltage to the anode of a SCR.  Two small signal transistors are connected in a switch configuration so that when the voltage on the 2.2uF capacitor reaches about 8 volts, the transistors will switch on and discharge the capacitor through the SCR gate causing it to begin conducting.  The time delay from the beginning of each half cycle to the point where the SCR switches on is controlled by the 50K resistor which adjusts the time required for the 2uF capacitor to charge to 8 volts.  As the resistance is reduced, the time is reduced and the SCR will conduct earlier during each half cycle which applies a greater average voltage across the load.  With the resistance set to minimum the SCR will trigger when the voltage rises to about 40 volts or 15 degrees into the cycle.   __ Designed by Bill Bowden

MOS transistors form current-mode Schmitt trigger -  12/03/98 EDN Design Ideas:  Schmitt triggers are useful in both analog and digital circuits for reducing sensitivity to noise and disturbances.  Current-mode Schmitt triggers are particularly useful in photodetectors, bar-code readers, and optical remote controls.  The resistor less current-mode Schmitt triggers are useful in both analog and digital circuits for reducing sensitivity to noise and disturbances.  Current-mode Schmitt triggers are particularly useful in photodetectors, bar-code readers, and optical remote controls.  The resistor less current-mode Schmitt.      FILE
has several circuits, scroll to this one __ Circuit Design by Tai-Shan Liao, Chun-Ming Chang, and Wen-Yaw Chung, Chung-Yuan, Christian University, Taiwan, China

MOSFET, Inverter 12 volt unit -  A Very Reliable, Efficient and Practical Design.  Do Not ask how to Build this for Power ratings over 1000 watts, That is NOT Practical.   __ Designed by G.L. Chemelec

Multi-Purpose Inverter -  Permanent lash-up for driving anything.  Complete with over-current and temperature shutdown! __ 

Oscillator extends Schmitt triggers' reach -  EDN Design Ideas:  01/19/95    Fig 1a shows input filters and Schmitt triggers wired to square up tachometer signals.  However, given normal variations in IC lots and operating environments, Fig 1a's fixed-bias scheme (comprising RV and RG) stands little chance of holding the dc level at the Schmitt triggers' inputs anywhere near halfway between their thresholds.  Because the strength of tachometer signals is proportional to speed, below a certain speed, this circuit does not respond properly to the resulting low-level signals.    __ Circuit Design by Phil Harvey, Technology Integration Inc, Bedford, MA

Poor man's analog to digital converter (ADC) using a 2N222 transistor & a few passives -  Years ago some of the then-old engineers working in the cost-completive area of consumer electronics told me, ďif it canít be done with a handful of resistors, caps, a 1N4148 diode and an MPS3904 or MPS2907 transistor, it ainít worth doing.  Ē __ Designed by Dave Wissel @ Wave Technology

Resistor network extends Schmitt trigger's reach -  09/13/01 EDN Design Ideas:  The circuit in Figure 1 shows a familiar technique for converting a low-level analog signal to digital form.  Resistors R1 and R2 set the quiescent dc level at the Schmitt inverter's input to a value roughly equal to the midpoint of the hysteresis band.  Capacitor C1 removes dc content from ViN, such that the Schmitt trigger's input signal, Vi, centers itself on the mid-hysteresis level __ Circuit Design by Anthony Smith, Scitech, Biddenham, UK

SC Schmitt Comparator Head -  A simple little design by Martin Keen and Wilf Rigter __ Designed by Wilf Rigter

Schmidt trigger -  Article is in Dutch __ Designed by Jan Hammer

Schmitt Trigger -  Can also be called AN inverter or a SCHMiTT inverter.  We have animated the circuit to show how the output goes high or low according to the input level.  The animation shows a wide gap between the input levels.  __ 555-Timer

Schmitt Trigger -  This circuit uses a single op-amp and the output is triggered by two different voltage levels.   __ Designed by Andy Collison

Schmitt trigger adapts its own thresholds -  EDN Design Ideas:  03/16/2015    if you need to condition a widely-varying signal, a simple Schmitt wonít work, but this Di will __ Circuit Design by Anthony Smith

Schmitt trigger has dynamic threshold -  06/05/97 EDN Design Ideas:  Schmitt triggers usually switch only at predefined static setpoints.  For example, to allow user-defined setpoints, you can use a comparator in a standard hysteresis configuration (Figure 1).  However, the design in Figure 2 allows dynamic setpoints, which are beneficial for variable-noise applications.  This circuit is useful for rejecting noise that fluctuates in amplitude. __ Circuit Design by Isaac Eng, GSI Inc, Ottawa, ON, Canada

Schmitt trigger uses two transistors -  Hereís a Di circuit that displays Schmitt-trigger action and can work at high current or voltage. __ Circuit Design  Einar Abell

Schmitt Trigger: an unusual -  This is a Schmidt unlike any you have seen before.  it has some unusual properties - some of which are distinct advantages, some are disadvantages.  There is no 'best circuit' - different ways of doing a particular function have different uses.   __ Designed by Richard Torrens

SCR phase control yields solid-state switch -  03/15/01 EDN Design Ideas:  SCRs (silicon-controlled rectifiers]/ PDF contains multiple circuits scroll to find the one of interest, or thyristors, have higher current and voltage ratings, lower conduction losses, and more robustness than TRIACs.  For these reasons, SCRs are better suited to high-power applications __ Circuit Design by James Keith

SCR Voltage Regulator -  Though not as accurate as a linear or a high-frequency switching regulator, an SCR voltage regulator wastes little power and creates no RFi.   __ Designed by Andrew R. Morris

SCR-Controlled Eht Power Supply -  Presented here is an extra-high-tension (EHT) power supply capable of delivering variable DC voltage from about 100 V to 5 kV with load current up to 500 mA.  One way of...__ Electronics Projects for You

Simple Circuit changes improve Schmitt trigger -  05/13/99 EDN Design Ideas:  The classical Schmitt trigger circuit that youíll find in textbooks provide as some noise immunity, such as for the front end of magnetic pickup in position-sensor circuits (Figure 1a].  You adjust the two threshold levels   PDF contains many circuits, scroll to find this one.    __ Circuit Design by Ron Patrick, ECM, Los Altos, CA

Simple Circuit Inverter -  This circuit will provide a fairly stable "Square Wave" Output Voltage.  Frequency of operation is Mainly determined by the 220 uF Feedback Caps.  Currently about 60 Hz.  Various "off the shelf" transformers can be used. __ Designed by G.L. Chemelec

Simple Circuit Switching Power Supply -  This is a Somewhat Experimental Circuit and I Especially designed this circuit for those persons that want to Dabble in Switching Power Supply Designs. This Circuit is based on a UC3843 integrated Circuit. it does Not allow for Feedback control of the output voltage.  __ Designed by G.L. Chemelec

Thermostat for 1KW Space Heater SCR controlled -  Below is a thermostat circuit I recently built to control a 1300 watt space heater.  The heater element (not shown) is connected in series with two back to back 16 amp SCRs (not shown) which are controlled with a small pulse transformer.  The pulse transformer has 3 identical windings, two of which are used to supply trigger pulses to the SCRs, and the third winding is connected to a PNP transistor pair that alternately supply pulses to the transformer at the beginning of each AC half cycle.  The trigger pulses are applied to both SCRs near the beginning of each AC half cycle but only one conducts depending on the AC polarity. __ Designed by Bill Bowden

Transistor Schmitt Trigger Oscillator -  The Schmitt Trigger oscillator below employs 3 transistors, 6 resistors and a capacitor to generate a square waveform.  Pulse waveforms can be generated with an additional diode and resistor (R6).  Q1 and Q2 are connected with a common emitter resistor (R1) so that the conduction of one transistor causes the other to turn off.  Q3 is controlled.   __ Designed by Bill Bowden

VCO from CMOS Schmitt Trigger IC -  By changing the supply voltage fed to a classic 4584 Schmitt trigger type oscillator, the oscillator frequency can be changed over a range of 50:1.  A 74HCU04 inverter is used at the output of the 4584 to maintain a constant TTL logic level signal . . . Hobby Circuit designed by David A. Johnson P.E.-March, 2002

Very Basic 12 volt Inverter -  This circuit will provide a fairly stable "Square Wave" Output Voltage.  Frequency of operation is Mainly determined by the 220 uF Feedback Caps.  Currently about 60 Hz.  Various "off the shelf" transformers can be used. __ Designed by G.L. Chemelec


Schmitt Triggers:  #'s - C      D - Z

 


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