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Electrical Engineering

Questions tagged [schmitt-trigger]

Anything related to Schmitt trigger circuits. Schmitt triggers are positive feedback comparator circuits exhibiting hysteresis.

147 questions
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Calculating resistor values for a Schmitt Trigger and LDR circuit

I am trying to make a light sensing circuit which has hysteresis. I want an op-amp (LM358) to output logic 1 (12v) when the light level rises above 250 lux, and output logic 0 (0v) when the light ...
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0answers
48 views

Driving transistors without using MCUs

I'm trying to drive transistors with just a push of a button without using a MCU. The circuit I drawn drives different transistor on every button push and resets back. First part is a debounce circuit ...
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3answers
47 views

Really occasional malfunction of the Schmitt-trigger input

I'm using some Schmitt-trigger inputs for debouncing the interrupt problems. Referring to above circuit, the circuit has a RC circuit and the output of the RC circuit goes to the Schmitt-trigger IC(...
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0answers
68 views

Asymmetrical Schmitt trigger circuit

I'm designing a circuit to switch a solenoid with hysteresis. I'd like to switch the solenoid off, shown by R12, when the signal is above 0.8V and switch it back when it's below 0.7V. With the ...
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1answer
122 views

STM32L0: Fast processing of an analog sinusoidal signal

I have an embedded system based on a STM32 ARM Cortex M0+ microcontroller (STM32L051K6) and want to use it to convert an analog sinusoidal input signal into a digital pulse signal and do some SW ...
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5answers
94 views

Schmitt Trigger hysteresis

I am studying comparators and Schmitt triggers. And I did not find anywhere how to choose the value of hysteresis. I understand its purpose and I know how to calculate it. But what value is needed for ...
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2answers
44 views

Voltage appears on comparator input

I have made a pcb . A part of the circuit is the Schmitt trigger comparator seen above . The positive feedback resistors are chosen to give the noniverting input values from zero to 0.5 volts . ...
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62 views

Flashing an LED with Schmitt trigger

I'm trying to build the above circuit, which is supposed to flash an LED with a schmitt trigger (with the possibility to vary the frequency with the knob of the 47kOhm potentiometer). I don't have a ...
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1answer
121 views

Schmitt Trigger: Problems between theory and reality

I want to say that I am not a native English speaker so you may find some writing errors. Also, I am just learning electronics, so sorry if some questions are poorly formulated. I am trying to build ...
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0answers
56 views

Schmitt trigger oscillators interfere with eachother (74HC14)

I am using a single 74HC14 (hex schmitt trigger) to implement three oscillators. I now have a test build ready and encounter problems. See schematic, it shows component values. Also proper 5V power ...
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2answers
100 views

Need help understanding an electronic oscillator (Schmitt trigger + capacitor) [duplicate]

When we use this circuit, the LED blinks. I know an inverter transforms high to low voltage and low to high voltage, but here the voltage source is connected to the inverter all the time so the ...
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35 views

Simplest schmitt trigger with fewest part count for microcontroller

I own several AT89C4051 microcontrollers and I'm currently trying to read signature bytes of the micros that I probably broke (by applying 7.2V to the VCC pin before noticing the 5V regulator became a ...
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26 views

Lowest resistor value for enclosed light sensor unit with nearby lighting without losing sensitivity

This is a drawing I made of a light sensor unit I'm creating. Inside of it, I have a circuit board containing 3 7-segment displays and I have two photo-transistors (yellow half-circles in the picture) ...
3
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1answer
488 views

Why is this BJT Schmitt trigger producing a sine wave?

I am trying to build a Schmitt trigger from a pair of BJTs to convert a sine to a square wave. The sine wave is from a Colpitts oscillator running at over 150 MHz. I want to measure the ...
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1answer
39 views

Determining U_ref on Schmitt Trigger

If I have only starting values a U_high=3V and U_low=2V (pulse signal on V3 on schematics), can I determine a U reference, that's given us on the inverting input of the op. amp.? My calculations were:...
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1answer
82 views

Op. amp. with integrator - enough values to start?

All the red-circled values (Uref, C2, R31 and R36) are missing. I'm supposed to calculate them, but I think there's at least one value missing. Shouldn't Uref be known to calculate the rest of the ...
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3answers
275 views

Schmitt Trigger not reaching full saturation

I'm trying to develop a sensor based on the optoelectronic device CNY70. I want to filter the signal in order to be read by a microprocessor, where the threshold to change between logic levels could ...
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2answers
73 views

Need help to increase schmitt trigger sensivity in a circuit

I need help on a circuit I've designed to detect hits on a piezo sensor on a drum. It uses an opamp with 2 channel, on goes to a schmitt trigger, the other to the ADC input on the XMEGA ...
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2answers
56 views

Schmitt trigger inverters or regular inverters for clean high speed data processing

I made a circuit in which data is passed in from phototransistors (part# PT334-6C) into a microcontroller (part# AT89C4051) serial port via schmitt trigger inverters (part# 74HC14) and a demultiplexer ...
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1answer
215 views

Schmitt trigger with 741 op-amp not behaving as in simulation

I am implementing a Schmitt trigger using the circuit shown below. This circuit consists of one LM741 op-amp, which acts as an asymmetrical Schmitt trigger with a single power supply. According to ...
0
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1answer
135 views

cd40106 Problems

so im trying to make this simple oscillator using ic cd40106 without any succsess. it's the usual astable multivibrator configuration using a 9v pwr supply, 220k resistor and a 2.2uf capacitor, the ...
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2answers
204 views

Why do I get a triangle wave in this Schmitt trigger oscillator?

I'm trying to design a function generator that can generate square, triangle and sine waves, with frequency varying between 100Hz and 100kHz. The circuit in the blue box is supposed to be a schmitt ...
3
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2answers
382 views

Flip a Schmitt-Trigger when current flows through a Zener diode

I am trying to design a circuit using an intermitent power source (a bicycle hub generator), which is rectified and filtered, and regulated at 6,8V. Now I want to "detect" when the power source is ON ...
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0answers
61 views

Schmitt trigger versus Hysterisis Comparator

I'm working to create an ultrasonic sensor to be used in object recognition. I've been studying various schematics and current sensors on the market - the most common being the HC-SR04. When viewing ...
6
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1answer
815 views

How does a “speed up capacitor” work in Schmitt trigger?

Hello I'm trying to understand how adding a capacitor across R2 in below circuit increases the switching speed. I don't see how C2 supplies charge to C1. With the additional capacitor C2, it seems ...
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0answers
82 views

Analytically obtaining the hysteresis of an opamp Schmitt trigger with RC network in its inverting input

This is a follow-up from here. I have got the following Schmitt trigger circuit implemented already on a breadboard. As seen, the input signal at the non-inverting and inverting terminals of the op ...
0
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1answer
49 views

Strange state in input at the amplifier

I have this schematic, an invert Schmitt trigger attached to the RC component to create a triangle wave. It's an oscillator. The two oscillators go in to the amplifier, but I don't understand why I ...
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1answer
134 views

Comparing two variable voltages with hysteresis

All of the designs I have seen for adding hysteresis to a comparator (Schmitt triggers) assume that one of the two inputs to the comparator is set at a fixed reference voltage (typically with a ...
0
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1answer
149 views

Are Schmitt trigger and peak detector comparator the same?

Here is a peak detector comparator schematic ,its symbol,and its simulation.I have some question about them. First,we all know the Schmitt trigger symbol is the same as the second picture,so are ...
3
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3answers
234 views

Calculating R and C for schmitt trigger debouncer

I've been looking all over the internet to try to figure out the optimal values for R1, R2, and C but couldn't find info. I'm trying to ideally make a debouncer that will work with any button on the ...
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2answers
1k views

Can multiple Schmitt triggers in series fully debounce a switch?

After dealing with software debouncing for a while, I find it takes a huge toll on the system, so I thought of initially making a hardware debouncer with one Schmitt trigger (74HC14), a capacitor, ...
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1answer
48 views

Schmitt trigger issues… lumpy outputs and wrong switching voltages

I'm trying to implement the Schmitt trigger found in "CMOS" by J. Baker. Here's what the circuit should look like: And this is how the transistors should be dimensioned to achieve switching voltages ...
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1answer
351 views

Inverting schmitt trigger with pnp transistors

I have a question regarding Schmitt Trigger. I am trying to design an inverting output (at UTP=Low, at LTP=High) Schmitt Trigger for an application. However, I need to use PNP transistors since the ...
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0answers
242 views

Schmitt trigger with three transistors

I usually understand well transistors circuits, but I just can't get to work with this one: (Note the circuit is powered with +/- 12V) It is supposed to be a schmitt trigger circuit, and I'm trying ...
3
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3answers
1k views

Schmitt trigger - why is there no current over the second transistor?

I'm reading through The Art of Electronics, and I'm trying to wrap my head around a Schmitt trigger. simulate this circuit – Schematic created using CircuitLab Why is there no current over Q2 ...
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5answers
2k views

Hardware debouncing of key matrix with minimum passive components

I have recently bought this cheap 4x4 keypad matrix. It only has the push-buttons and nothing else therefore I want to add a proper debouncing to it. The debouncing in software is something I want to ...
1
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1answer
320 views

Calculate transfer function H(w) of Schmitt trigger with RC at inverting input

I have got the following Schmitt trigger circuit implemented already on a breadboard. As seen, the input signal at the non-inverting and inverting terminals of the op amp is the same, but with the ...
3
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3answers
795 views

How to determine the saturation level when an opamp schmitt trigger starts worknig?

The Opamp inverting schmitt trigger is constructed as shown. The output signal is So I ask why is the output at the start of operation saturated to positive? Also, if the input voltage is moved ...
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127 views

Design Schmitt Trigger

Use Schmitt trigger to design a 1 kHz square wave oscillator. Assume the Op Amp supply voltages to be +15V, and the maximum bias current of the Op Amp to be 500nA. Assume that the maximum output of ...
0
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1answer
140 views

ADC preamp using Schmitt trigger, opamps and transistor reset

I would like to validate this design I use for input to a microcontroller for a piezo microphone trigger. I use 3 lines: a Schmitt trigger for use with an interrupt, an analog line for measuring the ...
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1answer
349 views

Sine to square wave high frequency [closed]

I have a school project that requires a sine to square wave converter for a sine wave input of 0 - 3.1 V pk from 0Hz to 500kHz. The output must be a square wave with maximum voltage 2.8V - 3.1V. So ...
0
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2answers
2k views

Schmitt trigger in button debouncer

While researching how to debounce a switch for digital applications, I often come around this diagram : simulate this circuit – Schematic created using CircuitLab Or other similar diagrams, ...
0
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1answer
162 views

Schmitt Trigger configuration for enabling power from guitar pickup

I would like to enable power to a regulator from a 1Vpp guitar pickup. Threshold can be between 0.2V and 1V. And I need it to disable after about 60 seconds of no signal from the pickups. I'm ...
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5answers
1k views

Why do TTL pulse generators generate an asymmetrical square wave (unlike CMOS)?

I've read that the asymmetrical (about 1/3 mark-to-space) output waveform is due to input gate characteristics of a TTL inverter, but I want to know more about which characteristics of the TTL input ...
0
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2answers
124 views

Analog buffer/voltage follower with function table?

I'm looking for a buffer as I am going to fan out a VCM signal from an ADC to multiple ADC drivers. ADC VCM out: 0.95V 10mA ADC dr in : 10Kohm x 3 ...
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0answers
91 views

Schematic review for simple LED circuit?

I'm pretty new to circuit design, I am trying to make a small board with a few LEDS that uses a toggle to turn on and another toggle to either show the LEDS always on or to blink the LEDS. I believe ...
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2answers
179 views

RC integral and differential functions, Schmitt triggers. How does this circuit work?

I'd be happy if someone explained me why this circuit is the way it is; how does it work ? Also i would like to know what the value for C1 is. Taken from https://www.electroninvest.com/shop/items/...
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0answers
36 views

Parameter tolerance estimation with non-pure ratios

I am trying to estimate the exact tolerance of a simple circuit, consisting of an op-amp based, inverting comparator with hysteresis. This is the schematic (electronic-tutorials.ws) For which I ...
4
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2answers
483 views

Why doesn't this schmitt PWM circuit work as expected?

I've designed and built an adjustable PWM generator using schmitt trigger inverters. However, it doesn't seem to be working. Here is the circuit: The capacitors at the bottom are intended to be ...
0
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1answer
236 views

Schmitt Trigger for logic level conversion voltages up to +-20V

I want to be able to safely convert any voltages above a threshold voltage of +-1V with a maximum voltage level of +-20V to the logic level (3.3V). I ended up using an op-amp to construct a Schmitt ...

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