Questions tagged [555]

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation and oscillator applications. The part is still in widespread use, thanks to its ease of use, low price and good stability. The 556 timer is simply two 555 timers in a single package.

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111 views

7555 monostable timer not resetting

I'm using a 7555 timer in monostable configuration to control a load of about 1A. If I disconnect the 1A load or use a bench supply it works fine, but the drop in voltage from the batteries seems to ...
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53 views

555 timer unstable pulses

I'm using a 555 timer to drive the clock of my circuit. However, even with capacitors from VCC to GND, and from Pin 5 to ground, I'm still getting this "bump" when the timer transitions from ...
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49 views

LM555 no output even when trigger is high or low

Good Day! I have been banging my head on the desk because I am failing to get the attached circuit work after PCB assembly. I am using Circuit Wizard and my circuit diagram and PCB simulation works ...
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54 views

Building a buck converter using CMOS 555 with mosfet driver

Can I use ICM7555 IC to generate 300 KHz PWM signal and feed that PWM to IRL2104 mosfet driver to build a non-isolated DC to DC buck converter? I'm asking this question because I couldn't find any ...
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3answers
529 views

Boost converter massive voltage

I made a boost converter with 1 1mH inductor, a mosfet, a 100uF capacitor rated for 400v, a 20 ohm 1/2 watt resistor, and an ICM7555 cmos timer. Using previous knowledge and wikipedia pages on the ...
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555 timer to control a servo with 2 variable positions

If possible, I'd like a circuit with a 555 timer, 2 potentiometers and I want to control the circuit with 1 digital input (5V / 0V). With the 2 potentiometers, I want to fine tune two fixed positions. ...
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3answers
4k views

independent control of frequency and duty cycle in 555 timer (formulas)

I want to control frequency and duty cycle of output pulse of 555 timer. I searched and find this schematic in a post in SOV but I don't know how calculate frequency and duty cycle in the circuit. ...
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1answer
651 views

power on power off pulses to two seperate controllers

I would like to request a circuit where a 500 ms pulse is sent to one rail when 12 volt power is supplied and another 500 ms pulse is sent to a different rail when power is turned off. 555 is the way ...
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1answer
46 views

How to limit pulse duration?

I'm trying to design automotive-oriented circuit to limit ignition pulse duration from OEM ECU to an aftermarket ECU plug-in device. The device expects +12v pulses no longer than 9ms, while the car in ...
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1answer
177 views

NE555 Circuit stops working after random time

i finished my NE555 circuit and created some pcbs. After a few attempts i could get the circuit working, and tested it successfully. I placed my circuit between a 12V 1.5Hz square wave signal and a ...
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445 views

How can I use the component CD4538 or a 555 timer on Multisim?

How can I use the component CD4538 or a 555 timer on Multisim for a delay of 1 second ? I want both of the nor gates to be 1 for roughly 1 second when the output of the op-amps is either 01 or 10.
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How the pin2 of 555 timer triggers this simple circuit?

First of all, I will go through my concept which make the doubt. When we connect positive side of LED to a positive terminal of a battery and negative of LED to floor (not to -ve of battery), current ...
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49 views

How to bypass continuous input on Trigger pin of 555 IC after some time working in Mono-Stable/ One shot version?

I configured the 555 IC such that it gives the output pulse for 3 Seconds (Approx.) as soon as there is input on trigger pin, but my project requirement is; even if there is input continuously on ...
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86 views

General Schematic and PWM questions

I'm new to EE. I've made my first schematic: To explain my project: I have 1 Nichia E21A LED that needs to be powered by any 5V power bank and be user dimmable via a dial (potentiometer.) The PCB and ...
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41 views

Triggering the 555 timer for a short period

simulate this circuit – Schematic created using CircuitLab This is the mechanism which was used in a 555 timer used in the mono-stable mode, it was designed so that even if the switch is closed ...
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73 views

A circuit that converts contiuous pulse signal to a stable level signal, and reverse if pulse not present

I have a 12V 3-pin computer fan that has a tachometer signal output: when the fan is spinning normally, the tacho wire is either floated or shorted to ground periodically. If you connect a pull-up ...
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64 views

Proximity IR Sensor Circuit using TSOP VS1838 output problem

I am assembling a proximity IR Sensor using TSOP instead of Photodiode. I followed the diagram below. When I tested the circuit, and put my hand close to the IR LED. The receiver receives the signal ...
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1answer
343 views

Toggle 555 timer IC both with switch and arduino

I want to use 555 timer IC (NE55P) as a latching toggle switch. I successfully did it using a switch as described in this toggle 555 schematics except, I am using 5V power with led as output ...
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82 views

555 trigger amplitude slightly too large to trigger

I have the following circuit which is designed to take a longer pulse (on the order of miliseconds) from a microcontroller (source v3 below) and use two 555 timers in cascade to output two consecutive ...
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1answer
98 views

555 timer not working in monostable mode

I am a newbie electronics learner and trying my hands on 555 timer to get it running in the monostable mode. Am trying the circuit as in the attached diagram. I am just unable to get the LED blink. I ...
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1answer
68 views

Duty cycle of 555 timer

I am trying to understand the exact working of this circuit, I have been told that this circuit provides a duty cycle of 50% from my previous questions, the same which I successfully verified in ...
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1answer
175 views

Low cost PWM sweep

I have this project where I need to try and get a PWM duty sweep starting at around 30% up to 100%. The issue I have is that we don't have anything left in the design (BOM Cost). I would normally use ...
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1answer
54 views

LED blinking circuit design

I am trying monitor activity on Rx/Tx lines of UART signals with led's. I have more number of channels(20) so i dont have place to use micro controller for this purpose. NE556 timer in monostable ...
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4answers
120 views

Reducing IR proximity sensor module power consumption

I have built a rechargeable automatic hand sanitiser using an IR proximity sensor(HW 201.) It consists of an IR proximity sensor module, TIP 32 transistor, 3-6 V DC pump, TP4056 charging module and a ...
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1answer
39 views

How does this specific boost converter work?

So I found this Geiger counter at https://mightyohm.com/blog/products/geiger-counter/. You can also find the detailed electronic schematics there. I tried to figure out how this apparatus works, but I'...
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156 views

Will my 555 timer circuit work the way I want it to?

Essentially, I am trying to implement a safety system for another project of mine. I am running a very high current through a rather large solenoid and want to ensure that a failure in its control ...
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38 views

Alternating vibration motor

I would like to build a circuit similar to the two alternating flashing lights circuit, but using two disc vibration motors instead. I’d like it to have a speed control. The vibration motors have ...
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1answer
208 views

555 pump controller not triggering

I built this 555 pump controller and it works correctly if I short the wires, however, when trying to use the electrodes in water it doesn't do anything. I am using a 12V 1A power supply so I don't ...
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2answers
86 views

Super low duty cycle circuit

I am looking for a way to recharge some glow in the dark paint in a way that isn't noticeable to others. My idea is to use a very fast pulse of light from a bunch of UV LEDs every few seconds, but ...
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3answers
5k views

Why does this circuit keep killing my 555 timers?

I have a 555 timer set up in a standard monostable oscillator configuration. Nothing fancy, no modifications whatsoever. I'm driving it with about 12V. If I trigger the 555 with the ground directly, ...
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2answers
352 views

555 PWM motor driver controlled by external analog signal

I used the below 555 timer PWM circuit to control the speed of a dc motor, and it works like a charm :) now i have a requirement to change the PWM speed externally from another module, that module ...
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1answer
1k views

LED driver circuit interfering with 555 timer?

Below is a circuit I put together that uses a 555 timer and an LED Driver: But the strange thing I see is that the timer does not follow the 1.1*R*C equation. The led remains lit for much longer. I ...
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303 views

555 timer not switching at threshold voltage

This is a 555 timer circuit which is supposed to generate two short pulses, back to back, at a regular frequency. The top 555 is configured as astable to control the frequency. It feeds the first 555 ...
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32 views

Will this “off delay” circuit work if a continuous trigger is applied to pin 2?

This is an off delay circuit using a 555 timer. I want to know if this can be used even if the trigger signal is continuous. If, not what modification is needed?
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87 views

555 timer control voltage operation

Does anyone know how to use the 555 timer control voltage? My thoughts are if -input in the upper ("Threshold") comparator is at 2/3Vcc, then any voltage should act against the 2/3Vcc into ...
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63 views

How can I improve this circuit to drive a servo with a 555 timer?

I am trying to use a 555 timer to create the PWM signal for a servo motor. I found and constructed the circuit in the attached image. It does work as advertised, and I can adjust the servo's ...
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1answer
62 views

Purpose of this pulse shaping circuit for 555 timer input

In the circuit below the inverter is used to switch 12 volts into a pulse shaping circuit (10k resistor, 220-260pf capacitor, diode and 680 ohm resistor), the output of which is used as the trigger to ...
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1answer
135 views

Capacitor charging voltage showing ripples on scope. Origin?

I have an RC circuit delivering a square signal via a standard 555 timer set in monostable. I am powering the 555 with 4.88V DC directly from the Arduino, which itself is taking its power from the ...
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1answer
155 views

555 square wave generation with frequency feedback

Knowing that 555's behaviour varies according to temperature, I wondered: In an astable configuration, is there some way to measure output frequency, compare it with some desired value, and use this ...
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2answers
6k views

Is there a way to control the PWM duty cycle of a 555 timer without using a variable resistor?

I need to control the duty cycle of a Pulse Width Modulation (PWM) circuit from a DC voltage input. To do this, I've been looking into 555-timer circuits - but every circuit I've come across involves ...
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26 views

DC Supply voltage drop in a Schmitt trigger circuit

I developed a Schmitt trigger using IC NE555P. I supplied a Vcc of +6v from a DC source. My input is a sinusoidal wave (peak-peak = 4V). First I set the voltage in DC source (+6v) and when I connect ...
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49 views

one-shot circuit with infrared sensor

If our hand is near the infrared sensor, it will remain in HIGH condition until we release the hand from the sensor. How can an additional circuit (without a microcontroller and without another ne555) ...
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1answer
223 views

Latching switch to single pulse circuit? (monostable multivibrator with 555?)

I am looking at using a latching switch (SPDT) to momentarily connect two pins. This is for a power button for a raspberry pi, so to power the machine from a hold state you have to momentarily short ...
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57 views

Unstable behavior of Dc-Dc converter

I am currently working on a high voltage boost converter based on Dos4Evers 555 timer based one https://www.dos4ever.com/flyback/flyback.html (12v to 140-220V). I am running into an issue with the ...
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3answers
94 views

how to solve the phase shift of a ne555 timer

Why is the first pulse wave is not the same as the rest of the wave in this 555 timer? Is there any way to remove the wave before 2 ms or is there anyway to make it same as the rest in the graph.
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113 views

Problems on switching MOSFET for boost converter

**EDITED I am supposed to build a boost converter that steps-up a 1.5V input to 5V (also I only have 1.5V as my power source). I have designed the circuit out but the only problem I face right now is ...
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2answers
317 views

how the calculate the specific resistor in a parallel led circuit?

This is a Sequential LED flasher circuit i found in you tube. He uses 11 leds in 5v power supply source and he connect them in parallel with a resistor 470ohms. I try figure out how he measure this ...
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1answer
81 views

Circuit Idea about 555 Timer

I have a 555 timer which outputs an enable high 500ms after power-up. So it is basically a step response at t = 500ms. I am tasked with processing this enable signal with a 20 Hz square wave signal ...
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1answer
69 views

Is there a component that will OR the last 1-2ms of its input?

I need a component/circuit which will output 1 if a 1 has been input at any time in the last 1-2ms. I could make such a circuit out of several shift registers, an oscillator and several OR gates, or ...
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1answer
53 views

555 timer question

R1=500k variable resistance R2= 10k when the timer's operation time is 5sec, R1 86.7k What is the operation time when 4V is applied to 5(red point)? im student, so I would very appreciate it if you ...

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