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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1answer
81 views

Working of Voltage-to-Frequency Converter

I have seen this circuit in a thesis "Voltage to Frequency Converter: Modeling and Design" submitted by Jyoti Ranjan Behra and Rajesh Kumar Barik (thesis abstract, thesis document). In the ...
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1answer
64 views

555 timer circuit causes spikes on power supply line - how to decouple?

I'm using a 555 timer circuit similar to this one to blink a couple of LEDs at around 1 to 30 Hz: The oscillations are causing huge spikes on the 5V supply line. There is an audio circuit running off ...
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49 views

Building a Comparator

For my final project, we are building an ultrasound range finder, without using a microcontroller. I have been able to build a block diagram (attached document). In the circuit, I'm using a 555 timer ...
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1answer
36 views

Buzzer not buzzing in proteus 7.7v - used ic555

I am trying to simulate a mosquito repellent in Proteus v7.7. It uses an NE555 in astable mode. My problem is that I cannot hear the buzzer buzzing. I checked my circuit and everything seems correct ...
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35 views

What is equation for the 555 timer control voltage in monostable

How do i get the 555 timer in monostable output frequency when there is voltage apply at control voltage. I only able to find the formula for astable which is Orignal post:- What is the equation for ...
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36 views

Using an NMOS as a switch for a 10V DC source in a 555 timer circuit

I used NI multisim and created a circuit with a 555 timer that will allow a diode to flash at a frequency of about 4HZ. This is the circuit: As you can see in the above image, the oscilloscope graph ...
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44 views

555 Timer Astable Mode

Just to clear things up. This is NOT a homework question, but it is lecture notes used as a practice exam. I am trying to understand the 555 timer in oscillation (Astable) mode particularly the ...
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37 views

why the 555 timer output is not the same as my calculation

Hi may i ask why is my calculation for the 555 timer of U2 is not the same as the simulator. U1 output signal 22064.24Hz, 92.81% duty cycle. t=1.1* R_1*C_1 t=1.1* 10k* 2.2n t=1.1* 10k*2.2n t=0.0242ms ...
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28 views

Multisim : Wrong Output for 1 way traffic light using 555 timers

I made a curcuit using the given diagram in Multisim but my output is of the order Green->Yellow->Green->(Yellow and Red) . Pls tell what should I do to get the output of the order Green->...
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3answers
858 views

555 timer - large inaccuracies with precision components [duplicate]

This is a problem I have been slowly chasing down. At first I was using 10% caps that caused the poor output accuracy. After changing the capacitor to a 1% I thought the problem would be fixed, but it ...
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1answer
45 views

programmable timer / clock generator

I need to generate a square wave / clock with configurable frequency between say 60 to 500Hz. There are not stringent requirements on the frequency stability. I need to be able to modulate this ...
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46 views

How does this timer 555 circuit work?

Is this the way this circuit works ? Vcc = 15v With vref = 5v on the pin #5, then Vthreshold = 5v, and Vtrigger = 2.5v, meaning that ...
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48 views

How does this timer 555 and transistor circuit work?

Is this the way this circuit works ? If vref = 5v on the pin #5, then Vthreshold = 5v, and Vtrigger = 2.5v With Vthreshold = 5v, if voltage on pin #6 Vp6 > 5v, then Vp3 is Vo = 0 With Vtrigger = ...
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1answer
51 views

Ra and Rb 555 Timer

Frequency - 10.53 Hz Duty Cycle - 52.63% C2 - 100 uF (e12 value) Time High - 49.97 ms Time Low - 44.99 ms Ra - ? Rb - ? please help me, people have offered websites but never what I need if you know ...
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51 views

Create a circuit that saves battery

I am trying to make a timer for myself. I select how long the timer runs for via a switch. The timer should begin counting down via a tilt sensor (or just a momentary button/switch to start) and count ...
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1answer
68 views

Reset and trigger 555 timer with one push button

I want to turn on a LED with a single push button. When the button is pressed, the LED has to be turned on for an X amount of time. But what I also want, is to turn of the LED with the same push ...
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32 views

Calculate Ra and Rb on a 555 Timer

I have all the units and calculations I need but I'm not sure which formula to use, and how to go about it. Please help. Frequency - 10.53 Hz Duty Cycle - 52.63% C2 - 100 uF (e12 value) Time High - ...
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2answers
61 views

How can I simulate an 8 LED (complemented) pattern device?

How can I simulate an 8 led with timer and ic? I have tried simulating it like this but still it’s not working, it blinks for less than a second and then it turns off I want it to work like First all ...
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1answer
145 views

How can I fix this LED dimmer circuit?

simulate this circuit – Schematic created using CircuitLab The circuit reverse-engineered above is a LED dimmer which is driven by 555 timer in astable mode which then drives an op-amp to ...
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2answers
52 views

555 darkness latch timer

I found a circuit to do what I thought I wanted it to do. I want an LED to turn on for a few seconds when an LDR detects darkness. The circuit works perfectly but now, of course, if the light source ...
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27 views

Delayed Switching Between USB Peripherals

I have two USB sensor pads that cannot be connected simultaneously to the computer. Currently I am using a USB hub with individual on/off switches for each port. To change pads the user MUST turn off ...
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58 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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51 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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1answer
65 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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2answers
93 views

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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1answer
55 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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88 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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42 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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2answers
53 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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124 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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2answers
78 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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3answers
84 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
129 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
70 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
41 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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39 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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158 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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4answers
212 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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2answers
89 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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34 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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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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2answers
118 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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76 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
72 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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29 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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51 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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83 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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102 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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114 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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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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