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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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27 views

Total Power Cutoff circuit

I'm designing a battery controlled circuit using a 555 timer to control a mosfet to provide power to a load. The problem I'm trying to solve is to reduce the current draw while the circuit is not ...
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36 views

Wireless power transfer circuit to attain ~5W of power on the receiving end

I am designing a WPT system to run a ws1812 based pixel chain. The ws2812 pixel chain runs on 5v and consumes 500-800ma of power, means 2.5w-4w. The system I made is not able to transfer adequate ...
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44 views

Backup PWM signal for DC fans

Currently, I have a board that powers 4 DC fans. A PWM signal is received from an external microcontroller to control the fan speeds. Unfortunately, the microcontroller sometimes fails to send the PWM ...
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60 views

Using the same potentiometer for two 555 timers

simulate this circuit – Schematic created using CircuitLab I have two 555 timers hooked up and I want them their duty cycle to be controlled by the same potentiometer. The second one has twice ...
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44 views

555 timed power at high to low edge in battery powered circuit

I have a lovely Atmel touch sensor whose output is high only as long as it's touched. I want both off-on and on-off edges of its output to initiate two 3 sec pulses (and the time between edges is > 3 ...
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48 views

Comparing the results of two electronic dice

I made two electronic circuits each consisting of a 555 Timer, a CD4017 and 7 leds in the shape of what you'd find on a dice. They work great and all, but I want to "compare" the results of both and ...
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23 views

Time step Error In Multisim Using 555 timer

I am trying to simulate a circuit in multisim and I keep running into the following error. (new to multisim) I attached a picture of the circuit and error. Any advice on how to fix this? The purpose ...
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55 views

Back EMF protection

I made an ignition coil driver circuit which is nothing special - they are everywhere on the internet. What's really bothering me is the back EMF that would fry the 555IC. If I put a rectifying ...
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Where do overtones in a 555 generated square wave come from?

I have built a 555 oscillator and connected it to a speaker. Using an oscilloscope I adjusted the 555 to generate a 2.5kHz square wave. I then held a microphone up to the speaker and fed the input ...
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54 views

Getting trigger signal for 555 timer from elevator button

I want to turn a load like light on for a certain time when one of elevator buttons pressed say button 1 and while the button pressed the load should be on. In the figure below circuit 1 describe how ...
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41 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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63 views

2-Bit timer with 1 ms period

I am trying to find a simple hardware solution to implement a 2-bit timer that gives out 2-bits continuously repeating data 00, 01, 10, 11, 00, 01.... whose time period is approx 1ms. The accuracy and ...
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46 views

Why should we charge the capacitor halfway in 555 timer circuit(as given in datasheet)?

In the Texas Instruments datasheet for LM555 IC, at Page 11 below Figure 15, the calculations for charging and discharging of the capacitor are given. In those calculations, the capacitor is made to ...
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44 views

Cascade of 555 timer with Control Voltage not triggering

Hi I'm currently working on a cascade 555 circuit, both operating in the monostable mode. I also want to be able to control the pulse width with a voltage so am using applying 0-5v to the ctrl pin (...
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2answers
61 views

555 Timer - How to quickly discharge RC capacitor

I'm using a 555 timer to turn off an LED with delay. Here is the circuit. All I want to implement is, to get the input voltage changes in output with a constant delay. When I close the switch, the ...
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45 views

Capacitor Discharge Pin 7 555 Timer

I am very new to electric engineering, so bear with me ;) Before building the circuit IRL, I wanted to try to build a simple 555 timer with a simulator following ...
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110 views

555 timer to drive transistors with low load resistance

Recently, I have a project that needs to heat up a metal filament with a single pulse voltage. I built a circuit with 555 timer and transistors to heat up the metal filament(0.2 ohm). The circuit ...
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39 views

Using a CMOS 555 as a window comparator

I've been working on a small project inspired by this question that uses a CMOS 555 timer as a power button controller (short press to turn on, 3s hold to turn off), the goal being to design a ...
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1answer
50 views

Power-on delay with 555 Timer

I am trying to create a power-on delay with a 555 timer IC. I have never used one of these before and I am finding it a bit tricky to make applications with it - a lot going on. I found this circuit ...
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54 views

Any improvements you can suggest, to these two 555 circuits? [duplicate]

This is a continuation of my original question that got put on hold... Any IC, to control a LED with a single push-button (ON,OFF,FLASH) I have come up with two solutions that work for me: a push ...
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3answers
103 views

Rapidly driving a keyboard signal

My goal is to build something that simulates rapidity (50 to 1k Hz) pressing a key on a USB keyboard. My first inclination was drive a transistor from a 555 timer with the two keyboard matrix pins on ...
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2answers
66 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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1answer
129 views

What is 0.693, and 1.1, and 1.44 in IC 555 Calculations

I tried a lot to figure out but could not find any answer to this question anywhere. For calculating pulse width in a standard IC 555 astable and monostable configurations we use the following ...
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Designing a 555 led blinker [closed]

Found a nice guide on how to make a led turning signal for bikes based the 555 timer which contained this schematic: But no matter how I do it, I cannot make it work.The leds won't blink.... What's ...
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50 views

Trigger based on Time Difference between two sensors / Catch a Miss on sensor

I have two Sensors S1 and S2, S1 is a 24v inductive proximity sensor which i isolated using octocoupler to work at 5v and S2 is a transmissive type phototransistor sensor, both are placed at a fixed ...
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Gating an astable 555 output signal in a way that oscilation always starts with a Low to High transition

simply, the circuit is a 38KHz signal generator for an IR remote project. the output signal should be gated by an MCU according to IR timing intervals recorded earlier. the design with the 4148 diode ...
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LMC555 Fading led problem

I'am developing a simple badge with a fading led. My idea was a LMC555 timer powered by a cr1025 battery, these batteries have a nominal voltage of 3v. I chose the LMC555 for its low operating voltage....
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92 views

Why would you loop 'Out' back to 'Vcc'?

I do not understand the NE556 circuit depicted in this data sheet: https://cdn-reichelt.de/documents/datenblatt/A200/NE-SA-SE556-TI.pdf on page 6 in figure 1. More specifically I do not understand ...
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Super Duper Vdd stiffening required on 555 timer, what is the best way?

I am using a 555 timer for a (16bit) frequency sensor/counter. It works by counting the number of pulses read in the 125ms sample time set by a 555 timer; resets & repeats... I am using the ...
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68 views

Lower amps than expected?

I build an inverter to power some panels of EL paint (If you don't know what EL paint is check out this link). It puts out some very high voltage and I thought I'd check to see what amperage it is ...
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46 views

555 Monostable delay circuit misbehaving

I have designed a basic application of a 555 in a monostable configuration to delay the LOW/off state of an output signal. (The output drives some power electronics through an optocoupler). As per my ...
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2k views

Astable 555 circuit not oscillating

I'm a complete beginner to electronics, but I'm trying to follow Ben Eaters video series "Building an 8-bit computer". I tried to do the first part of an astable 555 timer, but the LED does not ...
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1answer
71 views

Multiple NE555 timers, disable retriggering until all have finished

I plan to build a small timer device that, when triggered, lights up 3 leds. After 30 min, the first goes dark, after another 30 min the second and yet another 30 min later the third. It's pretty ...
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1answer
52 views

555 timer that does not output low when reset

I'm trying to design a circuit with the following goals: When not active, output can be either Vcc or floating When triggered by pressing a button, output pulses several times to GND at some ...
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1answer
43 views

Simulation behaves differently in Proteus vs Icircuit

I'm an electrical engineer student and I'm trying to make an LED Flasher circuit using a 555 Timer. When I simulated the circuit in Proteus simulator, it's not working! But in Icircuit simulator it ...
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1answer
110 views

Differences between LM555CN-R and LM555CN/NOPB

I am trying to buy a LM555CN-R online, however I can only find an LM555CN/NOPB. What are the differences, if any, on these chips?
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32 views

Suitable protection for elements on power line

I am working on mini project with 555 timer. The LED diode is not a diode, but a 12V LED string. What happens if there is a sudden drop in voltage? Motor will induce voltage of opposite polarity. The ...
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77 views

Astable 555 used for AC to DC Halfwave to DC stable conversion, is what I have done correct?

I have this falstad-circuit: And here it is per request, as a SCH file screen: I'm trying to use a 555 astable to convert a variable AC with maximum of 12V (coming from Bicycle Hub) to 8VDC, ...
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111 views

Timer Protection Circuit

I need to create a circuit that sends out a signal only if the input it on for longer than a specified time. Lets say 20 seconds for this example. So if the input to the circuit was pulled high for 10 ...
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60 views

555 IC Astable Mode - Does the voltage generally affect the frequency?

Sorry if it's been asked before, I'm asking to satisfy a curiosity. I'm new to electronics, and I'm messing around with the perennial 555 IC. I've been introduced to the following formula which allows ...
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1answer
92 views

NE555 power controller not working with big motors

simulate this circuit – Schematic created using CircuitLab Backstory: Ok, so I thought that a making a PWM controller would be a fun weekend project, it's been a week now and I still can't ...
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1answer
75 views

555 timer only works when I disconnect pin 4 from V+ and touch the jumper

I set up a pulse circuit on a breadboard with a 555 timer. Input voltage is 5 V. My values are roughly: C = 100nf R1 = 1K R2 = 1M I'm using this schematic: (Source: https://www.allaboutcircuits....
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Why can't my 555-based DC-DC boost converter supply even 3 milliamps at 12V?

I hope someone can help me. I've been tearing my hair out for the past couple of weeks trying to make a simple DC-DC boost circuit. It puts out a nice 12-ish volts when not loaded, but as soon as I ...
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1answer
72 views

Simulated 555 timer not working

https://www.tinkercad.com/things/2CN1eOTbmTe I am a beginner in electronics. I've been trying to make an astable 555 Timer in TinkerCAD as an oscillator for my own project of making a clock, without ...
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1answer
153 views

Why does this Mosfet get Hot?

I have an IRF740 mosfet that doesn't get hot in one circuit but then gets completely hot in another identical circuit and for the life of me can not figure out why. Well the circuits aren't exactly ...
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51 views

CircuitLab simulation of 555 timer - OUT HIGH always delivering 5V irrespective of Vcc?

I've scratched together a design for a 555 timer based driver for an IR540 MOSFET. But in CircuitLab the simulator shows the 555's OUT voltage is always 5V when high, for Vcc ranges 3.3V through 24V. ...
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62 views

555 circuit acting weirdly

In essense, whatI have are four 555s (2x556) One is a 0.5 s monostable,the other a 147 Hz tone generator. The other is a (30 s) monostable, and a 0.3 s astable. If I run the 0.3 s astable on its own, ...
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81 views

Why does this 555 timer not work correctly when I plug in the Z80 CPU ground?

I am trying to build this circuit here: https://www.youtube.com/watch?v=AZb4NLXx1aM But instead of using the same timer setup I am using this: When I connect the ground pin of the CPU, the LED ...
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1answer
103 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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30 views

555 Timer with controllable reset

I have a 555 monostable set up which is triggered when an output from another circuit goes low. This then remains on for 10s. This all works almost perfectly. My issue is that when the output from ...