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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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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62 views

How to protect my 555 timer against DC motor noise?

I have this circuit: (Sorry for such a bad schematic.) As you can see, there is a DC motor that gets power from 12V source, using a NPN transistor controlled by a 0-5V signal. Please note that ...
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1answer
89 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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121 views

Capacitance via 555 timer & resonance. Sources and possible cure?

I apologise in advance if this topic has already been discussed here. I am no EE and have have no choice but to ask experts to move my project forward. I am developing a capacitive sensor via a ...
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149 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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112 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
53 views

Blinking an LED once when a slide pot is pulled to ~zero ohms

I am developing a little circuit to control a servo linear actuator that is used to control fine injection onto a microscopy set-up. I am using a 555 circuit (see below) to generate the PPM signal ...
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56 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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2answers
60 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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2answers
297 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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76 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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1answer
44 views

Mono and Astable multivibrators not working when connected together

I have made a monostable multivibrator and an astable multivibrator using 555 timers using a popular circuit design found on the web. The monostable (out via pin 3) is used to control the astable (...
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1answer
72 views

PNP Transistor - Use IC 555's internal resistance as pulldown?

I have a circuit that uses a PNP transistor to enable or not the current to flow and turn on a LED. The point is, is it a good engineering practice to conect the base of the transistor to the Vcc of ...
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83 views

556 circuit not working

I just got my 556 timers and I wired it up just like the 555 but now: it flashes one HighTime and stays off then... I used this calculator and basic diagram: http://www.ohmslawcalculator.com/555-...
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147 views

IRFZ34N doesn´t switch on when a NE555 timer pulse is applied

simulate this circuit – Schematic created using CircuitLab I have the above circuit in my breadboard. The problem in a nutshell is that when the NE555 timer is switching at 50kHz in astable ...
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372 views

Retriggering 3V PIR sensor with 555 timer circuit and LEDS

Hi y'all I'm putting together a PIR sensor circuit that will trigger a 555 timer in monostable and run a set of LEDS for about 5 sec all on a 3v cr2032 button cell battery and than reset until next ...
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144 views

Can I control the charge of a Cell-Phone with a 555 Timer and a Transistor?

I want to charge my phone in a controllable manner, using a 555 and a Mosfet transistor. The 555 is a countdown timer that gives an output (pin 3) of 5V for 1 minute, and then remains at 0V until an ...
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233 views

How to vary the range of a potentiometer…is this even possible?

I am a total noob so apologize if this doesn't belong here but I haven't had any luck finding an answer to this... I have a simple circuit with two 555 timers...similar to an Atari Punk Console. I ...
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344 views

Dark detector with 555 timer and output pin has a LED

I am a complete novice and I had done it in a hurry with my kiddo around. I have redrawn it, with the values I used. The circuit works. Also between pins 6 and 7, if I use a 100 K/10 K it works. ...
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126 views

clarification on a particular 555 implementation for 4017 johnson counters

I'm trying to build a 13 count johnson ring counter (which flashes LEDs sequentially 1 thru 13 and then repeats), and I found this circuit which looks perfect: I assembled it with an extra LED on the ...
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472 views

555 to debounce comparator output for PIR circuit

I'm trying to create a circuit that takes an input from a PIR and outputs a high signal when movement is detected. My circuit currently looks like the schematic below (VCC is 5V). The circuit works ...
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3k views

How to calculate the Ra and Rb values for the desired frequency and duty cycle?

I am designing a DC-DC boost converter for Vin = 5V to Vout = 15V. To generate gate pulses, I will be using a NE555P Timer by TI - http://pdf1.alldatasheet.com/datasheet-pdf/view/161277/TI/NE555P.html....
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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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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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28 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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56 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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25 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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44 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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47 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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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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35 views

555 timer: light LED for 2 seconds

I turned it on and nothing happens. Now what?
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1answer
87 views

LED bar pattern shift (right to left) using 555 timer resistors and LEDs and SIPO shift register

I've build the 555 timer and got my resistors and LEDs ready. What I don't know or understand is how to shift a pattern using the serial in parallel out shift register (SN74LS164N). I want to shift ...
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1answer
51 views

Multisim - Circuit Design with a 555-timer

I am currently working on a design project. I am trying to get my 555-timer to turn on (1-minute) a motor and LED when activated and then turn back off after the 1-minute has passed. I am taking the ...
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30 views

Need to have two volume levels for a magnetic transducer buzzer

I am using an ATMEGA328PB TQFP and the Arduino IDE to activate a magnetic transducer buzzer (CUI CSS-14B20-SMT-TR). I'm using the Arduino Tone Library to produce 3 short beeps and then a 1 second ...
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57 views

555 timer delay circuit: resume after supply outage

I have created a 555 delay circuit where output goes down after a delay of T minutes. The 555 IC is in astable mode and is triggered automatically upon turning on the supply, Vcc. After turning on ...
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70 views

How to make a Ramp generator with a NE555 from 0V to 2/3VCC?

Hi Ladies and Gentlemen, It is related to an existing post here from early 2019. Voltage to PWM Circuit, need to understand frequency I am trying to make a simple 0-10V to PWM converter (idealy ...
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54 views

How to adjust duty cycle of an existing square-wave, based on light level

I am making a wall-powered, battery-backed, BCD alarm clock with discrete logic. I'd like to adjust the brightness of the LEDs based on light level, as this clock will be used on a nightstand. So ...
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41 views

Signal modulation at 38kHz using a 16-1 mux w/ 4bit counter

A little back story to what I am trying to achieve: I want to be able to control the bit pattern using DIP switches to send a controlled IR signal at 38kHz. I want to create a "game" where each IR ...
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2answers
42 views

Why can a capacitor connected to ground in a 555 astable circuit change pin 2s output?

beginner here. Basically my question is exactly as it says in the title. I was watching a video ( https://youtu.be/qfWIjb48mjE ) about 555 timers and was wondering how the capacitor can change the ...
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1answer
54 views

Feedback on astable 555 timer circuit to control MAC valve for turbo control

I have some questions and wanted to get feedback on this circuit I have put together. Basically to see if there is something I missed or obvious that I should change or should have designed ...
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1answer
267 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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1answer
52 views

555 NOISE BUTTON/ OP AMP

I have this circuit from the image below that I am designing myself. part of this circuit is cut so 2 78xx is present. This circuit is being designed and tested in parts. This part of the circuit has ...
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84 views

PWM with 555 timer IC

I am trying to build a PWM signal with 555 timer. I am following this website to build my circuit. simulate this circuit – Schematic created using CircuitLab I have placed my components in my ...
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33 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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49 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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1answer
48 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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95 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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62 views

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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76 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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51 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 ...